GIRK Channels

This is a place to post research you have done on the topic along with your conclusions.
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Ghost
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Re: GIRK Channels

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Update on the writing:

Here is a newer version of the introduction. The rest of the article is piecing together well, but is still a ways out.

Intro:


The seven 5-HT G-Protein Coupled Receptors (GPCRs) families (5-HT1-7) can be divided into three major subgroups depending on which G protein signaling pathway they activate. 5-HT1 receptors (Ex: 5-HT1A) couple mainly to the Gi/o pathway, 5-HT4-7 receptors couple to the Gs pathway, and 5-HT2 receptors activate the Gq pathway. 5HT3 receptors are inotropic ligand-gated ion channels, and therefore aren’t GPCRs.

In the Raphe Nuclei (RN), the 5HT1A receptor acts as a presynaptic somatodendritic autoreceptor. At the ends of its projections in the in the hippocampus, frontal cortex, and hypothalamus, it functions a presysnaptic autoreceptor and a postsynaptic heteroreceptor (Sotelo et al., 1990; Burnet et al., 1995; Riad et al., 2000). When more Serotonin (5-HT) is found in the synapses in the RN, activation of autoreceptors inhibits for the release of 5-HT in the projections of RN neurons (Koek et al., 1998; Gobbi et al., 2001). In this manner, 5-HT1A autoreceptors work as the major negative regulator of 5-HT activity (Albert, 2012) (Bang et al., 2012). Decreased 5-HT transmission has long been associated with Major Depressive Disorder (MDD) (Van Praag et al. 1970) and it is thought that the RN is where SSRI antidepressants exhibit their therapeutic effects. It then comes as little surprise that the 5-HT1A has been heavily implicated in effective clinical treatment of depression and anxiety. SSRIs are believed to block 5-HT reuptake by binding to SERT (5-HTT) and reducing its reuptake abilities (Murphy et al., 2004). In theory, increased somatodendritic and terminal autoreceptor binding would inhibit release of 5-HT into the synapse: resulting in no increased 5-HT levels. Through a process that is still unknown, serotonin transmission is eventually enhanced by “desensitization” of both the somatodendritic and terminal autoreceptors (Chaput et al., 1985), allowing synaptic 5-HT to accumulate in the synapse. This accounts for the characteristic 4-8 week delay between treatment origins and therapeutic relief (Gartside et al., 1995; Blier, 2010; Richardson-Jones et al., 2010).

5-HT induces hyperpolarization by activating 5-HT1A autroreceptors whose Gi/o alpha subunit activates GIRK channels located within the presynaptic membrane (Innis and Aghajian, 1987) (Bayliss, 1997) (Katayama, 1997). In the DRN, GABAB receptors use the same intracellular G-protein pathway as 5-HT1A autroreceptors: though coupling to pertussis-toxin-sensitive G-Proteins (Innis and Aghajian, 1987). Chronic treatment with the SSRI fluvoxamine reduces both 5-HT1A autoreceptor and GABAB receptor-mediated GIRK currents (Cornelisse et al., 2007). This suggests that desensitization of 5-HT1A autoreceptors by SSRI treatment occurs downstream of the receptor, and a mechanism shared with GABAB receptors.

In this literature review, I propose a G-Protein model of 5-HT1A autoreceptor desensitization occuring downstream of the receptor through GIRK channels that explains this autoreceptor desensitization. The clinical implications of understanding 5-HT1A autoreceptor disinhibition are very important in creating new-age antidepressant treatments that quickly and effectively raise 5-HT levels in patients who either cannot wait for treatments to work, or are treatment resistant to current SSRI medications. Additionally, permanent sexual changes occasionally occur in both animals and humans treated with SSRI antidepressants. Male mice who had mothers on SSRIs showed a permanent decrease in sexual drive (Gouvêa et al., 2008). Recent studies suggest that these lingering side effects are also seen in humans (Sheetrit et al., 2015) (Farnsworth et al., 2009) (Stinson, 2009) (Waldinger et al., 2015) (Leiblum et al., 2008) (Bolton et al., 2006) (Csoka et al., 2006). The implications of this persistent Post-SSRI Sexual Dysfunction (PSSD) have widespread emotional, social, and sexual implications in patients, and often leads to them to feel alienated from their peers and loved ones (Stinson, 2013). It has been hypothesized that PSSD is a result of persistent 5-HT1A desensitization after SSRI treatment has been stopped (Ghost, 2016). Understanding the mechanisms that lead to 5-HT1A desensitization could help develop treatment plans for patients with PSSD.
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Re: GIRK Channels

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Updates on the writing I've been doing. A lot more to come, but this is the first few pages.
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pete
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Re: GIRK Channels

Unread post by pete »

Ghost, where exactly is rgs4 upregulated? just in drn?
i have read about amphetamine induced downreguatlion of rgs4. what if this guy on reddit was right?
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Re: GIRK Channels

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Updated Writing that has come of my interest in GIRK channels last spring.

GIRK Channel Uncoupling: A Mechanism for 5-HT1A Autoreceptor Desensitization in the DRN.

Ghost1,2
1Admin, http://www.pssdforum.com
2Moderator, http://www.reddit.com/r/PSSD


Abstract:

Multiple studies have suggested that Selective Serotonin Reuptake Inhibitor (SSRI) induced desensitization of 5-HT1A autoreceptors occurs downstream of 5-HT1A autoreceptors: between the 5-HT1A autoreceptor and the target G-Protein Inward Rectifying Potassium (GIRK) channels that hyperpolarize the pre-synaptic serotonergic neurons in the Dorsal Raphe Nucleus (DRN). In this literature review, a possible mechanism of G-protein-based desensitization as a result of chronic SSRI treatment is proposed.

Introduction:


The seven 5-HT receptor families (5-HT1-7) can be divided into three major subgroups depending on which G protein signaling pathway they activate. 5-HT1 receptors (Ex: 5-HT1A) couple mainly to the Gi/o pathway, 5-HT4-7 receptors couple to the Gs pathway, and 5-HT2 receptors activate the Gq pathway. 5HT3 receptors are ionotropic ligand-gated ion channels, and therefore aren’t G-Coupled Protein Receptors (GPCRs).

In the Dorsal Raphe Nuclei (DRN), the 5HT1A receptor acts as a presynaptic somatodendritic autoreceptor (Aghajanian et al., 1990). At the ends of its projections in the in the hippocampus, frontal cortex, and hypothalamus, it functions a presysnaptic autoreceptor and a postsynaptic heteroreceptor (Sotelo et al., 1990; Burnet et al., 1995; Riad et al., 2000; Verge´ et al., 1986). When more Serotonin (5-HT) is found in the synapses in the DRN, activation of autoreceptors inhibits for the release of 5-HT in the projections of DRN neurons (Koek et al., 1998; Gobbi et al., 2001). In this manner, 5-HT1A autoreceptors work as the major negative regulator of 5-HT activity (Albert, 2012) (Bang et al., 2012). Decreased 5-HT transmission has long been associated with Major Depressive Disorder (MDD) (Van Praag et al. 1970) and it is thought that the DRN is where SSRI antidepressants exhibit their therapeutic effects. It then comes as little surprise that the 5-HT1A has been heavily implicated in effective clinical treatment of depression and anxiety. SSRIs are believed to block 5-HT reuptake by binding to SERT (5-HTT) and reducing its reuptake abilities (Murphy et al., 2004). In theory, increased somatodendritic and terminal presynaptic autoreceptor binding would inhibit release of 5-HT into the synapse: resulting in no increased 5-HT levels. Through a process that is still unknown, serotonin transmission is eventually enhanced by “desensitization” of both the somatodendritic and terminal autoreceptors (Chaput et al., 1985), allowing synaptic 5-HT to accumulate in the synapse. This accounts for the characteristic 4-8 week delay between treatment origins and therapeutic relief (Gartside et al., 1995; Blier, 2010; Richardson-Jones et al., 2010).

5-HT induces hyperpolarization by activating 5-HT1A autroreceptors whose Gi/o alpha subunit activates GIRK channels located within the presynaptic membrane (Innis and Aghajian, 1987) (Bayliss, 1997) (Katayama, 1997). In the DRN, GABAB receptors use the same intracellular G-protein pathway as 5-HT1A autroreceptors: through coupling to pertussis-toxin-sensitive G-Proteins (Innis and Aghajian, 1987). Chronic treatment with the SSRI fluvoxamine reduces both 5-HT1A autoreceptor and GABAB receptor-mediated GIRK currents (Cornelisse et al., 2007). This suggests that desensitization of 5-HT1A autoreceptors by SSRI treatment occurs downstream of the receptor, and a mechanism shared with GABAB receptors.

In this literature review, I propose a G-Protein model of 5-HT1A autoreceptor desensitization occurring downstream of the receptor that explains this autoreceptor desensitization. The clinical implications of understanding 5-HT1A autoreceptor disinhibition are very important in creating new-age antidepressant treatments that quickly and effectively raise 5-HT levels in patients who either cannot wait for treatments to work, or are treatment resistant to current SSRI medications. Additionally, permanent sexual changes occasionally occur in both animals and humans treated with SSRI antidepressants. Male mice who had mothers on SSRIs showed a permanent decrease in sexual drive (Gouvêa et al., 2008). Recent studies suggest that these lingering side effects are also seen in humans (Sheetrit et al., 2015) (Farnsworth et al., 2009) (Stinson, 2009) (Waldinger et al., 2015) (Leiblum et al., 2008) (Bolton et al., 2006) (Csoka et al., 2006). The implications of this persistent Post-SSRI Sexual Dysfunction (PSSD) have widespread emotional, social, and sexual implications in patients, and often leads to them to feel alienated from their peers and loved ones (Stinson, 2013). It has been hypothesized that PSSD is a result of persistent 5-HT1A desensitization after SSRI treatment has been stopped (Ghost, 2016). Understanding the mechanisms that lead to 5-HT1A desensitization could help develop treatment plans for patients with PSSD.

GIRK Channels:


Under physiological conditions the resting membrane potential of a typical neuron is positive to EK, and the small outward K+ current through GIRK channels decreases the excitability of a neuron. Different types of neurotransmitters, such as acetylcholine, dopamine, opioids, serotonin, somatostatin, adenosine and GABA, activate these channels by stimulating their cognate G protein coupled receptors (GPCRs), which in turn couple specifically to pertussis toxin (PTX) sensitive heterotrimeric G proteins that activate GIRK channels (4). Strong evidence supports the conclusion that Gβγ dimers released from PTX-sensitive (Gαi/Gαo) G proteins bind directly to GIRK channels causing them to open (5-9). Conformational changes induced by binding of Gi/o Gβγ dimers control the opening of GIRK channels (CITE). Mammals express four types of GIRK channel subunits (GIRK1-4) (Lüscher and Slesinger, 2010). However, only GIRK1-3 are common within the brain (Wickman et al., 2000). These subunits assemble into tetrameric channels (3,19-23).

Several GIRK channel modulators are known to alter their activity. Na+(44-45) and Ethanol (46-48) appear to stimulate GIRK channels through specific binding sites on the channels. Additionally, phosphorylation by PKA and PKC kinases modulate GIRK channel function (49-57). PKC-dependent phosphorylation decreases while PKA-dependent phosphorylation enhances channel activity. Finally, levels of the membrane phospholipid phosphatidylinositol 4,5 bisphosphate (PIP2), can regulate the activity of GIRK channels (58-60).

Alpha Subunit Changes After SSRI Treatment:

[35S]GTPγS binds to alpha subunits. The DRN and Hippocampus show high levels of 5-HT1A stimulated [35S]GTPγS binding (Sim et al., 1997), suggesting that these regions are populated with 5-HT1A receptors using G-protein signalling. 5-HT1A agonist 8-OH-DPAT increases [35S]GTPγS binding in a concentration-dependant manner (Castro et al., 2002) This increase in [35S]GTPγS binding is totally abolished in the DRN after 14 days of treatment with the SSRI Fluoxetine (Castro et al., 2002), suggesting desensitization of autoreceptors there. However, [35S]GTPγS binding in the Hippocampus is increased (Castro et al., 2002). This suggests that G-protein alpha subunits are important in the desensitization of 5-HT1A autoreceptors seen after 14 days of Fluoxetine treatment, and that alpha subunits play a role in increased activation in downstream postsynaptic targets of the DRN. Additionally, chronic treatment with the selective 5-HT reuptake inhibitor fluoxetine leads to regionally differentiated regulation of 5-HT1A receptor-activated G-proteins. [35S]GTPγS binding assays further suggest that somatodendritic and terminal 5-HT1A autoreceptors function as feedback inhibitors of serotonergic cell firing, so their desensitization leads to increased serotonergic neurotransmission and, subsequently, to desensitization of postsynaptic 5-HT1A receptors.Desensitization of 5-HT1A autoreceptors can be seen without changes in their density (Castro et al., 2002, Le Poul et al., 2000; Herva´s et al., 2001), suggesting that desensitization occurs downstream of the receptor level, and is likely due to changes in subunit levels instead of transcription rates of 5-HT1A Autoreceptors. It would appear that changes in the levels of alpha subunits in the DRN are behind the desensitization seen in SSRI treatment.

Reduction in the levels of G-protein alpha subunits Gi and Go have been noted in rat midbrain after chronic SSRI treatment (Li et al. 1996). Go proteins are coupled to somatodendritic 5-HT1A receptors (Barnes and Sharp, 1999), and a decrease in their levels might be related to the desensitisation observed in[35S]GTPγS assays showing 5-HT1A autoreceptor desensitization. Additionally, increased levels of Gi1 and Gi2 alpha proteins in the hippocampus have been reported following administration of SSRI antidepressants (Dwivedi and Pandey, 1997). This supports findings that show increased [35S]GTPγS binding in the Hippocampus 14 days after SSRI treatment.


Fluoxetine induces region-specific changes to individual Gi/o proteins. Go and Gi2 proteins in the midbrain are significantly reduced after 3 days, and Gi1 and Gi3 levels are significantly reduced in the hippocampus after 7 and 14 days of SSRI treatment (Li et al., 1996). This suggests that 5-HT receptors on the presynaptic and postsynaptic sides couple to different G-protein subunits. After DRN 5-HT1A autoreceptors are desensitized by Fluoxetine within 3 days, the disinhibition of 5-HT allows for an increase in 5-HT release, which subsequently leads to a desensitization of postsynaptic 5-HT receptors in the hippocampus after 7 and 14 days. These data also suggest that Go and Gi1 subunits are used by autoreceptors, while heteroreceptors use Gi1 and Gi3 subunits in the hippocampal projections. This would support other findings in the literature: somatodendritic 5-HT1A autoreceptors in the raphe nuclei are coupled to Go proteins and lead to an increase in the opening of K+ channels (Kelly et at., 1991), and postsynaptic 5-HT1A receptors have a high affinity for G-proteins (rank of affinity is Gi3 > Gi1> Gi2 > G0) (Raymond et at. , 1993). 5-HT1A receptors are coupled to Go and/or Gi proteins (Raymond et at., 1993; Fargin et at., 1991; Kelly et at., 1991; Emerit et at., 1990).

Regulators of G-Proteins (RGS) as Candidates for 5-HT1A Autoreceptor desensitization.

Regulator of G protein signaling (RGS) proteins are a family of more than 30 proteins that function as GTPase accelerating proteins (GAPS) that bind and rapidly deactivate Gα subunits, thereby greatly limiting the life of active Gα signaling molecules. Thus, RGS proteins function as the principal negative regulators of Gαi/o-mediated signaling (4–6). Animals rendered insensitive to RGS protein regulation through a mutation in Gi2 (G184S) exhibit spontaneous antidepressant- and anxiolytic-like behaviors (Talbot et al., 2010). Li et al.’s finding that Gi2 subunits decreased in SSRI treatment suggests that Gi2 is involved in 5-HT1A autoreceptor desensitization, and demonstrates that RGS proteins likely play a role in this desensitization. RGS-insensitive mice were also 5–10 times more responsive to the antidepressant-like effects of the SSRI fluvoxamine and 5-HT1A–selective agonist 8-hydroxy-2-Dipropylaminotetralin (Talbot et al., 2010). Antianxiety and antidepressive behaviors of Gi2 RGS insensitive mice were blocked by treatment with selective 5-HT1A antagonist WAY 100635 (Talbot et al., 2010), giving more evidence that Gi2 is involved in 5-HT1A desensitization and subsequent antidepressant effects. In particular, RGS4 is a possible candidate for a regulator of Gi2 subunits. RGS4 is up-regulated in the nucleus accumbens NAc after chronic treatment with the SSRI fluoxetine. Behavioral studies of mice lacking RGS4 suggest that RGS4 in the NAc region acts as a positive modulator of the antidepressant-like and antiallodynic-like actions in SSRI antidepressants. Additionally, postmortem human brain tissue have robust up-regulation of RGS4 expression in the nucleus accumbens (NAc) of subjects receiving standard antidepressant medications that target monoamine systems at the time of their death. NAc Rgs4 levels are reduced following chronic amphetamine treatment (30).

What I still need to add/ what questions I still have:

What is the role of RGS4 in the DRN?

RGS4 is also involved in Schizophrenia in some brain regions. Would altering RGS4 for PSSD need to be region-specific? I would assume it would...so...

What is causing the changed expression of RGS4 in the NAc (and maybe DRN) in PSSD if Gi2 and RGS4 are the PSSD culprit? That would be another layer of complexity that needs to be researched.

What animal studies could show RGS4 is a culprit for PSSD? How could it be done cheaply?

What role does RGS4 have in sexuality as a whole?

What role does RGS4 have in development and aging? Why do younger animals given SSRIs get PSSD, but older ones don’t?

What RGS inhibitors exist? Are they region-specific? How much do they cost? What is their safety? What other drugs are known to affect their levels?

Finally I need to cite all my sources, make sure all the wording is my own, and finalize all of that fun stuff.
- Medical Student & Friendly poltergeist - Lexapro Sept '14. [Hx] [PSSD Lab] [r/PSSD] [Treatment Plan] - Add "Ghost" in replies so I see it :)
pete
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Re: GIRK Channels

Unread post by pete »

This spicy food thing lead me to something.
I don't got time to dig deeper into this stuff.
So i'm just throwing it in here.

https://en.m.wikipedia.org/wiki/Substance_P
https://en.m.wikipedia.org/wiki/Tachykinin_receptor_1
https://en.m.wikipedia.org/wiki/Tachykinin_receptor
https://www.ncbi.nlm.nih.gov/pubmed/16219031
Coraggio
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Re: GIRK Channels

Unread post by Coraggio »

This is what I've found about Forskolin, its activity about Adenylyl Cyclase pathway, RGS, 5-HT, D2 receptors and SERT.

1) Meccanism of action of Forskolin. It enhances Adenilate Cyclase function. This can raises cAMP. Raising cAMP PKA is activated. PKA activates GIRK channels

https://www.ncbi.nlm.nih.gov/pubmed/2988553
Forskolin activation of serotonin-stimulated adenylate cyclase in the liver fluke Fasciola hepatica.
McNall SJ, Mansour TE.
Abstract
Properties of forskolin activation of adenylate cyclase in the liver fluke Fasciola hepatica are described. Forskolin stimulated adenylate cyclase activity in cell-free fluke particles to levels more than 30-fold above the basal rate. This activation was not dependent on guanine nucleotides and, upon washing of the particles, was rapidly reversed. Forskolin potentiated the activation of adenylate cyclase by serotonin (5-HT) and lysergic acid diethylamide (LSD), resulting in both an increase in the maximal level of enzyme activity and a decrease in the apparent activation constant (KA). The 5-HT antagonist 2-bromo-LSD did not inhibit enzyme activation by forskolin. Furthermore, forskolin had no effect on specific [3H]LSD binding to fluke particles. Activation of adenylate cyclase by sodium fluoride or guanine nucleotides was modified in a complex manner by forskolin with both stimulatory and inhibitory effects present. The results suggest that forskolin does not interact directly with the 5-HT receptor coupled to adenylate cyclase. Instead, it appears that forskolin effects are, at least in part, due to its ability to alter the interaction between the regulatory and catalytic components of adenylate cyclase. Incubation of intact flukes with forskolin increased their cAMP levels 2- to 3-fold. The concentration dependence of this response was similar to that for forskolin activation of adenylate cyclase in fluke particles, with 300 microM forskolin giving the maximum response. Forskolin and other agents that increased fluke cAMP levels also stimulated fluke motility.

Another study about forskolin. It seems leads to sensitization of catalyst part of AC and decreased stimulation of AC by Galphas pathway. No changes in Gi, Gs and Gbeta subunits were detected after Forskolin stimulation.

https://www.ncbi.nlm.nih.gov/pubmed/8931487

J Neurochem. 1996 Dec;67(6):2532-9.
Long-term effect of forskolin on the activation of adenylyl cyclase in astrocytes.
el Jamali A1, Rachdaoui N, Jacquemin C, Corrèze C.
Author information
Abstract
Long-term (48-h) forskolin treatment of rat astroglial cells led to a slight decrease (30-40%) in the response to isoproterenol, vasoactive-intestinal peptide, guanyl 5'-(beta gamma-imido)diphosphate, guanosine 5'-O-(3-thiotriphosphate) [GTP(S)], and AIF4- in crude membrane fractions. In contrast, the acute stimulatory effect of forskolin was increased by 1.25-1.5-fold. These two opposite effects of forskolin were mediated by a cyclic AMP-dependent mechanism. No changes in Gs alpha, Gi alpha, or G beta protein levels could be determined by immunoblotting using specific antisera. No significant differences were observed in the ability of G proteins extracted from control and forskolin-treated cells to reconstitute a full adenylyl cyclase activity in membranes from S49 cyc- cells, lacking Gs alpha protein. Gs alpha proteins were detected in two pools of membranes, one in the heavy sucrose fractions and the other in light sucrose fractions. Forskolin treatment of the cells shifted Gs alpha protein toward the light-density membranes. We did not find any significant change in the distribution of adenylyl cyclase. In contrast to the decreased stimulation of adenylyl cyclase activity by agonists acting via Gs alpha, observed in the crude membrane fraction, the responses of adenylyl cyclase to forskolin as well as to GTP(S) were increased in the purified plasma membrane fractions. These results may indicate that sensitization of the catalyst appears to be the dominant component in the astroglial cell response to long-term treatment by forskolin.
PMID: 8931487




2)This is an article treating Forskolin effect on RGS.Forskolin can reduce RGS4 by nearly 50% after 3h, and strong induces RGS2 after 1h. If cronic treatment of SSRI increases RGS4, forskolin may counteract this effect.


https://www.ncbi.nlm.nih.gov/pubmed/?te ... PC12+cells

Regulation of RGS mRNAs by cAMP in PC12 cells.

Pepperl DJ1, Shah-Basu S, VanLeeuwen D, Granneman JG, MacKenzie RG.
Author information
Abstract
The RGS (regulators of G protein signaling) proteins represent a novel family of proteins which attenuate G protein mediated signaling. Using antisense riboprobes selective for rat RGS4, RGS7, and RGS2, we examined the regulation of these RGS mRNAs inPC12 cells in response to agents which elevate intracellular cAMP. Treatment of the PC12 cells with forskolin, dibutryl cAMP, or 8-CPT-cAMP for three hours decreased RGS4 message by nearly 50%. Actinomycin D, a potent inhibitor of transcription, did not affect the forskolin-induced decrease in RGS4 message, suggesting that forskolin does not alter RGS4 message half-life. RGS7 message is also present in these cells, but was not affected by forskolin. In contrast, RGS2 message is not evident in unstimulated cells but is strongly induced by one hour of treatment with forskolin. Taken together, these data suggest that mRNA levels of different RGS2 family members respond in an idiosynchratic fashion to cAMP challenge.
PMID:9473478 DOI:10.1006/bbrc.1997.8056

3)This article proves Inhibitory effects of RGS4, RGS10 and RGZ1 on Galphai protein( 5ht-1° pathway). Also RGS4 and RGS10 can inhibit Forskolin action on Adenilate Cyclase. But RGS2, RGS7, RGSZ1 don’t inhibit forskolin action. RGS2 reduces Galphaq activity mediated signiling by 5.HT2Areceptors. If Forskolin upregulates RGS2, Forskolin can also decreases Galphaq activity so 5ht2 pathway.


https://www.ncbi.nlm.nih.gov/pubmed/?te ... e+activity

Differential effects of regulator of G protein signaling (RGS) proteins on serotonin 5-HT1A, 5-HT2A, and dopamine D2 receptor-mediated signaling and adenylyl cyclase activity.

Ghavami A1, Hunt RA, Olsen MA, Zhang J, Smith DL, Kalgaonkar S, Rahman Z, Young KH.
Author information

Abstract
Regulator of G protein signaling (RGS) proteins function as GTPase accelerating proteins (GAP) for Galpha subunits, attenuating G-protein-coupled receptor signal transduction. The present study tested the ability of members of different subfamilies of RGS proteinsto modulate both G-protein-dependent and -independent signaling in mammalian cells. RGS4, RGS10, and RGSZ1 significantly attenuated Galphai-mediated signaling by 5-HT1A, but not by dopamine D2, receptor-expressing cells. Additionally, RGS4 and RGS10 significantly inhibited forskolin-stimulated cAMP production in both cell lines. In contrast, RGS2, RGS7, and RGSZ1 had no effect on forskolin-stimulated cAMP production in these cells. RGS2 and RGS7 significantly decreased Galphaq-mediated signaling by 5-HT2Areceptors, confirming that the RGS4 and RGS10 effects on forskolin-stimulated cAMP production were specific, and not simply due to overexpression. Interestingly, similar expression levels of RGS4 protein resulted in greater inhibition of G-protein-independent cAMP production compared to G-protein-dependent GAP activity. Our results suggest specificity and selectivity of RGS proteins on G-protein-dependent and -independent signaling in mammalian cells.
PMID: 15093612 DOI: 10.1016/j.cellsig.2003.11.006


4)Forskolin on Dopaminergic neurons. It can Up-regulates D2Long receptors by 43% but in particolar can Up-regulates hD2Shoert receptors. I don’t know if it is good becouse I’ve read hD2Short are pre-synaptic autoreceptors. So it can enhances negative dopamine feedback firing. I don’t know, we must see better. But D2 receptor family is Gi associated receptors like 5ht1a. If this regulation is the same with 5ht1a I think would be great.

https://www.ncbi.nlm.nih.gov/pubmed/9353595

Molecular mechanisms underlying forskolin-mediated up-regulation of human dopamine D2L receptors.ù

Wanderoy MH1, Westlind-Danielsson A.

Author information
Abstract
1. Human dopamine (DA) D2long (hD2L) receptors, expressed by Ltk- cells, can be up-regulated by treating the cells with forskolin for 16 hr (Johansson and Westlind-Danielsson, 1994). We have examined some of the molecular mechanisms underlying this forskolin-mediated up-regulation. 2. Forskolin (100 microM, 16 hr), but not 1,9-dideoxyforskolin, a forskolin analogue that is unable to activate adenylyl cyclase and raise intracellular cAMP concentrations, up-regulates the hD2L receptor population by 43%. The implication of a cAMP-dependent increase in the receptor up-regulation was further substantiated by treating the cells with 8-bromo-cAMP or prostaglandin E1 (PGE1). The forskolin-mediated rise in receptor number was blocked by cycloheximide or an antisense phosphorothioate oligodeoxynucleotide (ODN) directed toward the hD2L mRNA. KT5720, a specific protein kinase A (PKA) inhibitor, completely blocked the receptor rise, whereas pertussis toxin (PTX) attenuated the increase considerably. Forskolin also produced an increase in the level of the DA hD2short (hD2S) receptor expressed by Ltk- cells. This increase was 2.5-fold higher than that found for the hD2L receptor. 3. The forskolin-mediated hD2L receptor rise is dependent on de novo protein synthesis, a rise in cAMP levels, PKA activation, and, at least partially, PTX-sensitive G proteins. 4. Long-term increases in intracellular cAMP levels may change the sensitivity of a DA receptor expressing cell to DA by increasing D2 receptor density through enhanced cAMP-dependent transcription.



5) This article confirms RGS2 upregulation by forskolin.


https://www.ncbi.nlm.nih.gov/pubmed/?te ... losa+cells

Expression and regulation of regulator of G-protein signaling protein-2 (RGS2) in equine and bovinefollicles prior to ovulation: molecular characterization of RGS2 transactivation in bovine granulosa cells.

Sayasith K1, Sirois J2, Lussier JG2.

Author information
Abstract
The luteinizing hormone preovulatory surge stimulates several signal pathways essential for ovulation, and the regulator of G-proteinsignaling protein-2 (RGS2) is thought to be involved in this process. The objectives of this study were to characterize the regulation ofRGS2 transcripts in equine and bovine follicles prior to ovulation and to determine its transcriptional control in bovine granulosa cells. To assess the regulation of equine RGS2 prior to ovulation, RT-PCR was performed using total RNA extracted from equine folliclescollected at various times after human chorionic gonadotropin (hCG) injection. Results showed that RGS2 mRNA levels were very low at 0 h but markedly increased 12-39 h post-hCG (P < 0.05). In the bovine species, results revealed that RGS2 mRNA levels were low in small and dominant follicles and in ovulatory follicles obtained at 0 h, but markedly increased in ovulatory follicles 6-24 h post-hCG (P < 0.05). To study the molecular control of RGS2 expression, primary cultures of bovine granulosa cells were used. Stimulation with forskolin induced an up-regulation of RGS2 mRNA in vitro. Studies using 5'-deletion mutants identified a minimal region containing full-length basal and forskolin-inducible RGS2 promoter activities. Site-directed mutagenesis indicated that these activities were dependent on CRE and ETS1 cis-elements. Electrophoretic mobility shift assays confirmed the involvement of these elements and revealed their interactions with CREB1 and ETS1 proteins. Chromatin immunoprecipitation assays confirmed endogenous interactions of these proteins with the RGS2 promoter in granulosa cells. Forskolin-inducible RGS2 promoter activity and mRNA expression were markedly decreased by PKA and ERK1/2 inhibitors, and treatment with an antagonist of PGR (RU486) and inhibitors of PTGS2 (NS398) and EGFR (PD153035) blocked the forskolin-dependent RGS2 transcript expression, suggesting the importance of RGS2 inovulation. Collectively, this study reports for the first time the gonadotropin-dependent up-regulation of RGS2 in equine and bovinepreovulatory follicles and presents some of the regulatory controls involved in RGS2 gene expression in granulosa cells.
© 2014 by the Society for the Study of Reproduction, Inc.
KEYWORDS:
follicle; gene regulation; granulosa cells; ovulation; signaling pathways
PMID:25339105 DOI: 10.1095/biolreprod.114.121186



6) This article says cAMP and its anologue can Up-regulate SERT activity and expression. It’s suppoused by PKA activity ( AC pathway). This is found in embryonic rat RN cells.

https://www.ncbi.nlm.nih.gov/pubmed/?te ... -regulates

Long-term exposure of RN46A cells expressing serotonin transporter (SERT) to a cAMP analog up-regulates SERT activity and is accompanied by neural differentiation of the cells.
Yammamoto H1, Tanaka S, Tanaka A, Hide I, Seki T, Sakai N.
Author information
Abstract
To examine the functional regulation of serotonin transporter (SERT) by cAMP, we examined whether SERT uptake activity was affected by dibutyryl cAMP (dbcAMP), a cAMP analog, in SERT-transfected RN46A cells derived from embryonic rat raphe neurons. Long-term exposure (> 4 h) of dbcAMP (1 mM) to SERT-expressing RN46A cells significantly up-regulated SERT activity. In addition, a selective PKA activator, but not a selective EPAC activator, increased the serotonin uptake activity of SERT, suggesting that this regulation was mainly mediated via PKA. Time-dependent up-regulation of SERT activity by dbcAMP was accompanied by neural differentiation of RN46A cells. Further investigation of dbcAMP-induced up-regulation of SERT revealed that dbcAMP elevated SERTprotein levels without affecting SERT mRNA transcription. The chase assay for residual SERT protein revealed that dbcAMP slowed its degradation rate. Immunohistochemical analysis revealed that plasma membrane-localized SERT was more abundant in dbcAMP-treated cells than in non-treated cells, suggesting that dbcAMP up-regulated SERT by decreasing its degradation and increasing its plasma membrane expression. These results raise the possibility that the elevation of intracellular cAMP up-regulated SERT function through a mechanism linked to the differentiation of RN46A cells and show the importance of SERT function during the developmental process of the serotonergic nervous system
PMID: 23269237

Ghost, I hope it could be usefull. Give it a look! :)
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Re: GIRK Channels

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I'm trying DESMODIUM ADSCENDENS for now, since a friend of mine had improvements with another herb of this same genre.

it is a Potassium channel agonist. so in theory, this would help? (it also inhibits IgE allergic response, histamine and serotonin...)

I do feel some headache taking it, so I still don't know if this will or won't help for me. but in theory... this K channel agonist makes sense?
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Re: GIRK Channels

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It sounds very reasonable. I hope its not redudant but I found this paper: http://www.intechopen.com/books/mood-di ... -therapies It says that there are two types of 5HT1a AR desensitization. 1. fast and reversible - that is simple reduction of receptor (I thing they are retracted to membrane) 2. progresive and long lasting - receptors are replaced by receptors uncoupled to its G-protein. I belive to that theory as I talked to some neurobiologist and he told me that receptors reacts pretty quickly to level of stimulation that thay go back and forth in mambrane and it can be within minutes. But in those paper are said that the 2. type of desensitization was observed only with fluoxetine not sertralin nor citolopram. But even people with those drugs are pssd patients right.. another chronic change they mention on that paper is reduction of surface expresion of SERT. I am still hoping that increasing SERT somehow can help. There is one more thought that neurobiologist told me I want to share. He said that its quite reacent evidence that erection promoting drugs can help the brain for a libido. Like that penis and brain are linked in both direction and promoting eretion can tell your brain that penis is there and ready. So the brain should track the victim :). I dont know how much truth is behind that. But it may worth to try take chronicly low dose of viagra?
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Re: GIRK Channels

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marsupial wrote:He said that its quite reacent evidence that erection promoting drugs can help the brain for a libido. Like that penis and brain are linked in both direction and promoting eretion can tell your brain that penis is there and ready. So the brain should track the victim :). I dont know how much truth is behind that. But it may worth to try take chronicly low dose of viagra?
I don't know about viagra, but it works with daily cialis.
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Re: GIRK Channels

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Ghost, you talk a lot about Forskolin, but have you tried it? It gave me only temporary relief. It last 3 days.
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