Regulation of 5-HT2A/C receptors and DOI-induced behaviors by protein kinase Cγ

Abstract

Protein kinase C γ (PKCγ) null mutant mice demonstrate increased behavioral impulsivity and ethanol consumption. Pharmacological studies have shown that 5-HT 2A/C receptors modulate impulsivity and ethanol consumption in rodents and that PKC can regulate 5-HT 2A/C receptors. To determine whether PKCγ plays a selective role in 5-HT 2A/C receptor regulation, biochemical and behavioral experiments were performed in PKCγ mutant and wild-type mice. DOI-stimulated phosphoinositol hydrolysis and [ 125 I]-DOI saturation binding in the PFC, and quantitative autoradiography of [ 125 I]-DOI binding sites in 15 brain regions were analyzed. DOI-induced head twitch responses (HTR) were measured in naïve mice after an acute 2.5 mg/kg injection of DOI. Results indicated that DOI-induced HTR was significantly greater in mutant mice compared to wildtype mice. Results of the phosphoinositol hydrolysis, membrane binding, and autoradiography experiments indicated that in mutant mice, increased HTR was associated with increased 5-HT 2A/C receptor function in the PFC, but not increased receptor number or affinity suggesting that PKCγ regulates receptor function but not receptor number. These data support a role for 5-HT 2A/C receptors in the PFC in mediating some of the behavioral differences observed between PKCγ mutant and wild-type mice.

Protein Kinases Alter the Allosteric Modulation of the Serotonin Transporter In Vivo and In Vitro

“…Keeping in mind that staurosporine did not seem to augment the extracellular 5‐HT levels (no effect in both electrophysiological recordings and HTR paradigm), we can hypothesize that protein kinase blockade led to an enhanced sensitivity/responsiveness of some 5‐HT receptors in response to the 5‐HT elevation produced by escitalopram. This hypothesis is in line with results showing that the HTR is increased in PKC‐gamma null mutant mice compared to wild‐type littermate controls after an injection of 5‐HT2A/C receptor agonist, 2,5‐dimethoxy‐4‐iodoamphetamine (DOI), probably related to increased 5‐HT2A/C receptor responsiveness . Similar to our electrophysiological data, staurosporine prevented the attenuating effect of R‐citalopram on escitalopram action on L‐5‐HTP‐induced HTR paradigm.…”

“…Despite having no effect by itself on HTR, R-citalopram significantly diminished the escitalopram-induced increase of head twitches, in accordance with previous studies [6,37]. Furthermore, staurosporine had no effect by itself on this parameter, which concords with data showing no difference in the number of HTR in PKC-gamma null mutant versus wild-type mice [41]. However, staurosporine potentiated the HTR enhancement induced by escitalopram.…”

Head‐twitch response in rodents induced by the hallucinogen 2,5‐dimethoxy‐4‐iodoamphetamine: a comprehensive history, a re‐evaluation of mechanisms, and its utility as a model

“…Mice lacking the neuronal specific, PKCγ, show enhanced DOI-induced phospholipase C activation and increased number of DOI-induced HTRs, suggesting a suppressive effect of PKCγ on DOI-mediated intracellular functions. [201] Importantly PKCγ knockout mice do not show alterations in brain 5-HT 2A receptor density. [201] …”

“…[201] Importantly PKCγ knockout mice do not show alterations in brain 5-HT 2A receptor density. [201] …”

Insights into the regulation of 5-HT2A serotonin receptors by scaffolding proteins and kinases

“…In addition, the Ser and Thr mutagenesis data do not rule out the involvement of atypical PKC members or noncanonical PKC phosphorylation sites. Recent studies showed that PKCγ knockout elevates 5-HT 2A signaling in vivo as DOI-induced head twitch responses are significantly elevated by PKCγ knock-out, effects that are not due to changes in receptor number or agonist affinity (Bowers et al, 2006). Other recent studies suggest that calmodulin (CaM) also interacts with 5-HT 2A at consensus CaM binding motifs in intracellular loop 2 and the carboxy-terminal tail in a calcium dependent manner (Turner and Raymond, 2005).…”