Guinea pig terminal 5-HT1D autoreceptors do not display a circadian variation in their responsiveness to serotonin.
Many of the components involved in the synthesis and release of serotonin (5-HT) display a circadian variation in their activity. Autoreceptors located on nerve terminals were recently suggested to underlie some of these circadian variations. The aim of this study was to examine whether terminal 5-HT1D autoreceptors in the cerebral cortex of the guinea pig exhibit a circadian variation in their responsiveness. The responsiveness of these autoreceptors was assessed by the ability of exogenously applied 5-HT to inhibit the potassium-evoked release of [3H]5-HT from slices of guinea pig cortex. Identical experiments were conducted at four different, equally spaced time points during the light:dark cycle of the guinea pig. The results presented here demonstrate that terminal 5-HT1D autoreceptors do not exhibit a circadian variation in their responsiveness. Therefore, terminal 5-HT1D autoreceptors bear similarity to terminal 5-HT1B autoreceptors identified in rat brain in being devoid of a significant rhythm in their responsiveness.
Singh
A
A
Pharmacology Group, School of Pharmacy and Pharmacology, University of Bath, Avon, England.
Redfern
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P
D000818:Animals; D017660:Autoreceptors / Q000502:physiology*; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D002940:Circadian Rhythm / Q000187:drug effects; D003624:Darkness; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007700:Kinetics; D008027:Light; D008297:Male; D008719:Methiothepin / Q000494:pharmacology; D009411:Nerve Endings / Q000187:drug effects / Q000502:physiology; D011188:Potassium / Q000494:pharmacology; D011985:Receptors, Serotonin / Q000502:physiology*; D012701:Serotonin / Q000378:metabolism* / Q000494:pharmacology*
D017660:Autoreceptors; D011985:Receptors, Serotonin; D012701:Serotonin; D008719:Methiothepin; D011188:Potassium