title: Single unit response of suprachiasmatic neurons to arginine vasopressin (AVP) is mediated by a V1-like receptor in the hamster.
abstract: A large population of local circuit neurons within the suprachiasmatic nucleus (SCN) exhibit immunopositive staining for arginine-vasopressin (AVP). AVP has been reported to be released from SCN neurons in a circadian pattern that peaks during the subjective day. Using an in vitro hypothalamic slice preparation, the present study investigated how SCN neurons respond to AVP over the circadian cycle and whether the response to AVP is mediated by V1- or V2-like AVP receptors. Exposure of the slice to AVP 10(-8) M produced excitatory responses in 51% of the 74 SCN neurons examined. A statistically significant day-night difference in the percentage of SCN units responding to AVP was observed (chi 2 = 15.62; P less than 0.01). During the dark phase 73% were excited by AVP, while during the light phase only 24% had excitatory responses. The threshold concentration of AVP ranged from 10(-9) to 10(-10) M and 10(-7) to 10(-8) M during the dark and light phase, respectively. In a second experiment the effects of selective V1 and V2 agonists and antagonists were determined. A V1, but not a V2 receptor antagonist was found to block the effects of AVP on single unit activity. Similarly, a V1 but not a V2 receptor agonist mimicked the effects of AVP.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Biology, Georgia State University, Atlanta 30303.
authors.forename: S Y
authors.initials: SY
authors.lastname: Liou
authors.forename: H E
authors.initials: HE
authors.lastname: Albers
mesh_terms: D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology*; D002940:Circadian Rhythm; D006224:Cricetinae; D005071:Evoked Potentials / Q000187:drug effects; D066298:In Vitro Techniques; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D011945:Receptors, Angiotensin / Q000502:physiology*; D017483:Receptors, Vasopressin; D013493:Suprachiasmatic Nucleus / Q000187:drug effects / Q000502:physiology*
chemical_list: D011945:Receptors, Angiotensin; D017483:Receptors, Vasopressin; D001127:Arginine Vasopressin