Different roles of alpha-noradrenergic receptor subtypes in regulating lordosis.
Ovariectomized guinea pigs were given free estradiol (E) at hr 0 and 28, and progesterone (P) at hr 39. Experiment 1: The alpha-1 noradrenergic antagonist prazosin, but not the alpha-2 noradrenergic antagonist idazoxan, prevented display of lordosis behavior when administered systemically 30 min prior to E injections at either hr 0 or 28, or 30 min prior to both injections. Experiment 2: Multiple injections of idazoxan (i.e., 30 min prior to and 60 and 120 min after each E injection) failed to prevent display of lordosis. Experiment 3: E-primed animals were given a single injection of idazoxan 1 hr before P, or 5 hr after P. In those animals given idazoxan 1 hr before P, display of lordosis was not prevented. However, in animals given idazoxan once lordosis display had begun (i.e., 5 hr after P) ongoing lordosis behavior was blocked. These data suggest differential roles of alpha-noradrenergic receptor subtypes in regulation of lordosis: noradrenergic transmission through the alpha-1 subtype may mediate hormone-priming processes leading to lordosis, whereas transmission through the alpha-2 subtype may modulate ongoing lordosis responses.
Vincent
P A
PA
Institute of Animal Behavior, Rutgers University, Newark, NJ 07102.
Thornton
J E
JE
Peterson
C S
CS
Feder
H H
HH
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D004146:Dioxanes / Q000494:pharmacology*; D004147:Dioxins / Q000494:pharmacology*; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D006168:Guinea Pigs; D019329:Idazoxan; D011187:Posture; D011224:Prazosin / Q000494:pharmacology*; D011374:Progesterone / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D012726:Sexual Behavior, Animal / Q000187:drug effects* / Q000502:physiology; D015016:Yohimbine / Q000494:pharmacology*
D000317:Adrenergic alpha-Antagonists; D004146:Dioxanes; D004147:Dioxins; D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; D011374:Progesterone; D004958:Estradiol; D011224:Prazosin; D019329:Idazoxan