title: Noradrenergic transmission and female sexual behavior of guinea pigs.
abstract: Treatment with the dopamine beta-hydroxylase (DBH) inhibitor U-14,624 (50, 100, or 150 mg/kg) blocked the induction of lordosis behavior be estradiol benzoate (EB) and progesterone (P) in ovariectomized guinea pigs. After treatment with U-14,624 (100 mg/kg), norepinephrine (NE) content of medial basal hypothalamus, preoptic area and cortex was reduced (by 55%) and dopamine (DA) content of medial basal hypothalamus was increased (by 155%) during the period when females treated with EB and P normally display lordosis. Treatment with the NE receptor stimulator clonidine (1.0 mg/kg) restored lordosis behavior in females treated with EB, P, and U-14,624 (100 mg/kg), but the putative DA and serotonin (5-HT) receptor blockers pimozide (1.0 mg/kg) and methysergide (20.0 mg/kg) were ineffective in this respect. Thus, inhibition of lordosis after treatment with U-14,624 appeared to be attributable primarily to a reduction in NE neurotransmission, rather than to increase in DA or 5-HT activity. Because clonidine induced lordosis in females treated with EB, P, and U-14,624, it seemed unlikely that the facilitatory effects of clonidine on lordosis were mediated by activation of presynaptic alpha-adrenergic receptors (i.e. inhibitory NE autoreceptors) rather than by postsynaptic alpha-receptors. In addition, pretreatment with the postsynaptic alpha-adrenergic antagonist phenoxybenzamine (20.0 mg/kg) blocked the facilitation of lordosis by clonidine (1.0 mg/kg) in females primed with EB alone and with EB plus P. Thus, the facilitatory effects of clonidine on lordosis appear to be mediated by activation of postsynaptic alpha-adrenergic (i.e. NE) receptors. The results of this study provide further evidence that NE neurotransmission facilitates the expression of female sexual behavior in guinea pigs.
mesh_terms: D000818:Animals; D002369:Castration; D002540:Cerebral Cortex / Q000378:metabolism; D003000:Clonidine / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism; D004299:Dopamine beta-Hydroxylase / Q000037:antagonists & inhibitors; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D006168:Guinea Pigs; D007031:Hypothalamus / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism / Q000502:physiology*; D010643:Phenoxybenzamine / Q000494:pharmacology; D011301:Preoptic Area / Q000378:metabolism; D011374:Progesterone / Q000494:pharmacology; D011941:Receptors, Adrenergic / Q000187:drug effects; D011954:Receptors, Dopamine / Q000187:drug effects; D012726:Sexual Behavior, Animal / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects
chemical_list: D011941:Receptors, Adrenergic; D011954:Receptors, Dopamine; D010643:Phenoxybenzamine; D011374:Progesterone; D004958:Estradiol; D004299:Dopamine beta-Hydroxylase; D003000:Clonidine; D004298:Dopamine; D009638:Norepinephrine