Effects of estrous cycle, estrogen and progesterone administration on the antidromic and orthodromic reaction threshold of medial preoptic neurons in the rat hypothalamus.
In the present study, attempts were made to evaluate the effects of the estrous cycle and the administration of estradiol (Ovx-E) or progesterone (Ovx-P) after ovariectomy on the threshold of antidromic (AD) and orthodromic (OD) responses of neurons in the medial preoptic area (POA) induced by electrical stimulation of the median eminence-arcuate nucleus (ARC) of the hypothalamus. Single units were evaluated with extracellular recording. The threshold of AD and OD response in POA neurons declined during estrus and proestrus of the estrous cycle and in the Ovx-E group, but increased in the Ovx-P group and during diestrus. The number of neurons with the inhibitory OD response increased during proestrus and in the Ovx-E group, but decreased during diestrus. The neurons with the excitatory OD response increased in the Ovx-P group and during diestrus, and decreased during proestrus. The threshold of the inhibitory and excitatory OD response decreased during proestrus, estrus and in the Ovx-E group, but increased in the Ovx-P group. It is apparent from these studies that estrogen appears to activate the neurons of the POA receiving inhibitory synaptic input via the axonal collateral branches of the ARC neurons, and that progesterone seems to activate the neurons of the POA receiving excitatory synaptic input.
Watanabe
T
T
Department of Veterinary Physiological Chemistry, College of Agriculture and Veterinary Medicine, Nihon University, Kanagawa, Japan.
D000704:Analysis of Variance; D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000502:physiology; D016009:Chi-Square Distribution; D004558:Electric Stimulation; D004967:Estrogens / Q000494:pharmacology*; D004971:Estrus / Q000502:physiology*; D005071:Evoked Potentials; D005260:Female; D008473:Median Eminence / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D010052:Ovariectomy / Q000662:veterinary; D011301:Preoptic Area / Q000187:drug effects / Q000502:physiology*; D011374:Progesterone / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D004967:Estrogens; D011374:Progesterone