[Study of estrogen feedback mechanism in the hypothalamus-- identification of estrogen sensitive neurons and influence of catecholamines by multi-barrel microiontophoresis].

163 castrated matured female rats were used to identify single estrogen-sensitive neuron by the technique of microiontophoresis and the multi-barrel glass microelectrode was utilized to study the effects of dopamine, epinephrine, norepinephrine and acetylcholine on the identified estrogen-sensitive neurons. A total of 15 estrogen-sensitive neurons were identified and all of these were located in the preoptic area. Fourteen neurons were responded strongly to estrogen and one was suppressed. Out of the identified estrogen-sensitive neurons, 10 showed suppression by dopamine and one showed excitation. To epinephrine 12 neurons showed suppressive response and one showed excitation. To norepinephrine, 13 neurons showed suppressive response, while none of 15 neurons was excited. In contrast only 2 neurons showed suppression to acetylcholine and a showed excitatory response. All of these changes in the firing rates involved rapid response and the latencies were within a few seconds. It is suggested from these studies that (1) estrogen can directly effect the neurons in the preoptic area, (2) estrogen can act at the level of the membrane of the neuron, (3) dopamine, epinephrine and norepinephrine mainly regulate the estrogen-sensitive neuron suppressive, while acetylcholine excites it.