| Abstract: | The effect of the microiontophoretic application of dopamine (DA) into the arcuate region of the hypothalamus on the sensitivity of single neurons and on the plasma and hypophysis LH levels was examined at various stages of the estrous cycle. During the estrous cycle in rats there was no significant differences in the relative number of neurons showing activation and inhibition or non-responsive to DA. However, in the first half of proestrus (P) a significant increase in the number of neurons with the excitative reaction to the iontophoretic application of DA was observed. At all the stages of the cycle, except the second half of P, the excitative reaction of neurons correlated with increased LH level in the plasma. In the hypophysis only in diestrus-2 there was a significant increase of the LH level in response to the iontophoretic application of DA in the arcuate neurons of the hypothalamus. |
