Neurokinin A in the hypothalamus and anterior pituitary during the estrous cycle in the golden hamster.

The fluctuations in the neurokinin A concentrations in the hypothalamus and anterior pituitary of female golden hamsters were studied in the different stages of the estrous cycle, and they were correlated with the changes in serum estradiol levels. Neurokinin A levels in the hypothalamus were lowest at day 4 of the cycle (proestrus), when serum estradiol levels were highest. Neurokinin A levels in the hypothalamus of hamsters in day 1 (estrus), day 2 (diestrus I), and day 3 (diestrus II) were not significantly different from each other. In the anterior pituitary, the highest neurokinin A concentrations were found during day 1 of the cycle (estrus), the levels in day 2 (diestrus I), day 3 (diestrus II), and day 4 (proestrus) were significantly lower than at estrus, again showing the lowest levels during proestrus, when estradiol levels were maximal. These results show that neurokinin A levels in the hypothalamus and anterior pituitary of the female hamster undergo significant changes during the estrous cycle.