Substance P variations in the hypothalamus of golden hamsters at different stages of the estrous cycle.

The changes in substance P concentrations in the hypothalamus of female golden hamsters were studied at the different stages of the estrous cycle. Substance P levels in the hypothalamus of hamsters were highest during estrus and lowest during diestrus I and proestrus. The concentrations of substance P during diestrus II were not significantly different from those observed during estrus. These results show that substance P levels in the hypothalamus of female hamsters undergo significant changes during the estrous cycle.