Biology of Reproduction, Vol 17, 386-389, Copyright © 1977 by Society for the Study of Reproduction

Hypothalamic Ventromedial Nucleus and Hormonal Regulation of Estrous Rhythm in the Rat

¹ Institute of Histology, Faculty of Medicine, Strasbourg, France and ERA n^o 566 (C.N.R.S.)

Peripheral concentration of progesterone decreased from the morning of diestrus I to that of diestrus II in females maintaining a 4-day cycle following small ventromedial nucleus (VMN) lesions. The same picture was observed in natural 4-day cyclers as well as in sham VMN and dorsomedial nucleus (DMN) lesioned females with 4-day cycles. In contrast, no decrease was noted in natural 5-day cyclers. In 4-day cyclic females displaying a 24-h cycle prolongation following small VMN lesions, blood progesterone increased, reaching a significantly higher level on diestrus II than in unoperated 5-day cyclers.

Note:
ACKNOWLEDGMENTS We thank M. T. Kauffman and C. Lazarus for their technical assistance and V. Sieffer for typing the manuscript. We would also like to thank M. G. Weisman for his helpful revision of the manuscript. This work was financed by the C.N.R.S. (ERA n^o 566).