title: The luteinizing hormone releasing hormone (LHRH) neuronal networks of the guinea pig brain. III. The regulation of cyclic gonadotropin secretion.
abstract: The effects of selected CNS lesions on the ovulatory cycle as well as the distribution of LHRH terminals in the median eminence of the female guinea pig were examined. Radiofrequency lesions were placed in the medial preoptic area (MPOA) or suprachiasmatic nucleus (SCN). Animals were studied for varying lengths of time (1-5 months) following lesion placement. The occurrence of at least two ovulatory cycles was determined by cyclicity in vaginal opening, the presence of viable corpora lutea and measurements of luteal phase elevations in serum progesterone. The distribution of LHRH immunoreactivity was determined by immunocytochemical procedures on Bouin's fixed, paraffin-embedded brain sections. Lesions of the MPOA or SCN resulted in different degrees of loss of LHRH fibers in the zona externa of the ventral and lateral aspects of the infundibular stalk as well as complete loss of terminals throughout the zona interna. Despite depletion of LHRH fibers, all animals with SCN (n = 8) and the majority with MPOA (4/6) lesions showed regular ovulatory cycles. Two females with MPOA lesions presented two different anovulatory syndromes. Anovulation appeared unrelated to the size or site of the lesions or in the degree of depletion of LHRH fibers in the infundibulum. It would appear that these brain areas and their LHRH projections are not essential for cyclic gonadotropic release.
mesh_terms: D000818:Animals; D004971:Estrus; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D006168:Guinea Pigs; D007031:Hypothalamus / Q000502:physiology*; D007033:Hypothalamus, Middle / Q000502:physiology; D007986:Luteinizing Hormone / Q000097:blood; D008526:Medulla Oblongata / Q000502:physiology; D009415:Nerve Net / Q000502:physiology*; D009424:Nervous System Physiological Phenomena; D009474:Neurons / Q000502:physiology; D009897:Optic Chiasm / Q000502:physiology*; D010060:Ovulation; D011247:Pregnancy; D011301:Preoptic Area / Q000502:physiology*; D013495:Supraoptic Nucleus / Q000502:physiology*
chemical_list: D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone