The number of luteinizing hormone-releasing hormone immunoreactive neurons is significantly decreased in the forebrain of old-aged female rats.

To see changes in the number of luteinizing hormone-releasing hormone (LHRH) neurons during aging, young (3 months old)- and old (26 months old)-aged female rats, four of each, were used 4 weeks after ovariectomy for immunocytochemistry. The estimated total number (mean +/- SEM) of LHRH immunoreactive (ir) neurons in the forebrain of old-aged rats (353 +/- 34) was significantly smaller than that in young-aged rats (672 +/- 51). In the forebrain, the decrease in the number of LHRH-ir neurons with age in rostral parts was greater than that in caudal parts, suggesting heterogeneous impairment of LHRH neurons in the rat forebrain during aging.