In situ hybridization for LHRH mRNA following estrogen treatment.

Elucidation of mechanisms governing the synthesis and release of the decapeptide luteinizing hormone-releasing hormone (LHRH) in the female are central for understanding how the brain influences the ovulatory surge of luteinizing hormone and facilitates female rat mating behavior. Previous immunocytochemical results suggested that estrogen treatment might increase LHRH forebrain content, but measures of peptide content often are confounded by alterations in synthesis versus peptide processing versus release. Therefore, we have used in situ hybridization with an oligomer for the LHRH coding region to detect LHRH gene expressing cells and to study LHRH message levels in estrogen treated compared to control ovariectomized rats. Neurons expressing the gene for LHRH are in the medial preoptic area and amongst the fibers of the diagonal bands of Broca. When the numbers of neurons with detectable LHRH message levels were multiplied by the average numbers of grains per cell, to achieve a metric proportional to LHRH message content, we saw a significant stimulatory effect of seven days of estrogen treatment.