Figure 7. Representation of in vivo techniques used in our laboratory for the investigation of LHRH neuronal activity under normal cycling, sex steroid manipulations and stress conditions. This schema also illustrates the possible involvement of the immediate-early genes c-fos and c-jun in the regulation of LHRH gene transcription as well as the LHRH release into the infundibular system during the proestrus surge of LH. LHRH, luteinizing hormone-releasing hormone; LH, luteinizing hormone; MPOA, medial preoptic area of the hypothalamus; PIT, pituitary (adenohypophysis). Note that intranuclear Pro-LHRH mRNA corresponds to LHRH heteronuclear (hn) RNA (primary transcript) also assayed by in situ hybridization histochemistry.