Neuropeptide receptor transcripts are expressed in the rat clitoris and oscillate during the estrus cycle in the rat vagina

Vasoactive intestinal peptide (VIP), calcitonin gene-related peptide (CGRP) and angiotensin 2 are key neuropeptides that innervate the sexual organs. For further understanding of neuropeptide involvement in female sexual function, we investigated peptide receptor mRNA expression using reverse transcription-polymerase chain reaction (RT-PCR) in the rat vagina and clitoris, and alteration during the shift from the proestrus to the estrus phase. VIP, angiotensin 2 and CGRP receptor subtypes transcripts were found to be expressed in the vagina and the clitoris. Significantly increased levels of angiotensin 2 and CGRP receptor subtypes transcripts were observed in the vagina as compared to the clitoris. Significant increases in the expression of the VIP receptor type 2 (VPAC2) mRNA and parallel increases in a novel VIP responsive gene, activity-dependent neuroprotective protein (ADNP) mRNA were detected in the rat vagina during the estrus phase. The expression pattern of neuropeptide receptors in the female sexual organs suggest an intimate involvement of the corresponding neuropeptides in female sexual function.