Chemosensory Cues are Essential for Mating-Induced Dopamine Release in MPOA of Male Syrian Hamsters

Abstract

The medial preoptic area (MPOA) is crucial for male sex behavior. Dopamine (DA) is released in MPOA during copulation, and contributes to the reinforcing effects of mating. The aim of the present study was to identify sensory stimuli responsible for mating-induced DA release. Specifically, we determined if chemosensory cues are essential for mating-induced MPOA DA release using in vivo microdialysis in male Syrian hamsters. Hamsters were used because chemosensory cues from the olfactory mucosa and vomeronasal organ are essential for sexual behavior in this species. Sexually experienced adult male hamsters were implanted with a microdialysis guide cannula over MPOA. At the same time, males received sham olfactory bulbectomy (Sham Bx, n = 11), bilateral bulbectomy (Bibx, n = 6), or unilateral bulbectomy (Ubx) ipsilateral (Ipsi Ubx, n = 9) or contralateral (Contra Ubx, n = 8) to the microdialysis probe. This model takes advantage of the predominantly ipsilateral projections of the olfactory bulbs. Microdialysis samples were collected from the MPOA during baseline, exposure to a receptive female, and after removal of female. Extracellular DA was measured using high-performance liquid chromatography with electrochemical detection. During mating, DA increased in MPOA of Sham Bx males (to 146.7 +/- 17.5% of baseline). Bibx males did not mate, and MPOA DA did not increase (96.1 +/- 15.8% of baseline). Although both groups of Ubx males mated to ejaculation, MPOA DA increased significantly only in Contra Ubx males (to 161.8 +/- 35.3% of baseline), and not in males with Ipsi Ubx (107.6 +/- 11.5% of baseline). The results demonstrate that chemosensory cues are essential for MPOA DA release during mating in male Syrian hamsters.