Nucleus accumbens dopamine and the disinhibitory effect of alcohol on conditioned sexual inhibition in male rats: A microdialysis study (#276)
Male rats trained alternatively with a scented (almond) nonreceptive female and an unscented receptive female display a conditioned ejaculatory preference (CEP) for the unscented female when given the choice, during a copulatory test, between two receptive females, one scented and one unscented. We have previously demonstrated that an acute treatment of alcohol (0.5g/kg or 1g/kg) before the copulatory test can disrupt this CEP. We have also observed that males injected with 0.5g/kg of alcohol show a greater number of Fos-immunoreactive cells in the nucleus accumbens (NAc) when exposed to the almond odor alone, compared to males injected with saline or with alcohol 1g/kg. One of the major inputs to the NAc are dopaminergic neurons originating from the ventral tegmental area (VTA). Here we examined the extracellular dopamine concentrations following a single injection of alcohol and exposure to the almond odor. Sexually naïve male Long-Evans rats were conditioned alternatively with an unscented receptive female or a scented non-receptive female. They were then injected with saline, alcohol 0.5g/kg, or alcohol 1g/kg before a copulatory test. Following testing, males were reconditioned before being exposed to almond odor alone under the influence of alcohol while undergoing in vivo microdialysis to assess dopamine concentrations in the NAc. Following a single injection of alcohol, we observed increased dopamine in the NAc. Moreover, when exposed to the almond odor, males injected with the low dose of alcohol show higher extracellular dopamine concentrations compared to males injected with saline or the high dose of alcohol. Taken together, these data demonstrate that dopamine concentrations in NAc reflect the learned association between odor and sexual inhibition, and its disinhibition by alcohol.