Neural and Endocrine Correlates of Extinction of Conditioned Sexual Incentive Salience in Male Rats.

Conditioned sexual arousal (CSA) can develop when initially neutral social cues acquire sexual incentive value through associative learning. In male rats, pairing the D2-type receptor agonist quinpirole (QNP) with cohabitation with an almond-scented juvenile male induces a conditioned sexual response toward that stimulus. Here, we examined how this response changes following repeated nonreinforced exposure to the conditioned social cue. Adult male rats underwent three conditioning trials followed, in the extinction-training groups, by three additional drug-free exposures to the almond-scented juvenile male. Conditioned responding was subsequently assessed toward both a receptive female and the juvenile male. QNP-Paired males showed robust juvenile-directed non-contact erections (NCEs), whereas QNP-Extinction males showed markedly reduced NCE responding. Genital investigation also showed a significant Partner × Treatment interaction, while the remaining behavioral measures did not survive correction for multiple comparisons. Free testosterone did not differ significantly among treatments. Exploratory Fos-immunoreactivity (Fos-IR) analyses revealed treatment-related differences in several brain regions; however, no direct QNP-Paired versus QNP-Extinction regional comparison remained significant after correction for multiple testing. Thus, repeated nonreinforced exposure to the conditioned social cue was associated with a marked reduction in conditioned sexual responding. Because the Paired and Extinction conditions differed in elapsed time and additional experience, this reduction is compatible with extinction but cannot be attributed uniquely to extinction learning. The endocrine and Fos-IR findings should be considered exploratory.