Differenze di genere in un modello di auto-somministratione di una bevanda al gusto di cioccolato: evidenze comportamentali e neurochimiche

Gender differences in food-related disorders have repeatedly been described, with females appearing to be more vulnerable than males. The present study investigated gender differences in neurochemical (dopamine activity in the nucleus accumbens by intracerebral microdialysis) and behavioral (acquisition and maintenance) features in a rat model of operant self-administration of a chocolate-flavored beverage (CFB), the latter possessing strong reinforcing properties and being avidly consumed by rats. Comparison of male and female rats revealed a similar behavioral profile of CFB self-administration; microdialysis showed an increase – of comparable magnitude in male and female rats – in extracellular dopamine mainly during the appetitive phase of CFB self-administration. However, CFB self-administration profile in female rats changed across the estrus cycle, reaching its nadir during the estrus phase. Accordingly, microdialysis showed lower dopaminergic outputs during proestrus/estrus than diestrus/metestrus phases. No change was recorded in ovariectomized rats. These results suggest that CFB self-administration in female rats is influenced by sexual hormones, possibly interfering with mesolimbic dopamine. This study confirms the importance of (i) gender as a factor to be carefully considered in animal models of drug and food self-administration, and (ii) estrus cycle hormonal changes as a source of variability between males and females.