Brain mediation of Anolis social dominance displays III.: Differential forebrain 3H-sumatriptan binding in dominant vs. submissive males

Measures of serotonin (5-HT) turnover in A. carolinensis forebrain increase acutely when males exhibit dominant social/territorial display routines, but decrease during submissive displays [Baxter et al., 2001a, b]. The present investigation sought to determine whether a difference in presynaptic regulatory receptors - one that might affect 5-HT flux - distinguish dominant vs. submissive anoles. Both 5-HT1B and 5-HT1D receptors are presynaptic regulators of output; this role is prominent at 5-HT terminals, where stimulation inhibits 5-HT release. Here, H-3-sumatriptan binding at sites similar to mammalian 5-HT1BD receptors was significantly higher in forebrain regions of submissive anoles than in dominant cagemates; this receptor site seemed pharmacologically more like a 5-HT1B than a 5-HT1D receptor. Higher densities of presynaptic 5-HT1B receptors in subordinates than in dominants might account for differences in 5-HT flux (lower in subordinates than in dominants) observed in displaying anoles of different status. Knockout mice missing the 5-HT1B receptor show heightened male territorial aggressiveness, thus similar 5-HT regulatory mechanisms might influence the likelihood of dominance in both mammals and reptiles. Copyright (C) 2001 S. Karger AG, Basel.