Abstract
Galanin-like peptide (GALP) is located in the arcuate nucleus (Arc) of the hypothalamus and is known to regulate both food intake and sexual behaviors in adult male rats. We have previously demonstrated that ICV GALP administration elicits a significant fos response within the medial preoptic area (mPOA). GALP is known to stimulate both food intake and male-typical sex behavior, presumably by direct actions within the mPOA. Recent data from our and other labs have led us to suspect that GALP effects on sex behaviors are due to activation of incertohypothalamic dopaminergic neurons that terminate within the mPOA. To test the hypothesis that GALP activates mPOA dopaminergic systems, we utilized an immunolesion technique to eliminate dopaminergic fiber input to the mPOA via a dopamine transporter-specific toxin (DATSAP, n = 8) and compared to control injections (SAP, n = 8). All animals were sexually experienced adult male Long-Evans rats. DATSAP-treated male rats showed a significant ( p < 0.001) reduction in male sexual behaviors compared to SAP controls. We found that elimination of dopaminergic fibers within the mPOA significantly ( p < 0.001) eliminated all aspects of male sexual behavior under normal mating paradigms. Injections of GALP (5.0 nmol) significantly increased ( p < 0.01) male sex behavior and food intake in SAP control male rats but GALP did not stimulate the expression of these behaviors in DATSAP-treated rats. The orexigenic and anorexigenic effects of GALP were significantly ( p < 0.001) attenuated in DATSAP-treated male rats compared to SAP controls; however, ICV GALP was still able to significantly ( p < 0.05) reduce 24 h body weight in both DATSAP and SAP rats. ICV GALP significantly ( p < 0.05) stimulated fos within the mPOA of SAP rats but not in DATSAP-treated male rats. These data suggest that GALP activates feeding and sexual behaviors in male rats by stimulating dopaminergic neurons that terminate within the mPOA.
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