title: Castration, dopamine and food choice: a cost/benefit test in male hamsters.
abstract: Testosterone is essential for copulation, and contributes to sexual motivation. In addition, castrated males are fatter and less active, suggesting that androgens may play a role in non-sexual behaviors, including food-related responses. To test this hypothesis, male hamsters were trained with a cost/benefit test, which compares operant responding for more-preferred food versus ad libitum consumption of lab chow. Males were tested before and after castration. The effect of the dopamine antagonist, haloperidol, on instrumental responses in intact and castrated males was also determined. Food-deprived hamsters responded vigorously for 45 mg Bio-Serv pellets in daily 30-min tests (665 presses, 6.0+/-0.9 g). When lab chow was available, males continued to respond for pellets (3.6+/-0.6 g) over chow ad libitum (1.2+/-0.3 g). Dopamine is central to this response because haloperidol (1.0 mg/kg i.p.) reversed food intake (pellets: 0.5+/-0.1 g; chow 2.0+/-0.5 g). Castration had no effect on operant responding for pellets alone (6.6+/-0.7 g). When chow was present, castrates consumed an even greater proportion of their total food intake as pellets [6.0+/-0.4 g pellets (92%), 1.6+/-0.5 g chow (8%), vs. 75 and 25%, respectively, for intact males]. This is contrary to our original hypothesis. In addition, castration did not change the effects of haloperidol on food intake: (0.4+/-0.1 g pellets; 1.6+/-0.5 g chow). These results support previous findings in rats that dopamine affects response allocation in a cost/benefit test. However, they do not support the hypothesis that testosterone modifies the allocation of food-related responses.
authors.affiliation: Department of Cell and Neurobiology, Keck School of Medicine at the University of Southern California, 1333 San Pablo Street, BMT 401, Los Angeles 90033, USA.
authors.forename: Lucy
authors.initials: L
authors.lastname: Chu
authors.forename: Ruth I
authors.initials: RI
authors.lastname: Wood
mesh_terms: D000818:Animals; D001835:Body Weight; D002755:Choice Behavior; D003216:Conditioning, Operant / Q000187:drug effects; D003362:Cost-Benefit Analysis; D006224:Cricetinae; D004298:Dopamine / Q000502:physiology*; D018492:Dopamine Antagonists / Q000494:pharmacology; D005518:Food Preferences / Q000187:drug effects / Q000502:physiology*; D006220:Haloperidol / Q000494:pharmacology; D008297:Male; D008647:Mesocricetus; D009919:Orchiectomy; D012055:Reinforcement Schedule; D013739:Testosterone / Q000494:pharmacology
chemical_list: D018492:Dopamine Antagonists; D013739:Testosterone; D006220:Haloperidol; D004298:Dopamine