OPIOID MODULATION OF SUCROSE INTAKE IN CD-1 MICE - EFFECTS OF GENDER AND HOUSING CONDITIONS

The effects of naltrexone (1 mg/kg, sc.) on consumption of a 5% sucros e solution were observed in nondeprived adult female CD-1 mice and in male mice. Males were either individually housed or were housed in pai rs. Naltrexone significantly reduced the consumption of the sucrose in both female and male mice; in the case of the males the administratio n of naltrexone produced an intake pattern identical to that obtained for a less palatable (1.5%) sucrose solution in control conditions. Th ere was no difference between subordinate and dominant males, neither in sucrose intake nor in the response to the naltrexone treatment. In a second experiment, it was shown that switching from a 5% to a 10% so lution was sufficient to overcome naltrexone's suppressant effect in f emale mice, conversely this was not seen in the males. In general, the data are consistent with the view that opioid antagonists reduce effe ctive palatability of sweet sucrose solutions in mice. There was no ev idence that social isolation and stress related to subordination affec ted male mice's sucrose intake and response to the naltrexone challeng e.