Dopamine D1 and opioid receptor antagonist-induced reductions of fructose and saccharin intake in BALB/c and SWR inbred mice

Sugar and fat intake in rodents are mediated in part by brain dopamine (DA) and opioid neurotransmitter systems although important strain differences exist. Thus, whereas sucrose intake of BALB/c and SWR mice was reduced by DA D1 (SCH23390: SCH) receptor antagonism, opioid (naltrexone: NTX) receptor antagonism reduced intake only in BALB/c mice. Both SCH and NTX reduced fat (Intralipid) intake in SWR, but not BALB/c mice. The present study extended this pharmacological analysis to caloric and non-caloric sweeteners by examining whether fructose (8%) or saccharin (0.2%) intakes were differentially suppressed in BALB/c and SWR mice by SCH (50–1600nmol/kg) or NTX (0.01–5mg/kg) over a 5- to 120-min time course. SCH significantly reduced fructose (200–1600nmol/kg) and saccharin (50–1600nmol/kg) intakes in both strains as did NTX (0.1–5mg/kg). Antagonist ID40 potencies were