Nitric oxide synthase inhibition attenuates saccharin or ethanol reinforced responding in long-evans rats

Abstract

1. 1. Effect of 7-nitro indazole (7-NI), brain specific inhibitor of nitric oxide synthase (NOS), on saccharin or ethanol reinforcement was investigated in male Long-Evans rats. 2. 2. Twenty-four rats were trained to lever press both for a 1-% (w/v) saccharin solution and 10% (v/v) ethanol solution using a lever-pressing schedule of progressive ratio. 3. 3. Well-trained rats were tested with 7-NI (10, 20 and 40 mg/kg) or a vehicle (methylcellulose, 2%) injected ip. 60 min before each test. In some tests, L-arginine (1000 mg/kg, ip), a NO precursor, was injected 30 min before a 7-NI (40 mg/kg) injection. 4. 4. Treatment with 7-NI reduced the lever pressing for either saccharin or ethanol reinforcement in a dose dependent manner. The inhibitory effects of 7-NI on the lever pressing for saccharin or ethanol were blocked by L-arginine pre-administration. 5. 5. Our results suggest that reduction in ethanol reinforcement by NOS inhibition may be related to central mechanisms modulating feeding behavior in rats.