Attenuation of intravenous amphetamine reinforcement by central dopamine blockade in rats
- Cite this article as:
- Yokel, R.A. & Wise, R.A. Psychopharmacology (1976) 48: 311. doi:10.1007/BF00496868
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Norepinephrine (NE) and dopamine (DA) receptor blockade differentially affected amphetamine self-administration. DA blockade (pimozide, 0.0625 to 0.5 mg/kg, or (+)-butaclamol, 0.0125 to 0.1 mg/kg) caused periods of increased rate of responding for amphetamine which were followed, in the case of higher doses, by response cessation. The response cessation produced by 0.5 mg/kg pimozide was not reversed by non-contingent amphetamine injections until well after the peak effect of the pimozide was over. When access to amphetamine injections was delayed until 4 h after animals received 0.5 mg/kg pimozide, rate of responding was elevated. Thus DA seems to be critically involved in mediation of the reinforcing effects of amphetamine. Alpha-NE blockade with phentolamine (2.5–10 mg/kg) produced dose-related decreases in responding; blockade with phenoxybenzamine (1.25–10 mg/kg) had no effect. Beta-NE blockade with l-propranolol (2.5–10 mg/kg) decreased responding, although probably not through a beta-blocking action. The effects of phentolamine and propranolol do not appear to result from attenuation of the reinforcing effects of amphetamine.