Further evidence for a change in central alpha-adrenergic receptor sensitivity after withdrawal from long-term haloperidol treatment.

Phenoxybenzamine, FLA-63 and alpha-MT produced less locomotor depression in mice withdrawn for 4 days from a 21 day treatment with haloperidol than that produced in vehicle-treated animals. There were no differences between the two groups when challenged with yohimbine or phentolamine. The data support the hypothesis that central alpha-adrenergic receptors had become supersensitive and suggest that the sensitivity changes are restricted to post-synaptic receptors.