Bromocriptine holiday: effects on dopamine receptors and turning behavior in rats.
In experimental Parkinson's disease, we studied the effects of chronic administration (30 days), withdrawal, and reinstitution of bromocriptine. Dopamine (DA) receptor supersensitivity was produced by 6-hydroxydopamine and reversed by chronic bromocriptine administration. Drug holiday reestablished sensitivity of DA receptors, but reinstitution of bromocriptine again downregulated receptors. The effects of a drug holiday on DA receptors are short-lived, and long-term clinical improvement cannot be expected. Apomorphine-induced contralateral turning produced by the lesion was unaffected by any drug regimen.