Failure of chronic haloperidol to affect prolactin secretion due to acute haloperidol administration

Withdrawal from chronic haloperidol exposure was associated to unaltered circulating levels of prolactin (PRL), decreased 3H-spiperone binding sites in the anterior pituitary and increased 3H-spiperone binding sites in the striatum of male rats. Haloperidol (0.1 mg/kg ip) induced similar rises in plasma PRL in haloperidol-or saline-treated rats and the dose of 0.01 mg/kg was ineffective in both groups. These findings illustrate the poor relatedness existing at the pituitary D2 receptor between biochemical and functional indices.