Rat cortical sigma receptors differentially regulated by pentazocine and haloperidol

Repeated administrations of 7.5 mg/kg of pentazocine (for 14 days) resulted in a significant decrease in the affinity of 3H-haloperidol binding to rat cortical sigma receptors without any changes in the maximal number of binding sites (Bmax). On the other hand, similar treatment with haloperidol (2 or 4 mg/kg) induced a dose dependent decrease in the Bmax values without affecting the affinity of the 3H-haloperidol binding. These findings indicate that rat cortical sigma receptors are differentially regulated by pentazocine and haloperidol.