Chronic clorgyline and pargyline increase apomorphine-induced stereotypy in the rat

The effects of monoamine oxidase inhibiting antidepressant drugs on behavioral and biochemical measures of dopamine receptor status were measured in the rat. Male Wistar rats received clorgyline (1 mg/kg/day for 21-28 days), pargyline (1 mg/kg/day for 21-28 days) or a combination of these regimens. They were then either tested for stereotypy induced by 1 mg/kg SC injection of apomorphine or were sacrificed and their striata used to measure specific [3H]spiroperidol binding. All three chronic treatment regimens produced statistically significant increases in apomorphine induced stereotypy: there was, however, no significant difference between the three drug regimens. None of the antidepressant drug treatments significantly affected [3H]spiroperidol binding in the corpus striatum. This study demonstrates that behavioral and biochemical measures of dopamine function may not always be closely correlated. It is proposed that the behavioral changes may be related to alterations in other monoaminergic systems, which are known to have fibres running into the nigrostriatal pathway.