Single or repeated administration of selective serotonin reuptake inhibitors fail to modulate apomorphine-induced responses in the rat

The objective of this study was to compare the effects of both acute and repeated administration of the selective serotonin reuptake inhibitors (SSRIs) sertraline (5 mg/kg), paroxetine (5 mg/kg), citalopram (5 mg/kg), fluoxetine (5 mg/kg) and the tricyclic antidepressant amitriptyline (10 mg/kg) on some aspects of dopaminergic function in the rat using apomorphine (0.1 mg/kg s.c.). Antidepressants were administered p.o. once daily for 14 days to adult male Sprague-Dawley rats. Apomorphine was administered 90 min after the first treatment as well as 24 h after the last treatment to assess any interaction with acute or chronic antidepressant treatment. Neither the acute nor the chronic SSRI treatments attenuated the hypothermia induced by apomorphine. Chronic amitriptyline treatment attenuated the hypothermic effect. Only acute treatment with paroxetine potentiated the hypokinesis induced by apomorphine, the other antidepressants tested having no significant effect. The results of these studies suggest that acute and chronic SSRI treatments fail to alter the functional sensitivity of dopaminergic receptors using the apomorphine test.