BEHAVIORAL AND NEURO-ENDOCRINE EFFECTS OF LOW-DOSE ET-495 - ANTAGONISM BY HALOPERIDOL

Low doses of the dopamine agonist ET-495 were administered to non-psychotic volunteer subjects by slow intravenous infusion, followed by a bolus of 1.5-2.5 mg haloperidol. ET-495 caused progressive dysphoria and sedation (in some cases, light sleep), effects believed to be mediated by dopaminergic inhibition. However, ET-495 also elevated growth hormone and suppressed prolactin, typical responses to dopamine agonist activity. Haloperidol reversed both the sedation and prolactin suppression induced by ET-495. These findings suggest: (1) that the sedation and hormonal responses were produced by stimulation of dopamine receptors; (2) that neurotransmitter systems mediating behavioral and neuroendocrine regulation may have differential neuropharmacological characteristics. © 1979 Springer-Verlag.