Biphasic changes in anterior pituitary Met-enkephalin concentration following reserpine treatment.
Met-enkephalin concentrations in the anterior pituitary gland were shown to decline dramatically within the first 24 h after reserpine treatment, with effects apparent as early as 6 h. This was followed by subsequent repletion and late augmentation of Met-enkephalin levels 3 weeks following reserpine. Treatment with the alpha-1-adrenergic agonist methoxamine had no effect, whereas the alpha-1-antagonist prazosin lowered Met-enkephalin concentrations. Treatment with the dopamine agonists bromocriptine or apomorphine had no effect, but haloperidol treatment increased anterior pituitary Met-enkephalin which was reversed by concomitant bromocriptine administration. We postulate that the changes in anterior pituitary Met-enkephalin following reserpine were related to alterations in the monoamine neurotransmitters. Adrenergic and dopaminergic mechanisms may have opposing roles in the maintenance of Met-enkephalin concentrations in the anterior pituitary gland.
George
S R
SR
Department of Physiology, Queen's University, Kingston, Ont., Canada.
Kertesz
M
M
D000818:Animals; D001971:Bromocriptine / Q000494:pharmacology; D004744:Enkephalin, Methionine / Q000378:metabolism*; D006220:Haloperidol / Q000494:pharmacology; D007274:Injections, Intraperitoneal; D007276:Injections, Intraventricular; D008297:Male; D008729:Methoxamine / Q000008:administration & dosage / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects; D011954:Receptors, Dopamine / Q000187:drug effects; D012110:Reserpine / Q000494:pharmacology*; D013997:Time Factors
D011942:Receptors, Adrenergic, alpha; D011954:Receptors, Dopamine; D001971:Bromocriptine; D004744:Enkephalin, Methionine; D012110:Reserpine; D008729:Methoxamine; D006220:Haloperidol