Re-evaluation of the stimulatory effect of norepinephrine on the secretion of amylase in the parotid gland of the rat.
The effect of the neurotransmitter norepinephrine(NE) in stimulating the secretion of amylase from the parotid gland of rats was studied by use of selective alpha- and beta-adrenergic antagonists. Its secretory response, mediated through beta-adrenoceptors, was slight during a short period of incubation, but rapidly increased after incubation for 10 min, showing a supersensitization phenomenon. Norepinephrine alone did not induce this phenomenon, but it induced the phenomenon in the presence of the alpha-adrenergic antagonist phentolamine or the alpha 1-antagonist prazosin. Isoproterenol-induced supersensitization was prevented by methoxamine. While, the accumulation of cyclic AMP in the tissue during incubation with isoproterenol and NE was not significantly affected by the presence of methoxamine and phentolamine, respectively. Phorbol dibutyrate did not inhibit the secretion induced by NE in the presence of phentolamine. These findings indicate that stimuli, mediated through alpha- and beta-adrenoceptors, induced secretion of amylase in parotid gland of the rat but that the alpha-effect inhibited the beta-effect when both stimuli were applied simultaneously and that the overall response of the tissue to NE resulted from the interaction of the two adrenoceptors.
Hata
F
F
Department of Veterinary Pharmacology, College of Agriculture, University of Osaka Prefecture, Sakai, Japan.
Yagasaki
O
O
D000681:Amylases / Q000378:metabolism*; D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008729:Methoxamine / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology*; D010306:Parotid Gland / Q000187:drug effects / Q000201:enzymology*; D010646:Phentolamine / Q000494:pharmacology; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology; D013268:Stimulation, Chemical
D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D015240:Phorbol 12,13-Dibutyrate; D000242:Cyclic AMP; D000681:Amylases; D008729:Methoxamine; D007545:Isoproterenol; D009638:Norepinephrine; D010646:Phentolamine