Interaction between pargyline, a monoamine oxidase inhibitor, and beta-adrenergic receptors in the rat pineal gland.
The hypothesis that pargyline, a monoamine oxidase inhibitor, may interact with pineal beta-adrenergic receptors to increase N-acetyltransferase (NAT) activity and, thereby, melatonin content was tested in intact and superior cervical ganglionectomized (SCGX) rats some of which were also treated with the tryptophan hydroxylase inhibitor para-chlorophenylalanine (PCPA). Pargyline injection increased both NAT activity and melatonin content, an effect nullified by conjunct propranolol injection. While pargyline injection also increased NAT activity in intact, PCPA-treated rats, the effects of this drug were most evident in SCGX, PCPA-treated rats. PCPA treatment prevented pargyline-induced increases in melatonin content in intact and SCGX rats suggesting an artificially-induced dissociation of melatonin biosynthesis from its rate-limiting enzyme. We suggest that pargyline may be capable of interacting with pineal beta-adrenergic receptors to increase NAT activity in the absence of pineal norepinephrine (NE) and serotonin.
D000818:Animals; D001191:Arylamine N-Acetyltransferase / Q000378:metabolism; D010134:Fenclonine / Q000494:pharmacology; D005728:Ganglia, Sympathetic / Q000502:physiology; D008297:Male; D008550:Melatonin / Q000378:metabolism; D010293:Pargyline / Q000494:pharmacology*; D010870:Pineal Gland / Q000187:drug effects* / Q000378:metabolism; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011941:Receptors, Adrenergic / Q000187:drug effects*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*
D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; D010293:Pargyline; D011433:Propranolol; D001191:Arylamine N-Acetyltransferase; D008550:Melatonin; D010134:Fenclonine