Actions of beta-endorphin and related peptide fragments on a pressor response induced by cholinergic stimulation.
The present study examined the antagonist potential of shorter beta-EP1-31 related peptide fragments in an opioid-sensitive model of blood pressure. In urethane-anesthetized rats, pretreated with methyl atropine, physostigmine (25-200 micrograms/kg i.v.) produced a pressor response that was stereoselectively depressed by i.c.v. levorphanol, an action reversed by naloxone. beta-EP1-31 and beta-EP1-27(H) (5-20 micrograms i.c.v.) also depressed the physostigmine-induced pressor response in a naloxone-reversible manner. However, injections of beta-EP1-27(O) or beta-EP1-26(H) failed to influence this response or to reverse the depressor action of levorphanol. These findings show that shorter fragments of beta-EP1-31 do not mimic the action of naloxone in an opioid-sensitive model of blood pressure.
Hong
M
M
Department of Pharmacology and Toxicology, Queen's University, Kingston, Ontario, Canada.
Jhamandas
K
K
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects* / Q000502:physiology; D007981:Levorphanol / Q000494:pharmacology; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology*; D010830:Physostigmine / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011950:Receptors, Cholinergic / Q000187:drug effects / Q000502:physiology; D001615:beta-Endorphin / Q000494:pharmacology*
D010446:Peptide Fragments; D011950:Receptors, Cholinergic; D007981:Levorphanol; D009270:Naloxone; D001615:beta-Endorphin; D010830:Physostigmine