Depression by morphine of excitatory junction potentials in the vas deferens of the mouse.
1 Intracellular recordings were made from smooth muscle cells of the mouse vas deferens. Excitatory junction potentials (e.j.ps) were evoked by stimulation of the intramural nerves. 2 Normorphine (50 nM-5muM) depressed the amplitude of the e.j.p. The ED50 was 430 nM. The latency of the e.j.p. and the resting membrane potential of the smooth muscle cells were unaffected by normorphine. 3 The depression of the e.j.p. by narcotic analgesic drugs was stereospecific. 4 Naloxone (100 nM) completely reversed the depression of the e.j.p. produced by normorphine (1 muM). Naloxone (100 nM) alone did not alter the amplitude of the e.j.p. 5 Normorphine (1 muM) did not prevent the depolarization of the smooth muscle cells produced by exogenous noradrenaline (10 muM). 6 It is concluded that narcotic analgesic drugs act directly upon the transmitter release sites to reduce the amount of noradrenaline liberated by each nerve impulse.
D000818:Animals; D005071:Evoked Potentials / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008815:Mice, Inbred Strains; D009020:Morphine / Q000494:pharmacology*; D009022:Morphine Derivatives / Q000494:pharmacology; D009469:Neuromuscular Junction / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology; D013997:Time Factors; D014649:Vas Deferens / Q000187:drug effects*
D009022:Morphine Derivatives; D009020:Morphine; D009638:Norepinephrine