Morphine depression and tolerance of nerve-induced parotid secretion.
1 The nerve-induced secretion produced by the rat parotid gland is proportional to the frequency of stimulation. Morphine decreased the flow rate during stimulation at 2.5 and 5 Hz, but not at 20 Hz. This frequency-dependent action of morphine and was partially reversed by naloxone. 2 The secretion produced by the rat parotid gland during an intravenous infusion of acetylcholine was not diminished by morphine. Therefore, the action of morphine on nerve-induced secretion is most probably on the motor nerve terminals, which release acetylcholine. 3 Animals that had been implanted with morphine base pellets tolerated 4 times as much morphine as controls; after 6 days the minute ventilation was less depressed by graded doses of morphine than non-implanted controls. 4 Nerve-induced secretion in morphine-implanted animals was less depressed by morphine than control animals 6 and 24 h after the pellets were removed. The flow rates in the 6 h group treated with morphine were greater after naloxone than control (precipitated withdrawal) but at 24 h when withdrawal symptoms were no longer evident, naloxone produced only a slight reversal.
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002412:Cations / Q000032:analysis; D003864:Depression, Chemical; D004343:Drug Implants; D004361:Drug Tolerance; D004558:Electric Stimulation; D008297:Male; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D010306:Parotid Gland / Q000187:drug effects* / Q000294:innervation / Q000378:metabolism; D051381:Rats; D012119:Respiration / Q000187:drug effects; D012463:Saliva / Q000032:analysis
D002412:Cations; D004343:Drug Implants; D009020:Morphine; D000109:Acetylcholine