title: Enkephalin-induced changes in ventilation and ventilatory pattern in adult dogs.
abstract: We studied the changes in ventilation induced by intracisternal administration of enkephalins in four unanesthetized adult dogs. Instantaneous minute ventilation (VT/TT) decreased markedly after D-Ala-Met-enkephalinamide (DAME). Mean VT/TT decreased maximally by 20-50 min after DAME and lasted an additional 15-60 min; by 2 h, VT/TT had returned to base line. Four doses (5, 25, 60, and 125 micrograms/kg) of DAME were used, and the ventilatory response depended on the dose. Mean inspiratory time decreased but mean expiratory time and mean TT showed a marked prolongation. Periodic breathing (2-3 breaths separated by long apneic pauses) occurred in every study and the frequency of sighs increased considerably. All these ventilatory changes were reversed by low doses of naloxone or naltrexone; in addition, VT/TT increased well above base line after the administration of these antagonists. However, naloxone did not increase VT/TT when injected without prior administration of DAME. We conclude that 1) the decrease in VT/TT is due to a decrease in respiratory duty cycle; 2) periodic breathing and increased frequency of sighs constitute part of the changes in the ventilatory pattern induced by DAME; 3) a ventilatory withdrawal reaction may occur after a receptor-agonist interaction of short duration; and 4) although enkephalins can modulate ventilation and the breathing pattern in a major way, these data provide no evidence suggesting that this modulation is tonic.
mesh_terms: D000818:Animals; D003243:Consciousness; D004285:Dogs; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D010507:Periodicity; D012119:Respiration / Q000187:drug effects*; D012146:Rest; D013990:Tidal Volume; D013997:Time Factors
chemical_list: D009292:Narcotic Antagonists; D009270:Naloxone; D004744:Enkephalin, Methionine; C022118:enkephalinamide-Met, Ala(2)-