European journal of pharmacology
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In anaesthetized, paralysed and artificially ventilated dogs, activities were recorded from the phrenic nerve and from respiratory units within the nucleus tractus solitarii (nTS), the nucleus ambiguus (nA) and the nucleus retroambigualis (nRA). The respiratory neurons were classified according to their discharge pattern and their response to lung inflation. Fentanyl injected into the vertebral artery (0.5-2 micrograms/kg) or intravenously (10 micrograms/kg) produced a depressant effect on the phrenic nerve motoneurons, on inspiratory cells (I alpha and I beta) and on phase-spanning expiratory-inspiratory neurons of the nTS and the nA. ⋯ Naloxone antagonized these effects but induced the appearance of tonic discharges in fentanyl-treated phase-spanning expiratory-inspiratory neurons. Stimulation of peripheral chemoreceptors with almitrine (0.2 mg/kg i.v.) antagonized the effects of fentanyl. In addition, fentanyl facilitated the lung inflation reflex on respiratory neurons.(ABSTRACT TRUNCATED AT 250 WORDS)