title: Selective depression by alfentanil of group III and IV somatosympathetic reflexes in the dog.
abstract: The effect of alfentanil on sympathetic reflexes evoked by supramaximal electrical stimulation of the radial nerve has been observed in five dogs anaesthetized with alpha-chloralose, paralysed with suxamethonium and artificially ventilated. In five dogs during the infusion of alfentanil at a rate of 20 micrograms kg-1 min-1 the late long latency sympathetic response evoked by unmyelinated fibres (group IV, C) was abolished at a mean dose of 68.8 (SE 2.85) micrograms kg-1. The infusion rate was then increased to 200 micrograms kg-1 min-1 and the early, short latency response evoked by small myelinated fibres (group III, A delta) was eliminated at mean total dose of 809 (SE 72) micrograms kg-1. When the infusion was stopped the group III reflex returned within 1-5 min and recovery to approximately 50% of control for both reflexes occurred within 15-60 min in different preparations. Mean arterial pressure and mean heart rate decreased from 140 (6) mm Hg and 132 (11) beat min-1 to 100 (7) mm Hg and 70 (6) beat min-1, respectively, by the time the group IV response was eliminated; that is, after a mean infusion time of 3.4 min. Thereafter, there was no further cardiovascular depression. Within 3 min of the administration of naloxone 2 mg i.v., the sympathetic reflexes, arterial pressure and heart rate returned to within control values.
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D015760:Alfentanil; D000777:Anesthetics / Q000494:pharmacology*; D000818:Animals; D003864:Depression, Chemical; D004285:Dogs; D005283:Fentanyl / Q000031:analogs & derivatives* / Q000494:pharmacology; D007668:Kidney / Q000294:innervation; D009412:Nerve Fibers / Q000502:physiology; D009413:Nerve Fibers, Myelinated / Q000502:physiology; D011826:Radial Nerve / Q000502:physiology; D012018:Reflex / Q000187:drug effects*; D013564:Sympathetic Nervous System / Q000187:drug effects*; D013997:Time Factors
chemical_list: D000777:Anesthetics; D015760:Alfentanil; D005283:Fentanyl