The effects of morphine administered into the vertebral artery on the somatosympathetic A- and C-reflexes in anesthetized cats.
The effects of morphine (0.2-200 micrograms/kg) administered into the brain stem via a vertebral artery on the somatosympathetic A- and C-reflexes evoked in a cardiac sympathetic nerve by electrical stimulation of somatic myelinated (A) and unmyelinated (C) afferent nerve fibers in anesthetized cats were examined. The intravertebral arterial administration of 20-200 micrograms/kg morphine depressed dose-dependently both the somatosympathetic A- and C-reflexes. Following the administration of 200 micrograms/kg morphine, the amplitudes of the sympathetic A- and C-reflexes were depressed to 71 +/- 8% and 80 +/- 8% of the control magnitude, respectively. Injection of 2-200 micrograms/kg morphine caused hypotension in a dose-dependent manner. It is concluded that morphine administered in the brain stem via the vertebral artery produced a nonselective and slight depression of both the somatosympathetic A- and C-reflexes by acting at the level of brain stem.
Kato
J
J
Department of Anesthesiology, School of Medicine, Surugadai Nihon University Hospital, Tokyo, Japan.
Meguro
K
K
Sato
A
A
Sato
Y
Y
D000758:Anesthesia; D000818:Animals; D001933:Brain Stem / Q000502:physiology*; D002415:Cats; D006329:Heart Conduction System / Q000187:drug effects; D007270:Injections, Intra-Articular; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D012018:Reflex / Q000187:drug effects*; D013564:Sympathetic Nervous System / Q000187:drug effects*; D014711:Vertebral Artery
D009020:Morphine