Effects of anaesthetics on reflexes elicited in the sudomotor system by stimulation of Pacinian corpuscles and of cutaneous nociceptors.
Sudomotor neurones supplying sweat glands in the hairless skin of the cat's paws can be activated by the cutaneous afferent inputs deriving from vibrational receptors (Pacinian corpuscles) in the paws and from cutaneous nociceptors. Both reflexes probably have separate spinal pathways. In the present investigation the effects of the anaesthetics ketamine, methohexital, chloralose, halothane and Althesin on both types of sudomotor reflexes were examined. For this purpose the skin potentials were recorded from the hairless skin of the paws with Ag--AgCl-electrodes. Before application of any anaesthetic the cats were in a state of light ketamine anaesthesia. The following results were obtained: (1) the resting activity in the sudomotor system and the synchronization of the activity between both hindpaws and between hind- and forepaws were depressed by all anaesthetics to a variable degree. After chloralose application large synchronous potentials of low frequency appeared; (2) ketamine (18--25 mg/kg injected intramuscularly) enhanced the reflexes on vibrational stimulation and depressed the reflexes on noxious stimulation of skin; (3) methohexital (3--10 mg/kg injected intramuscularly) mostly depressed the reflexes on vibrational stimulation and enhanced the reflexes on noxious cutaneous stimuli; (4) chloralose (4.5--20 mg/kg injected intraperitoneally) enhanced both types of reflexes; (5) halothane (1--1.5 vol. %) and Althesin (2.5--5 mg/kg injected intramuscularly) depressed both types of reflexes; (6) in chronic spinal cats ketamine, methohexital and chloralose had a slightly depressive effect on the resting activity of the sudomotor system, but practically no influence on the reflexes induced by cutaneous stimuli; and (7) these results argue that the effects of anaesthetics on the sudomotor system depend on the type of reflex tested and the type of anaesthetic used. They indicate furthermore that the anaesthetics affect largely supraspinal structures and influence the spinal reflex pathways via descending spinal pathways.
D000320:Adrenergic Fibers / Q000187:drug effects; D000530:Alfaxalone Alfadolone Mixture / Q000494:pharmacology; D000777:Anesthetics / Q000494:pharmacology*; D000818:Animals; D001338:Autonomic Fibers, Postganglionic / Q000187:drug effects; D002415:Cats; D002698:Chloralose / Q000494:pharmacology; D005071:Evoked Potentials / Q000187:drug effects; D006221:Halothane / Q000494:pharmacology; D007649:Ketamine / Q000494:pharmacology; D008465:Mechanoreceptors / Q000187:drug effects*; D008723:Methohexital / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects; D009619:Nociceptors / Q000187:drug effects*; D010141:Pacinian Corpuscles / Q000187:drug effects*; D012018:Reflex / Q000187:drug effects*; D012867:Skin / Q000294:innervation*; D013116:Spinal Cord / Q000187:drug effects; D013545:Sweat Glands / Q000294:innervation*
D000777:Anesthetics; D002698:Chloralose; D007649:Ketamine; D000530:Alfaxalone Alfadolone Mixture; D008723:Methohexital; D006221:Halothane