EFFECT OF INHALATION ANESTHETICS ON MONOSYNAPTIC AND POLYSYNAPTIC TRANSMISSION IN THE SPINAL CORD

¹ Departments of Anesthesiology and Pharmacology, University of Washington School of Medicine, Seattle, Washington

In decerebrate cats, we stimulated a lumbar dorsal root supramaximally and recorded the resultant reflex potentials in the ventral root. Ether, cyclopropane, chloroform, halothane, methoxyflurane or nitrous oxide was added to the inspired gas, and the ventral root responses were measured at several anesthetic concentrations. Higher concentrations of these anesthetics depressed the monosynaptic response somewhat more profoundly than the polysynaptic response. When the monosynaptic response had disappeared, a small but significant amount of transmission still persisted over the longer latency polysynaptic pathways. The relationship between ploysynaptic and monosynaptic responses was independent of the anesthetic concentration. We conclude that anesthetics depress the transmission of afferent impulses as readily at a single synapse in the spinal cord as at the several links of a serial synaptic chain.

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