Spinal Cord

Excitatory and inhibitory neurotransmissions in mammalian spinal cord may be altered by inhaled anesthetics.^[24] Anesthetic effects depend on the concentration of the agent and on the particular spinal cord pathway examined. Inhaled anesthetics alter responses of the spinal dorsal horn (sensory) to noxious and non-noxious stimuli.^[24] Volatile anesthetics also depress spinal motor neurons. Clinical inhaled agents depress the F-wave amplitude, a measure of the excitability of spinal motor neurons, in animals and humans.^[25] A reduction in the sensory processing and an inhibition of motor neuron excitation are likely to be involved in the anesthetic-induced lack of movement in response to a noxious stimulus. In addition to a direct action on the spinal cord, inhaled agents may indirectly influence activity of spinal neurons by altering the tonic input received from descending modulatory systems from the brain.^{[24] [26]} Conversely, inhaled anesthetics may act in the spinal cord to blunt transmission of noxious inputs to the thalamus and cerebral cortex and thereby indirectly contribute to amnesia and unconsciousness.^[27]