Inhibition of pontine omnipauser neurons in the cat by 5-hydroxytryptophan

We assessed ocular motor nerve discharges and omnipause neuronal activity in six adult alert cats before and after intravenous infusion of the serotonin precursor 5-hydroxytryptophan (5-HTP). In all animals, 5-HTP inhibited omnipause neuron activity synchronously with a disappearance of high-frequency bursts of the ocular motor nerves associated with vestibular-induced fast components. This effect was rapidly reversed by the serotonin blocker, methysergide. Our findings are most consistent with an indirect effect of 5-HTP on omnipause neurons.