Influence of serotonin upon optic evoked potentials, EEG, and blood pressure of cat

¹ Laboratory of Neurophysiology, Worcester Foundation for Experimental Biology, Shrewsbury, Massachusetts

In cats immobilized with Flaxedil and supplied with local anesthesia in the areas adjacent to the surgical openings, the optic evoked response, the EEG, and the blood pressure were studied in their reaction to intracarotid serotonin (5-HT). Our earlier findings that the effect of 5-HT on the amplitude of the evoked response is the compound effect of the drug action of at least three receptor sites have been confirmed. The carotid sinus area (factor x), the brain stem (factor y) and the specific sensory pathways (factor z) appear to be the three responsive sites. In comparison with the earlier experiments performed on Dial-anesthetized animals, the x-factor and the y-factor in the present series are shifted, in general, toward the facilitory side. Not much difference is found if the z-factor is compared in the two different conditions. EEG activation occurs in response to intracarotid serotonin. This effect is positively correlated to the dose of 5-HT. Injections into the innervated carotid sinus produce considerably stronger effects than those into the denervated carotid sinus. With repeated injections of 5-HT the effect upon the evoked potentials is altered in its quantitative and temporal aspects. The blood pressure usually reacts to 5-HT with a rise. With larger doses of 5-HT this rise is more pronounced and often preceded by an initial drop.