Effect of midbrain raphe nucleus stimulation on somatosensory evoked potential in cat

AbstractExperiments were carried out to clarify the effect of serotonin [5-hydroxytryptamine (5-HT)] upon the somatosensory evoked potential (SEP) elicited by superficial radial nerve stimulation in cat, and the following results were obtained: (i) in untreated (control) animals, a significant reduction occurred in amplitude of the SEP in response to conditioning stimulation of the dorsal raphe nucleus in the midbrain, within 100 ms of the interval between conditioning and test stimuli; (ii) in 5-HT depleted animals prepared by intraperitoneal injection of p-chlorophenylalanine (PCPA), the amplitude of SEP significantly increased in comparison with that of nontreated animals. Conditioning stimulation of the raphe nucleus in 5-HT depleted animals failed to cause any remarkable change in the SEP; (iii) the diminution of the SEP by raphe nucleus conditioning reappeared following intraventricular administration of a large dose of 5-HT (200 ¼g) in the PCPA-treated animals. These results have demonstrated that ...