Effects of yohimbine on CNS structures: Neurophysiological and behavioral correlations

Yohimbine (by intravenous and/or intraperitoneal routes at doses between 0.5 to 3 mg/kg) produces behavioral changes (in freely moving cats and dogs) characterized by: a) an increase in alertness, extreme agitation, and nervousness; b) an increase in motor reaction to a variety of sensory stimuli; and c) an appearance of muscular shaking and tremors. These behavioral changes are associated with electrographic alterations characterized by: a) an increase in the amplitude of the local evoked potentials (LEP) recorded from the mesencephalic reticular formation, posterior hypothalamus and intralaminar thalamic system; b) a decrease in the amplitude of the LEP recorded from preoptic area, lateral hypothalamus and septal region; c) a slight diminution in the LEP amplitudes of the amygdala and hippocampus; d) an initial increase (15 to 25 min) followed by a long period of strong diminution in the amplitude of the cortical LEP; e) an increase in the percent time of fast cortical activity and in the amplitude of all frequencies; f) an appearance of subcortical and cortical epileptiform discharges in the normal animals during administration of the compound at doses of 2 to 3 mg/kg; and g) a marked activation of epileptiform discharges in the subcortical or cortical epileptic animals in association with occasional clinical seizures. These results were discussed from the point of view of neuronal excitability changes in CNS structures.This project was supported in part by the Louisiana State Department of Hospitals, and in part by a USPHS Grant, Number 2-R10-MH-03701-13, Psychopharmacology Research Branch, NIMH, U.S.A.