It has been shown that graded doses of LSD (d-lysergic acid diethylamide-25) produce facilitation of evoked auditory and visual primary responses in the unanesthetized-paralyzed cat. At higher concentrations differential depression of the auditory responses was seen to occur while facilitation of the visual responses could still be detected.14
The present report extends the observations to include other, nonspecific, afferent pathways and presents evidence relating to the differential action of LSD on various synaptic arrangements.
METHODS
Methods were essentially similar to those reported previously, with the following additions: Recruiting responses were evoked by 5-10/sec. stimulation of the rostral pole of centrum medianum of the thalamus. They were generally recorded maximally from the sensorimotor cortex. Stimuli were delivered through a 0.5 mm. concentric electrode introduced by means of a three-dimensional micro-manipulator. In addition to studying the effect of LSD on cortical potentials evoked from a symmetrical point on one hemisphere