Effects of lysergic acid diethylamide on the spontaneous activity and visual receptive fields of cells in the lateral geniculate nucleus of the cat

The effects of LSD on neuronal activity in the LGN were studied in cats anaesthetised with urethane. LSD was given in doses of 25 μg, 100 μg, 200 μg and 300 μg per cat. Changes in neuronal activity were compared with those observed in a control population of cells recorded from animals that had received 0.5 ml of physiological saline or no treatment. The spontaneous firing rate, the responses to light stimuli delivered to the centre and to the surround regions of the receptive fields were all depressed by the drug. There was a dose response relationship which was almost identical (slope, b = -0.19 to -0.20) for each of these aspects of LGN neuronal activity. In a given cell changes in spontaneous activity were not correlated with changes in the responses to field centre or surround stimulation. Changes in response to field centre stimulation were not predictive of changes in response to field surround stimulation except in the LSD≧ 100 μg treatment groups. In these groups the variances of the change in spontaneous activity were greater than those in the controls. It is concluded that, in the doses used, LSD does not exert a uniformly depressant action on postsynaptic membranes: the effects observed are consistent with an action on the release of transmitter substance and/or its interaction with receptors. BOL 148, the non-psychoactive analogue of LSD did not completely reproduce the effects of any dose of LSD used in this study. The possible consequences of the action of LSD on LGN neurones for the processing of visual information is discussed.