Following from evidence supporting GABA as a putative inhibitory transmitter in the visual cortex, we have iontophoretically applied the GABA antagonist N-methyl bicuculline (Nmb) to simple cells in order to block the inhibitory inputs acting on them. We found that under these conditions previously sharply-tuned simple cells responded equally to all orientations. Moreover receptive field dimensions, judged by the response to stimuli at the optimal and orthogonal orientations, equated best with that expected from a single dLGN cell input. It seems thus, that asymmetries in the excitatory input are not a significant factor in the generation of simple cell orientation selectivity. The asymmetry underlying orientation selectivity rather originates from the operation of an intracortical inhibitory mechanism.

Journal Article The effects of blocking catecholamine uptake on amphetamine-induced circling behaviour in mice with unilateral destruction of striatal dopaminergic nerve terminals Get access C Pycock, C Pycock University Department of Neurology, Institute of Psychiatry & King's College Hospital Medical School, Denmark Hill, London, SE5 8AF, U.K. Correspondence: University Department of Neurology, Institute of Psychiatry & King's College Hospital Medical School, Denmark Hill, London, SE5 8AF, U.K. Search for other works by this author on: Oxford Academic Google Scholar J A Milson, J A Milson University Department of Neurology, Institute of Psychiatry & King's College Hospital Medical School, Denmark Hill, London, SE5 8AF, U.K. Search for other works by this author on: Oxford Academic Google Scholar D Tarsy, D Tarsy University Department of Neurology, Institute of Psychiatry & King's College Hospital Medical School, Denmark Hill, London, SE5 8AF, U.K. Search for other works by this author on: Oxford Academic Google Scholar C D Marsden C D Marsden University Department of Neurology, Institute of Psychiatry & King's College Hospital Medical School, Denmark Hill, London, SE5 8AF, U.K. Search for other works by this author on: Oxford Academic Google Scholar Journal of Pharmacy and Pharmacology, Volume 28, Issue 6, June 1976, Pages 530–532, https://doi.org/10.1111/j.2042-7158.1976.tb02785.x Published: 12 April 2011 Article history Received: 29 December 1975 Published: 12 April 2011

1. The effects of drugs acting on cerebral 5-hydroxytryptaminergic mechanisms on drug-induced turning behaviour in mice with unilateral destruction of nigro-striatal dopaminergic nerve terminals have been studied. 2. Administration of L-tryptophan (400 mg/kg) or 5-hydroxytryptophan (200 mg/kg) increased brain 5-hydroxytryptamine and decreased the turning induced by both apomorphine (2 mg/kg) and amphetamine (5 mg/kg). 3. Parachlorophenylalanine (3 X 500 mg/kg) decreased brain 5-hydroxytryptamine and increased both apomorphine and amphetamine-induced circling behaviour. 4. Varying the protein content of dietary intake significantly altered brain 5-hydroxytryptamine and tryptophan levels, spontaneous locomotor activity and amphetamine-induced circling behaviour in these mice. 5. Systemic administration of methysergide (0.5-4 mg/kg), lysergic acid diethylamide (0.025-0.2 mg/kg), cyproheptadine (2.5-20 mg/kg) or clomipramine (0.6-20 mg/kg) produced no consistent effect on drug-induced turning behaviour. 6. The results suggest that circling behaviour due to striatal dopamine receptor stimulation is depressed by an elevation of brain 5-hydroxytryptamine and enhanced by a reduction in brain 5-hydroxytryptamine. 7. The possible physiological relationship between dopamine and 5-hydroxytryptamine neurones in the basal ganglia is discussed.