GABAmimetic drugs in hyperkinetic involuntary movement disorders and their effects on mental status

GABA agonist-induced changes in motor, oculomotor, and attention measures correlate in schizophrenics with tardive dyskinesia

Saccadic distractibility, Stroop color-word scores, and serial dyskinesia assessments were obtained on 10 schizophrenic patients with tardive dyskinesia during a pharmacologic challenge with placebo or 7 mg muscimol, a potent, direct-acting GABA agonist. Although no significant difference in the measures was evident between conditions, a significant correlation was found between GABA agonist-induced changes in saccadic distractibility and dyskinesia scores where no correlation existed between these measures on placebo. Improvement in saccadic distractibility was also correlated with reduction in attention performance, as measured by Stroop. These effects are not due to sedation. The correlation between dyskinesia and saccadic distractibility is consistent with a model of parallel motor and oculomotor cortico-striatal-thalamic circuits in humans. This work supports the hypothesis that a dysfunction in GABA-mediated neurotransmission may be the basis for tardive dyskinesia.

GABA and behavior: the role of receptor subtypes

The discovery of different GABA receptor subtypes has stimulated research relating this neurotransmitter to a variety of behavioral functions and clinical disorders. The development of new and specific GABAergic compounds has made it possible to try to identify the specific functions of these receptors. The purpose of the present review is to evaluate the data regarding the functions of the GABA receptor subtypes in different behaviors such as motor function, reproduction, learning and memory, and aggressive-defensive behaviors. A description of GABAergic functions (stress, peripheral effects, thermoregulation) that might directly or indirectly affect behavior is also included. The possible involvement of GABA in different neurological and psychiatric disorders is also discussed. Although much research has been done trying to identify the possible role of GABA in different behaviors, the role of receptor subtypes has only recently attracted attention, and only preliminary data are available at present. It is therefore evident that still much work has to be done before a clear picture of the behavioral significance of these receptor subtypes can be obtained. Nevertheless, existing data are sufficient to justify the prediction that GABAergic agents, in the near future, will be much used in the field of behavioral pharmacology. It is hoped that the present review will contribute to this. Some specific suggestions concerning the most efficient way to pursue future research are also made.

Antagonism of phencyclidine-induced hyperactivity in mice by elevated brain GABA concentrations

Vigabatrin and (S)-4-allenylGABA (MDL 72483), two anticonvulsant GABA-T inhibitors, partially antagonize phencyclidine (PCP)-induced hyperactivity in mice at doses that do not affect spontaneous motor activity. The PCP antagonism is related to whole-brain GABA concentrations. The results indicate the potential use of GABA-T inhibitors in the therapy of PCP intoxications and perhaps also in the treatment of certain forms of endogenous psychoses.