GABAB receptors

GABAB receptors are a distinct subclass of receptors for the major inhibitory transmitter 4-aminobutanoic acid (GABA) that mediate depression of synaptic transmission and contribute to the inhibition controlling neuronal excitability. The development of specific agonists and antagonists for these receptors has led to a better understanding of their physiology and pharmacology, highlighting their diverse coupling to different intracellular effectors through Gi/G(o) proteins. This review emphasises our current knowledge of the neurophysiology and neurochemistry of GABAB receptors, including their heterogeneity, as well as the therapeutic potential of drugs acting at these sites.

Lamotrigine protects against kainate but not ibotenate lesions in rat striatum

Pretreatment of rats with 8-16 mg/kg of lamotrigine 1 h before intrastriatal injections of 2 nm of kainic acid significantly attenuated the neurotoxicity as evidenced by measurements of striatal choline acetyltransferase and glutamate decarboxylase activities. No significant effect was seen on the toxicity of intrastriatal injections of quinolinic acid or ibotenic acid. These differential effects are further evidence that these neurotoxins act at different excitatory amino acid receptors and that the neurotoxicity of kainate is uniquely dependent on neuronally released glutamate.

Quantitative electrocortical changes in the rat induced by phencyclidine and other stimulants

An automated technique for the continuous analysis of different frequency bands of the electrocorticogram (ECoG) of the rat has been used to quantify the actions of phencyclidine (PCP) and various other stimulant drugs. It has been demonstrated that phencyclidine, etoxadrol and LY154045 produced similar changes in the individual frequency bands whereas amphetamine and apomorphine had different profiles of activity. The phencyclidine-like compounds exhibited extremely strong stimulation of the ECoG with very large increases recorded in high frequency (15-50 Hz) activity and reductions in all other frequency bands. Various compounds have been used in an attempt to antagonise the changes in the ECoG. Chlorpromazine caused a slight shift in the dose-response curves as did chlordiazepoxide when used with phencyclidine. The GABA agonists, THIP and muscimol, had no effect on the stimulation of the ECoG. In contrast another presumed GABA agonist, baclofen, proved to be the most effective agent for blocking the stimulation induced by phencyclidine. The role of the GABAB receptor in the action of phencyclidine is discussed.