Behavioral and electrophysiological effects of pallidal GABA B receptor activation and blockade on haloperidol-induced akinesia in rats

Abstract

The globus pallidus plays an important role in movement regulation. Morphological studies have revealed GABA B receptor expression in the globus pallidus. To investigate the behavioral and electrophysiological effects of pallidal GABA B receptors on haloperidol-induced akinesia, microinjection and extracellular recordings were performed in the present study. Unilateral microinjection of GABA B receptor agonist, baclofen, into globus pallidus produced ipsilateral dystonic posturing in haloperidol-induced akinesia rats. However, microinjection of GABA B receptor antagonist, CGP55845, induced contralateral dystonic posturing, suggesting the tonic activity of pallidal GABAergic neurotransmission. Micro-pressure ejection of baclofen into globus pallidus decreased the spontaneous firing of pallidal neurons. Furthermore, local administration of CGP55845 alone induced a weak but consistent increase in the frequency of pallidal firing. The presence of CGP55845 prevented baclofen-induced effects completely. From the present in vivo findings it may be concluded that pallidal GABA B receptors may contribute to the therapy of parkinsonian akinesia by modulating the activity of globus pallidus.