Anticataleptic effects of 5-HT1B receptors in the globus pallidus

Abstract The globus pallidus occupies an important position in the indirect pathway of the basal ganglia. Being a monoamine neurotransmitter, 5-HT is involved in mediating many physiological functions and pathophysiological processes in several movement disorders. Morphological studies have revealed that the globus pallidus receives serotonergic innervation arising from the raphe nuclei, mainly the dorsal raphe nucleus. A high level of 5-HT and 5-HT 1B receptors were detected in the globus pallidus. In the present study, bilateral microinjection of 5-HT or 5-HT 1B receptor agonist, CP-93129, into the globus pallidus significantly alleviated the symptoms of rigidity caused by haloperidol. To further elucidate 5-HT 1B receptor-induced anticatalepsy, in vivo extracellular recordings were performed to examine the effects of 5-HT 1B receptor activation on the firing activity of the globus pallidus neurons under the presence of haloperidol. Micro-pressure ejection of 5-HT or CP-93129 increased the spontaneous firing rate of the pallidal neurons. Furthermore, by using immunohistochemistry, positive staining of 5-HT 1B receptor was observed in the globus pallidus neurons. Taken together, the present findings provide evidence that activation of 5-HT 1B receptor may exert anticataleptic effects by increasing the activity of pallidal neurons.