Electrophysiologic study of globus pallidus projections to the thalamic reticular nucleus

• Electrical and chemical stimulation of the GP inhibits TRN neurons.
• Electrical stimulation of the SNr inhibits TRN neurons.
• These results suggest that the pallidoreticular and nigroreticular pathways might disinhibit the thalamocortical neurons.

This study was designed to explore the electrophysiological relationships between the globus pallidus (GP), the substantia nigra pars reticulata (SNr) and the thalamic reticular nucleus (TRN) in urethane-anesthetized rats. The neuronal activity of the rostral part of the TRN was recorded by microelectrodes. Single pulse electrical stimulation of the GP and SNr produced inhibition of the spontaneous activity of the majority of TRN neurons. Stimulation of the GP by microinjections of bicuculline (25 ng/300 nl) produced also inhibition of the spontaneous activity of the reticular neurons. This could lead to facilitation of the cerebral cortex, as the reticular nucleus is reciprocally connected to, and inhibits, the thalamic motor nuclei, that in turn excite the motor cortex.