Muscimol injection in the thalamic reticular nucleus reverts the effect of dopaminergic lesion on short-term memory in the rat globus pallidus externus

Abstract

The thalamic reticular nucleus (TRN) is a GABAergic nucleus essential for regulating information flow between the thalamus and cortex. It is involved in various cognitive processes, such as memory and attention, and receives GABAergic input from the external globus pallidus (GPe). The GPe is part of the indirect pathway of the basal ganglia, which is involved in the modulation of motor, limbic, and cognitive functions. Dopaminergic denervation in the GPe (DDGPe) has been linked to a decrease in short-term memory, which reflects the cognitive deficits often observed in the early stages of Parkinson’s disease. We hypothesize that DDGPe might disrupt GABAergic modulation in the TRN, impacting memory. To test this, rats with DDGPe were injected with varying concentrations of muscimol into the TRN and underwent an object recognition test. Results showed that muscimol restored the discrimination index (DI) values reduced by DDGPe, with recovery blocked by bicuculline. These findings suggest that a reduction in the GABAergic influence from the GPe on the TRN compromises the TRN’s functionality during memory processing.