Stereological Analysis of the Subthalamic Nucleus in a Parkinsonian Wistar Rat Model Induced by 6-Hydroxydopamine

Parkinson's disease is characterised by the progressive loss of dopaminergic neurons in the substantia nigra pars compacta and consequent hyperactivity of the subthalamic nucleus within the basal ganglia circuit. The subthalamic nucleus has emerged as the primary target for deep brain stimulation in the surgical management of Parkinson's disease, making detailed stereological characterisation of its neuronal population in experimental models clinically relevant. This study aims to evaluate neuronal density, nuclear volume, and cytoarchitectural integrity of the subthalamic nucleus in Wistar rats with unilateral 6-hydroxydopamine-induced Parkinsonism. Twenty rats will undergo unilateral stereotaxic 6-hydroxydopamine injection into the medial forebrain bundle, with sham controls receiving vehicle injections. Four weeks post-lesion, behavioural confirmation of the lesion will be performed by the apomorphine rotation test. Brains will be processed for stereological analysis of the subthalamic nucleus using the optical fractionator and nucleator probes. Tyrosine hydroxylase immunofluorescence will confirm dopaminergic lesion extent. Findings will characterise subthalamic nucleus neuronal changes associated with experimental Parkinsonism, contributing to the neuroanatomical evidence base supporting deep brain stimulation targeting in clinical practice.

Keywords: subthalamic nucleus, Parkinson's disease, stereology, 6-hydroxydopamine, deep brain stimulation