Defect in Synaptic Pruning of Motor Cortex Neurons is Associated with Early Perturbed Dopaminergic System

Background: Early stress exposure during neurodevelopmental stages has been linked to some adult neuropsychiatric disorders. The dopaminergic system which has been implicated in movement and reward system has been linked to movement and mood disorders when perturbed at early development. This study is designed to check the mechanisms involved in movement disorders such as dyskinesia, associated with early perturbed dopaminergic system in the motor cortex Methods: Haloperidol was used to block D2R in neonatal albino Wistar rats in utero by administering 20 mg/kg BW (intraperitoneally) to pregnant adult wistar rats (n=8) in the third week of gestation. Behavioural studies such as the rotarod test were carried out on the neonatal animals (n=5) to test their motor function at postnatal day twentyeight (P28). Electrophysiological recordings were carried out on the motor cortex (M1) to determine the significance of D2R inhibition on calcium neural activity. Immunofluorescence was done to demonstrate synaptic vesicle protein (SV) and microtubule associated protein kinases (MAP K) as a measure of synapses count and microtubule phosphorylation respectively. Results: Behavioural studies showed a decline in motor function of animals exposed to haloperidol in utero compared to the control. This motor deficit was accompanied by a significant increase in the Ca2+ neural activity of the motor cortex as shown by electrophysiological recordings. Immunofluorescence staining showed there was significant increase in the number of MAPK+ and SV+ cells in the motor cortex of haloperidol exposed animals compared to the control. Conclusion: These findings showed that early perturbation in dopaminergic system is associated with an increase in synapses and neuronal density, as well as an increase in phosphorylation of microtubules of neurons in the motor cortex.