Effect of loss of dopaminergic innervation of the subthalamic nucleus on motor behavior of rats

Abstract

At present Parkinson’s disease is considered as a dysfunction of the central nervous system that affects the
basal ganglia. The more prominent anatomopathologic characteristic of this illness is: the degeneration of the dopaminergic
cells of the substantia nigra pars compact (SNc), gliosis and the eosinofilic inclusion bodies. The physiologic relevance
of the direct modulation of the neurons of the subthalamic nucleus (STN) by dopaminergic neurons of SNc becomes
a polemic topic. The main objective of this work was to evaluate the effect of the selective lesion of the dopaminergic
neurons that innervate the STN on the motor behavior. The animals were divided in three experimental groups: I: with
6-OHDA lesion of SNc (n = 20); II: with loss of the dopaminergic innervations of the STN for injection of 6-OHDA in this
nucleus (n = 30) and III: healthy animal (n = 20). One month after having injected the neurotoxin, the rotational activity
induced by D-amphetamine and apomorfine and the changes in skilled forelimb use were evaluated. The behavioral and
morphological studies evidenced that the injection of 6-OHDA in NST, induces a partial loss of neurons in SNc, in the
injured hemisphere. The loss of the dopaminergic innervations of STN provokes an asymmetry in the motor behavior of
the animals that provoke a worse acting in the skilled forelimb use and an increase in their rotating behaviour, ipsilateral
to the injured hemisphere induced by injection.