Intracranial self-stimulation behaviour in rats elicited by STN-stimulation

Abstract

High frequency stimulation (HFS) of the subthalamic nucleus (STN) has emerged as a powerful therapeutic strategy in the treatment of levodopa-sensitive motor symptoms in late stage Parkinson's Disease (PD). Recently, there has been an increasing number of case reports indicating that STN-HFS also influences various non-motor aspects of behaviour, such as cognition, mood and motivation. These consequences of STN-HFS could be attributed to associative, limbic and motor cortical and subcortical loops involving the STN, suggesting STN-HFS to directly affect both motor as well as non-motor behavioural functions. The question arises as to whether psychotropic sensations experienced during STN-HFS could have reinforcing impact on the behaviour. This concern is considered relevant since it is known that commonly abused drugs eliciting similar hedonic effects can act as positive reinforcers contributing to the development of addictive behavior. It therefore is tempting to speculate that STN-HFS would also affect the reward systems, largely depending on dopamin(DA)ergic transmission in the Nucleus accumbens (NAc). Likewise, in a previous in-vivo microdialysis study we could demonstrate transient increase in levels in DA and its metabolites in the NAc induced by STN-HFS in anaesthetised rats. So far, no animal behavioral study has been done to confirm this notion.