Mesolimbic-mesocortical tracts

Mesolimbic-mesocortical tracts—cell bodies in midbrain project to cerebrocortical... 

Postmortem studies of patients with idiopathic Parkinson s disease demonstrate cell loss in the striatal system (A-9), directly implicating this tract vis-a-vis the neuroleptic-induced pseudoparkinsonian side effects. The assumption that psychosis is related to the A-10 system is made by exclusion. Evidence also indicates that clozapine may differentially block DA pathways. Specifically, it seems to act on the mesolimbic dopaminergic system (A-10), while being relatively inactive in the striatal system (A-9) however, this remains controversial. Chronic administration of clozapine decreases the firing rate of A-10 mesocortical tract dopamine neurons... 

The working assumption that the striatal system is only involved with extrapyramidal function (e.g., parkinsonian side effects, dystonias, and TD) and that the mesolimbic or mesocortical systems are only involved with psychosis may be an oversimplification. Many of the neuroanatomical studies on the identified dopaminergic tracts are done with rats. In the monkey, by contrast, there are many more DA tracts that are either absent in the rat or at least markedly different human systems could be different from the rat s or monkey s. Understanding the neuropharmacology of the antipsychotics is further complicated, given that neither the mesolimbic-mesocortical nor the striatal systems are homogeneous but may also include various subsystems. 

Chlorprothixene (25 to 50 mg p.o. t.i.d.) is indicated in the management of manifestations of psychotic disorders. Chlorprothixene is absorbed rapidly, distributed throughout the body, is bound to plasma protein to the extent of 90 to 95%, and is excreted mostly unchanged via the biliary tract in feces. It exerts its antipsychotic effects in part by blocking dopamine receptors in the mesolimbic and mesocortical systems and like chlorpromazine, it produces movement disorders such as parkinsonism (see also Table 2). 

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