Brain mesolimbic dopaminergic pathway

Should addiction be viewed as a brain disease Consider the implications of drug actions on the mesolimbic dopaminergic pathway. 

The mesolimbic dopamine pathway projects from dopaminergic cell bodies in the ventral tegmental area of the brainstem to axon terminals in limbic areas of the brain, such as the nucleus accumbens (Fig. 10—8). This pathway is thought to have an important role in emotional behaviors, especially auditory hallucinations but also delusions and thought disorder (Fig. 10—9)-... 

Fig. 19.3 Sagittal brain section illustrating dopaminergic pathways. I. Mesolimbic pathway (overactive in psychotic illness according to the dopamine hypothesis of schizophrenia).VTA= ventrotegmental area. 2. Nigrostriatal pathway (involved in motor control, underactive in Parkinson s Disease and associated with extrapyramidal motor symptoms). 3. Tuberoinfundibular pathway (inhibits prolactin release from the hypothalamus).

The mesolimbic dopaminergic system is the principal reward pathway in the brain. Amphetamine, cocaine, and opiates cause dopamine release in the nucleus accumbens. Food seeking and sexual behavior do so as well. 

There are three dopaminergic pathways in the brain the nigrostriatal, the mesolimbic-mesocortical and the tuberculoinfundibular. In addition to being a neurotransmitter, dopamine is a precursor of noradrenahne and adrenaline. 

Schizophrenia appears to be caused by an overactivity of dopamine pathways in certain parts of the brain such as the limbic system.2,23 This idea is based primarily on the fact that most antipsychotics block dopamine receptors, thereby reducing dopaminergic hyperactivity in mesolimbic pathways and other limbic structures (see the next section of this chapter). The increased dopamine influence underlying psychosis could be caused by excessive dopamine synthesis and release by the presynaptic neuron, decreased dopamine breakdown at the synapse, increased postsy-naptic dopamine receptor sensitivity, or a combination of these and other factors. 

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