The distribution of DA in the brain is more restricted that NA. A large proportion of DA content of the brain is found in the corpus striatum (a part of the extra pyramidal motor system concerned with coordination of movement), in certain parts of the limbic sys tem and in the hypothalamus.

DA-ergic pathways in the CNS

DA-ergic neurons form 3 main system. About 75% of the DA in brain , occurs in the nigrostriatal pathway, with cell bodies in the substantia

nigra and the axons termi­na­ting in the corpus striatum (Fig.2). These fibers run in the medial forebrain bundle along with many NA and 5-HT-containing fibers.

The second important system is the mesolimbic/ mesocortical pathway, whose cell bodies occurring in groups in the midbrain with fibers projecting, also via the medial forebrain bundle, to parts of the limbic system, especially the nucleus accumbens and amygdaloid nucleus and to the cortex.

Finally, the tuberohypophyseal system is a group of short neurons running from the arcuate nucleus of the hypothalamus to the median eminence and pituitary gland, the secretion of which they regulate.