Reward nucleus accumbens

A10 Ventral tegmental area Nucleus accumbens Reward... 

The nucleus accumbens is part of the limbic system. It receives dopaminergic input through the mesolimbic system that originates from cell bodies in the ventral segmental area (A 10 cell group). This mesolimbic dopaminergic pathway is part of the reward pathways. Drugs of abuse (cocaine, amphetamine, opiates or nicotine) have been shown to increase the level of dopamine release in these neurons. 

Initiation of behaviour Mesolimbic pathway to nucleus accumbens from VTA (AIO) Mesocortical pathways to prefrontal cortex from VTA (AIO) Animals Increases locomotor activity and intracranial self-stimulation Humans Hallucinations, psychoses (reward, reinforcement) Animals Decreases activity and self-stimulation Humans Reduces positive symptoms of schizophrenia D2 ... 

As a result of these observations it has been suggested that DA released in the nucleus accumbens is important in motivation by linking reward (especially when it is food) with the motor activity required to achieve it (Mogenson, Jones and Yim 1980). It is difficult, however, to distinguish a pure behavioural role for DA in actually initiating the sense of reward and motivation from its undisputed part in facilitating the motor response necessary to obtain the reward, e.g. a lever press in rats. 

Salamone, Cousins and Snyder (1997) in fact suggest that the function of DA in the nucleus accumbens should not be described by terms such as motivation, reinforcement and reward. Rather it should be considered to mediate the higher-order motor and sensory processes that are important for the activation of aspects of motivation and responsiveness to conditioned stimuli. 

Vaccarino, F.J. Bloom, F.E. and Koob, G.F. Blockade of nucleus accumbens opiate receptors attenuates intravenous heroin reward in the rat. Psychopharmacology 86 37-42, 1985. 

The neuroehemical sites for psyehomotor stimulant reward are likely to be the presynaptic dopamine terminals located in the region of the nucleus aeeumbens, frontal cortex, and other forebrain structures that originate in the ventral tegmental area. Note, however, that intraeranial self-administration of eoeaine is elicited from the frontal cortex, but not from the nucleus aeeumbens (Goeders and Smith 1983). Thus, eoneomitant activation of structures other than the nucleus accumbens may be an important part of the circuitry involved in initiation of cocaine intravenous self-administration, as has been hypothesized for the opiates (Smith and Lane 1983 Smith et al. 1982). 

O Virtually all abused substances appear to activate the same brain reward pathway. Key components of the reward pathway are the dopamine (DA) mesocorticolimbic system that projects from the ventral tegmental area (VTA) and the nucleus accumbens (NA) to the prefrontal cortex, the amygdala, and the olfactory tubercle (Figs. 33-3 and 33-4).5 Animal studies... 

Tzschentke T., Schmidt W. (2000). Functional relationship among medial prefrontal cortex, nucleus accumbens, and ventral tegmental area in locomotion and reward. Crit. Rev. Neurobiol. 14, 131-42. 

Sellings, L.H. and Clarke, P.B., Segregation of amphetamine reward and locomotor stimulation between nucleus accumbens medial shell and core, J. Neurosci., 23, 6295, 2003. 

Carlezon, W.A., Jr. and Wise, R.A., Rewarding actions of phencyclidine and related drugs in the nucleus accumbens shell and frontal cortex, J. Neurosci., 16, 3112, 1996. 

Robledo P., Maldonado-Lopez R., Koob G. Role of the dopamine receptors in the nucleus accumbens in the rewarding properties of cocaine. Ann. N.Y. Acad. Sci. 654 509, 1992. 

Nucleus accumbens A forebrain structure innervated by a branch of the mesolimbic dopaminergic tract, implicated in reward and motivation. 

Fiorino DF, Coury A, Fibiger HC and Phillips AG (1993). Electrical stimulation of reward sites in the ventral tegmental area increases dopamine release in the nucleus accumbens of the rat. Behavioral Brain Research, 55, 131-141. 

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