Dopamine

Dopamine is a catecholamine neurotransmitter that is involved in many aspects of food intake, feeding behavior, food motivation, and appetite. Whole forebrain dopamine depletions are known to produce aphagia (i.e., lack of eating). Although this effect has been erroneously attributed to actions on the so-called “reward” system, considerable evidence indicates that dopamine depletions that are restricted to the nucleus accumbens do not generally impair food intake. In fact, the critical dopamine terminal area at which dopamine depletions or dopamine antagonism impairs food intake is the ventrolateral neostriatum or ventral putamen. This region is generally thought to be somotatopically organized and appears to regulate specific aspects of food-intake behavior. Dopmaine depletions in this region impair the motor components of feeding, as demonstrated by impairments in feeding rate (in grams/min), food handling, and oral motor dysfunctions. In contrast to these effects of neostriatal dopamine depletions, accumbens dopamine depletions or dopamine antagonism leave appetite intact but appear to reduce [Page 196]behavioral activation and the tendency to work for food; these manipulations reduce the exertion of effort in food-seeking behavior, and alter effort-related choice by shifting organisms toward food sources that do not require much work to obtain.

While all of the effects of dopamine have not been determined, this neurotransmitter is involved in controlling appetite.

Dopamine in the hypothalamus is also involved in the regulation of food intake. In this case, dopaminergic involvement appears to be more important for features of appetite regulation. Many well-known appetite suppressants, such as amphetamines, mazindol, and phenylpropanolamine, facilitate dopamine transmission by increasing release, blocking uptake, or both.

Several drugs that are known to be appetite suppressants act as dopamine agonists. The antidepressant buproprion, which blocks dopamine uptake, can suppress appetite, while dopamine antagonists have been shown to increase body weight gain. There is evidence that enhancement of dopamine transmission in perifornical/lateral hypothalamus can act to suppress appetite, and this is at least one of the mechanisms that is thought to be involved in the effects of appetite suppressants that act on dopamine. In addition, there is evidence that alterations in dopamine function are related to aspects of obesity.

Dopamine is a neurotransmitter that is involved in a wide variety of functions related to food intake. Each distinct dopamine terminal area has specific functions related to eating (i.e., appetite regulation, behavioral activation, effort processes, decision making, compulsiveness, motoric functions), and for that reason, dopamine appears to be involved in so many different aspects of normal and pathological features of food consumption.