UBC Theses and Dissertations
Involvement of dopamine in feeding behaviours Blackburn, James Robert
This study investigated the involvement of the neurotransmitter dopamine in feeding behaviours. A conditioned feeding paradigm was used to study incentive responses. After conditioning rats responded to a conditional stimulus (CS+) by approaching a feeding site. Approach responses were attenuated by 0.4 or 0.6mg/kg of the dopamine antagonist pimozide. Neurochemical investigation revealed that exposure to the CS+ increased dopamine turnover in the forebrain. Thus, dopamine appears to be actively involved in the initiation of appetitive responses. In contrast, another experiment indicated that consumption of a liquid diet was not altered by up to 0.6mg/kg pimozide. These data were interpreted as supporting an "incentive-response hypothesis" of dopamine function, which states that "When an animal observes an incentive stimulus, the release of dopamine in the forebrain is increased, resulting in approach to the stimulus by the animal. Once the animal is in contact with a goal object, consummatory reactions occur which are not mediated by dopamine systems". A final experiment investigated the activity of dopamine systems following ingestion. After one hour during which food pellets or liquid diet were available to rats, dopamine turnover was increased in the n. accumbens and the striatum, relative to non-fed animals. No increase was observed in the brains of rats which had consumed similar quantities of saccharin solution. Thus, the increase observed following consumption of pellets or liquid diet could not be attributed to motor or "reward" effects. It was concluded that in addition to their involvement in incentive-responding, dopamine systems are also affected by the ingestion of nutrients.