Effects of long term consumption of sugar as part of meal on serotonin 1-a receptor dependent responses.

In view of an effect of high intake of sugar on brain serotonin (5-hydroxytryptamine, 5-HT) and a role of serotonin in the regulation of appetite, the present study concerns pre and postsynaptic responses to a selective 5-HT-1A receptor agonist 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) following long term consumption of sugar as part of meal in rats. Sugar diet was prepared by mixing standard rodent diet and table sugar in ratio of 3:1 (w/w) and rats were fed freely on this diet for five weeks. Control rats were fed freely on standard rodent diet. After five weeks 8-OH-DPAT at a dose of 0.5mg/kg/ml was injected to both the groups to compare effectiveness of the drug to elicit hyperphagia (presynaptic response) and elicited hyperactivity syndrome (postsynaptic response). Results showed that 8-OH-DPAT-induced forepaw treading and flatbody posture were smaller in sugar than normal diet treated rats. Conversely 8-OH-DPAT-induced hyperlocomotion was greater in sugar than normal diet treated rats. 4h Food consumption was greater in sugar than normal diet treated rats while 8-OH-DPAT-induced hyperphagia significant in normal diet treated rats was not observed in sugar diet treated rats. The results show a decrease in the effectiveness of pre as well as postsynaptic 5-HT-1A receptor dependent responses following long term consumption of sugar diet. Role of serotonin receptor responsiveness on mood and impaired adaptation to stress is discussed.