Attenuation of somatodendritic responses to 8-hydroxy-2-di-n-propylamino tetralin following long-term dietary sugar consumption in rats

To determine changes in response to a selective serotonin-1 A receptor agonist 8-hydroxy-2-[di-n-propylamino] tetralin [8-OH-DPAT] following long-term consumption of sugar as part of meal in rats. Experimental study. The Department of Biochemistry, University of Karachi, from June to August 2005. The study was conducted on 24 male albino Wistar rats. Sugar containing diet was prepared by mixing standard rodent diet and table sugar in the ratio of 3:1 [w/w] and rats were fed freely on this diet. Control rats were fed freely on standard rodent diet. After five weeks of treatment, control and sugar diet treated animals were injected with 8-OH-DPAT, at a dose of 0.5 mg/ml/kg, to monitor the effects of drug on food intake and brain serotonin [5-hydroxytryptamine, 5-HT] metabolism. Dissected neural tissue was analyzed electrochemically and findings were compared by Newman-Keuls test. Administration of 8-OH-DPAT elicited hyperphagia and decreased 5-HT metabolism in normal diet treated rats. The neurochemical and hyperphagic responses to 8-OH-DPAT were smaller in sugar than normal diet treated animals suggesting a downregulation of somatodendritic responses in sugar diet treated animals. A decrease in serotonin metabolism but not an increase in the responsiveness of somatodendritic 5-HT-1A receptors is involved in sugar-rich diet induced hyperphagia

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