Serotonin manipulations and the structure of feeding behaviour.

Experimental manipulations of 5-HT by central or peripheral procedures produce clear effects on food intake. Interpretation of these effects can be improved by monitoring changes in the behavioural structure of feeding and by designing experiments which adjust the contextual and temporal dimensions of feeding. Experimental techniques include micro-analysis of behaviour, macro-analysis of meal patterns, dietary self-selection of macro-nutrients, analysis of appetite and satiety sequences, appetitive and consummatory aspects of instrumental performance and dietary-induced hyperphagia. Using these procedures in conjunction with various pharmacological treatments including the administration of tryptophan, 5-hydroxy-tryptophan, 5-HT, re-uptake blockers, synaptic releasers, synthesis blockers, receptor blockers and others it has been demonstrated that 5-HT manipulations give rise to a specific constellation of changes in feeding parameters. The most prominent changes following peripheral or central (paraventricular nucleus) injections are a reduction in meal size and a curtailment of eating rate. These changes can be distinguished from those induced by other pharmacological treatments and are consistent with a modulation of the process of satiation and the state of satiety. Changes in feeding induced by 5-HT manipulations are not secondary to non-specific behavioural alterations.