Effects of 8-OH-DPAT,buspirone and ICS 205-930 on feeding in a novel environment: comparisons with chlordiazepoxide and FG 7142

Previously, the 5-hydroxytryptamine (5-HT)_1A receptor agonists 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and buspirone and the 5-HT₃ receptor antagonist ICS 205-930 have been shown to exert anxiolytic-like effects in several animal models. In the experiments reported here the effects of these compounds on feeding behaviour and food preference in a novel environment were examined, and compared with the effects of the anxiolytic drug chlordiazepoxide and the anxiogenic compound FG 7142. Chlordiazepoxide significantly reduced the latency to begin eating and prolonged the total time spent eating; chlordiazepoxide also abolished food neophobia, by significantly increasing the time spent eating novel food items. In contrast, FG 7142 significantly increased eating latency and reduced eating duration. Both 8-OH-DPAT and buspirone significantly enhanced eating duration, but unlike chlordiazepoxide eating was directed only towards the familiar food. In addition buspirone, but not 8-OH-DPAT, reduced eating latency. ICS 205-930 significantly increased eating latency and reduced eating duration; however, these effects were observed only at the lowest dose tested. All of these behavioural effects were observed only when animals were unfamiliar with the testing situation, and cannot be accounted for in terms of changes in mechanisms controlling hunger. The behavioural paradigm used in these experiments may induce a competition between the drives to explore a novel environment and to eat. It is suggested that the tendency of buspirone and 8-OH-DPAT to suppress exploratory activity may thus result in enhanced feeding duration. Similarly enhanced exploratory activity induced by ICS 205-930 may result in animals taking longer to contact food, and spending less time eating. These results serve to illustrate that compounds which have different pharmacological actions, but which have been shown in other tests to have anxiolytic-like activity, can induce different behavioural effects. The suitability of this behavioural test for assessing anxiolytic effects of drugs is discussed.