A sensitive open field measure of anxiolytic drug activity

Anxiolytic drugs including diazepam (DZP), chlordiazepoxide (CDX), pentabarbitol (PB) and ethanol (EtOH) produce specific alterations in the behavior of fasted rats given access to a single food pellet secured in the center of a novel open field environment. These drugs increase the total amount of food eaten in a 15 min test and the mean amount eaten per approach to the food pedestal. This latter effect appears to be the more sensitive index of anxiolytic drug action and occurs at doses which have no effect on rearing or grooming. DZP was effective following either acute or chronic (15 day) treatment at doses which have no effect on the food consumption by fasted rats tested in their home cages. The effects of the sedative benzodiazepine, flurazepam, were similar to those of DZP but were not statistically significant. Behavioral effects similar to those of DZP were seen in animals receiving additional handling prior to testing or in animals habituated to the open field. Neither the anti-psychotic haloperidol nor morphine mimicked the actions of DZP.