A microgram dose of diazepam produces specific inhibition of ambulation in the rat

There is considerable consistency in the experimental literature showing that non-sedating doses of benzodiazepines can enhance the consumption of food, water and salt solutions. It is of great interest, therefore, that in a previous report low dose treatments with diazepam were found to significantly suppress the level of consumption of a palatable 0.005 M sodium saccharin solution in nondeprived male rats. The present study was designed to elucidate the behavioral characteristics of the inhibitory action of low dose diazepam treatments. Food consumption and general activity measures were chosen for analysis to examine the possibilities that low dose diazepam treatments might suppress ingestive behavior in a general way, or that the treatments might affect nonconsummatory responses including components of spontaneous motor activity. The results of two experiments succeeded in locating a highly specific inhibitory effect produced by 100 micrograms/kg diazepam. First, food consumption was not inhibited. Instead, 1.0 mg/kg diazepam produced significant elevations in food intake in both food-deprived and nondeprived animals. Second, vertical activity (rearing) and fine body movements were unaffected over the dose-range 0.1-3.0 mg/kg diazepam. Hence, low dose treatments with diazepam did not produce a generalised nonspecific behavioral depression. However, 100 micrograms/mg diazepam significantly inhibited coarse activity (measured automatically) and the corresponding ambulation measure (recorded by direct observation). The effect was present throughout a 1 hr test period and did not interact with the declining baseline level of activity. The results therefore confirm the presence of low dose diazepam-induced behavioral inhibition in quite a different context from the saccharin solution consumption study.(ABSTRACT TRUNCATED AT 250 WORDS)