ANXIOGENIC ACTION OF CAFFEINE - AN EXPERIMENTAL-STUDY IN RATS

The anxiogenic action of caffeine (10, 25 and 50 mg/kg, i.p.) was inve stigated in rats and compared with that of yohimbine (2 mg/kg, i.p.). The experimental methods used were the open-field, elevated plus-maze, social interaction and novelty-suppressed feeding latency tests. Caff eine produced a dose-related profile of behavioural changes, which wer e qualitatively similar to those induced by yohimbine and which indica te an anxiogenic activity in rodents. Thus, both the drugs reduced amb ulation and rears, and increased immobility and defaecation in the ope n-held test. They decreased the number of entries and time spent on th e open arms of the elevated-plus maze, reduced social interaction in p aired rats and increased the feeding latency in an unfamiliar environm ent in 48-h food-deprived rats. Lorazepam, a well known benzodiazepine anxiolytic agent, attenuated the anxiogenic effects of caffeine and y ohimbine. Subchronic administration of caffeine (50 mg/kg, i.p.) for 2 1 days, in different groups of animals, induced a significant degree o f tolerance in the elevated plus-maze test, which was statistically si gnificant after 14 and 21 days' treatment. Yohimbine, however, did not induce similar tolerance. When caffeine (50 mg/kg, i.p.) was withdraw n after 21 days' administration, to a separate group of rats, signific ant withdrawal anxiety was observed 48 h later as noted in the elevate d plus-maze test. The investigations support clinical evidence of caff eine-induced anxiety, tolerance to anxiety on continued use, and withd rawal anxiety in chronic caffeine-containing beverage users.