Effects of caffeine on tactile startle in rats

The effects of graded doses of caffeine (1.5 to 100 mg/kg) on tactile startle responding were examined in rats given 121 air-puff stimuli at 15 second intervals. Doses of caffeine up to 50 mg/kg were found to significantly increase tactile startle consistently throughout the 30 minute test session. The highest dose of caffeine tested initially increased and subsequently decreased startle amplitude. An examination of the time-course of the augmentation in startle produced by 12 mg/kg caffeine revealed that the effect was maximal 15 minutes after the subcutaneous injection. The results are discussed in relation to the differences between the effects reported here for caffeine and the known effects of other psychostimulants.