Abstract Neurotransmission in rat cerebellum following fluid percussion injury (FPI) was studied by extracellular recording method. An increased amplitude of population spikes from presynaptic mossy fibers was detected at 3 days after FPI. However, there were no differences at 1 h, 1 day, 1 week or 2 weeks after FPI compared to naı̈ve controls. An enhanced amplitude of the population spikes, as well as the after hyperpolarization component from presynaptic response of the parallel fibers, was seen in the groups at 3 days and 1 week post FPI, but not in other groups. These results indicate a presynaptic hyperexcitation was induced by FPI within a specific time window. This hyperexcitability may contribute to the reported loss of Purkinje cells after FPI.