Effects of muscimol on reflex eyelid responses. A, Effects of a single injection of muscimol into the posterior interpositus nucleus (1.25 μg/kg), on the latency (a) and amplitude (b) of air-puff-evoked (100 msec; 3 kg/cm²) eyelid responses. Time after drug injection is indicated. B, Quantitative data from the experiment in A, collected (n = 5 times) from the three nonconditioned animals. Data were normalized by dividing each collected value by the corresponding value obtained at 0 min. Means ± SEM latency (unfilled circles and dotted line) and amplitude (filled circles and dashed line) of evoked eyelid responses are indicated. Note that the amplitude of air-puff-evoked eyelid responses was completely recovered 24 hr after muscimol injection. C, Latency (a) and amplitude (b) of reflex eyelid responses to the same air puff used in A and B, but presented as part of a CS-US pair, after the injection of muscimol (1.25 μg/kg).The drug was injected 20 min before the fifth conditioning session (S5). D, Quantitative data from the experiment in C, collected from three animals. Muscimol was injected before the fifth and sixth conditioning sessions. Data were normalized by dividing each collected value by the maximum value obtained in any of the conditioning sessions. Note a significant decrease in the amplitude of the evoked eyelid response (filled circles and dashed line), but not in its latency (unfilled circles and dotted line). ^*p < 0.05; ^***p < 0.001 (ANOVA).