Figure 1.
Yohimbine dose-dependently decreases conditioned freezing and bar-press suppression, but does not enhance long-term extinction retention. (a) A high dose of yohimbine (5.0 mg/kg, i.p.) significantly reduced freezing and bar-press suppression during extinction. (b) A reduced dose of yohimbine (2.0 mg/kg, i.p.) decreased freezing, but not bar-press suppression, during extinction. (c) The lowest dose of yohimbine (1.0 mg/kg, i.p.) decreased freezing, but not bar-press suppression, during extinction. No dose of yohimbine enhanced long-term retention of extinction on either measure of fear. Data are shown in blocks of 2 trials. * p < 0.05.