2.3. Assessment of the head-twitch response

The head twitch response (HTR) was assessed using a head-mounted magnet and a magnetometer coil, as described previously (Halberstadt and Geyer, 2013, 2014). Food and water were provided ad libitum, except during behavioral testing. 25CN-NBOH was administered immediately prior to the start of a 30-min assessment. Total HTR counts were analyzed by non-linear regression, as well as by one-way analysis of variance (ANOVA) and post-hoc Tukey’s test. The alpha level was set at 0.05.