Antagonism of etonitazene's effects in rats and pigeons.

The effects of etonitazene were studied in the pigeon under a mult FR FI schedule of food presentation and in the rat under a continuous avoidance-escape schedule. A low dose of etonitazene increased rates of responding by pigeons under the FI component of the multiple schedule, whereas higher doses produced dose-related decreases in rates of responding under both components of the multiple schedule. These effects were blocked by cyclazocine. Under the continuous avoidance-escape schedule, etonitazene produced only dose-related decreases in rates of responding by rats, and these decreases were blocked by naloxone.