Acetaminophen Effects on Behavioral Thermoregulation in Albino Rats

Acetaminophen (N-Acetyl-p-aminophenol) was administered intra-peritoneally to 15 Sprague-Dawley rats partitioned into 3 studies (5 rats per study) using a within-subjects, repeated-measures reversal design. Behavioral thermoregulation was assessed in a cold Skinner Box using 5-sec. exposures of microwave radiation [Specific Absorption Rate = 0.34 Watts/kg/(mW/cm²)] as reinforcing stimuli under a fixed-interval 2-min. schedule of positive reinforcement. Doses of 10, 20, 30, 40, and 50 mg/kg (in solutions of 1%, 2%, 3%, 4%, and 5%) acetaminophen showed stable rates of operant responding for heat compared with significant changes in rates for comparable doses of aspirin in a 1993 study by Vitulli, et al. Weight reductions and temperature increases varied significantly with before-session and after-session measures, respectively. 1994–95 biochemical data of Murphy, et al. from humans following aspirin or acetaminophen ingestion which affect thermoregulation and sleep patterns are discussed in conjunction with behavioral data from rats.