Role of vagal afferents in the mediation of chlorpyrifos-induced fever in the rat

Subdiaphragmatic, bilateral vagotomy (VG) attenuates fever, suggesting that vagal afferents may activate febrile processes in the CNS, Rats exposed to the organophosphate (OP)-based insecticide chlorpyrifos (CHP) undergo a prolonged fever. To test the hypothesis that CHP-induced fever involves vagal pathways, the febrile effects of CHP were assessed in male VG and sham VG (SH) rats. Core temperature (T-c) and motor activity (MA) were monitored telemetrically, The corn oil vehicle (CO) or 20 mg/kg CHP was given at 1400 h by gavage. CHP resulted in hypothermia in SH and VG rats that lasted similar to 12 h. This was followed by a similar to 0.5 degrees C rise in T-c of the SH group throughout the day. However, T-c of VG rats exposed to CHP was only marginally elevated. Baseline T-c of VG rats was reduced during the dark phase compared to SH rats whereas MA was similar in both groups. It appears that peripheral activation of the CNS via vagal afferents has a key role in the mediation of CHP-induced fever. Published by Elsevier Science Ltd.