Restraint alters temperature responses to cocaine in spontaneously hypertensive rats

The body temperature responses to intraperitoneal (IP) or intravenous (IV) cocaine in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats were examined under restrained and freely moving conditions. Resting values for rectal temperature (RT), in ambient temperatures of 22-24 degrees C, were significantly (p less than 0.01) higher in SHR than in WKY rats, under both restrained (39.19 +/- 0.07 vs. 38.01 +/- 0.06 degrees C) and freely moving (39.39 +/- 0.08 vs. 38.08 +/- 0.06 degrees C) conditions. Resting RT did not differ between restrained and freely moving conditions within a strain. An heterogeneity of RT response to both IV and IP cocaine was expressed by restraint in SHR. The SHR could be divided into animals which demonstrated hyperthermia to cocaine (SHRH) and those in which RT fell (SHRL) . However, cocaine produced hyperthermia in all freely moving SHR, regardless of the route of administration. The effects of IV cocaine in restrained WKY rats were similar to those in freely moving SHR, whereas IP cocaine decreased RT in all restrained WKY rats. Under conditions of restraint, divergent RT responses to cocaine were demonstrated following IV and IP administration in WKY rats, but not in SHR. These results indicate that restraint stress can significantly modify the body temperature responses to acute cocaine administration in both SHR and WKY rats.