Effects of placebo (saline) injections on core temperature in the rat.

1. Core temperature was telemetrically measured in 15 rats before (i.e., at baseline) and at 10-min intervals for 120 min following the injection of normal saline (1 ml/kg ip) or "no injection." 2. The sample exhibited a mean temperature increase of 0.60 +/- 0.10 degree C (mean +/- SEM) following injection. 3. This differed significantly from the mean increase of 0.13 +/- 0.03 degree C following "no injection" (p less than 0.001). 4. The injection of saline (1 ml/kg) affected a mean rise in core temperature of 0.55 +/- 0.07 degree C (p greater than 0.000001) in 46 animals in a second experiment. 5. These data indicate that routine handling and a simple injection comprise significant and measurable stress which must be controlled in neuropharmacological studies employing a thermoregulation paradigm.