Thermoregulatory behaviour induced by intrathecal injection of substance P in the rat

A climatic chamber at an ambient temperature (Ta) of 20 and 30 degrees C was used to examine the effect on thermoregulation in the rat of substance P (SP) injected into the lumbar subarachnoid space via a chronic indwelling catheter. In the first series of experiments, the rats had no access to the lever in the climatic chamber. At Ta of 20 degrees C, intrathecal (IT) injections of SP or saline had no effect on body temperature. In the second series of experiments, the rats had access to the lever which actuated a fan that drew cool outside air into the chamber. At Ta 20 and 30 degrees C, IT injection of SP stimulated the activation of bar-pressing to obtain air for cooling. This behaviour was more evident when Ta was 30 degrees C. Under similar conditions, IT injection of saline did not activate bar-pressing. These findings suggest that spinal cord SP receptors may be involved in the control of body temperature.