Effects of substance P and shorter analogs on body temperature in the rat.

The thermoregulatory effects of intraperitoneally administered substance P (SP1-11) (250 micrograms/kg), or equimolar quantities of SP1-4 and SP5-11 were studied in conscious rats at an ambient temperature of 4 degrees C. SP1-11 produced hypothermia, whereas SP1-4 and SP5-11 had no influence. The hypothermic effect of SP1-11 was partially antagonized by naloxone. Thus, an opiate-dependent step seems to be involved in the action of SP1-11.