Temperature responses of lambs after centrally injected prostaglandins and pyrogens

It has been proposed that pyrogens may produce their febrile response by the release of prostaglandins in the hypothalamus. To test this theory, prostaglandin E1 (PGE1) was injected into a lateral ventricle in dosages of 2-200 ug into conscious newborn lambs, ages 4-168 h. Fiifteen of 40 injections were followed by rises in rectal temperature but the remainder were followed either by no change or by falls. Temperature responses did not appear to be related to age and a variation in responses to the same dosage of PGE was often observed. Some lambs were able to develop fevers in response to intravenous bacterial pyrogen yet did not develop fever after intraventricular PGE 1. Intraventricular bacterial pyrogen (3 ng) produced no change in body temperature, whereas three of four injections of 300 ng pyrogen caused fever. The results suggest that the newborn lamb may be able to develop a fever independently of the central involvement of PGE1. Alternatively, the intraventricular approach may not be useful for the study of the central control of body temperature in the newborn lamb.