Studies on the pyrexic effect of PGE1 injected into the region of the cochlear nuclei

In 30 of 33 unanesthetized rats, unilateral injection of PGE1 (100 ng in 1 microliter) into or near the cochlear nuclei (CN) produced a body temperature increase of at least 0.5 degrees C. Usually, the rise started within the first minute after injection. Bilateral destruction of the highly PGE1-sensitive anterior hypothalamic/preoptic region (AH/PO) eliminated the response. In approximately two-thirds of rats in which concentrated dye or 3H-PGE1 was injected into CN, there was evidence that a small portion of the injectate had rapid access to the AH/PO. In the remaining rats, the tracer material did not reach AH/PO tissue. In the rats involved in the tracer studies, there was no correlation between the magnitude of the response to PGE1 injected into CN and the extent of transport of tracer from CN to AH/PO. The results suggest that PGE1 injected into CN produced pyrexia through an action on tissue at or near the injection site and that neuronal pathways in AH/PO are necessary for the expression of the response.