Response of thermoresponsive neurons of rat's hypothalamus during intracarotid infusion of prostaglandin E2.

We investigated the effect of intracarotid infusion of prostaglandin E2 (PGE2) on the single-unit activity of neurons in the preoptic and anterior hypothalamic (PO/AH) region. A total of 35 neurons in the PO/AH region were examined: 10 were warm-responsive neurons, 6 were cold-responsive neurons, and 19 were thermally insensitive neurons. In the warm-responsive neurons, the activities of 4 neurons were facilitated, while 3 neurons were inhibited and 3 neurons were not affected after intracarotid infusion of PGE2. In the cold-responsive neurons, the activities of 2 neurons were facilitated and 4 neurons were not affected by PGE2 infusion. Furthermore, 15 out of 19 thermally insensitive neurons were not affected by PGE2 infusion. These results suggest that thermoresponsive neurons of the PO/AH region respond well to intracarotid infusion of PGE2, compared with thermally insensitive neurons. However, the direction of neuronal response induced by intracarotid infusion of PGE2 could not be generally categorized based on the thermoresponsiveness of individual neurons.