Effects of endogenous pyrogen and prostaglandin E2 on hypothalamic neurons in guinea pig brain slices

To investigate the direct effects of endogenous pyrogen (EP) and prostaglandin E2 (PGE2) on the activity of neurons in the preoptic and anterior hypothalamic (PO-AH) region, single-unit activity was recorded from brain tissue slices prepared from the PO-AH region of guinea pigs. When EP was applied into the perfusate 18% of warm-responsive neurons decreased their activity, and 23% of warm-responsive neurons increased their activity. Most of the thermally insensitive neurons did not respond to EP. PGE2 inhibited 29% of warm-responsive neurons and facilitated 15% of them. Moreover, when EP and PGE2 were applied to the same neurons at different times, the same directions of changes in neuronal activity were observed in 72% of total neurons examined. These results suggest that EP and PGE2 change the neuronal activity of the thermoresponsive neurons in the PO-AH region involved in fever induction. However, by these results, the direction of neuronal response induced by these substances could not be generally categorized based on the thermoresponsiveness of the individual neuron.