AV3V neurons that send axons to hypothalamic nuclei respond to the systemic injection of IL-1β

The single neuron activity in the anteroventral region of the third ventricle (AV3V) was extracellularly recorded in urethan and α-chloralose anesthetized rats. Electrical stimulation of the medial preoptic area (mPOA) and the paraventricular nucleus (PVN) revealed a reciprocal neural connection between the AV3V and these hypothalamic nuclei with an ipsilateral preponderance. All the AV3V neurons, which were antidromically activated by the stimulation of the mPOA or the PVN, altered their activity after the systemic injection of interleukin (IL)-1β. On the other hand, only about 60% of the AV3V neurons that showed orthodromic responses were affected by IL- 1β. In seven of nine AV3V neurons that were electrophysiologically identified to send their axons to the mPOA or the PVN, the recombinant human IL-1β-induced excitation and inhibition were attenuated by a local application of sodium salicylate through multibarreled micropipettes. These results suggest that the AV3V neurons alter their activity in response to the blood-borne IL-1β, at least in part, through a local synthesis of prostanoids and then send the information to the mPOA and PVN.