EP 3 and EP 4 receptor mRNA expression in peptidergic cell groups of the rat parabrachial nucleus

Abstract

This study examines the distribution of prostaglandin E 2 receptors of subtype EP 3 and EP 4 among brain stem parabrachial neurons that were characterized with respect to their neuropeptide expression. By using a dual-labeling in situ hybridization method, we show that preprodynorphin mRNA expressing neurons in the dorsal and central lateral subnuclei express EP 3 receptor mRNA. Such receptors are also expressed in preproenkephalin, calcitonin gene related peptide and preprotachykinin mRNA positive neurons in the external lateral subnucleus, whereas preprodynorphin mRNA expressing neurons in this subnucleus are EP receptor negative. In addition, EP 3 receptor expression is seen among some enkephalinergic neurons in the Kölliker-Fuse nucleus. Neurons in the central part of the cholecystokininergic population in the regions of the superior lateral subnucleus express EP 4 receptor mRNA, whereas those located more peripherally express EP 3 receptors. Taken together with previous findings showing that discrete peptidergic cell groups mediate nociceptive and/or visceral afferent information to distinct brain stem and forebrain regions, the present results suggest that the processing of this information in the parabrachial nucleus is influenced by prostaglandin E 2. Recent work has shown that prostaglandin E 2 is released into the brain following peripheral immune challenge; hence, the parabrachial nucleus may be a region where humoral signaling of peripheral inflammatory events may interact with neuronal signaling elicited by the same peripheral processes.