Sympathetic-related neurons in the preoptic region of the rat identified by viral transneuronal labeling

The viral transneuronal labeling method was used to localize sympathetic-re lated neurons in the preoptic region following pseudorabies virus (PRV) inj ections into either the superior cervical ganglion, stellate ganglion, celi ac ganglion, or adrenal gland of rats. A general pattern of infection was d etected. First, neuronal labeling was found in the medial preoptic area, me dial preoptic nucleus, median preoptic nucleus, and lateral preoptic area, and then it spread to the anteroventral periventricular, anteroventral preo ptic, and parastrial nuclei. Finally, the forebrain circumventricular organ s: organum vasculosum of the lamina terminalis (OVLT) and subfornical organ (SFO) became infected. Neuropeptide-containing preoptic neurons were analy zed following PRV injections in the stellate ganglion. Some thyrotropin-rel easing hormone and neurotensin neurons were labeled, but none of the calcit onin gene-related peptide, cholecystokinin, corticotropin-releasing factor, galanin, luteinizing hormone-releasing hormone, enkephalin, substance P, o r tyrosine hydroxylase neurons were PRV infected. Two major sympathetic net works appear to be represented in the preoptic region. One is linked to the OVLT, SFO, and anteroventral third ventricular (AV3V) region, sites previo usly implicated in fluid and electrolyte balance as well as cardiovascular control. The other descending sympathetic pathway appears to target the med ial preoptic nucleus as its key nodal point, receiving inputs from infralim bic cortex and limbic regions, such as the lateral septum, medial nucleus o f the amygdala, subiculum, and amygdalohippocampal area, and then, projecti ng caudally to the hypothalamus and brainstem. This second sympathetic netw ork may subserve affiliative, defensive and sexual behaviors. (C) 1999 Wile y-Liss, Inc.