TRANSNEURONAL LABELING OF CNS NEUROPEPTIDE AND MONOAMINE NEURONS AFTER PSEUDORABIES VIRUS INJECTIONS INTO THE STELLATE GANGLION

The viral transneuronal labeling method was used in combination with i mmunohistochemical procedures to identify CNS neuropeptide and monoami ne neurons that innervate the sympathetic preganglionic neurons (SPNs) which project to the stellate ganglion-the principal source of the sy mpathetic supply to the heart. Transneuronal labeling was found at thr ee CNS levels: spinal cord, brainstem, and hypothalamus. In the thorac ic spinal cord, apart from the pseudorabies virus (PRV)-labeled stella te SPNs, PRV-labeled neurons were localized in laminae I/II, IV, V, VI I, and X as well as in the lateral spinal nucleus and lateral funiculu s. In the C1-C4 spinal segments, labeled neurons were found in the lat eral funiculus as well as laminae V and VII of the spinal gray matter. PRV-labeled cells were identified in lamina V and the dorsolateral fu niculus of the lumbar spinal cord. Three medullary areas were consiste ntly labeled: rostral ventromedial medulla (RVMM), rostral ventrolater al medulla (RVLM), and caudal raphe nuclei. The greatest concentration of labeling was found in the RVMM. This projection arose from adrener gic, serotonergic (5-HT), thyrotropin releasing hormone (TRH), substan ce P, somatostatin, enkephalin, and vasoactive intestinal peptide (VIP ) immunoreactive neurons. The RVLM projection originated mainly from C 1 adrenergic neurons, some of which contained immunoreactive neuropept ide Y (NPY). C3 adrenergic-NPY neurons lying near the floor of the 4th ventricle were also labeled. Enkephalin-, somatostatin- and VIP-immun oreactive RVLM neurons also contributed to this projection. 5-HT neuro ns of the caudal raphe nuclei (raphe pallidus, raphe obscurus, and rap he magnus) were labeled; some of these contained substance P or TRH-im munoreactivity with an occasional neuron staining for all three putati ve neurotransmitters. In the pens, catecholamine neurons in the A5 cel l group, subcoeruleus and Kolliker-Fuse nuclei were labeled. The midbr ain contained relatively few infected cells, but some were present in the Edinger-Westphal and precommissural nuclei. Forebrain labeling was concentrated in the paraventricular hypothalamic nucleus (PVN) with l esser amounts in the lateral hypothalamic area (LHA) and the periforni cal region. In the PVN, oxytocin-immunoreactive neurons accounted for the greatest chemically-defined projection while corticotrophin releas ing factor (CRF), vasopressin-, and angiotensin II-immunoreactive neur ons provided successively lesser inputs. In the LHA, angiotensin II-im munoreactive neurons were labeled. In summary, this study provides the first detailed map of the chemically-coded CNS neurons involved in th e control of the cardiosympathetic outflow.