RESUMEN
Herpes viruses have been used as retrograde transsynaptic tracers to identify pathways from the CNS to specific target tissues. We used herpes simplex virus to identify central nervous system neurons responsible for control of the kidney. Herpes simplex type 1 or herpes simplex type 2 was injected into rat kidneys and herpes simplex type 1 was microinjected into hamster and guinea pig kidneys. After three to seven days, ganglia, spinal cords and brains were examined using immunohistochemistry to visualize the virus-infected neurons. Our first experiments demonstrated that rats were not susceptible to infection with neurotropic strains of herpes simplex type 1. Injections of a wildtype strain of herpes simplex type 2 into rat kidneys led to nonspecific infection of many central nervous system neurons and glia. In contrast, herpes simplex type 1 injections in hamsters and guinea pigs caused specific infection of limited numbers of neurons in approximately one-third of the animals and the study was continued using hamsters. Sympathetic preganglionic neuron labelling was found in the ipsilateral intermediolateral cell column of the spinal cord as well as the lateral funiculus. Most infected preganglionic neurons were located in the seventh to the ninth thoracic spinal segments. Infected neurons were not found in the dorsal or ventral horn of the spinal gray matter and only one or two cells were found in the brainstem. Sympathetic preganglionic neuron morphology was usually normal, showing detailed dendritic arborizations, and lysis was infrequent. Small infected cells were sometimes observed close to sympathetic preganglionic neurons. Because herpes simplex type 1 virus was not detected immunocytochemically in ganglionic neurons in these same hamsters, the polymerase chain reaction was used in some additional hamsters to detect viral DNA in the T12 and T13 chain ganglia and splanchnic ganglia ipsilateral to the kidney injected with herpes simplex type 1. Finally, the overall distribution of renal postganglionic and splanchnic preganglionic neurons in hamsters was examined for comparison to the number and locations of virus-labelled neurons. Retrograde transport of the fluorescent dye FluoroGold demonstrated that (i) renal postganglionic neurons are distributed in the T10-L1 chain ganglia and in the prevertebral splanchnic ganglion and (ii) splanchnic preganglionic neurons are located in the T3-T12 spinal segments, predominantly in the intermediolateral and funicular spinal autonomic nuclei. In conclusion, herpes simplex type 1 virus infected an exclusive population of "renal" neurons in hamsters without lysis and with little cellular reaction to the infection after a survival period of three days, permitting these neurons to be studied in detail.
Asunto(s)
Infecciones por Herpesviridae/patología , Riñón/inervación , Neuronas/citología , Sistema Nervioso Simpático/anatomía & histología , Sinapsis/ultraestructura , Animales , Transporte Axonal , Cricetinae , Ganglios Simpáticos/anatomía & histología , Ganglios Simpáticos/microbiología , Ganglios Simpáticos/patología , Herpesvirus Humano 1/aislamiento & purificación , Herpesvirus Humano 2/aislamiento & purificación , Riñón/microbiología , Masculino , Neuronas/patología , Reacción en Cadena de la Polimerasa , Ratas , Ratas Wistar , Sistema Nervioso Simpático/patología , Sinapsis/patologíaRESUMEN
The ganglionic location of hindlimb vasoconstrictor sympathetic neurons in several species is known but the locations of neurons innervating limb arteries or veins, specifically, have not been compared and neurochemical differences between them have not been examined in detail. This study was designed to determine whether neurons innervating arteries and veins are organized as distinct populations and whether neurons innervating arteries, veins or footpads contain the same peptides. Retrograde transport of fluorescent dyes was used to identify, separately, paravertebral postganglionic neurons in the 13th thoracic to 6th lumbar (T13-L6) chain ganglia that innervate the femoral arteries, femoral veins and footpads of the rat hindlimb. The proportions of venous and arterial vasomotor neurons and footpad neurons containing neuropeptide Y- and vasoactive intestinal polypeptide-immunoreactivity (NPY-Ir, VIP-Ir) were then compared. Venous vasomotor neurons were found mostly (62%) in the L1 and L2 ganglia. The majority of arterial vasomotor neurons (81%) were distributed slightly more caudally in L1-L3. Veins and arteries were not innervated by the same cells. Footpad neurons were located mostly in L4-L6. NPY-Ir was identified in 17% of the venomotor neurons, in 94% of arterial neurons and in 24% of footpad neurons. VIP-Ir was found in 3% of the venomotor neurons, 8% of the arterial neurons and in 44% of the footpad neurons. In conclusion, hindlimb venous and arterial vasomotor neurons are anatomically distinct, are mixed randomly within the chain ganglia and differ markedly in their content of NPY, consistent with reported differences in neuromuscular transmission to arteries and veins. The most likely hindlimb postganglionic neurons to contain VIP were those innervating footpads, probably controlling sweat gland function.