Physiological Changes in Sympathetic Ganglia Infected With Pseudorabies Virus

Abstract

Pseudorabies virus (Aujeszky strain) was grown by continuous passage on chorio-allantoic membranes of chick embryos. Infected membranes were ground in saline to prepare an inoculum which was injected into the vitreous humor of rats under temporary anesthesia. After about 2 days, the animals began to scratch around the inoculated eye, virus could be recovered from the ipsilateral superior cervical ganglion, and histological changes characteristic of this virus were found in the ganglion cells. Electrical recording showed that at about the same time many ganglion cells began spontaneously to discharge groups of impulses over the postganglionic nerve. Later impulses were discharged also over many preganglionic fibers. Finally the postganglionic nerve became silent and synaptic transmission failed, while impulses continued to be discharged over the preganglionic nerve. No spontaneous activity was observed in superior cervical ganglia of normal animals, in inoculated animals prior to the appearance of symptoms of the disease, or in ganglia on the side opposite to the injection. The spontaneous neuronal activity caused by the virus was intermittent: periods of activity usually lasting about one second alternated with intervals of rest which lasted one or more seconds. Discharges on the preganglionic and postganglionic nerves were concurrent. The spontaneous activity continued when the ganglion was excised, and when it was cooled to room temperature. D-tubocurarine, in concentrations which greatly depressed synaptic transmission, abolished the spontaneous discharges over the postganglionic nerve with relatively little effect on the preganglionic discharges. The speculation is advanced that infection of the ganglion may cause spontaneous activity by rendering the presynaptic fiber terminations hyperexcitable, thereby generating spontaneous impulses and allowing one of these terminations to be excited by impulses in another.