Regulation of Acetylcholine synthesis in normal and neurotropic viral infected sympathetic ganglia

The acetylcholine (ACh) metabolism was analyzed in the superior cervical ganglia (SCG) excised from healthy or neurotropic viral (Aujeszky) infected rats. The ACh content of uninfected freshly excised ganglia was 184±14pmol(n= 1). In vitro under the effect of echothiophate iodide this value increased to476 ± 16pmol (n= 12) for uninfected resting ganglia and to395 ± 19pmol (n= 12) for uninfected ganglia stimulated at 3 Hz. In the same experimental conditions ACh release was0.77 ± 0.02pmol/min (n= 29) for uninfected resting ganglia and10.4 ± 1.0pmol (n= 17) for uninfected ganglia stimulated at 3 Hz. In view of these results ACh synthesis of healthy ganglia in vitro equals their ACh release during the observation period. Inoculation of the pseudorabies virus in the anterior chamber of one eye of the rat provokes an infection of the ipsilateral SCG and a subsequent increase in vivo, of the ACh content in these ganglia within 30 h after inoculation. During that same time the ACh content of the homologous ganglia remains constant and is considered as reference. Thirty-eight hours after inoculation the ACh content of the infected ganglia is increased by 300%. This increase was measured by a bioassay as well as by gas chromatography and could also be observed in vitro under the effect of anticholinesterase, in spite of the accumulation of a ‘surplus’ ACh in the homologous ganglia. For infected ganglia the ACh synthesis was estimated at 2.5 pmol/min. Axotomy prevents the arrival of the virus in SCG and consequently prevents the increase of the ACh content provoked by the virus. Axotomy does not change the ACh content of healthy ganglia. Decentralization provokes a 95% decrease of ACh content in healthy ganglia. The presence of the virus in the decentralized infected ganglia does not modify their reduced ACh content. It is concluded that the pseudorabies virus increases ACh synthesis, content and release in the ganglia and that these phenomena seem to be exclusively presynaptic.