Lacrimal preganglionic neurons form a subdivision of the superior salivatory nucleus of rat: transneuronal labelling by pseudorabies virus

Transneuronal viral tracing was applied to localize preganglionic parasympa thetic neurons in the brainstem which innervate the extraorbital lacrimal g land in the rat. The Bartha strain of pseudorabies virus was injected into the lacrimal gland, and after different survival times, the superior cervic al and Gasserian ganglia, the upper thoracic spinal cords and the brainstem s were immunostained by antiviral antiserum. Virus-labelled neurons appeare d in the ganglia and in the ventrolateral part of the ipsilateral brainstem at the pontomedullary junction 45 h after inoculation. The virus-labelled brainstem neurons comprised a subgroup of the superior salivatory nucleus ( SSN) located between the root fibers of the facial nerve and the nuclei of the superior olive, and were clearly distinguished from the tyrosine hydrox ylase (TH)-immunopositive, A5 catecholaminergic neurons by double immunosta ining. The number of infected cells in the ipsilateral SSN was increased by 72 h, and labelled neurons appeared in the intermediolateral cell column ( IML) of the ipsilateral thoracic spinal cord. In rats with cervical ganglio nectomy prior to the virus injection in the lacrimal gland, virus-infected cells appeared in the SSN, but not in the thoracic spinal cord, indicating that preganglionic SSN cells were infected via parasympathetic axone of the facial nerve. A double-virus tracer labelling technique was applied to det ermine the topographical relationship between the preganglionic parasympath etic neurons of the lacrimal gland and those of the submandibular gland wit hin the SSN. Simultaneous injection of Bartha strain of pseudorabies virus into the submandibular gland, and a lacZ gene-containing Bartha-derived vir us strain into the lacrimal gland (and vice versa) demarcated a ventral lac rimal and a dorsal submandibular subgroup in the SSN. (C) 1999 Elsevier Sci ence B.V. All rights reserved.