Research articleThe neural pathway for lacrimal gland tear secretion in New Zealand White rabbits

- Lacrimal gland tear secretion in rabbits is connected with the frontal cortex, the field CA1 of hippocampus, the paraventricular nucleus of hypothalamus, the pons, and the medulla oblongata.
- The neural pathway that regulates tear secretion from the lacrimal gland proceeds from the PVN to the superior olivary complex of the pons to the SSN, and finally to the lacrimal gland.
- This research provides a new idea for the study of the pathogenesis of dry eye.

ObjectiveWe investigated the neural pathway for tear secretion from the lacrimal gland of New Zealand White rabbits.MethodsNine healthy adult New Zealand White rabbits were randomly divided into three experimental groups, namely, an irritant-stimulated group, a non-stimulated group, and a saline-stimulated group. Sanitized dry cotton swabs with menthol were used to wipe both of the rabbits' eyelids in the irritant-stimulated group, and the non-stimulated group and saline- stimulated group were compared as controls. The animals in the three groups were killed 2 h later and the expressions of c-Fos in the frontal cortex, hippocampus, hypothalamus, pons, and medulla oblongata of the rabbits were detected using immunofluorescence labeling. According to the distribution of c-Fos protein expression, 12 healthy adult New Zealand rabbits were similarly divided into three groups for retrograde tract tracing via pseudorabies virus (PRV) injection into the lacrimal gland. Immunofluorescence labeling was used to analyze PRV-infected neurons in the brains of rabbits after survival for 30 h, 38 h, and 46 h.ResultsThe most c-Fos-positive immunolabeled cells were observed in the menthol-stimulated group, whereas fewer c-Fos-positive immunolabeled cells were observed in the saline-stimulated group.The non-treated group showed the least c-Fos-positive immunolabeled cells. At 30 h after PRV injection, PRV-positive neurons were found only in the superior salivary nucleus of the pons (SSN). At 38 h, PRV-infected neurons were observed in the lateral nucleus of the superior olive (LSO) and the medial nucleus of the superior olive (MSO). At 46 h, PRV-infected neurons were found in the nucleus of the trapezoid body (Tz) and the hypothalamic paraventricular nucleus (PVN), and their distributions were dense in the LSO and MSO.ConclusionsMenthol-induced c-Fos protein expression and PRV-mediated tract tracing suggest that in New Zealand White rabbits, the neural pathway that regulates tear secretion from the lacrimal gland proceeds from the PVN to the superior olivary complex of the pons to the SSN and finally to the lacrimal gland.