Anatomic Evidence for Information Exchange between Primary Afferent Sensory Neurons Innervating the Anterior Eye Chamber and the Dura Mater in Rat

Abstract

Citation: Liu H, Zhu X, Ling Y, et al. Anatomic evidence for information exchange between primary afferent sensory neurons innervating the anterior eye chamber and the dura mater in rat. Invest Ophthalmol Vis Sci. 2018;59:3424-3430. https://doi.org/ 10.1167/iovs.18-24308 PURPOSE. Our previous studies suggested that mechanosensitive trigeminal ganglion (TG) nerve endings innervating the inner wall of the anterior eye chamber (IWAEC) might play a role in baroreception of the IOP. It has been reported that mechanosensitive TG nerve endings also innervate the dura mater. An acute IOP elevation evokes eye pain accompanied by an ipsilateral headache, suggesting that information exchange may occur between the primary afferent neurons (PANs) innervating the IWAEC and the dura mater. To verify the information exchange between PANs of the two locations, we investigated the anatomic connection between them.METHODS. Non-trans-synaptic tracers, 1,1 0 -dilinoleyl-3,3,3 0 ,3 0 -tetramethylindo-carbocyanine, 4-chlorobenzenesulfonate (FAST Dil) and cholera toxin subunit-B with a 488-nm fluorescent tag (CTB-488), were applied to the dura of the anterior cranial fossa (DACF) and the anterior eye chamber (AEC) to label the PANs. A trans-synaptic tracer, GFP-expressing pseudorabies virus (PRV152), was injected into the AEC while FAST Dil was applied to the DACF to explore the connection between PANs. Fluorescent localization in the TG was studied with a confocal fluorescent microscope.RESULTS. Nine days after rats were treated with CTB-488 in the AEC and FAST Dil on the DACF, FAST Dil-labeled (red), and CTB-488-labeled (green) TG neurons were observed in the medial part of the TG, while double-labeled neurons were absent. If PRV152 was used to substitute CTB-488, then FAST Dil (red) and PRV152 (green) double-labeled TG neurons and axons were observed 3 days later. CONCLUSIONS.Our results indicate that synapses exist between PANs of the IWAEC and the DACF, providing anatomic evidence for information exchange between them.Keywords: IOP, trigeminal ganglion, dura mater, anterior cranial fossa, anterior eye chamber, primary afferent neuron T he lamina cribrosa forms the interface between the intraocular compartment and the retrobulbar compartment. Because the optic nerve is part of the central nervous system, it is surrounded by meninges and cerebrospinal fluid (CSF).1,2 The translaminar pressure difference (TPD) is defined as the difference between the IOP and the intracranial pressure (ICP).1,2 Any change in one of them can be associated with a disturbance of homeostasis of the optic nerve head, such as papilledema or glaucomatous optic neuropathy.The IOP and ICP systems are relatively independent pressure systems, which keep themselves in a relatively stable state through aqueous and CSF circulations.1-3 Significant correlations between the IOP and ICP have been widely reported. However, mechanisms by which the organism maintains the balance between the IOP and ICP have so far remained elusive. 1,3,4 In a recent experimental study, ...