Abnormal Motor Reflexes and Dormant Facial Motor Neurons in Rats with Facial–Facial Anastomosis

Abstract

After facial nerve injury, some post-paralysis sequelae, such as synkinesis, hemispasm and 'crocodile tears' syndrome appear. The psychosocial impact of these sequelae is unavoidable. Despite recent advances and the growing popularity of this field, the pathophysiological mechanisms of facial nerve injury and regeneration are still not well understood. In this report, an abnormal motor reflex coincident with synkinetic facial movement was examined in a rat model using the blink reflex technique. Some dormant facial motor neurons were found which could not innervate through the suture site but remained alive. These results suggest that such dormant neurons might exert roles distinct from those of re-innervated neurons during facial nerve injury and regeneration. Further study is required to elucidate the biomolecular structure and electrophysiological features of such neurons.

Gene expression of NMDA and AMPA receptors in different facial motor neurons

“…13 One of our previous studies also demonstrated that the remodeling activity of the facial nucleus may play an important role in the functional recovery of facial motor neurons at the late stage. 17 Therefore, in this study, the changes 90 days after the operation might contribute to late remodeling activity and not to neuronal degeneration.…”

“…Furthermore, of all remodeling activities, synaptic connection elimination and rearrangement around FMNs take place concomitantly to orchestrate dynamic structural changes. 2,5,10,17 One study showed that, in mammalians, the downregulated glutamate receptor expression by short-interfering RNA against specific regions of the GluR2 transcript significantly reduced the dendritic arborization of motoneurons, but motoneuron survival and network activity were not affected. 28 In another study, the knockdown or overexpression of GluA1 (GluR1) modulated the dendrite elaboration on spinal motor neurons during the developmental phase.…”

“…Sprague-Dawley rats, each weighing 220 to 250 g, were subjected to facial-facial anastomosis as previously described. 4,16,17 All of the animal experiments were conducted in strict accordance with the guidelines for the handling and treatment of animals and were approved by the Institutional Animal Care and Use Committee of Tongji Medical College, Wuhan, China. All of the animals were raised in a room at 208C to 258C, with 12-hour alternating light/dark cycles, and with free access to standard food and water.…”

“…LCM, in combination with gene expression analyses, has the potential to provide the expression profiles of highly homogeneous clusters of neurons, rendering it possible to study the underlying mechanism of nerve injury or other pathogenesis . In a previous study, we found two types of FMNs in different regenerative states, namely dormant and reinnervating FMNs, in an ipsilateral facial nucleus after peripheral axotomy, and extracted their RNA with reliable quality by using LCM . On the basis of previous research and literature review, we were hypothesized that, after peripheral injury, the ionotropic glutamate receptor subunits' messenger RNA (mRNA) expression of these two types of FMNs may be different.…”

“…[11][12][13][14][15] In a previous study, we found two types of FMNs in different regenerative states, namely dormant and reinnervating FMNs, in an ipsilateral facial nucleus after peripheral axotomy, and extracted their RNA with reliable quality by using LCM. 16,17 On the basis of previous research and literature review, we were hypothesized that, after peripheral injury, the ionotropic glutamate receptor subunits' messenger RNA (mRNA) expression of these two types of FMNs may be different. In this study, we quantitatively measured, by using real-time quantitative reversetranscriptase polymerase chain reaction (qRT-PCR), the mRNA levels of the AMPAR subunits (GluR1, GluR2, GluR3 and GluR4) and NMDAR subunits (NR1, NR2a, NR2b, NR2c and NR2d) in the two types of FMNs isolated by LCM.…”