Muscarinic receptor-mediated calcium changes in a rat model of facial nerve nucleus injury

The muscarinic receptor modulates intracellular free calcium ion levels in the facial nerve nucleus via different channels. In the present study, muscarinic receptor-mediated free calcium ions levels were detected by confocal laser microscopy in the facial nerve nucleus following facial nerve injury in rats. There was no significant difference in muscarinic receptor expression at the affected facial nerve nucleus compared with expression prior to injury, but muscarinic receptor-mediated free calcium ion levels increased in the affected side following facial nerve injury （P 〈 0.01）. At day 30 after facial nerve injury, 50 pmol/L muscarinic-mediated free calcium ion levels were significantly inhibited at the affected facial nerve nucleus in calcium-free artificial cerebrospinal fluid, and the change range was 82% of artificial cerebrospinal fluid （P 〈 0.05）. These results suggest that increased free calcium ion concentrations are achieved by intracellular calcium ion release, and that the transmembrane flow of calcium ions is also involved in this process.

Altered prosaposin expression in the rat facial nerve nucleus following facial nerve transection and repair

BACKGROUND： Studies have demonstrated that damaged facial nerves synthesize prosaposin to promote repair of facial neurons. OBJECTIVE： To observe time-course changes of prosaposin expression in the facial nerve nucleus of Sprague Dawley rats following facial nerve transection and repair. DESIGN, TIME AND SETTING： A randomized control neuropathological animal experiment was performed in Chongqing Medical University between March 2007 and September 2008. MATERIALS： A total of 48 adult, male, Sprague Dawley rats were selected and randomly divided into transection and transection ＋ end-to-end anastomosis groups （n =24）. Rabbit anti-rat prosaposin antibody, instant SABC immunohistochemical kit, and antibody dilution solution were purchased from Wuhan Uscn Science Co., Ltd., China. METHODS： In the transection group, the nerve trunk of the distal retroauricular branch of the left facial nerves was ligated in Sprague Dawley rats, and a 5-mm nerve trunk at the distal end of the ligation site was removed. In the transection ＋ end-to-end anastomosis group, epineurial anastomosis was performed immediately following transection of the left facial nerves. The right facial nerves in the two groups served as the normal control group. MAIN OUTCOME MEASURES： The number of prosaposin-positive neurons, as welt as intensity of immunostaining in facial nerve nucleus, following transection and end-to-end anastomosis were determined by immunohistochemistry at 1, 3, 7, 14, 21, and 35 days after injury. RESULTS： Transection group： transection of facial nerves resulted in increased number of prosaposin-positive neurons and immunoreactivity intensity in the facial nucleus on day 1. These values significantly increased by day 3. Expression was greater than in the control side. The peak of the reduction was reached at 7 days post-surgery. Transection ＋ end-to-end anastomosis group： the number of prosaposin-positive neurons and immunoreactivity intensity was reduced in the facial nerve nucleus following immediate end-to-end anastomosis on day 7 post-surgery. These values began to gradually increase by day 14 post-anastomosis. By day 35 post-anastomosis, the number of prosaposin-positive neurons in the operated side recovered to normal levels. The number of prosaposin-positive neurons, as well as immunoreactivity intensity, was significantly greater in the facial nerve nucleus, compared with the transection group on days 14, 21, and 35 post-surgery （P 〈 0.05）. The rhythmic whisking of vibrissa recovered, and recovery time was consistent with increased numbers of prosaposin-positive neurons. CONCLUSION： Within 7 days after injury, prosaposin expression in the facial nerve nucleus exhibited an initial increase, followed by a decrease, and was not affected by facial nerve repair. Following facial nerve damage, neural anastomosis was shown to increase prosaposin expression in the facial nerve nucleus after 14 days. Recovery of prosaposin occurred simultaneously with reinnervation.

Olfactory ensheathing cells promote nerve regeneration and functional recovery after facial nerve defects

Olfactory ensheathing cells from the olfactory bulb and olfactory mucosa have been tbund to increase axonal sprouting and pathfinding and promote the recovery of vibrissae motor performance in facial nerve transection injured rats. However, it is not yet clear whether olfactory ensheathing cells promote the reparation of facial nerve defects in rats. In this study, a collagen sponge and silicone tube neural conduit was implanted into the 6-mm defect of the buccal branch of the facial nerve in adult rats. Olfactory ensheathing cells isolated from the olfactory bulb of newborn Sprague-Dawley rats were injected into the neural conduits connecting the ends of tile broken nerves, the morphology and function of the regenerated nerves were compared between the rats implanted with olfactory ensheathing cells with the rats injected with saline. Facial paralysis was assessed. Nerve electrography was used to measure facial nerve-induced action potentials. Visual inspection, anatomical microscopy and hematoxylin-eosin staining were used to assess the histomorphology around the trans planted neural conduit and the morphology of the regenerated nerve. Using fluorogold retrograde tracing, toluidine blue staining and lead uranyl acetate staining, we also measured the number of neurons in the anterior exterior lateral f：acial nerve motor nucleus, the number of myelinated nerve fibers, and nerve fiber diameter and myelin sheath thickness, respectively. After surgery, olfactory ensheathing cells de- creased facial paralysis and the latency of the facial nerve-induced action potentials. There were no differences in the general morphology of the regenerating nerves between the rats implanted with olfactory ensheathing cells and the rats injected with saline. Between-group results showed that olfactory ensheathing cell treatment increased the number of regenerated neurons, improved nerve fiber morphology, and increased the number of myelinated nerve fibers, nerve fiber diameter, and myelin sheath thickness. In conclusion, implantation of olfactory ensheathing cells can promote regeneration and functional recovery after facial nerve damage in rats.

Gene expression microarray analysis of the spinal trigeminal nucleus in a rat model of migraine with aura

Cortical spreading depression can trigger migraine with aura and activate the trigeminal vascular system. To examine gene expression profiles in the spinal trigeminal nucleus in rats following cortical spreading depression-induced migraine with aura, a rat model was established by injection of 1 M potassium chloride, which induced cortical spreading depression. DNA microarray analysis revealed that, compared with the control group, the cortical spreading depression group showed seven upregulated genes-myosin heavy chain 1/2, myosin light chain 1, myosin light chain （phosphorylatable, fast skeletal muscle）, actin alpha 1, homeobox B8, carbonic anhydrase 3 and an unknown gene. Two genes were downregulated-RGD1563441 and an unknown gene. Real-time quantitative reverse transcription-PCR and bioinformatics analysis indicated that these genes are involved in motility, cell migration, CO2/nitric oxide homeostasis and signal transduction.