Spinal Gap Junction Channels in Neuropathic Pain

Damage to peripheral nerves or the spinal cord is often accompanied by neuropathic pain, which is a complex, chronic pain state. Increasing evidence indicates that alterations in the expression and activity of gap junction channels in the spinal cord are involved in the development of neuropathic pain. Thus, this review briefly summarizes evidence that regulation of the expression, coupling, and activity of spinal gap junction channels modulates pain signals in neuropathic pain states induced by peripheral nerve or spinal cord injury. We particularly focus on connexin 43 and pannexin 1 because their regulation vastly attenuates symptoms of neuropathic pain. We hope that the study of gap junction channels eventually leads to the development of a suitable treatment tool for patients with neuropathic pain.

The relaxing effect of Poncirus fructus and its flavonoid content on porcine coronary artery / 한국실험동물학회지

Coronary artery disease is a common occurrence in human, and causes enormous social cost. Poncirus fructus (PF), the dried immature fruits of Poncirus trifoliata Rafinesquem, is used in the treatment of womb contraction and dyspepsia, as a prokinetic, and in improving blood circulation. This study was performed to investigate the effects of PF and some of its flavonoids components on the coronary from the pig. The arterial ring was suspended by a pair of stainless steel stirrups in an organ bath. The end of the upper stirrup was connected to an isometric force transducer. A dose-dependent induction of relaxation was observed by both water and 70% ethanol extracts of PF in the porcine coronary artery precontracted with U46619 (100 nM), a stable analogue of the potent vasoconstrictor thromboxane A2. The 70% ethanol extract showed more efficacy than the water extract. Pretreatment of the artery with L-NAME (100 microM), a nitric oxide synthase inhibitor, resulted in a significant reduction in the relaxation induced by PF extract. In addition, ODQ (10 microM), a soluble guanylate cyclase inhibitor, also significantly reduced the effects of PF extracts. Hesperidin, a flavonoid present in PF, induced very weak relaxation of the porcine coronary artery at a high concentration (100 microM), while its aglycone, hesperetin, demonstrated a dose-dependent relaxation. In conclusion, PF extracts induced relaxation in the porcine coronary artery, partially through the nitric oxide-cGMP pathway, and the aglycones of flavonoids might be also involved in the relaxation of the same artery.

Neuronal Hyperexcitability Mediates Below-Level Central Neuropathic Pain after Spinal Cord Injury in Rats / 한국실험동물학회지

Spinal cord injury often leads to central neuropathic pain syndromes, such as allodynic and hyperalgesic behaviors. Electrophysiologically, spinal dorsal horn neurons show enhanced activity to non-noxious and noxious stimuli as well as increased spontaneous activity following spinal cord injury, which often called hyperexcitability or central sensitization. Under hyperexcitable states, spinal neurons lose their ability of discrimination and encoding somatosensory information followed by abnormal somatosensory recognition to non-noxious and noxious stimuli. In the present review, we summarize a variety of pathophysiological mechanisms of neuronal hyperexcitability for treating or preventing central neuropathic pain syndrome following spinal cord injury.

Preventing Extracellular Diffusion of Trigeminal Nitric Oxide Enhances Formalin-induced Orofacial Pain

Nitric oxide (NO), a diffusible gas, is produced in the central nervous system, including the spinal cord dorsal horn and the trigeminal nucleus, the first central areas processing nociceptive information from periphery. In the spinal cord, it has been demonstrated that NO acts as pronociceptive or antinociceptive mediators, apparently in a concentration-dependent manner. However, the central role of NO in the trigeminal nucleus remains uncertain in support of processing the orofacial nociception. Thus, we here investigated the central role of NO in formalin (3%)-induced orofacial pain in rats by administering membrane-permeable or -impermeable inhibitors, relating to the NO signaling pathways, into intracisternal space. The intracisternal pretreatments with the NO synthase inhibitor L-NAME, the NO-sensitive guanylate cyclase inhibitor ODQ, and the protein kinase C inhibitor GF109203X, all of which are permeable to the cell membrane, significantly reduced the formalin-induced pain, whereas the membrane-impermeable NO scavenger PTIO significantly enhanced it, compared to vehicle controls. These data suggest that an overall effect of NO production in the trigeminal nucleus is pronociceptive, but NO extracellularly diffused out of its producing neurons would have an antinociceptive action.

Peripheral Nerve Injury Alters Excitatory and Inhibitory Synaptic Transmission in Rat Spinal Cord Substantia Gelatinosa

Following peripheral nerve injury, excessive nociceptive inputs result in diverse physiological alterations in the spinal cord substantia gelatinosa (SG), lamina II of the dorsal horn. Here, I report the alterations of excitatory or inhibitory transmission in the SG of a rat model for neuropathic pain ("spared nerve injury"). Results from whole-cell recordings of SG neurons show that the number of distinct primary afferent fibers, identified by graded intensity of stimulation, is increased at 2 weeks after spared nerve injury. In addition, short-term depression, recognized by paired-pulse ratio of excitatory postsynaptic currents, is significantly increased, indicating the increase of glutamate release probability at primary afferent terminals. The peripheral nerve injury also increases the amplitude, but not the frequency, of spontaneous inhibitory postsynaptic currents. These data support the hypothesis that peripheral nerve injury modifies spinal pain conduction and modulation systems to develop neuropathic pain.

Relationship between optic nerve head parameters of Heidelberg Retina Tomograph and visual field defects in primary open-angle glaucoma

To investigate the correlation between optic nerve head configuration and visual field defects, optie nerve head analysis using confocal scanning laser tomography (Heidelberg Retina Tomograph, HRT) and automated static threshold perimetry using a Humphrey Field Analyzer (program C3O-2) were performed on 81 eyes of 44 primary open-angle glaucoma (POAG) patients. The optic nerve head parameters-rim area, rim volume, mean retinal nerve fiber layer thickness, height variation contour, and third moment in contour were measured by HRT and were analyzed for correlation with visual field indices-mean deviation, and corrected pattern standard deviation. All optic nerve hend parameters except HVC correlated significantly with the visual field indices; the highest correlation was between rim area and mean deviation (r = 0.6172, p < 0.O0001). The rim area of the superior and inferior quadrants correlated significantly with the visual field defects in corresponding sectors. Structural optic disc measurements by HRT correlated significantly with funetional optic nerve head damage in POAG

The effect of low-and high-dose adjunctive mitomycin C in trabeculectomy

To compare the effects of three different concentrations of mitomycin C (MMC) as an adjunct therapy to trabeculectomy, we reviewed 26 patients (36 eyes) who underwent trabeculectomy in which MMC was applied intraoperatively. The time of application was 5 minutes, and the concentration of MMC was 0.1 mg/ml (n = 10), 0.2 mg/ml (n = 17) and 0.4 mg/ml (n = 9), respectively. Complete success was defined by intraocular pressure (IOP) of 21 mmHg or less without medication at postoperative 3 months. There was no statistical difference among the three groups in mean age of patients, preoperative IOPs, and the numbers of premedication. The mean IOP at postoperative 3 months was significantly lower in the 0.4 mg/ml group (10.4 +/- 5.5 mmHg) than in the 0.2 mg/ml group (16.1 +/- 4.7 mmHg) (p 0.05). There was no statistical difference among the three groups in the success rate regardless of medication, and the size and longevity of the filtering bleb. Postoperative hypotony was noted in two eyes of the 0.4 mg/ml group.

Low-dose and High-dose of Mitomycin-C in Trabeculectomy

The purpose of this study is to compare the effects of three different concentrations of mitomycin-C(MMC) as an adjunct therapy to trabeculectomy. We reviewed 26 patients(36 eyes) who underwent trabeculectomy in which MMC was applied intraoperatively. The application time was 5 minute, and concentration of MMC was 0.1mg/ml(n=10), 0.2mg/ml(n=17) and 0.41mg/ml(n=9) respectively. The mean IOP at postoperative 3 months was significantly lower in 0.4mg/ml group (10.4 +/- 5.5mmHg) than in the 0.2mg/ml group(16.1 +/- 4.7mmHg)(p<0.05). There was no statistical difference among the three groups in the success rate regardless of medication, the size and longevity of bleb. The postoperative hypotony(2 eyes) was noted in the 0.4mg/ml group. In conclusions, It is desirable to use the lowest concentration of MMC that will facilitate bleb formation.

Reversibility of Optic Disc Cupping after Trabeculectomy in Adult Glaucoma Patients Measured by Heidelberg Retina Tomograph

Using Heidelberg Retina Tomograph (HRT, Heidelberg Engineering, Heidelberg, Germany) we investigated whether reversal of glaucomatous optic disc cupping occurs in adult glaucoma patients following intraocular pressure (IOP) reduction by trabeculectomy, and whether there is any regional difference in topographic change of optic disc. Thirteen eyes of 13 glaucoma patients in whom the percent IOP reduction was 25% or more at postoperative follow-up of 2 months, were enrolled. Cup-to-disc area ratio was decreased significantly, while rim area and rim volume were increased significantly(p<0.05, Wilcoxon signed rank test) at postoperative follow-up of 2 months. Among the optic disc sectors, rim area in superior and inferior quadrant, especially in superotemporal and inferotemporal octant, increased significantly. Decrease in maximum cup depth correlated significantly with the percent IOP reduction (r=0.698, p=0.016). Reversal of glaucomatous optic disc cupping after IOP reduction following trabeculectomy in adult patients was confirmed by HRT, Furthermore, the regions of selective reversal in superior and inferior quadrant coincide with the well-known portion of early functional and structural glaucomatous optic nerve head damage.

Evaluation of Antiproliferative Agents in Tissue Culture Model

The authors investigated the effect of single intraoperative exposure of mitomycin C(MMC), 5-fluorouracil(5-FU), and cyclosporine A(Cs A) on the glaucoma filtering surgery. Human Tenon's fibroblasts were cultured and exposed to various concentrations of each drug for 5 minutes. Cell viability was measured using MTT assay, and cell proliferation was studied by 3H-thymidine uptake test. None of MMC(up to 0.04%), 5-FU(up to 40mg/ml), Cs A(up to 20micro gram/ml) was cytocidal. However, both MMC and 5-FU inhibited proliferation of fibroblasts significantly, but not Cs A. We concluded that MMC and 5-FU improve the results of filtering surgery not by direct cytocidal effect, but by the inhibition of proliferation. As for Cs A, longer exposure time and higher concentrations were needed to have similar effect on cellular viability and proliferation.

Experimentally designed glaucoma implant surgery with mitomycin C in rabbit

An attempt was made to observe the possibility of controlling intraocular pressure (IOP) without hypotony and ocular motility disorder by installing an experimentally designed glaucoma implant through a small conjunctival incision with the aid of a stylet and maintaining the aqueous reservoir using mitomycin C (MMC). The implant was made of silicone tube, of which one end was occluded by glue and on the same end 4 check-valve-like slits were made. Thirty-five healthy white rabbits were used and subdivided into 4 groups. In groups I to III, implants having 2.0, 2.5, 3.0 mm slit lengths, respectively, were installed with MMC application in one eye of each of the 10 rabbits. In group IV, a 2 mm slit-length implant was installed without MMC in one eye of each of the 5 rabbits. Pneumatonometry and ultrasonography were performed to check the IOP and the formation of aqueous reservoir in the implanted eyes for 8 weeks. In group I through III, there was a statistically significant 4-5 mmHg pressure-lowering effect in the implanted eyes compared to the contralateral control eyes for 8 weeks. The aqueous reservoirs were observed throughout the follow-up period. In group IV, we could observe neither a pressure-lowering effect nor aqueous reservoir formation in the implanted eyes after 2 weeks postoperatively. Hypotony did not occur in implanted eyes in any of the groups. This study shows the possibility of IOP control by installing a specially designed glaucoma implant with application of MMC.

Quantitative analysis of changes of automated perimetric thresholds after pupillary dilation and induced myopia in normal subjects

We quantitatively analyzed the changes of the (retinal) threshold sensitivities between normal status and dilated emmetropic status, and between dilated emmetropic status and -1.0D induced myopic status. Three consecutive visual field examinations by Humphrey Field Analyzer C-30-2 threshold test and STATPAC program were performed in 36 eyes of 21 normal subjects who ranged in age from 23 to 40 years. The results were as follows: 1) There was a statistically significant decrease (0.87 +/- 0.91dB)in the mean threshold sensitivity within the central 30 degrees at the dilated emmetropic status (27.90dB) as compared with the normal status (28.77dB)(p = 0.0001). 2) There was a statistically significant decrease(0.99 +/- 0.61dB) at -1.0D induced myopic status(26.91dB) as compared with the dilated emmetropic status(27.90dB)(p = 0.0001). 3) After dilation, the mean threshold sensitivity between 20 and 30 degrees of field showed statistically significant decrease as compared with those within the central 20 degrees of visual field(p 0.05). Therefore, we emphasize the importance of consistent pupillary size and correct refractive state in performing the serial automated visual field tests.

Effects of intracameral carbachol and acetylcholine on early postoperative intraocular pressure after cataract extraction

We performed a randomized, prospective study to evaluate the effect of intraoperative, intracameral carbachol or acetylcholine on early postoperative intraocular pressure(IOP) after extracapsular cataract extraction(ECCE) and posterior chamber lens(PCL) implantation. Fifty-six eyes of 56 patients scheduled for routine ECCE and PCL implantation were randomly assigned into three groups: (1)carbachol infusion (19 eyes) (2) acetylcholine infusion (15 eyes) (3)balanced salt solution (BSS) infusion (control, 22 eyes). We compared the preoperative IOP, early postoperative IOP, postoperative 24 hours IOP and postoperative 1 week IOP. In the measurement of early postoperative IOP, IOP was measured at least twice at 3, 6 or 9 hours postoperatively. There was no significant difference in IOP between the three groups preoperatively, at postoperative 3 hours, and 1 week. At postoperative 6 hours, both the carbachol infusion group and acetylcholine infusion group were significantly different from the BSS infusion group. At postoperative 9 and 24 hours, only carbachol infusion group had a significant difference from BSS infusion group in suppression of postoperative IOP increase. Our results suggest that intraoperative, intracameral administration of carbachol or acetylcholine prevents early postoperative IOP increase, and that carbachol has a more lasting effect.

The effects of intraoperative mitomycin-C or 5-fluorouracil on glaucoma filtering surgery

We compared the success rate of filtering surgery of a single 5-minute intraoperative application of mitomycin-C (MMC) or 5-fluorouracil (5-FU). Animal experiment and clinical study were done. In animal study, thirty pigmented rabbits (60 eyes) weighing 2.0 to 2.5 Kg were enrolled. We divided into 4 groups, such as BSS, 5-FU 50 mg/ml, MMC 0.2 mg/ml and MMC 0.4 mg/ml subconjunctival soaked group. Each group consisted of 15 eyes. In each group, 10 eyes was for examination of bleb survival and complications, 3 eyes for light microscopic examination and 2 eyes for electron microscopic examination. Bleb was survived 6.1 days (3 to 13 days) for BSS treated group, 16.3 days (9 to 23 days) for 5-FU 50mg/ml treated group, 32.7 days (17 to 55 days) in MMC 0.2 mg/ml treated group, and 64.4 days (49 to 84 days) in MMC 0.4 mg/ml treated group. Duration of bleb survival was significantly prolonged in 5-FU, MMC 0.2 mg/ml and MMC 0.4 mg/ml group respectively. In clinical study, fifty-five eyes of 40 patients were enrolled. 29 eyes of 21 patients were treated with MMC 0.2 mg/ml and 26 eyes of 19 patients were treated with 5-FU 50 mg/ml. The success rate was 89.7% in MMC 0.2 mg/ml treated group and 84.6% in 5-FU 50 mg/ml treated group at postoperative 3 months, and postoperative 6 months 89.7% in MMC 0.2 mg/ml treated group and 76.9% in 5-FU 50 mg/ml treated group. There was no statistical significance at postoperative 3 months (P > 0.05), but statistical significance at postoperative 6 months (P < 0.05). There was no serious complications using a MMC 0.2 mg/ml or 5-FU 50mg/ml.

The effects of intraoperative mitomycin-C or 5-fluorouracil on glaucoma filtering surgery

We compared the success rate of filtering surgery of a single 5-minute intraoperative application of mitomycin-C (MMC) or 5-fluorouracil (5-FU). Animal experiment and clinical study were done. In animal study, thirty pigmented rabbits (60 eyes) weighing 2.0 to 2.5 Kg were enrolled. We divided into 4 groups, such as BSS, 5-FU 50 mg/ml, MMC 0.2 mg/ml and MMC 0.4 mg/ml subconjunctival soaked group. Each group consisted of 15 eyes. In each group, 10 eyes was for examination of bleb survival and complications, 3 eyes for light microscopic examination and 2 eyes for electron microscopic examination. Bleb was survived 6.1 days (3 to 13 days) for BSS treated group, 16.3 days (9 to 23 days) for 5-FU 50mg/ml treated group, 32.7 days (17 to 55 days) in MMC 0.2 mg/ml treated group, and 64.4 days (49 to 84 days) in MMC 0.4 mg/ml treated group. Duration of bleb survival was significantly prolonged in 5-FU, MMC 0.2 mg/ml and MMC 0.4 mg/ml group respectively. In clinical study, fifty-five eyes of 40 patients were enrolled. 29 eyes of 21 patients were treated with MMC 0.2 mg/ml and 26 eyes of 19 patients were treated with 5-FU 50 mg/ml. The success rate was 89.7% in MMC 0.2 mg/ml treated group and 84.6% in 5-FU 50 mg/ml treated group at postoperative 3 months, and postoperative 6 months 89.7% in MMC 0.2 mg/ml treated group and 76.9% in 5-FU 50 mg/ml treated group. There was no statistical significance at postoperative 3 months (P > 0.05), but statistical significance at postoperative 6 months (P < 0.05). There was no serious complications using a MMC 0.2 mg/ml or 5-FU 50mg/ml.

The Effect of Mitomycin on the Experimental Filtering Surgery

In tiis study, an expenmental model of glaucoma filtering surgery in rabblts was used to evaluate the effect of single intraoperative application of Mitomycin Full-thickness filtering surgery, posterior lip sclerectomy, was performed after application of 0.5mg/ml Mitomycin-soaked Week-Cel(TM) sponge for 5 minutes in one eye of 15 pigmented rabbits and was irrigated copiously with balanced salt solution(BSS(TM)). The same procedure was done in the contralateral eye as a control, using BSS(TM). In Mitomycin-treated group, the filtering blebs were more prominent with sparse vascular tissues and were maintained through postoperative 8 weeks or more. Histologically, there loas was amount of inflammatory reactions in Mitomycin-treated group. The fibroblastic activity and proliferations of the collagen were also suppessed markedly in Mitomycin-treated group. These results suggest that a single intraoperative application of Mitomycin can be used adjunctively to improve the success rate of glaucoma filtering surgery.

Effects of Topical Mitomycin C on Glaucoma Filtration Surgery

We studied the efficacy and safety of using topical mitomycin C(MMC) as an adjunct to glaucoma filtration surgery. Trabeculectomy was performed in 23 eyes of 19 patients with poor surgical prognosis. After the preparation of a scleral flap. 0.2mg or 0.4 mg/ml MMC was applied to the exposed tissue for 5 minutes. The wound was then irrigated with 250ml of normal saline. The follow-up period was from 2 to 12 months(mean 7.8 +/- 4.3 months). Preoperative mean intraocular pressure(IOP) was 33.8 +/- 7.1 mmHg, ranged from 25 to 51 mmHg. The mean IOPs after 1, 3, 6 and 12 months were 10.3 +/- 4.4, 12.5 +/- 6.9, 12.4 +/- 6.6 and 12.3 +/- 6.7 mmHg, respectively. Nineteen(82.6%) among 23 eyes were successfully controlled with the IOP below 20 mmHg without any antiglaucomatous therapies, and success rate was 0.747 by Kaplan-Meier method at Postoperative 12 months. There were early postoperative complications of aqueous leaking from conjunctival wound in 3 eyes(13.0%), shallow anterior chamber in 2 eyes, and hyphema in one eye and one eye had long-term hypotony lasting more than 3 months. Although MMC is simple to use and a potent adjunct to glaucoma filtration surgery, more work will be needed to determine the mechanism of action, indications, dosage and optimal exposure time of MMC.

Postural Response of Intraocular Pressure in Primary Open-angle Glaucoma Following Trabeculectomy

Forty-six eyes with primary open-angle glaucoma(POAG) and 34 eyes which had previously undergone trabeculectomy for POAG were studied and the postural response of the intraocular pressure(IOP) compared with that of 80 normal eyes, In all groups the increment in IOP occurred when the subject changed from the sitting to the lying position. The pressure increment when changed from the sitting to lying position, averaged 2.4 mmHg in normal eyes, 3.6 mmHg in the group who were treated medically and 3.8 mmHg in the group who had undergone trabeculectomy. There was greater postural response in primary open-angle glaucoma patient compared to normal subject. And also there was no statistically significant difference of postural response in intraocular pressure between the group who were treated medically and the group who had undergone trabeculectomy. It is suggested that abnormal postural response of intraocular pressure in POAG appears to be retained and to be unaffected in those eyes which had undergone trabeculectomy.

Effects of topical mitomycin C on glaucoma filtration surgery

We studied the efficacy and safety of using topical mitomycin C (MMC) as an adjunct to glaucoma filtration surgery. Trabeculectomy was performed in 23 eyes of 19 patients with poor surgical prognosis. After the preparation of a scleral flap, 0.2 mg or 0.4 mg/ml MMC was applied to the exposed tissue for 5 minutes. The wound was then irrigated with 250ml of normal saline. The mean follow-up period was 7.8 months. Preoperative mean intraocular pressure (IOP) was 33.8mmHg, and the mean IOPs on 1, 3, 6, and 12 months after operation were 10.3, 12.5, 12.4 and 12.3mmHg, respectively. At postoperative 12 months, 74.7% achieved an IOP of less than or equal to 20mmHg without any antiglaucoma medication. There were early postoperative complications of aqueous leaking from conjunctival wounds in 3 eyes (13.0%), shallow anterior chamber in 2 eyes, and hyphema in one eye and one eye had long-term hypotony lasting more than 3 months. Although MMC is simple to use, it is a potent adjunct to glaucoma filtration surgery, more work should follow to determine the mechanism of action, indications, dosage and optimal exposure time of MMC.

Effects of sodium hyaluronate on filtration bleb in rabbits

Sodium hyaluronate can be used during a trabeculectomy to prevent early postoperative hypotony and shallow anterior chamber. To determine its long-term effect on the outcome of filtration surgery, fifteen rabbits underwent a osterior-lip sclerectomy in both eyes. Into their right eyes 0.2ml sodium hyaluronate, and into left eyes 0.2ml balanced salt solution were injected intracamerally. Gross and histopathological differences of bleb were observed. There was no statistically significant difference in longevity of the filtration bleb.