Antinociceptive effect of selective G protein-gated inwardly rectifying K+ channel agonist ML297 in the rat spinal cord.

The G protein-gated inwardly rectifying K+ (GIRK) channels play important signaling roles in the central and peripheral nervous systems. However, the role of GIRK channel activation in pain signaling remains unknown mainly due to the lack of potent and selective GIRK channel activators until recently. The present study was designed to determine the effects and mechanisms of ML297, a selective GIRK1/2 activator, on nociception in the spinal cord by using behavioral studies and whole-cell patch-clamp recordings from substantia gelatinosa (SG) neurons. Rats were prepared for chronic lumber catheterization and intrathecal administration of ML297. The nociceptive flexion reflex was tested using an analgesy-meter, and the influence on motor performance was assessed using an accelerating rotarod. We also investigated pre- and post-synaptic actions of ML297 in spinal cord preparations by whole-cell patch-clamp recordings. Intrathecal administration of ML297 increased the mechanical nociceptive threshold without impairing motor function. In voltage-clamp mode of patch-clamp recordings, bath application of ML297 induced outward currents in a dose-dependent manner. The ML297-induced currents demonstrated specific equilibrium potential like other families of potassium channels. At high concentration, ML297 depressed miniature excitatory postsynaptic currents (mEPSCs) but not their amplitude. The ML297-induced outward currents and suppression of mEPSCs were not inhibited by naloxone, a µ-opioid receptor antagonist. These results demonstrated that intrathecal ML297 showed the antinociceptive effect, which was mediated through direct activation of pre- and post-synaptic GIRK channels. Selective GIRK channel activation is a promising strategy for the development of new agents against chronic pain and opioid tolerance.

MC-SleepNet: Large-scale Sleep Stage Scoring in Mice by Deep Neural Networks.

Automated sleep stage scoring for mice is in high demand for sleep research, since manual scoring requires considerable human expertise and efforts. The existing automated scoring methods do not provide the scoring accuracy required for practical use. In addition, the performance of such methods has generally been evaluated using rather small-scale datasets, and their robustness against individual differences and noise has not been adequately verified. This research proposes a novel automated scoring method named "MC-SleepNet", which combines two types of deep neural networks. Then, we evaluate its performance using a large-scale dataset that contains 4,200 biological signal records of mice. The experimental results show that MC-SleepNet can automatically score sleep stages with an accuracy of 96.6% and kappa statistic of 0.94. In addition, we confirm that the scoring accuracy does not significantly decrease even if the target biological signals are noisy. These results suggest that MC-SleepNet is very robust against individual differences and noise. To the best of our knowledge, evaluations using such a large-scale dataset (containing 4,200 records) and high scoring accuracy (96.6%) have not been reported in previous related studies.

The Effect of Guidance regarding Home Exercise and ADL on Adolescent Females Suffering from Adverse Effects after HPV Vaccination in Japanese Multidisciplinary Pain Centers.

Background. Two prophylactic papillomavirus (HPV) vaccines have been available for primary prevention of cervical cancer. Although serious adverse effects (AE) were rare, more than 230 women have been suffering from severe AEs such as persistent pain and headache in Japan. Our research group started to treat adolescent females suffering from the AEs. Objective. To survey the characteristics of and the effects of cognitive behavioral therapy on adolescent female suffering from the AEs in Japanese multidisciplinary pain centers. Methods. One hundred and forty-five patients suffering from the AEs were reviewed retrospectively and 105 patients of them were provided guidance on home exercise and activities of daily living based partially on a cognitive-behavioral approach. The intensity of pain was rated by the patients using a numerical rating scale (NRS). Furthermore, the Hospital Anxiety and Depression Scale (HADS) and the Pain Catastrophizing Scale (PCS) were used. Results. Eighty out of the 105 patients who received the guidance were followed up, 10 displayed a marked improvement, and 43 showed some improvement. Conclusions. Guidance on home exercise and activities of daily living based on a cognitive-behavioral approach alleviated the AEs that women suffered from after HPV vaccination in Japan.

Direct Effect of Remifentanil and Glycine Contained in Ultiva® on Nociceptive Transmission in the Spinal Cord: In Vivo and Slice Patch Clamp Analyses.

BACKGROUND: Ultiva® is commonly administered intravenously for analgesia during general anaesthesia and its main constituent remifentanil is an ultra-short-acting µ-opioid receptor agonist. Ultiva® is not approved for epidural or intrathecal use in clinical practice. Previous studies have reported that Ultiva® provokes opioid-induced hyperalgesia by interacting with spinal dorsal horn neurons. Ultiva® contains glycine, an inhibitory neurotransmitter but also an N-methyl-D-aspartate receptor co-activator. The presence of glycine in the formulation of Ultiva® potentially complicates its effects. We examined how Ultiva® directly affects nociceptive transmission in the spinal cord. METHODS: We made patch-clamp recordings from substantia gelatinosa (SG) neurons in the adult rat spinal dorsal horn in vivo and in spinal cord slices. We perfused Ultiva® onto the SG neurons and analysed its effects on the membrane potentials and synaptic responses activated by noxious mechanical stimuli. RESULTS: Bath application of Ultiva® hyperpolarized membrane potentials under current-clamp conditions and produced an outward current under voltage-clamp conditions. A barrage of excitatory postsynaptic currents (EPSCs) evoked by the stimuli was suppressed by Ultiva®. Miniature EPSCs (mEPSCs) were depressed in frequency but not amplitude. Ultiva®-induced outward currents and suppression of mEPSCs were not inhibited by the µ-opioid receptor antagonist naloxone, but were inhibited by the glycine receptor antagonist strychnine. The Ultiva®-induced currents demonstrated a specific equilibrium potential similar to glycine. CONCLUSIONS: We found that intrathecal administration of Ultiva® to SG neurons hyperpolarized membrane potentials and depressed presynaptic glutamate release predominantly through the activation of glycine receptors. No Ultiva®-induced excitatory effects were observed in SG neurons. Our results suggest different analgesic mechanisms of Ultiva® between intrathecal and intravenous administrations.

Enhancement of GABAergic tonic currents by midazolam and noradrenaline in rat substantia gelatinosa neurons in vitro.

BACKGROUND: Substantia gelatinosa of the spinal dorsal horn is crucial for transmission and modification of noxious stimuli. Previous studies have demonstrated that intrathecal midazolam, a benzodiazepine agonist, enhanced perioperative analgesia. Not only synaptic but also extrasynaptic inhibitory currents contribute to modification of noxious stimuli. Thus, the effects of midazolam on extrasynaptic gamma-aminobutyric acid (GABA) type A receptors in substantia gelatinosa neurons and interaction with noradrenaline, a transmitter of the descending inhibitory systems, were investigated. METHODS: Using whole cell patch-clamp technique in the adult rat spinal cord slices, extrasynaptic GABAergic currents were recorded in substantia gelatinosa neurons in the presence of gabazine (1 microm), which blocked synaptic GABAergic currents, and then midazolam (5 microm) and noradrenaline (20 microm) were applied. RESULTS: Bath application of midazolam induced tonic outward currents in the presence of gabazine. Although the decay time of synaptic current was prolonged, neither frequency nor amplitude was affected by midazolam. In contrast, the application of noradrenaline markedly increased both frequency and amplitude of synaptic currents with a slight enhancement of tonic currents. Coapplication of noradrenaline and midazolam markedly increased tonic currents, and the increase was much greater than the sum of currents induced by noradrenaline and midazolam. CONCLUSIONS: Midazolam had much larger effects on extrasynaptic GABA type A receptors than the synaptic receptors, suggesting a role of the enhancement of GABAergic extrasynaptic currents in the midazolam-induced analgesia. Because noradrenaline is shown to increase extrasynaptic GABA concentration, simultaneous administration of noradrenaline and midazolam may enhance the increased GABA action by midazolam, thereby resulting in an increase in tonic extrasynaptic currents.

NR2 subunits and NMDA receptors on lamina II inhibitory and excitatory interneurons of the mouse dorsal horn.

BACKGROUND: NMDA receptors expressed by spinal cord neurons in the superficial dorsal horn are involved in the development of chronic pain associated with inflammation and nerve injury. The superficial dorsal horn has a complex and still poorly understood circuitry that is mainly populated by inhibitory and excitatory interneurons. Little is known about how NMDA receptor subunit composition, and therefore pharmacology and voltage dependence, varies with neuronal cell type. NMDA receptors are typically composed of two NR1 subunits and two of four NR2 subunits, NR2A-2D. We took advantage of the differences in Mg2+ sensitivity of the NMDA receptor subtypes together with subtype preferring antagonists to identify the NR2 subunit composition of NMDA receptors expressed on lamina II inhibitory and excitatory interneurons. To distinguish between excitatory and inhibitory interneurons, we used transgenic mice expressing enhanced green fluorescent protein driven by the GAD67 promoter. RESULTS: Analysis of conductance ratio and selective antagonists showed that lamina II GABAergic interneurons express both the NR2A/B containing Mg2+ sensitive receptors and the NR2C/D containing NMDA receptors with less Mg2+ sensitivity. In contrast, excitatory lamina II interneurons express primarily NR2A/B containing receptors. Despite this clear difference in NMDA receptor subunit expression in the two neuronal populations, focally stimulated synaptic input is mediated exclusively by NR2A and 2B containing receptors in both neuronal populations. CONCLUSIONS: Stronger expression of NMDA receptors with NR2C/D subunits by inhibitory interneurons compared to excitatory interneurons may provide a mechanism to selectively increase activity of inhibitory neurons during intense excitatory drive that can provide inhibitory feedback.

Direct excitation of deep dorsal horn neurones in the rat spinal cord by the activation of postsynaptic P2X receptors.

ATP mediates somatosensory transmission in the spinal cord through the activation of P2X receptors. Nonetheless, the functional significance of postsynaptic P2X receptors in spinal deep dorsal horn neurones is still not yet well understood. Using the whole-cell patch-clamp technique, we investigated whether the activation of postsynaptic P2X receptors can modulate the synaptic transmission in lamina V neurones of postnatal day (P) 9-12 spinal cord slices. At a holding potential of -70 mV, ATPgammaS (100 microm), a nonhydrolysable ATP analogue, generated an inward current, which was resistant to tetrodotoxin (1 microm) in 61% of the lamina V neurones. The ATPgammaS-induced inward current was accompanied by a significant increase in the frequency of glutamatergic miniature excitatory postsynaptic currents (mEPSCs) in the majority of lamina V neurones. The ATPgammaS-induced inward current was not reproduced by P2Y receptor agonists, UTP (100 microm), UDP (100 microm), and 2-methylthio ADP (100 microm), and it was also not affected by the addition of guanosine-5'-O-(2-thiodiphosphate) (GDPbetaS) into the pipette solution, thus suggesting that ionotropic P2X receptors were activated by ATPgammaS instead of metabotropic P2Y receptors. On the other hand, alpha,beta-methylene ATP (100 microm) did not change any membrane current, but instead increased the mEPSC frequency in the majority of lamina V neurones. The ATPgammaS-induced inward current was suppressed by pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) (10 microm), but not by trinitrophenyl-ATP (TNP-ATP) (1 microm). Furthermore, we found that ATPgammaS (100 microm) produced a clear inward current which was observed in all lamina V neurones over P16 spinal cord slices, in contrast to P9-12. These results indicate that distinct subtypes of P2X receptors were functionally expressed at the post- and presynaptic sites in lamina V neurones, both of which may contribute to the hyperexcitability of lamina V in a different manner. In addition, the data relating to the developmental increase in the functional P2X receptors suggest that purinergic signalling may thus be more common in somatosensory transmission with maturation.

[Changes in serum Na+ and blood hemoglobin levels during three types of transurethral procedures for the treatment of benign prostatic hypertrophy].

BACKGROUND: Transurethral holmium YAG laser resection of the prostate (HoLR-P) and transurethral electrovaporization of the prostate (TUV-P) have recently received increasing attention as an effective minimally invasive approach for the treatment of prostatic hypertrophy. However, less information is available regarding the intraoperative changes in the serum Na+ and blood hemoglobin levels during either HoLR-P or TUV-P. METHODS: Intraoperative changes in serum Na+ and blood hemoglobin levels were investigated in 17 patients undergoing transurethral resection of the prostate (TUR-P, n = 7), HoLR-P (n = 7) or TUV-P (n = 3). The 3% D-sorbitol solution was used as the irrigating fluid in all the patients. RESULTS: In three patients, severe hyponatremia (118-123 mEq x l(-1)) developed abruptly (< or = 15 min) at various time points during TUR-P with (n = 1) or without (n = 2) cystostomy. However, no clinical symptoms were observed after development of the hyponatremia in those awake patients. No large (> 10 mEq x l(-1)) decreases in the Na+ level were observed in any of the patients undergoing HoLR-P or TUV-P. In patients undergoing TUR-P and HoLR-P, percent changes in serum Na+ level significantly correlated with those in blood hemoglobin level, but not with the resection time; the slopes were significantly larger than unity. CONCLUSIONS: The TUR syndrome is less likely to occur during HoLR-P or TUV-P. During TUR-P, the onset of severe hyponatremia appears to be unpredictable, and may not necessarily be accompanied by clinical symptoms. Frequent measurements of the serum Na+ level appear essential for early detection of severe hyponatremia.

[Changes in acid-base balance and blood lactate levels during radio frequency ablation conducted for the treatment of hepatocellular carcinomata in patients with liver cirrhosis].

BACKGROUND: Radio frequency ablation (RFA) has recently received increasing attention as an effective minimally invasive approach for the treatment of hepatocellular carcinomata (HCCs). However, we experienced a patient with liver cirrhosis (LC, Child-Pugh class B) in whom severe lactic acidosis developed during RFA conducted for the treatment of a HCC (-4.5 cm in diameter). This case prompted us to reevaluate possible injurious effects of RFA on non-tumorous liver tissues in the vicinity of its target in LC patients. METHODS: Intraoperative changes in acid-base balance and blood lactate levels, and postoperative changes in serum transaminases were investigated in LC (Child-Pugh class A) patients undergoing either laparotomic RFA (for the treatment of HCCs [diameter < 3 cm]) or partial hepatectomy (with the aid of the Pringle's manuever), and non-LC patients undergoing pancreatectomy. RESULTS: During the intraoperative period, significant lactic acidosis developed only in the patients undergoing hepatectomy. Core temperature significantly increased following the RFA. Postoperative increases in the transaminases observed in the patients undergoing hepatectomy were far larger than those observed in the patients undergoing either RAF or pancreatectomy. CONCLUSION: RFA, conducted for the treatment of smaller HCCs, appears to be minimally invasive even in the presence of LC (Child-Pugh class A).

[Development of severe lactic acidosis during radio frequency ablation conducted for the treatment of hepatocellular carcinomata in a patient with liver cirrhosis].

A 60-year-old male with liver cirrhosis (Child-Pugh class B) underwent laparotomic radio frequency ablation for the treatment of a solitary hepatocellular carcinoma (-4.5 cm in diameter). Severe lactic acidosis (base excess < -12 mEq.l-1, lactate > 150 mg.dl-1) developed during the intraoperative period, when neither his hemodynamics nor arterial oxygenation was significantly impaired. The blood loss was small (-200 g), and the serum hemoglobin level was maintained -10 g.dl-1 during the procedure. There was no evidence for impairment of either peripheral perfusion or renal function. In addition, there was no evidence for development of either splanchnic ischemia or diabetic ketoacidosis. Thus, the acidosis appeared to be caused by significant impairment of liver function possibly resulting from the ablation (total ablation time = -60 min). The core temperature increased rapidly (-1.5 degrees C/60 hr) immediately after the ablation was started, suggesting that a large amount of heat was produced in the ablated area and/or that the vicinity of the ablated area was richly supplied by blood flow. As a result, intact liver cells in the vicinity of the tumor probably suffered from thermal injuries. In conclusion, depending on preoperative liver function, ablated area, and/or blood flow in the vicinity of ablated area, the ablation may become significantly invasive.