Tweety-Homolog 1 Facilitates Pain via Enhancement of Nociceptor Excitability and Spinal Synaptic Transmission / 神经科学通报·英文版

Tweety-homolog 1 (Ttyh1) is expressed in neural tissue and has been implicated in the generation of several brain diseases. However, its functional significance in pain processing is not understood. By disrupting the gene encoding Ttyh1, we found a loss of Ttyh1 in nociceptors and their central terminals in Ttyh1-deficient mice, along with a reduction in nociceptor excitability and synaptic transmission at identified synapses between nociceptors and spinal neurons projecting to the periaqueductal grey (PAG) in the basal state. More importantly, the peripheral inflammation-evoked nociceptor hyperexcitability and spinal synaptic potentiation recorded in spinal-PAG projection neurons were compromised in Ttyh1-deficient mice. Analysis of the paired-pulse ratio and miniature excitatory postsynaptic currents indicated a role of presynaptic Ttyh1 from spinal nociceptor terminals in the regulation of neurotransmitter release. Interfering with Ttyh1 specifically in nociceptors produces a comparable pain relief. Thus, in this study we demonstrated that Ttyh1 is a critical determinant of acute nociception and pain sensitization caused by peripheral inflammation.

Construction and implementation of a new system for fundamentals and frontiers of brain science curriculum for medical graduates / 医学研究生学报

In order to adapt to the rapid development of brain science and cultivate high-level innovative brain science research talents, combined with the practical teaching experience in the Department of Neurobiology of Air Force Military Medical University in recent years, the article constructs a new system for fundamentals and frontiers of brain science curriculum, which integrates advanced teaching concepts, diverse teaching forms and flexible teaching modes, expecting this new curriculum system will lay a solid foundation for the cultivation of talents in brain science.

Spinal CCL2 Promotes Central Sensitization, Long-Term Potentiation, and Inflammatory Pain via CCR2: Further Insights into Molecular, Synaptic, and Cellular Mechanisms / 神经科学通报·英文版

Mounting evidence supports an important role of chemokines, produced by spinal cord astrocytes, in promoting central sensitization and chronic pain. In particular, CCL2 (C-C motif chemokine ligand 2) has been shown to enhance N-methyl-D-aspartate (NMDA)-induced currents in spinal outer lamina II (IIo) neurons. However, the exact molecular, synaptic, and cellular mechanisms by which CCL2 modulates central sensitization are still unclear. We found that spinal injection of the CCR2 antagonist RS504393 attenuated CCL2- and inflammation-induced hyperalgesia. Single-cell RT-PCR revealed CCR2 expression in excitatory vesicular glutamate transporter subtype 2-positive (VGLUT2) neurons. CCL2 increased NMDA-induced currents in CCR2/VGLUT2 neurons in lamina IIo; it also enhanced the synaptic NMDA currents evoked by dorsal root stimulation; and furthermore, it increased the total and synaptic NMDA currents in somatostatin-expressing excitatory neurons. Finally, intrathecal RS504393 reversed the long-term potentiation evoked in the spinal cord by C-fiber stimulation. Our findings suggest that CCL2 directly modulates synaptic plasticity in CCR2-expressing excitatory neurons in spinal lamina IIo, and this underlies the generation of central sensitization in pathological pain.

Correlations between edema and the immediate and prolonged painful consequences of inflammation: therapeutic implications? / 生理学报

The precise relationship between the degree of pain and the degree of inflammation in the individual remains debated. A quantitative analysis simultaneously applied to the immediate and prolonged painful consequences of inflammation has not yet been done. Thus, the correlations between edema, nociception and hypersensitivity following an inflammatory insult were assessed in rodents. To better understand the therapeutic value of modifying specific aspects of inflammation, the effects of an anti-inflammatory drug were compared to the results. Inbred strains of mice and outbred rats received an intraplantar injection of honeybee venom and the between-group and within-group correlations were calculated for spontaneous nociceptive measures, thermal and mechanical hypersensitivity, and edema and temperature. The effect of indomethacin on the pain and inflammation measures was examined. Edema correlated with spontaneous flinching, licking and lifting of the injected paw (P< or =0.003), and not with thermal or mechanical hypersensitivity. Indomethacin affected edema and spontaneous nociception dose-dependently, and affected hypersensitivity only at the highest dose tested (P< 0.05). These results suggest that edema may contribute only to immediate spontaneous nociceptive responses to an inflammatory insult, and not to the more clinically relevant prolonged hypersensitivity. This analysis represents a method for determining which inflammatory processes are the most promising therapeutic targets against the multiple painful consequences of inflammation.

Differential actions of intrathecal nociceptin on persistent spontaneous nociception, hyperalgesia and inflammation produced by subcutaneous bee venom injection in conscious rats / 生理学报

Nociceptin is an endogenous ligand for the opioid receptor-like 1 (ORL1) receptor. The present study was designed to investigate spinal actions of nociceptin on the spontaneous nociception, hyperalgesia and inflammation induced by subcutaneous bee venom injection. Subcutaneous injection of bee venom into one hindpaw of conscious rat produced a persistent spontaneous nociception followed by a long-lasting primary heat and mechanical hyperalgesia as well as local inflammation. Compared with the pre-saline group, pretreatment with intrathecal injection of three doses (3, 10 and 30 nmol) of nociceptin produced significant suppression on the spontaneous paw flinching reflex. The inhibitory rates were 37+/-7, 43+/-6 and 57+/-11%, respectively, which were enhanced with an increase in the concentration of nociceptin. The inhibitory action of nociceptin was completely antagonized by a new selective ORL1 receptor antagonist CompB (30 nmol). Pre-treatment with 10 nmol nociceptin prior to bee venom produced no significant effect on the occurrence of primary heat and mechanical hyperalgesia, nor did post-treatment with the same dose again 3 h after bee venom injection. Additionally, pre-treatment with nociceptin had no effect on the bee venom-induced increase in paw thickness and volume and the plasma protein extravasation. These results indicate that intrathecal nociceptin has no effect on primary heat and mechanical hyperalgesia as well as inflammation, but has dose-related anti-nociceptive effect on the bee venom-induced persistent spontaneous nociception via activation of spinal ORL1 receptor.

Effects of etomidate on local synaptic transmission in substantia gelatinosa neurons of the adult rat spinal cord / 生理学报

By using blind spinal slice whole-cell patch-clamp technique, we observed the influence of etomidate (ET) on synaptic transmission in substantia gelatinosa neurons of the adult rat spinal cord. Male adult Sprague-Dawley rats (7~8 weeks old) were anaesthetized with urethane (1.2 g/kg, i.p.), and then lumbosacral laminectomy was performed. The lumbosacral spinal cord (L1~S3) was removed and placed in preoxygenated Krebs solution at 1~3 degrees C. After cutting all of the ventral and dorsal roots, the pia-arachnoid membrane was removed. The spinal cord was mounted on a vibrating microslicer and then a 500 microm thick transverse slice was cut. The slice was placed on a nylon mesh in the recording chamber, and then perfused at a rate of 15~20 ml/min with Krebs solution saturated with 95% O2 and 5% CO2, and maintained at 36+/-1 degrees C. Substantia gelatinosa neurons were identified by their location. Under a binocular microscope and with transmitted illumination, the substantia gelatinosa was clearly discernible as a relatively translucent band across the dorsal horn. The resistance of patch clamp electrodes was 8~12 Msigma. Signals were gained by using an Axopatch 200B amplifier with low-passfiltered at 5 kHz, and digitized at 333 kHz with an A/D converter. The results are as follows. (1) To see whether or not ET has any effects on the local miniature excitatory postsynaptic currents (mEPSC), the holding potential was set up at -70 mV. Under such a condition extracellular superfusion was made with 1 micromol/L TTX for 2 min first, which was followed by consistent application of 500 micromol/L ET and 1 micromol/L TTX for 1 min. It was shown that ET did not influence the decay time, frequency and amplitude of mEPSC, when compared to the control. (2) To see whether or not ET has any effects on the local miniature inhibitory postsynaptic currents (mIPSC) mediated by GABA(A) receptor, the holding potential was set up at 0 mV. Under this condition extracellular superfusion was made with 1 micromol/L TTX and 1 micromol/L strychnine, an antagonist of glycine receptor, for 2 min, and then with consistent application of 50 micromol/L ET, 1 micromol/L TTX and 1 micromol/L strychnine for 1 min. ET prolonged the decay time of GABAergic mIPSC by 45.57+/-12.46% (P<0.05), but did not influence the frequency and amplitude of GABAergic mIPSC, when compared with the control. (3) To see whether or not ET has any effects on the local mIPSC mediated by glycine receptor, the holding potential was also set up at 0 mV, and under this condition extracellular superfusion was made with 1 mmol/L TTX and 10 mmol/L bicuculline, an antagonist also set up at 0 mV, and under this condition extracellular superfusion was made with 1 micromol/L TTX and 10 micromol/L bicuculline, an antagonist of GABA(A) receptor, for 2 min, and then with consistent application of 50 micromol/L ET, 1 micromol/L TTX and 10 micromol/L bicuculline for 1 min. ET had no effects on decay time, frequency and amplitude of glycinergic mIPSC. The above-mentioned results show that ET plays anesthetic or analgesic roles by modulating the decay time of GABAergic mIPSC, i.e. by prolonging the mean open time of GABA(A) receptors, however, ET has no direct effect on local excitatory synaptic transmission in substantia gelatinosa neurons of the adult rat spinal cord.

INVOLVEMENT OF PERIPHERAL NMDA RECEPTORS IN PERSISTENT NOCICEPTION INDUCED BY SUBCUTANEOUS BEE VENOM INJECTION: A BEHAVIORAL STUDY / 神经解剖学杂志

The present study was to investigate whether peripheral NMDA receptors were involved in the persistent nociceptioninduced by subcutaneous (s. C. ) bee venom injection in the conscious rat by using quatitative pain scoring methods, a.c. Bee venom injection into one hindpaw resulted in a persistent, monophasic nociceptive response characterized by continuously flinching.lifting and licking the injected paw for more than I h. The non-competitive. NMDA receptor channel blockers, ketamine and ME-801, were administered s.c. 5 or 20 min after bee venom. Local ketamine injection produced a suppression of flinching reflex by 20. 90±2.88% and 45.76±13.9%, while that of lifting/bcking time by 39. 53±10. 05% and 59.94±5.53%, at doses of 25mmol/L and 50 mmol/L respectively without any motor disturbance, Local MK-801 resulted in an inhibition of flinching reflexby 22.84±3.12% and 49.53±5.35%. While that of lifting/licking time by 17. 49±5.67%and 53.49±3. 87%. At doses of 10μmol/L and 100 ,μmol/L respectively also with no motor disturbance. However, s. C. Administration of ketamine and MK-801 inior region symmetrical to the bee venom injection site on the contralateral hindpaw produced no change in the nociceptive behaviors, suggesting that the analgesic actions of keramme and MK-8Ol were not the result of systemic effects. The present resultsuggests that peripheral NMDA receptors are involved in the production of persistent pain.

PERIPHERALLY SUPPRESSIVE EFFECTS OF KETAMINE ON SUBCUTANEOUS BEE VENOM-INDUCED PROLONGED,PERSISTENT FIRING OF SPINAL WIDE-DYNAMICRANGE NEURONS IN THE CAT / 神经解剖学杂志

By using extracellular single unit recording technique, locally suppressive effects of a single dose of ketamine on sub-cutaneous (s. c. ) bee venom-induced increase in firing of wide dynamic-range (WDR) neurons in spinal dorsal horn were investi-gated on urcthane-chloralose anesthetized cats. Injection of bee venom s.c. into the cutaneous receptive field (RF) resulted in asingle phase of prolonged, persistently increased firing of WDR neurons over background activity for more than 1 h. Local pre-treatment with ketamine (100 mM, 0. 1 m l) into the center of RF where bee venom was injected produced a dramatic suppressionof the increased neuronal firing by 60% (3.10± 0.42 spikes/s, n= 5) when compared with saline pre-treated group (7.61 ± 0.17spikes/ s. n = 5 ). Moreover, local post-treatment with the same dose of ketamine also produced a profound suppression of the in-creased neuronal activity by 81% (1.51±0.06 spikes/s, n=5) when compared with the saline post-treated group (7.76±0.15spikes s, n=5). However, s.c. administration with the same dose of ketamine into a symmetrical region on the bee venom un-treated contralateral hindpaw produced no affection on the increased firing of the WDR neurons, suggesting that the suppressiveaction of local ketamine was not the result of systemic effects. The present result suggests that ketamine may exert its localantinociceptive effects mainly through the peripheral NMDA receptors in addition to its partially potential blocking effects onsodium and voltage-sensitive calcium channels.