Responses of Primary Afferent Fibers to Acupuncture-Like Peripheral Stimulation at Different Frequencies: Characterization by Single-Unit Recording in Rats / 神经科学通报·英文版

The pain-relieving effect of acupuncture is known to involve primary afferent nerves (PANs) via their roles in signal transmission to the CNS. Using single-unit recording in rats, we characterized the generation and transmission of electrical signals in Aβ and Aδ fibers induced by acupuncture-like stimuli. Acupuncture-like signals were elicited in PANs using three techniques: manual acupuncture (MAc), emulated acupuncture (EAc), and electro-acupuncture (EA)-like peripheral electrical stimulation (PES). The discharges evoked by MAc and EAc were mostly in a burst pattern with average intra-burst and inter-burst firing rates of 90 Hz and 2 Hz, respectively. The frequency of discharges in PANs was correlated with the frequency of PES. The highest discharge frequency was 246 Hz in Aβ fibers and 180 Hz in Aδ fibers. Therefore, EA in a dense-disperse mode (at alternating frequency between 2 Hz and 15 Hz or between 2 Hz and 100 Hz) best mimics MAc. Frequencies of EA output >250 Hz appear to be obsolete for pain relief.

Differential Inhibition of Nav1.7 and Neuropathic Pain by Hybridoma-Produced and Recombinant Monoclonal Antibodies that Target Nav1.7 : Differential activities of Nav1.7-targeting monoclonal antibodies / 神经科学通报·英文版

The voltage-gated Na channel subtype Nav1.7 is important for pain and itch in rodents and humans. We previously showed that a Nav1.7-targeting monoclonal antibody (SVmab) reduces Na currents and pain and itch responses in mice. Here, we investigated whether recombinant SVmab (rSVmab) binds to and blocks Nav1.7 similar to SVmab. ELISA tests revealed that SVmab was capable of binding to Nav1.7-expressing HEK293 cells, mouse DRG neurons, human nerve tissue, and the voltage-sensor domain II of Nav1.7. In contrast, rSVmab showed no or weak binding to Nav1.7 in these tests. Patch-clamp recordings showed that SVmab, but not rSVmab, markedly inhibited Na currents in Nav1.7-expressing HEK293 cells. Notably, electrical field stimulation increased the blocking activity of SVmab and rSVmab in Nav1.7-expressing HEK293 cells. SVmab was more effective than rSVmab in inhibiting paclitaxel-induced mechanical allodynia. SVmab also bound to human DRG neurons and inhibited their Na currents. Finally, potential reasons for the differential efficacy of SVmab and rSVmab and future directions are discussed.

The VR1-Positive Primary Afferent-Mediated Expression of pERK in the Lumbosacral Neurons in Response to Mechanical and Chemical Stimulation of the Urinary Bladder in Rats

OBJECTIVE: This study characterized the neurons in the lumbosacral cord that express phospho ERK (pERK) after distension or irritation of the bladder, and their relation to the vanilloid receptor 1 (VR1) positive primary afferents. METHODS: Mechanical distension and chemical irritation of the bladder were induced by intravesical injection of the saline and mustard oil, respectively. Spinal neurons expressing pERK and the primary afferent fibers were characterized using multiple immunofluorescence for neurokinin 1 (NK1), neuronal nitric oxide synthetase (nNOS) and VR1. RESULTS: Neurons in lamina I, medial dorsal horn (MDH), dorsal gray commissure (DGC) and sacral parasympathetic nucleus (SPN) were immunoreactive for pERK after either mechanical or chemical stimulation. The majority of pERK positive cells were positive for NK1 in lamina I and SPN, but not in the DGC. Most of pERK positive cells are not stained for nNOS except in a small population of the cells in the SPN and DGC. Contacts between perikarya and dendrites of pERK-positive cells and terminals of primary afferents expressing VR1 were identified in lamina I, lateral collateral path (LCP) and SPN. CONCLUSION: In this study, the lumbosacral neurons activated by mechanical and chemical stimulation of the urinary bladder were identified with expression of the pERK, and also provided the evidence that VR1-positive primary afferents may mediate the activation of these neurons.

Mechanical Hyperalgesia Induced by Blocking Calcium-activated Potassium Channels on Capsaicin-sensitive Afferent Fiber

Small and large conductance Ca2+-activated K+ (SKCa and BKCa) channels are implicated in the modulation of neuronal excitability. We investigated how changes in peripheral KCa channel activity affect mechanical sensitivity as well as the afferent fiber type responsible for KCa channel-induced mechanical sensitivity. Blockade of SKCa and BKCa channels induced a sustained decrease of mechanical threshold which was significantly attenuated by topical application of capsaicin onto afferent fiber and intraplantar injection of 1-ethyl-2-benzimidazolinone. NS1619 selectively attenuated the decrease of mechanical threshold induced by charybdotoxin, but not by apamin. Spontaneous flinching and paw thickness were not significantly different after KCa channel blockade. These results suggest that mechanical sensitivity can be modulated by KCa channels on capsaicin-sensitive afferent fibers.

The Chemical Markers of Plant Lectin B4 in the Enteric Nervous System of Mice / 医学研究杂志

Objective To investigate the relationship of the chemical coding enteric nervous system of the mice and expression for neurotransmittor of enteric primary afferent neurons for Nociceptors.Methods Immunocytochemical and morphometric techniques were used to quantify the distribution of IB4-containing neurons in mice enteric nervous system using three mice chiocing every vision 50 neurons undering confocal microscopy IB4 immunolabelling and colocalized with calretinin and lectin B4.Results IB4 being binded to primary afferent neurons of enteric pleuxes happend in small intestin and colon of mice,where it was selective for nociceptive neurons.IB4 revealed large round or oval(Dogiel type II)neurons,type I neurons with prominent laminar dendrites and small neurons of myenteric ganglia.The type II neurons were immunoreactive for calretinin,and some type I neurons were immunoreactive for nitric oxide synthase.Most neurons in the submucosal ganglia bound IB4,and some of these were vasoactive intestinal peptide immunoreactive.Conclusion The results indicate that IB4 labels specific subgroups of enteric neurons in the enteric nervous system of the mice.These include intrinsic primary afferent neurons,but other neurons,including secretomotor neurons,are labeled.The results suggest that IB4 is not a specific label for enteric nociceptive neurons.

Effects of 3-aminobenzamide (3-AB) on the alterations in primary afferent and spinal neurons induced by spinal nerve injury in rats / 대한정형외과연구학회지

PURPOSE: The authors studied the effect of the 3-AB, an inhibitor of poly(ADP-ribose)polymerase (PARP), on the changes of primary afferents and spinal cord after spinal nerve injury. METHOD: The L5 and L6 spinal nerve of the rats were cut, and 3-AB (10 mg/Kg) was injected intraperitoneally once per day. The animals were sacrificed 3 days, 7 days, 14 days and 28 days after nerve injury. Binding of isolectin B4 (IB4) and immunohistochemistry (IHC) of CGRP for the changes in primary afferents, IHC of NK1 for sensory neurons, and of cleaved caspase 3 and NeuN for the apoptotic changes in spinal neurons were performed. RESULT: Decreased binding of IB4 and immunoreactivity (IR) for CGRP, increase of IR for NK1, and cleaved caspase 3 in both neurons and glia in ipsilateral dorsal horn were observed after spinal nerve injury. These changes were attenuated, especially at between 3 days and 14 days, by administration of 3-AB. CONCLUSION: It is suggested that inhibition of PARP by 3-AB may attenuate alterations of primary afferents and spinal neurons, at least in early stage, after spinal nerve injury.

Effects of 3-aminobenzamide (3-AB) on the alterations in primary afferent and spinal neurons induced by spinal nerve injury in rats / 대한정형외과연구학회지

PURPOSE: The authors studied the effect of the 3-AB, an inhibitor of poly(ADP-ribose)polymerase (PARP), on the changes of primary afferents and spinal cord after spinal nerve injury. METHOD: The L5 and L6 spinal nerve of the rats were cut, and 3-AB (10 mg/Kg) was injected intraperitoneally once per day. The animals were sacrificed 3 days, 7 days, 14 days and 28 days after nerve injury. Binding of isolectin B4 (IB4) and immunohistochemistry (IHC) of CGRP for the changes in primary afferents, IHC of NK1 for sensory neurons, and of cleaved caspase 3 and NeuN for the apoptotic changes in spinal neurons were performed. RESULT: Decreased binding of IB4 and immunoreactivity (IR) for CGRP, increase of IR for NK1, and cleaved caspase 3 in both neurons and glia in ipsilateral dorsal horn were observed after spinal nerve injury. These changes were attenuated, especially at between 3 days and 14 days, by administration of 3-AB. CONCLUSION: It is suggested that inhibition of PARP by 3-AB may attenuate alterations of primary afferents and spinal neurons, at least in early stage, after spinal nerve injury.

Comparative Study on the Nociceptive Responses Induced by Whole Bee Venom and Melittin

The present study was undertaken to confirm whether melittin, a major constituent of whole bee venom (WBV), had the ability to produce the same nociceptive responses as those induced by WBV. In the behavioral experiment, changes in mechanical threshold, flinching behaviors and paw thickness (edema) were measured after intraplantar (i.pl.) injection of WBV (0.1 mg & 0.3 mg/paw) and melittin (0.05 mg & 0.15 mg/paw), and intrathecal (i.t.) injection of melittin (6microgram). Also studied were the effects of i.p. (2 mg & 4 mg/kg), i.t. (0.2microgram & 0.4microgram) or i.pl. (0.3 mg) administration of morphine on melittin- induced pain responses. I.pl. injection of melittin at half the dosage of WBV strongly reduced mechanical threshold, and increased flinchings and paw thickness to a similar extent as those induced by WBV. Melittin- and WBV-induced flinchings and changes in mechanical threshold were dose- dependent and had a rapid onset. Paw thickness increased maximally about 1 hr after melittin and WBV treatment. Time-courses of nociceptive responses induced by melittin and WBV were very similar. Melittin-induced decreases in mechanical threshold and flinchings were suppressed by i.p., i.t. or i.pl. injection of morphine. I.t. administration of melittin (6microgram) reduced mechanical threshold of peripheral receptive field and induced flinching behaviors, but did not cause any increase in paw thickness. In the electrophysiological study, i.pl. injection of melittin increased discharge rates of dorsal horn neurons only with C fiber inputs from the peripheral receptive field, which were almost completely blocked by topical application of lidocaine to the sciatic nerve. These findings suggest that pain behaviors induced by WBV are mediated by melittin-induced activation of C afferent fiber, that the melittin- induced pain model is a very useful model for the study of pain, and that melittin-induced nociceptive responses are sensitive to the widely used analgesics, morphine.

DEVELOPMENTAL ORGANIZATION OF PRIMARY AFFERENT FIBERS IN THE DORSAL HORN OF THE MOUSE LUMBAR SPINAL CORD / 神经解剖学杂志

The present study was designed to examine the morphological pattern of primary afferent projections into the spinal dorsal horn by labeling the lumbar dorsal root ganglia with carbocyanine fluorescent dye DiI in mouse embryos and neonatal pups aged embryonic day 12 to postnatal day 3 (E12-P3). Primary afferent fibers projected into dorsal funiculus at E13, but did not penetrated into gray matter of dorsal horn until E15. The afferent projections became dense and entered the spinal gray matter more deeply at E16 and E17. By E18 the intensity of primary afferent in the deep part of the dorsal horn increased and their branching patterns became more complicated. Some of these primary fibers were also observed to ramify extensively in the superficial laminae. The projection pattern of primary afferent remained unchanged after birth, but the intensity of afferent terminals increased in the superficial laminae. In addition, afferent fiber collaterals that projected into the contralateral dorsal horn were also observed. They were first examined at E16 and mainly originated from the medial and deep part of the dorsal horn. Around birth, the contralateral projections were also found to originate from the lateral part of dorsal horn. Our results indicate that laminar organization of primary afferents in the spinal dorsal horn is established during the late embryonic and early postnatal stages.This organization then undergoes further refinement to match the pattern seen in the adult.

EFFECTS OF MORPHINE ON THE TERMINAL OF AFFERENT FIBER OF INJURED SCIATIC NERVE IN SPINAL LAMINA Ⅱ OF RAT——A HISTOCHEMICAL STUDY OF THE FLUORIDE-RESISTANT ACID PHOSPHATASE (FRAP) / 解剖学报

Objective To explore the effects of morphine on the terminal of primary afferent fiber distributing in spinal lamina Ⅱ after the sciatic nerve crush. Methods The positive reactive areas of fluoride-resistant acid phosphatase(FRAP) at spinal lamina Ⅱ were measured by the FRAP histochemistry and microcomputer image analysis techniques, after sciatic nerve was injured 15 days and 30 days both in morphine and control groups of rats. Results The positive reactive areas of FRAP at spinal lamina Ⅱ were depleted on different degree in two groups of rat after sciatic nerve was injured. The positive reactive areas of FRAP were greater 40% on injured sciatic nerve in 30 days than in 15 days in control group. In morphine group, the positive reactive areas of FRAP were larger 22% on injured sciatic nerve in 30 days than in 15 days; simulaneously also were bigger 19% than on injured sciatic nerve 30 days of control group.Conclusion The positive reactive areas of FRAP at spinal lamina Ⅱ show recovering enlargement as the surviving time lengthens in both groups of rats injured sciatic nerve.Morphine may enhance the positive reactive area of FRAP at spinal lamina Ⅱ in rat of sciatic nerve crush.

SPINAL CORD DORSUM POTENTIALS EVOKED BY STIMULATION IN THE REGION OF THE NUCLEUS RAPHE MAGNUS IN THE RAT / 西安交通大学学报(医学版)

A series of the positive cord dorsum potentials (CDP)were recorded in the dorsal surface of the spinal cord when the region of the nucleus raphy magnus (NRM)was stimulated by electricity. This CDP (NRM—CDP) consisted of three potentials. They were a Compound potential with a short time course and two slow potentials with a long time course which followed the compound one. The characteristics of the slowly potentials—NRM—CDP—1 and NRM—CDP—2 waves were analysed the parameters concerned were recorded. Therefore, a good experiment animal model and new information are provided for the further a study of the NRM action.

Effects of local administration of capsaicin on primary afferent nerve and substance P / 第二军医大学学报

Objective: To study the effects of capsaicin applied locally to infraorbital nerve on primary afferent nerve inadult rats. Methods:Capsaicin solution (2% ) was directly applied onto one lateral intraorbital nerve, and the contralateralnerve was used as self-control. Both experimental and control infraorbita1 nerves were observed under electron tnicroscope on3, 7, 14, 21, 28, 35 or 42 d after local administration. Substance P(SP)--like immunoreactive positive granules in both lateralnucleus caudalis spinalis nervi trigemini (CNV) were examined by immunohistochemical method. Results: Degenerated un-myelinated fibers in capsaicin-treated nerves were found under electron microscope, and no myelinated fibers changes werefound. The gray scale value of SP-like immunoreactive positive granules in the experimental side was markedly lower thanthat in the control side (P＜0. 01), while no significant difference was observed between different time groups. Conclusion:Local administration of capsaicin can produce selective destruction of unmyelinated fibers in primary afferent nerves, and canreduce the levels of SP in regions of CNV. The results suggest that local administration of capsaicin has potential therapeuticvalue for trigeminal neuralgia.