Modulation of C-nociceptive Activities by Inputs from Myelinated Fibers.

To understand the mechanisms of neuropathic pain caused by demyelination, a rapid-onset, completed but reversible demyelination of peripheral A-fibers and neuropathic pain behaviors in adult rats by single injection of cobra venom into the sciatic nerve, was created. Microfilament recording revealed that cobra venom selectively blocked A-fibers, but not C-fibers. Selective blockade of A-fibers may result from A-fiber demyelination at the site of venom injection as demonstrated by microscope examination.

[Dendritic projections from meridian-related motoneurons to sympathic preganglion neurons in the spinal cord of rats].

Objective: Previous studies indicated a close involvement of reflex activities of motoneurons in the spinal cord in the mechanism of meridian phenomena. The present study was designed to investigate the dendrite projections of meridian-related motoneurons among the motoneurons and sympathetic preganglionic neurons in the spinal cord.

Methods: A total of 41 Sprague-Dawley rats were used in the present study.

Mechanisms of topical analgesics in relieving pain in an animal model of muscular inflammation.

Objective: To investigate the possible mechanisms of topical analgesics in relieving pain in an animal model of muscular inflammation.

Methods: Adult Sprague-Dawley rats of both sexes were injected with complete Freund's adjuvant to induce inflammation in the anterior tibialis muscle of left hindlimb. One of two types of topical analgesics: Xiaotong Tiegao (XTT), a Tibetan herb compound, or Capzasin (CAP), a cream containing 0.

A new animal model of trigeminal neuralgia produced by administration of cobra venom to the infraorbital nerve in the rat.

Background: Understanding the mechanism of trigeminal neuralgia may be elucidated by developing laboratory animal models that closely mimic the features of this specific type of neuropathic pain. We have developed an experimental animal model for trigeminal neuralgia using a technique of injecting cobra venom into the infraorbital nerve (ION) trunk.

Methods: Male Sprague-Dawley rats were subjected to the administration of cobra venom or saline into the ION trunk.

[Dense innervation of acupoints and its easier reflex excitatory character in rats].

Objective: To study the innervating character of tissues around the acupoints and along the meridian course and to analyze the reflex activity correlation between acupuncture points in a given meridian in the rat.

Methods: Forty Wistar and 15 SD rats were used in this study. Electrical activities of microfilaments of the afferent nerves (deep tibial nerve, peroneal nerve and the lateral cutaneous nerve of the leg) were observed for identifying their receptive field and the type of nerve fibers.

Glycosylation-induced depolarization facilitates subthreshold membrane oscillation in injured primary sensory neurons.

Subthreshold membrane potential oscillations (SMPO) in the injured dorsal root ganglion (DRG) neurons are involved in the generation of spontaneous activity, which can directly evoke neuropathic pain. Nerve injury usually triggers the synthesis of large quantities of membrane protein in nerve injured DRG neurons. Membrane proteins are glycosylated by addition of sugars, especially negatively charged sialic acid residues, which may depolarize the resting membrane potential (Vm), open voltage-gated channels in injured neurons, and cause spontaneous activity.

Sialic acid contributes to hyperexcitability of dorsal root ganglion neurons in rats with peripheral nerve injury.

Axonal injury of the dorsal root ganglion (DRG) neurons may alter the synthesis of certain membrane proteins that are responsible for the development of abnormal hyperexcitability. The external domains of most of these membrane proteins are sialylated. Because sialic acid carries heavy negative charges, the increase of sialylated proteins may increase neurons' negative surface charges, which will have predictable effects on the voltage-gated channels, and affect the excitability of injured neurons.

Human acupuncture points mapped in rats are associated with excitable muscle/skin-nerve complexes with enriched nerve endings.

As part of our ongoing investigation into the neurological mechanisms of acupuncture, we have tried to correlate the distribution of afferent nerve endings with acupuncture points (AP) in the rat hind limbs. In vivo extracellular microfilament recordings of Aalpha/Abeta/Adelta fibers were taken from peripheral nerves to search for units with nerve endings or receptive fields (RF) in the skin or the muscles. The location of the RFs for each identified unit was marked on scaled diagrams of the hind limb.

Sialic acid contributes to generation of ectopic spontaneous discharges in rats with neuropathic pain.

Ectopic spontaneous discharges (ESD) of teased myelinated fibers were recorded from the sciatic nerve proximal to the site of 'chronic constriction nerve injury' in the rat. Ca(2+), Mg(2+), Mn(2+), Ni(2+), La(3+) and some positively charged organic compounds (hexamethonium and poly-lysine) when applied topically to the injured site abolished or significantly reduced the rate of ESD. After enzymatic removal of sialic acid by neuraminidase (2 units/ml), the ESD was silenced in 11, reduced in four and unchanged in four of 19 fibers.