DOR activation inhibits anoxic/ischemic Na+ influx through Na+ channels via PKC mechanisms in the cortex.

Activation of delta-opioid receptors (DOR) is neuroprotective against hypoxic/ischemic injury in the cortex, which is at least partially related to its action against hypoxic/ischemic disruption of ionic homeostasis that triggers neuronal injury. Na(+) influx through TTX-sensitive voltage-gated Na(+) channels may be a main mechanism for hypoxia-induced disruption of K(+) homeostasis, with DOR activation attenuating the disruption of ionic homeostasis by targeting voltage-gated Na(+) channels. In the present study we examined the role of DOR in the regulation of Na(+) influx in anoxia and simulated ischemia (oxygen-glucose deprivation) as well as the effect of DOR activation on the Na(+) influx induced by a Na(+) channel opener without anoxic/ischemic stress and explored a potential PKC mechanism underlying the DOR action. We directly measured extracellular Na(+) activity in mouse cortical slices with Na(+) selective electrodes and found that (1) anoxia-induced Na(+) influx occurred mainly through TTX-sensitive Na(+) channels; (2) DOR activation inhibited the anoxia/ischemia-induced Na(+) influx; (3) veratridine, a Na(+) channel opener, enhanced the anoxia-induced Na(+) influx; this could be attenuated by DOR activation; (4) DOR activation did not reduce the anoxia-induced Na(+) influx in the presence of chelerythrine, a broad-spectrum PKC blocker; and (5) DOR effects were blocked by PKCßII peptide inhibitor, and PKCθ pseudosubstrate inhibitor, respectively. We conclude that DOR activation inhibits anoxia-induced Na(+) influx through Na(+) channels via PKC (especially PKCßII and PKCθ isoforms) dependent mechanisms in the cortex.

Referred pain pattern of the pronator quadratus muscle.

Pain patterns of the myofascial trigger points (TrP) for most muscles of the forearm have been documented. However, there are no published reports on the referred pain patterns for the pronator quadratus (PQ) muscle. The purpose of this study was to determine the referred pain pattern of the TrP in the PQ. Thirty-five arms of 35 healthy adult volunteers with no history of neck pain, arm pain or paresthesia were studied. Following skin sterilization, a Teflon-coated syringe needle was inserted into the PQ of the non-dominant forearm under electromyographic guidance, and 0.3mL of 6% hypertonic saline was injected. Subjects drew in their pain areas on a pain diagram, and this drawing was transferred into the Pain Chart System for analysis. Two main pain patterns were observed. The most common pattern involved pain spreading both distally and proximally from the injection site, along the medial aspect of the forearm (57%). In half of these cases, the pain area extended to the medial epicondyle proximally and the fifth digit distally. The second main pattern revealed pain spreading distally to the third and/or fourth finger (29%). The pain patterns originating from the PQ resemble the C8-T1 dermatomes, and ulnar and median nerve sensory distributions. Thus, myofascial pain of the PQ should be considered as a possible cause of pain in the medial forearm and hand, especially when no other neurological abnormalities are present.

A method for screening enzyme inhibitors using size exclusion chromatography and ESI-LC-MS/MS.

A pilot study was performed for the development of a method to screen compound libraries using an electrospray mass spectrometer interfaced with liquid chromatography (LC). The mixture of compounds was obtained by combining low-molecular weight inhibitors of carboxypeptidase A (CPA), a representative zinc-containing proteolytic enzyme. After the incubation of the mixture with CPA, the enzyme-bound compounds were separated by size exclusion chromatography (SEC) from unbound compounds. The separation of compounds was affected by LC. Three compounds were identified, which represent the tight binding inhibitors of the library. These compounds were quantitated using an automatic switching valve to avoid the interference of buffer salts with the detection of analytes. The quantitated amounts of the compounds were found to be in good accordance with the K(i) values.