Amplified cold transduction in native nociceptors by M-channel inhibition.

Topically applied camphor elicits a sensation of cool, but nothing is known about how it affects cold temperature sensing. We found that camphor sensitizes a subpopulation of menthol-sensitive native cutaneous nociceptors in the mouse to cold, but desensitizes and partially blocks heterologously expressed TRPM8 (transient receptor potential cation channel subfamily M member 8). In contrast, camphor reduces potassium outward currents in cultured sensory neurons and, in cold nociceptors, the cold-sensitizing effects of camphor and menthol are additive. Using a membrane potential dye-based screening assay and heterologously expressed potassium channels, we found that the effects of camphor are mediated by inhibition of Kv7.2/3 channels subtypes that generate the M-current in neurons. In line with this finding, the specific M-current blocker XE991 reproduced the cold-sensitizing effect of camphor in nociceptors. However, the M-channel blocking effects of XE991 and camphor are not sufficient to initiate cold transduction but require a cold-activated inward current generated by TRPM8. The cold-sensitizing effects of XE991 and camphor are largest in high-threshold cold nociceptors. Low-threshold corneal cold thermoreceptors that express high levels of TRPM8 and lack potassium channels are not affected by camphor. We also found that menthol--like camphor--potently inhibits Kv7.2/3 channels. The apparent functional synergism arising from TRPM8 activation and M-current block can improve the effectiveness of topical coolants and cooling lotions, and may also enhance TRPM8-mediated analgesia.

Phenotyping sensory nerve endings in vitro in the mouse.

This protocol details methods to identify and record from cutaneous primary afferent axons in an isolated mammalian skin-saphenous nerve preparation. The method is based on extracellular recordings of propagated action potentials from single-fiber receptive fields. Cutaneous nerve endings show graded sensitivities to various stimulus modalities that are quantified by adequate and controlled stimulation of the superfused skin with heat, cold, touch, constant punctate pressure or chemicals. Responses recorded from single-fibers are comparable with those obtained in previous in vivo experiments on the same species. We describe the components and the setting-up of the basic equipment of a skin-nerve recording station (few days), the preparation of the skin and the adherent saphenous nerve in the mouse (15-45 min) and the isolation and recording of neurons (approximately 1-3 h per recording). In addition, stimulation techniques, protocols to achieve single-fiber recordings, issues of data acquisition and action potential discrimination are discussed in detail.

Treatment of patients with chronic headaches in a hospital for traditional Chinese medicine in Germany. A randomised, waiting list controlled trial.

OBJECTIVE: To investigate the effectiveness of a clinical treatment program with traditional Chinese medicine for migraine and tension-type headache. METHODS: Ninety-one patients with migraine, episodic or chronic tension-type headache according to the criteria of the International Headache Society were randomised into an experimental or a waiting list control group. Patients in the experimental group were treated 4 weeks in a hospital for traditional Chinese medicine after a baseline period of one month. Patients in the waiting list group continued their previous headache treatment. Main outcome measure was the difference in the number of days with headache of at least moderate intensity during baseline (month 1) and month 7. RESULTS: The difference in the number of days with headache of at least moderate intensity was 5.6 (S.D., 6.1) days in the experimental group and 1.2 (S.D., 4.5) days in the waiting list group (P <0.001). A reduction of more than 50% in headache days was observed in 52% of the patients in the experimental group and 16% in the waiting list group. Patients with migraine and a combination of migraine and episodic tension-type headaches improved more than patients with other headaches. CONCLUSION: The results of this study indicate that treatment in the hospital for traditional Chinese medicine in Kotzting is associated with lasting improvements in the majority of patients.