[The capsaicin receptor. "TRPing" transduction for painful stimuli]

[Pharmacology of non-opioid analgesics]

Due to high prescription rates as well as the frequent use as over the counter drugs, it is of interest to consider non-opioid analgesics when evaluating the quality and appropriateness of a given overall medication. This article sums up the basic pharmacology and main adverse effects of these analgesics. Non-opioids can be further classified according to their additional mechanisms of action besides analgesia. High-dose acetylsalicylic acid, traditional nonsteroidal anti-inflammatory drugs, and coxibs exhibit antipyretic and anti-inflammatory properties. Acetaminophen and metamizole (dipyrone) are analgesics and antipyretic agents, while metamizole exhibits also spasmolytic effects. Capsaicin and intrathecal ziconotide are pure analgesics.

Perceptual uncertainty

The number of the distinct tactile percepts exceeds the number of receptor types in the skin, signifying that perception cannot be explained by a one-to-one mapping from a single receptor channel to a corresponding percept. The abundance of touch experiences results from multiplexing (the coexistence of multiple codes within a single channel, increasing the available information content of that channel) and from the mixture of receptor channels by divergence and convergence. When a neuronal representation emerges through the combination of receptor channels, perceptual uncertainty can occur-a perceptual judgment is affected by a stimulus feature that would be, ideally, excluded from the task. Though uncertainty seems at first glance to reflect nonoptimality in sensory processing, it is actually a consequence of efficient coding mechanisms that exploit prior knowledge about objects that are touched. Studies that analyze how perceptual judgments are "fooled" by variations in sensory input can reveal the neuronal mechanisms underlying the tactile experience.

[Chili for therapy of trigeminus neuralgia: a case report]

We report the case of a 39-year-old female patient who suffered from trigeminal neuralgia of the left lingual nerve for 6 years. The previous therapy according to the guidelines including a Jannetta operation was unsuccessful. Only after beginning with daily mastication and consumption of very hot chilli peppers has the patient become reliably pain-free.

[The role of TNF-alpha as pain mediator]

Tumor necrosis factor (TNF)-alpha is not only a proinflammatory mediator but also a pain mediator. Numerous nociceptors express the TNF receptors 1 and 2. By a direct action at the nociceptor TNF-alpha is involved in the generation and maintenance of inflammation-related pain.

TRPV1: on the road to pain relief

Historically, drug research targeted to pain treatment has focused on trying to prevent the propagation of action potentials in the periphery from reaching the brain rather than pinpointing the molecular basis underlying the initial detection of the nociceptive stimulus: the receptor itself. This has now changed, given that many receptors of nociceptive stimuli have been identified and/or cloned. Transient Receptor Potential (TRP) channels have been implicated in several physiological processes such as mechanical, chemical and thermal stimuli detection. Ten years after the cloning of TRPV1, compelling data has been gathered on the role of this channel in inflammatory and neuropathic states. TRPV1 activation in nociceptive neurons, where it is normally expressed, triggers the release of neuropeptides and transmitters resulting in the generation of action potentials that will be sent to higher CNS areas where they will often be perceived as pain. Its activation also will evoke the peripheral release of pro-inflammatory compounds that may sensitize other neurons to physical, thermal or chemical stimuli. For these reasons as well as because its continuous activation causes analgesia, TRPV1 has become a viable drug target for clinical use in the management of pain. This review will provide a general picture of the physiological and pathophysiological roles of the TRPV1 channel and of its structural, pharmacological and biophysical properties. Finally, it will provide the reader with an overall view of the status of the discovery of potential therapeutic agents for the management of chronic and neuropathic pain.