Pain perception

R = / -C H ), in low doses, exhibits the former behavior and is used primarily as an extradural agent in obstetrics. The lowest effective extradural concentration of etidocaine (21, X = CH, R = R = 2H, R = / -C H ), however, shows both adequate sensory and profound motor blockade so that it is useful in surgical situations where maximum neuromuscular blockade is necessary. In an isolated nerve preparation, bupivacaine blocks unmyelinated C fibers which are mainly responsible for pain perception at a much greater extent than the myelinated A fibers which carry motor impulses. It is postulated that absorption of bupivacaine by the vasculature at the site of injection, combined with the slow diffusion of this agent, results in an insufficient amount of the drug penetrating the large A fibers to cause motor conduction blockade. Clinically, motor block can be observed in some procedures. 

Capsaicin, also known as N-Vanillyl-8-methyl-6-(E)-noneamide, is the most pungent of the group of compounds called capsaicinoids It is a common ingredient in varieties of pepper such as habanero, Thai, tabasco, cayenne etc. One target with which capsaicin interacts is the capsaicin receptor, an ion channel belonging to the superfamily of TRP channels. Because of the structural relation to other TRP channels and because the vanilloid moiety is an essential component of capsaicin, the capsaicin receptor is also called TRPVI or vanilloid receptor (VR1). It is involved in heat and pain perception. 

In capsaicin-sensitive neurons, TRPVl is co-expressed with various receptors involved in pain perception (e.g. bradykinin B2, purine P2X3). There is important cross-talk among these receptors. For example, stimulation... 

The pathophysiologic mechanisms of TTH are not clearly understood. The pain is thought to originate in the myofascial tissues of the head, but central brain processing is believed to be an important modulator of pain perception.14... 

Trigeminal nerve The fifth cranial nerve responsible for pain perception in the head and face. 

Martin B, Lichtman AH. Cannabinoid transmission and pain perception. Neurobiol Dis 1998 5 447 161. 

Drugs that modify pain perception act in part through the histaminergic system 262... 

Diabetes insipidus occurs with a loss of vasopressin production in the Brattleboro rat model 330 Mutations and knockouts of peptide-processing enzyme genes cause a myriad of physiological problems 330 Neuropeptides play key roles in appetite regulation and obesity 330 Enkephalin knockout mice reach adulthood and are healthy 331 Neuropeptides are crucial to pain perception 331... 

Neuropeptides are crucial to pain perception. Substance P is released in the spinal cord by a subset of dorsal root ganglion neurons Substance P is crucial to the sensation of noxious stimuli. Substance P binds to the neurokinin-1... 

After activation of supraspinal pain perception structures, a headache occurs because of central modulation of incoming peripheral stimuli. 

Similar to exogenous cannabinoids, anandamide has analgesic effects (Fride and Mechoulam 1993). Peripheral anandamide (10 mg/kg IM) produces antinociception in primates. However, centrally administered anandamide does not alter pain perceptive thresholds (Murillo-... 

Several physiological roles of endocannabinoids have been identified, including memoiy, cognition, movement, and pain perception (Stella et al. 1997). Elucidation of the endocannabinoid systems is essential to the understanding of the effects of cannabis. There are both similarities and some pointed differences between the effects of exogenous and endogenous cannabinoids. 

Dorsal raphe Main serotonin (5-HT)-containing neurons that project through the brain. Other raphe neurons project down the spinal cord where they act as a gating mechanism for pain perception from the periphery. Main activity is in the regulation of mood, anxiety, sexual behaviour, sleep. 

Serotonin mediates many central and peripheral physiological functions, including contraction of smooth muscle, vasoconstriction, food intake, sleep, pain perception, and memory, a consequence of it acting on several distinct receptor types. Although 5-HT may be metabolized by monoamine oxidase, platelets and neurons possess a high-affinity mechanism for reuptake of 5-HT. This mechanism may be inhibited by the widely prescribed antidepressant drugs termed selective serotonin re-uptake inhibitors (SSRl), e.g. fluoxetine (Prozac ), thereby increasing levels of 5-HT in the central nervous system. 

Effects of opioids (B). The analgesic effect results from actions at the level of the spinal cord (inhibition of nociceptive impulse transmission) and the brain (attenuation of impulse spread, inhibition of pain perception). Attention Ltillmann, Color Atlas of Pharmacology 2000 Thieme All rights reserved. Usage subject to terms and conditions of license. 

CNS effects include decreased pain perception, altered reaction to pain, euphoria and hypnosis, nausea and vomiting, respiratory depression and suppression of cough reflexes. Increased tone of the gastrointestinal tract is primarily mediated by fx receptors in the bowel. 

Most of the serotonin in the brain is in the brainstem, specifically in the raphe nuclei considerable amounts also are present in areas of the hypothalamus, the limbic system, and the pituitary gland. Current evidence indicates that serotonin is involved in the regulation of several aspects of behavior, including sleep, pain perception, depression, sexual activity, and aggressiveness. Some of the most important antidepressant agents are believed to prevent the reuptake of serotonin (see Chapter 33). Serotonin also may be involved in temperature regulation and in the hypothalamic control of the release of pituitary hormones. 

PGI2 IP Antithrombotic function [28], a mediator of inflammation [28], enhancement of pain perception [28], augmented cardiac hypertrophy [29], modulation of pulmonary vascular remodeling [30], prevention of atherosclerosis [31]... 

T. Murata, F. Ushikubi, T. Matsuoka, M. Hirata, A. Yamasaki, Y. Sugimoto, A. Ichikawa, Y. Aze, T. Tanaka, N. Yoshida, A. Ueno, S. Oh-ishi, S. Narumiya, Altered pain perception and inflammatory response in mice lacking prostacyclin receptor, Nature 388 (1997) 678. 

Mechanism of Action Anticholinergic alkaloids that inhibit the action of acetylcholine at postganglionic (muscarinic) receptor sites. Morphine (10% of opium) depresses cerebral cortex, hypothalamus, and medullary centers. Therapeutic Effect Decreases digestive secretions, increases GI muscle tone, reduces G1 force, alters pain perception and emotional response to pain. 

Mechanism of Action An opioid that binds to opiate receptor sites in the CNS. Reduces intensity of pain stimuli incoming from sensory nerve endings. Therapeutic Effect Alters pain perception and emotional response to pain. 

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