Peripheral Control of Inflammatory but Not Neuropathic Pain by Endogenous Cholinergic System.
Summary of "Peripheral Control of Inflammatory but Not Neuropathic Pain by Endogenous Cholinergic System."
This study investigated the role of the cholinergic system in the modulation of inflammatory and neuropathic pain. The paw pressure test was used with inflammatory pain induced by intraplantar injection of carrageenan and neuropathic pain induced by sciatic nerve constriction. All drugs were locally administered into the right hindpaw of rats. Neostigmine, an acetylcholinesterase inhibitor (2, 4, 8 or 16 μg), inhibited the inflammatory pain induced by carrageenan (250 μg/paw), but not the hyperalgesia induced by prostaglandin E(2) (2 μg/paw). Neostigmine (8 μg) increased the nociceptive threshold only in the treated paw, suggesting only a local effect. The muscarinic antagonist atropine (150, 300 and 600 μg) caused a reduction in the nociceptive threshold induced by carrageenan (125 μg/paw), but not by prostaglandin E(2) (1 μg/paw). Atropine significantly decreased the nociceptive threshold only in the treated paw. On the other hand, in the presence of neuropathic pain, atropine (300 μg) did not alter the nociceptive threshold induced by constriction of the sciatic nerve. This study suggests that a peripheral endogenous cholinergic system involving muscarinic receptors may be activated during inflammation as a modulatory negative feedback control of inflammatory pain.
Department of Pharmacology, Institute of Biological Sciences, UFMG, Belo Horizonte, Brazil.
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Medical and Biotech [MESH] Definitions
Drugs that bind to but do not activate muscarinic cholinergic receptors (RECEPTORS, MUSCARINIC), thereby blocking the actions of endogenous acetylcholine or exogenous agonists. Muscarinic antagonists have widespread effects including actions on the iris and ciliary muscle of the eye, the heart and blood vessels, secretions of the respiratory tract, GI system, and salivary glands, GI motility, urinary bladder tone, and the central nervous system. Antagonists that discriminate among the various muscarinic receptor subtypes and might allow better control of peripheral and central actions are under development.
Receptors, Purinergic P2x4
A widely distributed purinergic P2X receptor subtype that plays a role in pain sensation. P2X4 receptors found on MICROGLIA cells may also play a role in the mediation of allodynia-related NEUROPATHIC PAIN.
Pain in the facial region including orofacial pain and craniofacial pain. Associated conditions include local inflammatory and neoplastic disorders and neuralgic syndromes involving the trigeminal, facial, and glossopharyngeal nerves. Conditions which feature recurrent or persistent facial pain as the primary manifestation of disease are referred to as FACIAL PAIN SYNDROMES.
Peripheral Nervous System
The nervous system outside of the brain and spinal cord. The peripheral nervous system has autonomic and somatic divisions. The autonomic nervous system includes the enteric, parasympathetic, and sympathetic subdivisions. The somatic nervous system includes the cranial and spinal nerves and their ganglia and the peripheral sensory receptors.
Peripheral Nervous System Agents
Drugs that act principally at one or more sites within the peripheral neuroeffector systems, the autonomic system, and motor nerve-skeletal system. (From Smith and Reynard, Textbook of Pharmacology, 1991, p75)
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