Neuropathy reduces viscero-somatic inhibition via segmental mechanisms in rats.
The effect of an experimental neuropathy on the viscero-somatic inhibition was studied in lightly anesthetized rats. In controls, colo-rectal distension at noxious intensities produced a multisegmental prolongation of the withdrawal response induced by noxious stimulation of the skin. In rats with a spinal nerve-ligation induced neuropathy this viscero-somatic inhibition was significantly reduced within the neuropathic segment (the hindlimb) but not outside of it (the tail). Naloxone, an opioid antagonist, attenuated this viscero-somatic inhibition in controls and it did not restore the inhibition in neuropathic rats. The results indicate that somatic neuropathy produces a segmental attenuation of viscero-somatic inhibition and this attenuation cannot be explained by a nerve injury-induced release of endogenous opioids. The decreased inhibition of somatic signals may contribute to the hypersensitivity observed in neuropathic conditions.
Pertovaara
Antti
A
Department of Physiology, Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, FIN-20520 Turku.
Kalmari
Jaakko
J
D000818:Animals; D003106:Colon / Q000294:innervation / Q000503:physiopathology; D006358:Hot Temperature / Q000009:adverse effects; D006930:Hyperalgesia / Q000473:pathology / Q000503:physiopathology; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009433:Neural Inhibition / Q000502:physiology*; D009475:Neurons, Afferent / Q000502:physiology; D009619:Nociceptors / Q000502:physiology*; D010146:Pain / Q000473:pathology / Q000503:physiopathology*; D010147:Pain Measurement; D017288:Pain Threshold / Q000502:physiology*; D010523:Peripheral Nervous System Diseases / Q000473:pathology / Q000503:physiopathology*; D010812:Physical Stimulation; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000502:physiology; D012021:Reflex, Abnormal / Q000502:physiology*; D012867:Skin / Q000294:innervation / Q000503:physiopathology; D013116:Spinal Cord / Q000503:physiopathology; D013127:Spinal Nerves / Q000293:injuries / Q000473:pathology / Q000503:physiopathology; D017833:Visceral Afferents / Q000503:physiopathology*
D009292:Narcotic Antagonists; D009270:Naloxone