Intracolonic zymosan produces visceral hyperalgesia in the rat that is mediated by spinal NMDA and non-NMDA receptors

The present study examined the effects of colonic inflammation on reflex responses to colorectal distension (CRD) in awake rats. Visceromotor responses (VMR) to CRD were recorded in rats that received either no treatment or intracolonic saline or zymosan. Three hours following zymosan treatment (25...

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Bibliographic Details
Published in:Brain research 1996-10, Vol.736 (1), p.7-15
Main Authors: Coutinho, S.V., Meller, S.T., Gebhart, G.F.
Format: Article
Language:English
Subjects:
Animals
Biological and medical sciences
Colon
Colon - innervation
Colon - pathology
Colon - physiopathology
Colorectal distension
Dizocilpine Maleate - administration & dosage
Dizocilpine Maleate - pharmacology
Excitatory amino acid
Excitatory Amino Acid Antagonists - administration & dosage
Excitatory Amino Acid Antagonists - pharmacology
Fundamental and applied biological sciences. Psychology
Hyperalgesia - physiopathology
Inflammation
Injections, Spinal
Male
N-Methyl- d-aspartate
Nociception
Quinoxalines - administration & dosage
Quinoxalines - pharmacology
Rats
Rats, Sprague-Dawley
Receptors, Glutamate - physiology
Receptors, N-Methyl-D-Aspartate - physiology
Somesthesis and somesthetic pathways (proprioception, exteroception, nociception)
interoception
electrolocation. Sensory receptors
Spinal Cord - drug effects
Spinal Cord - physiology
Spinal Cord - physiopathology
Vertebrates: nervous system and sense organs
Visceral
Zymosan
Zymosan - pharmacology
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Summary:The present study examined the effects of colonic inflammation on reflex responses to colorectal distension (CRD) in awake rats. Visceromotor responses (VMR) to CRD were recorded in rats that received either no treatment or intracolonic saline or zymosan. Three hours following zymosan treatment (25 mg/ml; 1 ml) VMR response magnitudes were significantly increased at all intensities of CRD tested (10–80 mmHg). The enhanced responses to CRD were attenuated in a dose-dependent fashion by intrathecal administration of the non-competitive N-methyl- d-aspartate (NMDA) receptor channel blocker MK-801 to 60% of control and by the non-NMDA receptor antagonist DNQX to less than 20% of control. The metabotropic receptor antagonist AP-3 was without effect. Signs of multi-focal colonic inflammation were clearly present 3 h after zymosan treatment, characterized by an ingress of inflammatory cells and damaged crypts in and around these foci. Taken together these findings suggest that tissue inflammation increases the sensitivity of the colon to mechanical stimuli, leading to enhanced responses to CRD. This enhancement involves the activation of spinal NMDA as well as non-NMDA receptors, but not metabotropic receptors.
ISSN:0006-8993
1872-6240
DOI:10.1016/0006-8993(96)00661-0