RESUMO
BACKGROUND: Using the urinary bladder as a model, neurophysiological studies of visceral primary afferents supplying inflamed tissue have been studied. In this study we have examined the response of the hypogastric afferents supplying the urinary bladder of the cat to intra-arterially injected algesic chemicals after experimental inflammation. METHODS: Twenty units were recorded from the strands of hypogastric nerve. Once a unit was found, the conduction velocity was determined by extracellular recording of single fiber. When the response of the unit excited by mechanical stimuli was found, chemical stimuli were applied by intra-arterial injection of algesic chemicals (bradykinin, KCl). And then, irritant chemical, 3% mustard oil injected into the urinary bladder for the induction of an experimental inflammation. After removal of the irritant and with the empty bladder, the response of the afferent unit to chemical stimuli by intra-arterially injected bradykinin and KCl were studied again. RESULTS: All units were found to be A delta fibers and responded to both mechanical and chemical stimuli. After experimental inflammation, the basal tone and spontaneous contraction of the urinary bladder were increased and spontaneous nerve activity of the hypogastric afferents appeared. Bladder contraction and nerve activity to intra-arterially injected bradykinin decreased more than those of controls before inflammation. The ratio of nerve activity to the bladder contraction after experimental inflammation was increased. CONCLUSIONS: The hypogastric afferents were sensitized after inflammation, which showed increased nerve response to intra-arterially injected bradykinin comparing to the contraction response of the urinary bladder.
