Physiology & behavior
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Physiology & behavior · Feb 2001
Clinical TrialOral irritation by sodium chloride: sensitization, self-desensitization, and cross-sensitization to capsaicin.
Psychophysical methods were used to investigate the irritant sensory properties of concentrated NaCl. The first experiment investigated potential sensitization and desensitization properties. Subjects rated the intensity of the irritation elicited by 10 successive applications of 5 M NaCl on one side of the dorsal surface of the tongue. ⋯ In a second experiment, the effect of amiloride on NaCl-evoked irritation was studied. One side of the tongue was treated with 1 mM amiloride, after which 5 M NaCl was applied bilaterally and subjects performed the same 2-AFC and rating procedures. Since amiloride significantly reduced the intensity of the irritant sensation, the contribution of amiloride-sensitive ionic currents or the Na+/H+ exchange pump (NHE) are suggested as possible transduction mechanisms in lingual nociceptors mediating NaCl-evoked oral irritation.
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The susceptibility to pentylenetetrazol (PTZ)-induced seizures during postnatal ontogeny [postnatal day (PN) 10-220] was investigated in two rat strains. The WAG/Rij strain, genetically prone for developing generalized absence epilepsy, and Wistar rats were tested and compared at PN 10, 26, 30, 70, 90, 125, and 220 on the PTZ-convulsive threshold. A subconvulsive dose of 25-mg/kg PTZ was administered every 15 min, and the occurrence of clonic and tonic-clonic seizures was scored. ⋯ From that age onwards, the seizure threshold significantly decreased and reached a minimum at PN 220. Between strain comparisons showed that WAG/Rij rats have a lower tonic-clonic seizure threshold than Wistar rats. The data indicate that changes in susceptibility first quickly decreases until PN 26-30 and then tend to monotonically increase with age, and that genetically prone nonconvulsive WAG/Rij rats are more vulnerable to convulsive seizures induced by PTZ than Wistar rats.