British journal of pharmacology
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1. Topical application of capsaicin to the human nasal mucosa induced a burning sensation and sneezing. A dose-dependent seromucous nasal secretion was also observed. ⋯ Topical pretreatment with lidocaine inhibited the painful sensation but failed to block the rhinorrhea. Desensitization to the effects of capsaicin occurred following 4-5 subsequent applications, and full recovery was observed within 30-40 days. 3. It is proposed that the effects of capsaicin in human nasal mucosa are due to excitation of primary afferent neurones that (a) convey burning and painful sensation, (b) evoke a sneezing reflex and (c) induce nasal secretion by releasing transmitter(s) from their peripheral terminals.
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1. Nociceptive thresholds to noxious mechanical (paw pressure) and thermal (tail flick) stimuli were recorded in conscious rats. The effects of three selective kappa-opioid receptor agonists on the responses to these stimuli were determined following intravenous, intracerebroventricular or intrathecal administration. ⋯ All three kappa-opioid receptor agonists produced naloxone-reversible antinociception in the paw pressure test, and to a lesser extent in the tail flick test, when injected directly into the third cerebral ventricle with the maximum effect occurring between 5 and 10 min after administration and declining back to control levels by 60 min. Morphine had a much slower onset of action with the peak effect being observed 30 min after dosing. 5. It is concluded that, under our experimental conditions in the rat, the antinociceptive effects of kappa-agonists are likely to be operated via an action at a supraspinal rather than a spinal site.