Article date: February 1996
By: Deborah J. Bootle, John J. Adcock, Andrew G. Ramage, in Volume 117, Issue 4, pages 724-728
The aim of the present experiments was to determine whether 5‐HT1A receptors play a role in the control of the reflex activation of pulmonary vagal motoneurones. This was carried out by investigating the effects of intracisternal injections (i.c.) of the 5‐HT1A receptor ligands, 8‐OH‐DPAT (50 μg kg−1), buspirone (200 μg kg−1), WAY‐100635 (100 μg kg−1), methiothepin (200 μg kg−1) and (−)−pindolol (100 μg kg−1) and the 5‐HT2 receptor antagonist, cinanserin (200 μg kg−1), on the reflex bronchocon‐striction evoked by inhaled capsaicin aerosol in α‐chloralose anaesthetized, neuromuscularly blocked and artificially ventilated cats. Recordings were made of heart rate, blood pressure and upper tracheal pressure.
Central application of all the 5‐HT1A receptor antagonists (methiothepin, WAY‐100635 and (−)−pindolol) attenuated the reflex bronchoconstriction in the upper trachea. However, the same dose of WAY‐100635 given i.v. had no effect on this reflex bronchoconstriction. The 5‐HT1A receptor agonist, 8‐OH‐DPAT (50 μg kg−1) given i.c., potentiated the capsaicin‐evoked reflex bronchoconstriction, whereas buspirone (200 μg kg−1) i.c. had no effect. The 5‐HT2 receptor antagonist, cinanserin (200 μg kg−1) also had no effect.
It is concluded that the reflex excitation of pulmonary vagal motoneurones by inhaled capsaicin in α‐chloralose anaesthetized cats involves the activation of central 5‐HT1A receptors.
The aim of the present experiments was to determine whether 5‐HT1A receptors play a role in the control of the reflex activation of pulmonary vagal motoneurones. This was carried out by investigating the effects of intracisternal injections (i.c.) of the 5‐HT1A receptor ligands, 8‐OH‐DPAT (50 μg kg−1), buspirone (200 μg kg−1), WAY‐100635 (100 μg kg−1), methiothepin (200 μg kg−1) and (−)−pindolol (100 μg kg−1) and the 5‐HT2 receptor antagonist, cinanserin (200 μg kg−1), on the reflex bronchocon‐striction evoked by inhaled capsaicin aerosol in α‐chloralose anaesthetized, neuromuscularly blocked and artificially ventilated cats. Recordings were made of heart rate, blood pressure and upper tracheal pressure.
Central application of all the 5‐HT1A receptor antagonists (methiothepin, WAY‐100635 and (−)−pindolol) attenuated the reflex bronchoconstriction in the upper trachea. However, the same dose of WAY‐100635 given i.v. had no effect on this reflex bronchoconstriction. The 5‐HT1A receptor agonist, 8‐OH‐DPAT (50 μg kg−1) given i.c., potentiated the capsaicin‐evoked reflex bronchoconstriction, whereas buspirone (200 μg kg−1) i.c. had no effect. The 5‐HT2 receptor antagonist, cinanserin (200 μg kg−1) also had no effect.
It is concluded that the reflex excitation of pulmonary vagal motoneurones by inhaled capsaicin in α‐chloralose anaesthetized cats involves the activation of central 5‐HT1A receptors.
DOI: 10.1111/j.1476-5381.1996.tb15250.x
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