Heterogeneity of neuronal nicotinic acetylcholine receptors in 5‐HT‐containing chemoreceptor cells of the chicken aorta

The effects of nicotinic agonists and antagonists on whole‐cell currents and 5‐hydroxytryptamine (5‐HT) release were studied in order to characterize nicotinic ACh receptors on the 5‐HT‐containing chemoreceptor cells of the chicken aorta. ACh, nicotine and dimethylphenylpiperazinium (DMPP) evoked concentration‐dependent inward currents accompanied by increases in current noise at a holding potential of −70 mV. The peak amplitude of the current response to DMPP was 50% larger than that to either nicotine or ACh. Hexamethonium, α – bungarotoxin (α – BTX) and methyllycaconitine decreased nicotine‐induced inward currents in a concentration‐dependent manner. Although hexamethonium (0.1 m M ) abolished the current response to nicotine (30 μ M ), a high concentration (1 μ M ) of α – BTX decreased it only by about 30% of the control response. Methyllycaconitine (0.1 μ M ) decreased the current response to nicotine to the same extent as did α – BTX whilst a high concentration (10 μ M ) abolished the response. ACh, nicotine and DMPP caused concentration‐dependent increases in 5‐HT output from the thoracic aorta which effect was blocked by hexamethonium (0.1 m M ). Pre‐treatment with α – BTX (1 μ M ) for 30 min reduced the output of 5‐HT induced by ACh to 70% of the control response. It is suggested that neuronal nicotinic ACh receptors, sensitive and insensitive to α – BTX, are present on the chemoreceptor cells of the chicken aorta, the activation of which causes the release of 5‐HT.British Journal of Pharmacology (2001) 132 , 1934–1940; doi: 10.1038/sj.bjp.0703978