Sulphur dioxide block of laryngeal receptors in rabbits

Abstract In 6 rabbits moving average of activity of superior laryngeal nerve (SLN) increased when pressure in upper airways (Pua) was positive and decreased when it was negative. After SO 2 exposure of upper airways SLN activity at Pua = 0 decreased to 40% and was no longer affected by changes in Pua. Activity of 67 fibers of SLN was recorded in 11 rabbits: 35 came from ‘pressure’ receptors, 27 from ‘drive’, and 5 from ‘flow’. Thirty-three pressure receptors discharged at Pua = 0:32 increased their firing rate with positive Pua and decreased it with negative Pua, one did the reverse. One pressure receptor silen at Pua = 0 fired with positive Pua, the other with negative Pua. Pressure receptors were slowly adapting. SO 2 blocked within 3–9 min 84% of pressure receptors, 56% of drive receptors, and 4 out of 5 flow receptors. The receptors recovered control activity within 5–10 min after SO 2 block of laryngeal receptors may represent a convenient experimental tool for studies of laryngeal reflexes.