Sinus hairs were isolated from rats and examined in an isolated organ bath while superfused with oxygenated synthetic interstitial fluid. The distal end of the deep vibrissal nerve was teased for single unit recordings of responses from slowly adapting mechanoreceptors to standard bending of the hair. Sinus hair type I and type II receptors could be clearly identified by their respective characteristic firing pattern. Their responses were stable for at least 5 h even if the sinus hair had been stored at 4 degrees C for 24 h beforehand. Electron microscopic examination of these hairs at the end of experiments showed well preserved ultrastructure without abnormalities. The short diffusion distances in this preparation make it well suited for studying drug effects with the aim of investigating the mechanoelectric transduction process in these receptors.
