Maintenance of chorda tympani salt taste responses after nerve transection in rats

To determine whether neurophysiological responses to salts change differentially or in parallel during long recording sessions after nerve transection, we recorded from the cut chorda tympani nerve in rats while stimulating the anterior tongue with NaCl, LiCl, NH4Cl and KCl. In nerve preparations that were not disturbed once recording began, responses were maintained at or above initial magnitudes for an average of 10 h and declined to 50% by 15 h. If the cut end of the nerve was redissected when responses began to decline, stable responses were maintained for an average of 12 h, and did not decline to 50% until 21-24 h. In all rats, responses to the 4 salts altered in parallel for at least 19 h. However in two animals, after 23 h the responses to NaCl and LiCl declined disproportionately, relative to NH4Cl and KCl. Therefore in the course of a typical recording session, i.e. 10-12 h, stable taste responses are obtained and even when responses begin to decline after longer periods, response magnitudes to 4 salts alter in parallel. This indicates that receptor membrane components interacting with specific monochloride salts do not degenerate differentially during the first 19 h after nerve cut.