Novel regulation of peripheral gustatory function by the immune system.

Soon after adult rats receive unilateral chorda tympani nerve section in combination with dietary sodium restriction, neural taste responses recorded from the intact, contralateral chorda tympani nerve are substantially reduced. We hypothesized that the immune system is compromised in sodium-restricted rats, which leads to functional alterations in the peripheral taste system after neural injury. Here, immune function was stimulated with a systemic injection of lipopolysaccharide (LPS), and neurophysiological responses were recorded from the uncut chorda tympani 4-10 days after nerve section to determine if normal sodium sensitivity was restored. Rats receiving nerve section, dietary sodium restriction, and LPS exhibited normal sodium responses. In intact rats, injection of LPS alone or LPS injection combined with sodium restriction had no effect on taste responses to sodium stimuli. Surprisingly, combining nerve section, LPS injection, and maintenance of rats on a normal diet induced supersensitive responses to sodium. These findings are the first to demonstrate that the immune system can regulate peripheral gustatory function.