title: Central representation of postingestive chemosensory cues in mice that lack the ability to taste.
abstract: The gustatory nerves of mice lacking P2X2 and P2X3 purinergic receptor subunits (P2X-dblKO) are unresponsive to taste stimulation (Finger et al., 2005). Surprisingly, P2X-dblKO mice show residual behavioral responses to concentrated tastants, presumably via postingestive detection. Therefore, the current study tested whether postingestive signaling is functional in P2X-dblKO mice and if so, whether it activates the primary viscerosensory nucleus of the medulla, the nucleus of the solitary tract (nTS). Like WT animals, P2X-dblKO mice learned to prefer a flavor paired with 150 mm monosodium glutamate (MSG) over a flavor paired with water. This preference shows that, even in the absence of taste sensory input, postingestive cues are detected and associated with a flavor in P2X-dblKO mice. MSG-evoked neuronal activation in the nTS was measured by expression of the immediate early gene c-Fos [c-Fos-like immunoreactivity (Fos-LI)]. In rostral, gustatory nTS, P2X-dblKO animals, unlike WT animals, showed no taste quality-specific labeling of neurons. Furthermore, MSG-evoked Fos-LI was significantly less in P2X-dblKO mice compared with WT animals. In contrast, in more posterior, viscerosensory nTS, MSG-induced Fos-LI was similar in WT and P2X-dblKO mice. Together, these results suggest that P2X-dblKO mice can form preferences based on postingestive cues and that postingestive detection of MSG does not rely on the same purinergic signaling that is crucial for taste.
authors.affiliation: Rocky Mountain Taste and Smell Center, Department of Cell and Developmental Biology, University of Colorado, Anschutz Medical Campus, Aurora, Colorado 80045, USA. jennifer.stratford@ucdenver.edu
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Stratford
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Finger
mesh_terms: D000818:Animals; D002628:Chemoreceptor Cells; D003463:Cues; D004435:Eating; D005260:Female; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D019518:Postprandial Period; D013649:Taste; D013651:Taste Disorders / Q000503:physiopathology*