Search

Oxytocin (OXT) suppresses food intake and lack of OXT leads to overconsumption of sucrose. Taste bud cells were recently discovered to express OXT-receptor. In the present study we tested whether administering OXT to wild-type mice affects their licking behavior for tastants in a paradigm designed to be sensitive to taste perception. We injected C57BL/6J mice intraperitoneally (i.p.) with 10mg/kg OXT and assayed their brief-access lick responses, motivated by water deprivation, to NaCl (300mM), citric acid (20mM), quinine (0.3mM), saccharin (10mM), and a mix of MSG and IMP (100mM and 0.5mM respectively). OXT had no effect on licking for NaCl, citric acid, or quinine. A possible effect of OXT on saccharin and MSG+IMP was difficult to interpret due to unexpectedly low lick rates to water (the vehicle for all taste solutions), likely caused by the use of a high OXT dose that suppressed licking and other behaviors. A subsequent experiment focused on another preferred tastant, sucrose, and employed a much lower OXT dose (0.1mg/kg). This modification, based on our measurements of plasma OXT following i.p. injection, permitted us to elevate plasma [OXT] sufficiently to preferentially activate taste bud cells. OXT at this low dose significantly reduced licking responses to 0.3M sucrose, and overall shifted the sucrose concentration - behavioral response curves rightward (mean EC50saline=0.362M vs. EC50OXT=0.466M). Males did not differ from females under any condition in this study. We propose that circulating oxytocin is another factor that modulates taste-based behavior.

The contributions of the two nerves innervating the taste buds, the chorda tympani (CT) and the glossopharyngeal (GL), to the behavioral pattern of quinine drinking were investigated in rats. These nerves were transected alone or in combination and the aversion to drinking by transected subjects was compared with the results from sham-operated controls. Results reveal that combined transection removed the aversion to quinine water, GL transection had an intermediate effect while CT transection did not have any effect.

The mechanisms of taste discrimination in water restricted rats were analyzed to determine the activity of the gustatory nerves during conditioned avoidance tasks. Water-deprived rats subjected to conditioned avoidance tasks exhibited taste discriminations involving sucrose and maltose. The discrimination performance of the water-deprived rats was not affected by the bilateral transection of the chorda tymphani (CT) or glossopharyngeal nerves. However, combined transection of the greater superficial petrosal nerve and CT attenuated taste discrimination in rats.

The sodium-specific taste-guided behavior of rats which have been been sodium depleted does not involve the glossopharyngeal nerve (GLX) and is not simply related to the number of taste buds. The licking responses to NaCl, KCl, CaCl2 and NH4Cl of rats receiving bilateral section of the GLX is unaffected even when almost 64% of the taste buds have been denervated. The licking responses of rats with bilateral section of the chorda tympani nerve (CTX) or sublingual and submaxillary salivary glands is less than that of control rats. The responses of the rats with section of the CTX to NaCl was similar to that of water and the other solutions.