Effects of concentration presentation order and intraoral delivery on sucrose intake.

In this article, intraoral intake of an ascending concentration series of sucrose was found to plateau between concentrations of 0.3 M and 2.0 M, and thus failed to show the typical inverted U-shaped intake function found in standard intake tests. Two experiments were conducted to explain this result. In Experiment 1, intraoral and standard 30-min, 1-bottle intake of ascending sucrose concentrations (0.03, 0.1, 0.3, 1.0, 1.3, and 2.0 M) were compared. Sucrose intake was similar for both delivery methods. In a second experiment we examined the effect of the order of sucrose concentration presentation on the 1-bottle 30-min intake of nondeprived intact rats. An ascending concentration order of the solutions produced a significantly greater intake of concentrated sucrose solutions than did a random order. This result strongly suggests that the standard decline in sucrose intake at higher concentrations is determined not only by postoral factors but also by experiential factors (i.e., order of presentation).