Ethanol, Saccharin, and Quinine: Early Ontogeny of Taste Responsiveness and Intake

Abstract

The findings of the present study indicate ontogenetic dissociations between taste reactivity to ethanol and saccharin and intake of these solutions, and suggest that high acceptance of ethanol early in ontogeny may not be associated with its orosensory properties but rather with the pharmacological effects of ethanol.

The effect of taste familiarity on intake and taste reactivity in infant rats

“…Therefore, this study aimed to characterize the effect of preexposure to a tastant (sucrose, quinine, a mixture of sucrose and quinine, or ethanol) on taste reactivity and intake in 14-day-old rats. The tastants were selected in accordance with previous results from both our own and other laboratories, which indicate that at this age, infant rats are capable of perceiving and responding to the taste of sucrose, quinine and ethanol (Hall & Bryan, 1981;Kozlov et al, 2008;Molina, Chotro, & Dominguez, 1995;Rudy et al, 1984). The mixture of sucrose and quinine was chosen in order to compare it with ethanol, on the basis of previous behavioral and electrophysiological studies showing that, in the gustatory dimension at least, rats perceive the taste of ethanol as a mixture of sweet and bitter (Di Lorenzo, Kiefer, Rice, & Garcia, 1986;Kiefer & Lawrence, 1988;Kiefer & Mahadevan, 1993), something that has also been found in infant rats (Chotro & Alonso, 2003).…”

“…Nevertheless, in those studies in which changes in intake were detected after taste preexposure, it remains unclear whether these changes reflect a shift in taste palatability or a different process altogether. The taste reactivity test has been adapted to infant rats and used successfully to analyze affective reactions to different tastants in early ontogeny (Hall & Bryan, 1981;Kozlov, Varlinskaya, & Spear, 2008;Vigorito & Sclafani, 1988). In a series of studies in which reactivity to saccharine was evaluated early in ontogeny (rat fetuses and neonates) as a function of previous exposure to this stimulus, a differential taste responsiveness was observed in subjects which had been preexposed to this tastant, indicating that even at this early age, subjects are capable of detecting the novelty of a gustatory stimulus (Mickley et al, 2000(Mickley et al, , 2003.…”

The role of social isolation in ethanol effects on the preweanling rat

“…. Several factors affect developmental changes of ethanol acceptance and intake during early ontogeny, such as prenatal experience [4, 5], peculiarities of infant taste perception [6], the reinforcing properties of ethanol [7], development of neurotransmitter systems [8, 9] and others. Interestingly, this period of maximal ethanol consumption as well as changes in sensitivity to the pharmacological effects of ethanol [10] corresponds to the “descending” phase of the stress hyporesponsive period (SHRP).…”

“…To achieve the goal of the present study we adopted a methodological approach that included combined assessment of voluntary intake and stress-related behavioral reactivity to social isolation. Voluntary intake and temporal patterns of ingestion were analyzed using a paradigm that permitted pups to freely extract fluid from an intraoral cannula [6, 10, 26]. This paradigm may be viewed as a model of early independent ingestive behavior.…”

“…To reproduce pharmacological effects of ethanol during voluntary drinking of low (10%) concentrations of ethanol solution we administered several doses (0.5 vs. 1.0 g/kg) to P12 pups that were comparable to the amount of 10 % ethanol consumed by the naive preweanling rat during 20 minutes of free access to this fluid [6]. However, to determine pharmacological effects of ethanol independently of its orosensory effects, we exposed animals to 0.1% saccharin–a sweet tastant similar to 10% ethanol in terms of palatability [6]. …”