Behavioural Analyses of Quinine Processing in Choice, Feeding and Learning of Larval Drosophila

Abstract

Gustatory stimuli can support both immediate reflexive behaviour, such as choice and feeding, and can drive internal reinforcement in associative learning. For larval Drosophila, we here provide a first systematic behavioural analysis of these functions with respect to quinine as a study case of a substance which humans report as “tasting bitter”. We describe the dose-effect functions for these different kinds of behaviour and find that a half-maximal effect of quinine to suppress feeding needs substantially higher quinine concentrations (2.0 mM) than is the case for internal reinforcement (0.6 mM). Interestingly, in previous studies (Niewalda et al. 2008, Schipanski et al 2008) we had found the reverse for sodium chloride and fructose/sucrose, such that dose-effect functions for those tastants were shifted towards lower concentrations for feeding as compared to reinforcement, arguing that the differences in dose-effect function between these behaviours do not reflect artefacts of the types of assay used. The current results regarding quinine thus provide a starting point to investigate how the gustatory system is organized on the cellular and/or molecular level to result in different behavioural tuning curves towards a bitter tastant.

Candidate ionotropic taste receptors in the Drosophila larva

“…Perhaps some IRs in the pharynx recognize certain key molecules only after they have been unmasked in transit toward the pharynx. Another possibility is that IRs and Grs have different dynamic ranges (e.g., they recognize the same tastants but with different sensitivities), possibly reflecting different roles in reflexive behaviors vs. gustatory learning (31)(32)(33).…”

GENETIC AND BEHAVIORAL INFLUENCES OF QUININE AND MONOSODIUM GLUTAMATE ON Drosophila melanogaster

“…PREF Gustatory = # QUI -# PURE # TOTAL Where # indicates the number of larvae on the respective side of the plate (El-Keredy et al, 2012;Koning et al, 2014).…”

“…quinine control result compatible with (El-Keredy et al, 2012) but the difference in results is due to the dosage effect of quinine, which was placed in vials, in addition to the located in Petri dishes when conducting the test, so the concentration was doubly. Drosophila taste behavior and characterize a neural population that controls a specific subprogram of this behavior (Gordon and Scott, 2008).…”

Common microbehavioral “footprint” of two distinct classes of conditioned aversion

“…Larvae avoid an odor after it has been paired with, for example, the bitter tastant quinine Schleyer et al 2011Schleyer et al , 2015aEl-Keredy et al 2012), or after it has been paired with the lack of, for example, sugar Saumweber et al 2011;Schleyer et al 2011Schleyer et al , 2015a. Likewise, larvae approach an odor after it has been paired with the lack of quinine, or with sugar Saumweber et al 2011;Schleyer et al 2011Schleyer et al , 2015aEl-Keredy et al 2012). We note that according to Pavlovian terminology, sugar and quinine in such an experiment would be called "appetitive unconditioned stimulus" and "aversive unconditioned stimulus," respectively.…”