lithium-chloride and amyl-acetate

Previously, published studies have reported mixed results regarding the role of the TRPM5 cation channel in signaling sweet taste by taste sensory cells. Some studies have reported a complete loss of sweet taste preference in TRPM5 knockout (KO) mice, whereas others have reported only a partial loss of sweet taste preference. This study reports the results of conditioned aversion studies designed to motivate wild-type (WT) and KO mice to respond to sweet substances. In conditioned taste aversion experiments, WT mice showed nearly complete LiCl-induced response suppression to sucrose and SC45647. In contrast, TRPM5 KO mice showed a much smaller conditioned aversion to either sweet substance, suggesting a compromised, but not absent, ability to detect sweet taste. A subsequent conditioned flavor aversion experiment was conducted to determine if TRPM5 KO mice were impaired in their ability to learn a conditioned aversion. In this experiment, KO and WT mice were conditioned to a mixture of SC45647 and amyl acetate (an odor cue). Although WT mice avoided both components of the stimulus mixture, they avoided SC45647 more than the odor cue. The KO mice also avoided both stimuli, but they avoided the odor component more than SC45647, suggesting that while the KO mice are capable of learning an aversion, to them the odor cue was more salient than the taste cue. Collectively, these findings suggest the TRPM5 KO mice have some residual ability to detect SC45647 and sucrose, and, like bitter, there may be a TRPM5-independent transduction pathway for detecting these substances.

Topics: Animals; Choice Behavior; Conditioning, Psychological; Dysgeusia; Guanidines; Lithium Chloride; Mice; Mice, Knockout; Odorants; Pentanols; Signal Transduction; Smell; Sucrose; Sweetening Agents; Taste; Taste Perception; TRPM Cation Channels

We showed recently that behavioural and striatal dopaminergic (DA) responses obtained in latent inhibition are crucially dependent on the parahippocampal region, the entorhinal cortex. In the present study, we investigated the influence exerted by the hippocampal ventral subicular region (SUB) on the DA responses in the anterior part of the dorsal striatum using in vivo voltammetry in freely moving rats and the same latent inhibition paradigm. To that end, the left SUB was temporarily blocked with tetrodotoxin (TTX) during pre-exposure to a new olfactory stimulus (banana odour). During the second session the animals were aversively conditioned to banana odour. With respect to the results obtained during the test session (third presentation of banana odour), similar changes in behaviour and DA levels were obtained in control and conditioned rats microinjected with the solvent, phosphate-buffered saline (PBS), in the SUB, consistently with a latent inhibition phenomenon. In contrast, after reversible inactivation of the SUB during the pre-exposure session, TTX-pre-exposed conditioned animals displayed aversive behaviour in the test session, and anterior striatal DA variations in these animals differed significantly from those obtained in pre-exposed rats injected locally with PBS. Striatal DA variations obtained in conditioned animals microinjected with TTX were also significantly different from those observed in conditioned non-pre-exposed animals. The present data suggest that, in parallel to the entorhinal cortex, the SUB regulates the latent inhibition-related behavioural and DA responses in the anterior part of the dorsal striatum. These data may provide new insight into the pathophysiology of schizophrenic psychoses.

Topics: Analysis of Variance; Anesthetics, Local; Animals; Behavior, Animal; Brain Chemistry; Corpus Striatum; Dopamine; Drug Interactions; Electrochemistry; Functional Laterality; Hippocampus; Lithium Chloride; Male; Microinjections; Neural Inhibition; Odorants; Pentanols; Rats; Rats, Sprague-Dawley; Tetrodotoxin; Time Factors

Wysocki et al. (1977) have previously compared the abilities of several inbred strains of mice to avoid odorized drinks after odor-aversion conditioning and have proposed C57BL/6 mice as an animal model to study the specific anosmia to isovaleric acid. We have compared the olfactory performances of C57BL/6J mice and AKR/J mice using one-bottle and two-bottle tests to study the latencies of contacts with odorized or control drinks after odor-aversion conditioning. In both inbred strains, sensitivities to airborne molecules of amyl acetate (control odor) or isovaleric acid are demonstrated. Differences in behavioral strategies are suggested but the results are consistent with the hypothesis of a selective hyposmia to isovaleric acid in C57BL/6J mice.

Topics: Animals; Association Learning; Avoidance Learning; Chlorides; Conditioning, Classical; Hemiterpenes; Lithium; Lithium Chloride; Male; Mice; Mice, Inbred AKR; Mice, Inbred C57BL; Pentanoic Acids; Pentanols; Smell; Species Specificity