Functional Dissociation of Group III Metabotropic Glutamate Receptors Revealed by Direct Comparison between the Behavioral Profiles of Knockout Mouse Lines.

BACKGROUND: Group III metabotropic glutamate receptors (mGlu4, mGlu7, mGlu8) display differential brain distribution, which suggests different behavioral functions. However, comparison across the available animal studies remains methodologically hazardous and controversial. The present report directly compares knockouts for each group III receptor subtype using a single behavioral test battery and multivariate analysis. METHODS: The behavioral phenotypes of C57BL/6J mice lacking mGlu4, mGlu7, or mGlu8 and their respective littermates were examined using a multimetric test battery, which included elements of neuromotor performance, exploratory behavior, and learning and memory. Multivariate statistical methods were used to identify subtype-specific behavioral profiles and variables that distinguished between these mouse lines. RESULTS: It generally appears that mGlu7 plays a significant role in hippocampus-dependent spatial learning and in some fear-related behaviors, whereas mGlu4 is most clearly involved in startle and motivational processes. Excepting its influence on body weight, the effect of mGlu8 deletion on behavior appears more subtle than that of the other group III receptors. These receptors have been proposed as potential drug targets for a variety of psychopathological conditions. CONCLUSION: On the basis of these controlled comparisons, we presently conclude that the different group III receptors indeed have quite distinct behavioral functions.

Willingness to replace animal-based products with pulses among consumers in different European countries.

The growing world population and increased meat consumption pose a challenge for current food production systems. While pulses present a promising position in terms of low impacts in primary production and high nutritional quality, it is unclear whether consumers are willing to consume pulses instead of meat. Based on an online survey answered by 4,322 respondents across five European countries, this study examined consumers' willingness to utilize pulses as a plant-based alternative to animal-based products. More than a third of pulse consumers (42%) were, to some extent, already using pulses as an alternative to animal-based foods. Beef was noted as the most frequently replaced type of food, mainly driven by arguments relating to health, environment, and sustainability, especially relevant for German and Danish consumers. Respondents who did not indicate a current replacement of animal-based foods stated a relatively low willingness to change in the future (40%). German pulse consumers were likely to be part of the low willingness segment. In contrast, Polish consumers possessed a relatively higher incidence of using pulses instead of meat, especially pork and poultry. Respondents with a low replacement willingness indicated a high importance of future pulse-based products to be natural, while respondents already using pulses instead of animal-based foods expected convenient and minimally processed foods. Respondents, who already replaced meat with pulses or expressed a low future willingness, stated to prefer plain pulses over processed pulse-based products, and meat-resembling forms considering the former segment, alternatively to meat. These preferences and expectations should be considered for future product development, especially if aiming to attract unwilling consumers to shift to pulse-based foods.

Hippocampal involvement in the acquisition of relational associations, but not in the expression of a transitive inference task in mice.

The hippocampus (HC) has been suggested to play a role in transitive inference (TI) on an ordered sequence of stimuli. However, it has remained unclear whether HC is involved in the expression of TI, or rather contributes to TI through its role in the acquisition of the sequence of elements (Frank, Rudy, & O'Reilly, 2003). Presently, the authors compared the effects of excitotoxic dorsal HC lesions in C57BL mice that received surgery before or after they were trained to discriminate between pairs of visual stimuli. Performance on a subsequent TI task was worse in mice with pretraining lesions than in those with posttraining lesions, which showed similar performance to shams without lesions. This indicates that HC is not involved in the expression of TI, but may merely help to acquire the underlying representations required for TI.

Deficits in acquisition and extinction of conditioned responses in mGluR7 knockout mice.

Metabotropic glutamate receptor 7 (mGluR7) is expressed in brain regions implicated in emotional learning and working memory, and previous behavioral experiments indicated contributions of mGluR7 to various complex behaviors. In the present study, we investigated the specific effects of mGluR7 deletion on a variety of conditioning paradigms that model crucial neurocognitive and psychopathological behavioral phenomena. Null-mutant mGluR7(-/-) mice displayed defects during scheduled appetitive conditioning, acquisition and extinction of appetitive odor conditioning, extinction of response suppression-based conditioned emotional responding (CER), acquisition of discriminative CER, and contextual fear conditioning. mGluR7(-/-) animals were slower to acquire the association between a conditioned stimulus and a positive or negative reinforcer, but eventually reached similar performance levels to their wildtype littermates. Notably, extinction learning of conditioned responses was slower in mGluR7(-/-) compared to wildtype animals. The observed delays in the acquisition of complicated stimulus associations across conditioning procedures may suggest a critical role for mGluR7 in neurocognitive functions and psychopathology.

Pre-exposure to Tempting Food Reduces Subsequent Snack Consumption in Healthy-Weight but Not in Obese-Weight Individuals.

Obesity has become a severe worldwide problem. Compared to healthy-weight individuals, obese individuals seem to show an increased sensitivity to tempting food. In the present study, we test the pre-exposure effect, which implies that consumption of tempting food is decreased after exposure to tempting food cues in a context of a task that discourages food consumption. Healthy-weight and obese-weight participants were recruited via social media and university channels. Participants took part in a scrabble task with either candy letters or foam letters and subsequently engaged in a taste test. Results showed that in healthy-weight participants, consumption was reduced after solving the scrabble task with candy letters in comparison to foam letters. In obese-weight participants, consumption was reduced in the condition using foam letters (in comparison with healthy-weight participants). The pre-exposure effect was replicated in healthy-weight participants, but could not be observed in participants with obesity, since consumption was reduced in general in this group. Our results suggest that more work should be done to understand how food nudges work in the context of obesity.

Differences in behavioural test battery performance between mice with hippocampal and cerebellar lesions.

Effects of hippocampal or cerebellar lesions have been described extensively, but the ability of behavioural tests for laboratory mice to distinguish between such lesions has not been studied in detail. We compared the behavioural consequences of large bilateral hippocampal and hemispheric cerebellar lesions with eight commonly used tests that included elements of neuromotor performance, exploratory behaviour, and learning and memory ability. Dissociation between the effects of the different lesions was most obviously demonstrated by neuromotor impairment in cerebellum-lesioned mice (typically in the rotarod task) and hyperactivity in hippocampus-lesioned mice (typically in cage activity recordings). Several of the behavioural variables derived from the test battery correlated differently with the size of the hippocampal and cerebellar lesions. In contrast, no absolute dissociation between the effects of these lesions was found in the Morris maze, a reportedly hippocampus-dependent learning and memory task. The contextual fear conditioning task, on the other hand, did reveal a selective decrease of context-dependent freezing in hippocampus-lesioned mice, whereas cerebellum-lesioned animals displayed an increase in freezing responses. By and large, the present battery of tests does allow differentiation between the effects of cerebellar and hippocampal lesions in laboratory mice.