Expression of Fos in the piriform cortex after acquisition of olfactory learning: An immunohistochemical study in the rat

The piriform cortex (PCx), the main area of the primary olfactory cortex, is assumed to play a role in olfactory memory. Involvement of this paleocortex in mnesic processes was investigated by using Fos immunocytochemistry after acquisition of a two-odor discrimination task. Trained rats had to associate one odor of a pair with water reward while pseudo-trained rats were randomly rewarded. We further used non-trained rats and home cage control animals to determine the effect of manipulation and basal Fos level respectively. Except in control rats, Fos immunoreactivity was mainly distributed in brain areas involved in olfactory processing, learning and arousal. The trained, pseudo-trained, a…

Hypothalamus-olfactory system crosstalk: orexin a immunostaining in mice

It is well known that olfaction influences food intake, and conversely, that an individual’s nutritional status modulates olfactory sensitivity. However, what is still poorly understood is the neuronal correlate of this relationship, as well as the connections between the olfactory bulb and the hypothalamus. The goal of this report is to analyze the relationship between the olfactory bulb and hypothalamus, focusing on orexin A immunostaining, a hypothalamic neuropeptide that is thought to play a role in states of sleep/wakefulness. Interestingly, orexin A has also been described as a food intake stimulator. Such an effect may be due in part to the stimulation of the olfactory bulbar pathway…

Neural activation induced by an odour mixture perceived elementally or configurally by the newborn rabbit

National audience; Perception of odours plays a crucial role in mammals facilitating interindividual communication, food choice and detection of danger, even from early in life (e.g. mother-young communication). However, little is known about the brain processing and perception of odorants in mixtures, which is by far the more common situation in life. To better understand how the brain processes odorants in mixtures, we used the newborn rabbit as a model. Rabbit pups display a clear sucking behaviour in response to the mammary pheromone (MP, the single molecule 2MB2) carried in the milk of lactating rabbit females. The MP also promotes associative conditioning and very rapid acquisition of…

Does taste or odor activate the same brain regions after retrieval of taste-potentiated odor aversion ?

Olfactory discrimination ability and brain expression of c-fos, Gir and Glut1 mRNA are altered in n-3 fatty acid-depleted rats

Abstract The long-chain polyunsaturated n  − 3 fatty acids ( n  − 3 PUFA), particularly docosahexaenoic acid (DHA), are abundantly present in the central nervous system and play an important role in cognitive functions such as learning and memory. We, therefore, investigated the effects of n  − 3 PUFA-depletion in rats (F2 generation) on the learning of an olfactory discrimination task, progressively acquired within a four-arm maze, and on the mRNA expression of some candidate genes, i.e., c-fos, Gir and glucose transporter (Glut1), which could reflect the level of cerebral activity. We observed that DHA contents were dramatically decreased in the olfactory bulb, the piriform cortex and the…

Olfactory bulbectomy, but not odor conditioned aversion, induces the differentiation of immature neurons in the adult rat piriform cortex.

International audience; The piriform cortex layer II of young-adult rats presents a population of prenatally generated cells, which express immature neuronal markers, such as the polysialylated form of the neural cell adhesion molecule (PSA-NCAM) or doublecortin (DCX), and display structural characteristics of immature neurons. The number of PSA-NCAM/DCX expressing cells in this region decreases markedly as age progresses, suggesting that these cells differentiate or die. Since the piriform cortex receives a major input from the olfactory bulb and participates in olfactory information processing, it is possible that the immature neurons in layer II are affected by manipulations of the olfac…

Crosstalk between hypothalamic neurons and olfactory system: a tracing and anatomo-fuctional investigation in mouse

Cerveaux de lapereaux : circuits mis en jeu par un signal phéromonal et un odorant phéromone-appris

National audience

Olfactory system in mammals: structural and functional anatomy

Olfactory system in mammals: structural and functional anatomy

Fos mapping of brain activation induced by the mammary pheromone in the newborn rabbit

The female European rabbit, Oryctolagus cuniculus, displays a surprising maternal behaviour. Indeed, she comes into the nest only once per day and for a very brief period (3-4 minutes), almost exclusively to nurse. A pheromonal signal identified as the 2-methylbut-2-enal and named the mammary pheromone (MP) is emitted in milk by all lactating rabbit females. This chemosensory cue induces typical head-searching and oral-seizing movements in newborn rabbits usually involved in the localisation of the nipples. The MP therefore appears as a biological signal important for sucking, survival and growth in pups. To date, only few data are available regarding the neuronal substrate which sustains t…

Etude de l’activation cérébrale induite par le comportement via la cartographie de l’expression de la protéine FOS chez le rongeur

Age-related expression of Fos inresponses to olfactory cue after taste-potentiated odor aversion retrieval in the rat: a behavioural and immunohistochemical study

Role of the basolateral amygdala in retrieval of conditioned flavors in the awake rat.

International audience; Learned association between odor, taste and further post-ingestive consequence is known as flavor nutrient conditioned preference. Amygdala is supposed to be one of the areas involved in these associations. In the present study, one flavor was associated with a 16% glucose (CS+) whereas another flavor was paired with less reinforcing 4% glucose (CS-). We showed that CS+ presentation after conditioning increased Fos expression in the basolateral nucleus of amygdala (BLA). Furthermore, we performed electrophysiological recordings in the BLA in free moving rats. After preference acquisition, rats were exposed to either the CS+ or the CS-. The proportion of neurons showi…

Intégration centrale de la perception sensorielle associée à l’alimentation

Poster; National audience

The histone acetyltransferase MOF activates hypothalamic polysialylation to prevent diet-induced obesity in mice

Overfeeding causes rapid synaptic remodeling in hypothalamus feeding circuits. Polysialylation of cell surface molecules is a key step in this neuronal rewiring and allows normalization of food intake. Here we examined the role of hypothalamic polysialylation in the long-term maintenance of body weight, and deciphered the molecular sequence underlying its nutritional regulation. We found that upon high fat diet (HFD), reduced hypothalamic polysialylation exacerbated the diet-induced obese phenotype in mice. Upon HFD, the histone acetyltransferase MOF was rapidly recruited on the St8sia4 polysialyltransferase-encoding gene. Mof silencing in the mediobasal hypothalamus of adult mice prevented…

Expression cérébrale de la protéine Fos au cours de l'acquisition d'une tâche de discrimination olfactive : étude par immunohistochimie chez le rat.

Comportement alimentaire

National audience

Impact of a high fat high sucrose maternal diet on the progeny's olfactory system

International audience

Cue valence representation studied by Fos immunocytochemistry after acquisition of a discrimination learning task.

The piriform cortex (PCx) and related structures such as hippocampus and frontal cortex could play an important role in olfactory memory. We investigated their involvement in learning the biological value of an odor cue, i.e. predicting reward or non-reward in a two-odor discrimination task. Rats were sacrificed after stimulation by either rewarded or non-rewarded odor and Fos immunocytochemistry was performed. The different experimental groups of rats did not show strongly differentiated Fos expression pattern in either the PCx or the hippocampus. A few differences were noted in frontal areas. In the ventro-lateral orbital cortex, rats, ramdomly rewarded during the conditionning had a high…

Multidisciplinary approach to explore interactions in odor mixture perception

Odors and aromas perceived in food and in the environment result from the processing of complex chemical mixtures of volatile compounds that should be efficiently processed by the olfactory system. It is known for decades that this processing generates perceptual interactions, such as masking, synergy, or perceptual blending, which contribute to elaborating a synthetic brain representation of the chemical information. Nevertheless, the perceptual processes underlying these interactions are still poorly known. In this project, we set out a multidisciplinary approach to identify the characteristics of odorants and olfactory receptors (ORs) that could support perceptual interactions. We hypoth…

Centrifugal projections to the main olfactory bulb revealed by trans‐synaptic retrograde tracing in mice

A wide range of evidence indicates that olfactory perception is strongly involved in food intake. However, the polysynaptic circuitry linking the brain areas involved in feeding behavior to the olfactory regions is not well known. The aim of this article was to examine such circuits. Thus, we described, using hodological tools such as transsynaptic viruses (PRV152) transported in a retrograde manner, the long-distance indirect projections (two to three synapses) onto the main olfactory bulb (MOB). The ß-subunit of the cholera toxin which is a monosynaptic retrograde tracer was used as a control to be able to differentiate between direct and indirect projections. Our tracing experiments show…

Spontaneous brain processing of the mammary pheromone in rabbit neonates prior to milk intake.

International audience; Chemical signals play a critical role in interindividual communication, including mother-young relationships. Detecting odor cues released by the mammary area is vital to the newborn's survival. European rabbit females secret a mammary pheromone (MP) in their milk, which releases sucking related orocephalic movements in newborns. Pups spontaneously display these typical movements at birth, independently of any perinatal learning. Our previous Fos mapping study (Charra et al., 2012) performed in 4-day-old rabbits showed that the MP activated a network of brain regions involved in osmoregulation, odor processing and arousal in comparison with a control odor. However, a…

Pheromone-induced odor learning modifies Fos expression in the newborn rabbit brain.

Research report; International audience; Associative learning contributes crucially to adjust the behavior of neonates to the permanently changing environment. In the European rabbit, the mammary pheromone (MP) excreted in milk triggers sucking behavior in newborns, and additionally promotes very rapid learning of initially neutral odor cues. Such stimuli become then as active as the MP itself to elicit the orocephalic motor responses involved in suckling. In this context, the rabbit is an interesting model to address the question of brain circuits early engaged by learning and memory. Here, we evaluated the brain activation (olfactory bulb and central regions) induced in 4-day-old pups by …

Impact of a maternal high fat high sucrose diet on progeny's olfactory system

International audience

A basal ganglia-like cortical-amygdalar-hypothalamic network mediates feeding behavior.

International audience; The network connecting the insular cortex, the central nucleus of the amygdala, and a caudal hypothalamic nuclear complex including the parasubthalamic nucleus (PSTN) is of interest due to its role in controlling feeding behavior. Here, we show that the organization of this network is similar to that of the basal ganglia network, implying that both fit within a simplified structural plan of the forebrain. Then, we demonstrate that the PSTN complex modulates behavior in response to hedonic factors normally inducing a “reward effect.” The PSTN complex is involved in a “non-feed” response equivalent of a “non-reward” evaluation: “I don’t want to consume this food, recog…

Brain anatomy of the 4‐day‐old European rabbit

International audience; The European rabbit (Oryctolagus cuniculus) is a widely used model in fundamental, medical and veterinary neurosciences. Besides investigations in adults, rabbit pups are relevant to study perinatal neurodevelopment and early behaviour. To date, the rabbit is also the only species in which a pheromone - the mammary pheromone (MP) - emitted by lactating females and active on neonatal adaptation has been described. The MP is crucial since it contributes directly to nipple localisation and oral seizing in neonates, i.e. to their sucking success. It may also be one of the non-photic cues arising from the mother, which stimulates synchronisation of the circadian system du…

Elemental or configural perception of an odour mixture induces differences in neural activation in the newborn rabbit

International audience

Pheromonal odour learning and brain activation in the newborn rabbit.

Brain processing of the mammary pheromone in newborn rabbits.

International audience; Chemosignals strongly contribute to social interactions in mammals, including mother-young relationships. In the European rabbit, a volatile compound emitted by lactating females in milk, the 2-methylbut-2-enal, has been isolated. Carrying the properties of a pheromone, in particular the spontaneous ability to release critical sucking-related movements in newborns, it has been called the mammary pheromone (MP). Lesion of the vomeronasal organ and preliminary 2-deoxyglucose data suggested that the MP could be processed by the main olfactory system. However, the neuronal substrate that sustains the MP-induced response of neonates remained unknown. Here, we evaluated Fo…