Serotonin (5-hydroxytryptamine, 5-HT) is acknowledged as a major neuromodulator of nervous systems in both invertebrates and vertebrates. It has been proposed for several decades that it impacts animal cognition and behavior. In spite of a completely distinct organization of the 5-HT systems across the animal kingdom, several lines of evidence suggest that the influences of 5-HT on behavior and cognition are evolutionary conserved. In this review, we have selected some behaviors classically evoked when addressing the roles of 5-HT on nervous system functions.In particular, we focus on the motor activity, arousal, sleep and circadian rhythm, feeding, social interactions and aggressiveness, anxiety, mood, learning and memory, or impulsive/compulsive dimension and behavioral flexibility. The roles of 5-HT, illustrated in both invertebrates and vertebrates, show that it is more able to potentiate or mitigate the neuronal responses necessary for the fine-tuning of most behaviors, rather than to trigger or halt a specific behavior. 5-HT is, therefore, the prototypical neuromodulator fundamentally involved in the adaptation of all organisms across the animal kingdom.The organization of the 5-HT systems is completely different between species ranging from a limited number of cells in Aplysia or Drosophila (100 5-HT immunoreactive cells) to several thousand neurons in vertebrates. The variety and the heterogeneity of 5-HT neurons have been highlighted in vertebrates [7] as well as in invertebrates [8]. In general, the 5-HT systems in animals comprise 5-HT neurons, which share a particular shape made of thousands of varicosities, leading to the concept of volume transmission [9], and several 5-HT receptors (5-HTRs). In vertebrates, 5-HT neurons are localized in the midbrain raphe nuclei described as the B1-B9 cell groups [1,10]. The raphe pallidus, obscurus, and pontis form a caudal cluster (B1-B5), whereas the dorsal raphe and median raphe form a rostral cluster in the pons (B6-B9) [11]. The caudal raphe group projects to the spinal cord and the rostral group to the forebrain via an extensive and diffuse innervation. The dorsal raphe nucleus contains the highest number of 5-HT neurons and its anatomical sub-regions display some degrees of specific innervation of the forebrain [12][13][14]. The median and dorsal raphe nuclei receive excitatory and inhibitory inputs from most brain areas [15]. In crustaceans or insects, 5-HT neurons are widely present in each of the ventral cord ganglia, display large local ramifications that act in multiple neuropil areas, and some axonal branches form three pairs of rostrocaudal fibers [16][17][18][19]. Presumably, two of those fibers would project anteriorly and one posteriorly to the entire nervous system [20]. 5-HT neurons are often localized close to sensory integration input area in the brain of arthropods and some 5-HT cells in the abdominal ganglia of crayfish nerve cord are sensitive to the mechanical stimulation of abdominal segmental fringe hairs [21]. In cnidarians, 5-HT cells ...

Previous studies have reported that visual impairment can affect the quality of life leading to mental health disorders. This study aimed to investigate associations between vision impairment, depression and anxiety using a mouse model of congenital blindness. We phenotyped 15 anophthalmic and 17 sighted adult mice in a battery of tests for anxiety and depression-like behaviors: open field test, elevated plus maze, coated test, splash test, and forced swim test. We found that: (1) Anxiety levels of the anophthalmic mice were significantly lower when compared with sighted mice, (2) Anophthalmic mice displayed more exploratory behaviors in a new environment than the sighted one, and (3) Depression levels between those groups were similar. In conclusion, this behavioral study showed that early visual deprivation lowers anxiety levels, associated with heightened exploratory activity, but does not induce depressive symptoms in a mouse model of congenital blindness, underlying several behavioral adaptations.

Les symptômes de la Covid-19 tels que la toux, la fièvre et l’essoufflement se résorbent généralement quelques jours après l’infection. Une récente étude de notre laboratoire de recherche en neuroanatomie chimiosensorielle (Québec, Canada) a investigué les effets à long terme de la Covid-19 sur les sens chimiques (odorat, goût et système trigéminal). Nos résultats soulignent qu’environ un an après avoir été infectés par la Covid-19, les participants rapportent encore souffrir de troubles chimiosensoriels.

Mice produce ultrasonic vocalizations (USVs) at different ages and social contexts, including maternal-pup separation, social play in juveniles, social interactions, and mating in adults. The USVs' recording can be used as an index of sensory detection, internal state, and social motivation. While sensory deprivation may alter USVs' emission and some social behaviors in deaf and anosmic rodents, little is known about the effects of visual deprivation in rodents. This longitudinal study aimed to assess acoustic communication and social behaviors using a mouse model of congenital blindness. Anophthalmic and sighted mice were assayed to a series of behavioral tests at three different ages, namely, the maternal isolation-induced pup USV test and the home odor discrimination and preference test on postnatal day (PND) 7, the juvenile social test on PND 30–35, and the female urine-induced USVs and scent-marking behavior at 2–3 months. Our results evidenced that (1) at PND 7, USVs' total number between both groups was similar, all mice vocalized less during the second isolation period than the first period, and both phenotypes showed similar discrimination and preference, favoring exploration of the home bedding odor; (2) at PND 30–35, anophthalmic mice engaged less in social behaviors in the juvenile play test than sighted ones, but the number of total USVs produced is not affected; and (3) at adulthood, when exposed to a female urine spot, anophthalmic male mice displayed faster responses in terms of USVs' emission and sniffing behavior, associated with a longer time spent exploring the female urinary odor. Interestingly, acoustic behavior in the pups and adults was correlated in sighted mice only. Together, our study reveals that congenital visual deprivation had no effect on the number of USVs emitted in the pups and juveniles, but affected the USVs' emission in the adult male and impacted the social behavior in juvenile and adult mice.

In mammals, mothering is one of the most important prosocial female behavior to promote survival, proper sensorimotor, and emotional development of the offspring. Different intrinsic and extrinsic factors can initiate and maintain these behaviors, such as hormonal, cerebral, and sensory changes. Infant cues also stimulate multisensory systems and orchestrate complex maternal responsiveness. To understand the maternal behavior driven by complex sensory interactions, it is necessary to comprehend the individual sensory systems by taking out other senses. An excellent model for investigating sensory regulation of maternal behavior is a murine model of congenital blindness, the ZRDBA mice, where both an anophthalmic and sighted mice are generated from the same litter. Therefore, this study aims to assess whether visual inputs are essential to driving maternal behaviors in mice. Maternal behaviors were assessed using three behavioral tests, including the pup retrieval test, the home cage maternal behavior test, and the maternal aggression test. Our results show that blind mothers (1) took less time to retrieve their offspring inside the nest, (2) spent more time nursing and licking their offspring in the second‐ and third‐week postpartum, and (3) exhibited faster aggressive behaviors when exposed to an intruder male, compared to the sighted counterparts. This study provides evidence that congenitally blind mothers show more motivation to retrieve the pups, care, and protection towards their pups than sighted ones, likely due to a phenomenon of sensory compensation.