Communication and social interaction in the cannabinoid‐type 1 receptor null mouse: Implications for autism spectrum disorder

Abstract

Clinical and preclinical findings have suggested a role of the endocannabinoid system (ECS) in the etiopathology of autism spectrum disorder (ASD). Previous mouse studies have investigated the role of ECS in several behavioral domains; however, none of them has performed an extensive assessment of social and communication behaviors, that is, the main core features of ASD. This study employed a mouse line lacking the primary endocannabinoid receptor (CB1r) and characterized ultrasonic communication and social interaction in CB1−/−, CB1+/−, and CB1+/+ males and females. Quantitative and qualitative alterations in ultrasonic vocalizations (USVs) were observed in CB1 null mice both during early development (i.e., between postnatal days 4 and 10), and at adulthood (i.e., at 3 months of age). Adult mutants also showed marked deficits in social interest in the three‐chamber test and social investigation in the direct social interaction test. These behavioral alterations were mostly observed in both sexes and appeared more marked in CB1−/− than CB1+/− mutant mice. Importantly, the adult USV alterations could not be attributed to differences in anxiety or sensorimotor abilities, as assessed by the elevated plus maze and auditory startle tests. Our findings demonstrate the role of CB1r in social communication and behavior, supporting the use of the CB1 full knockout mouse in preclinical research on these ASD‐relevant core domains. Lay Summary The endocannabinoid system (ECS) is important for brain development and neural function and is therefore likely to be involved in neurodevelopmental disorders such as Autism Spectrum Disorder (ASD). Here we investigated changes in social behavior and communication, which are core features of ASD, in male and female mice lacking the chief receptor of this system. Our results show that loss of this receptor results in several changes in social behavior and communication both during early development and in adulthood, thus supporting the role of the ECS in these ASD‐core behavioral domains.

Myt1l haploinsufficiency leads to obesity and multifaceted behavioral alterations in mice

“…Alterations in call clustering are paralleled by changes in acoustic features known to be important for categorical perception of ultrasonic vocalizations and are thus predicted to alter their communicative function and, consequently, the interaction between mother and pup [ 55 ]. Previous studies showed that call clustering is altered in multiple models with relevance to neurodevelopmental disorders, such as ASD [ 58 – 60 ]. Importantly, altered emission of isolation-induced ultrasonic vocalizations was detected despite intact maternal odor preference in the homing test.…”

Neural Hyperactivity Is a Core Pathophysiological Change Induced by Deletion of a High Autism Risk Gene Ash1L in the Mouse Brain

“…Moreover, some hyperactivity-related physiological changes, such as disturbed sleep in mutant mice, were not quantitatively measured. To fully assess the relationship between disruptive Ash1l mutations and autistic-like phenotypes in our mouse model, it is necessary to perform additional behavioral tests such as ultrasonic vocalizations, auditory startle responses, and direct social interactions in both young and adult animals ( Fyke et al, 2021a , b , c ). In addition, measurements of sleeping cycles by polysomnography are needed to quantify the disturbed sleep in mutant mice ( Tagaito et al, 2001 ).…”

Ultrasonic Vocalizations in Adult C57BL/6J Mice: The Role of Sex Differences and Repeated Testing

“…In experiment 1, both male and female B6 subjects were single-caged for the same time (72 h) in the test cage before each testing session to assess social behaviors and USVs: this allowed for us to assess sex differences in the same resident-intruder settings and pre-testing social isolation conditions. In experiment 2, the male mice were subjected to 10 min of isolation in the test cage, and their social behavior was compared with that of female mice exposed to 72-h pretesting isolation: this comparison served to evaluate sex differences under conditions that are commonly employed to assess male and female USVs in ASD mouse studies (Hebert et al, 2014 ; Pietropaolo et al, 2014 ; Oddi et al, 2015 ; Gaudissard et al, 2017 ; Gauducheau et al, 2017 ; Lemaire-Mayo et al, 2017 ; Fyke et al, 2021 ) and that are also more suitable for male behavioral assessment. USVs can in fact be also evaluated in male-female interactions without inducing a resident state in the male [e.g., Hebert et al, 2014 ; Oddi et al, 2015 ; Gaudissard et al, 2017 ; Lemaire-Mayo et al, 2017 ; Fyke et al, 2021 ], thus avoiding applying a social isolation period of at least 72 h that could interfere with several other behaviors.…”

“…Their USVs were compared with those of males that were either isolated for the same duration before testing (study 1) or only habituated to the testing cage for 10 min before tests (study 2). These two studies allow us to evaluate sex differences respectively (1) in the same resident-intruder settings, thus controlling for isolation effects and (2) using the most common (and practically more suitable) experimental settings for USV assessment used in previous studies with ASD mouse models, i.e., in the resident-intruder context for females and without pre-testing long isolation in males (Pietropaolo et al, 2011 , 2014 ; Hebert et al, 2014 ; Oddi et al, 2015 ; Gaudissard et al, 2017 ; Gauducheau et al, 2017 ; Fyke et al, 2021 ). In both studies, three subsequent social tests with a novel intruder were performed with an interval of 7–10 days in order to evaluate the potential stability of sex differences and their dependency on previous testing experience without confounding effects of social memory.…”

“…We chose B6 mice as the experimental subjects of our study because of the well-known relevance of this strain for behavioral neuroscience due to its large use for engineering genetically modified mouse lines. Stimulus females for all social tests were instead chosen from the CD1 strain because of its common use in social studies (Moles and D'Amato, 2000 ; Moles et al, 2007 ), especially those using genetic mouse models of ASD (Hebert et al, 2014 ; Pietropaolo et al, 2014 ; Oddi et al, 2015 ; Gaudissard et al, 2017 ; Gauducheau et al, 2017 ; Lemaire-Mayo et al, 2017 ; Fyke et al, 2021 ). This strain is preferentially employed in social interaction tests, since it is characterized by high levels of sociability and it facilitates behavioral analysis during social encounters with B6 animals because of its albino phenotype.…”