Chronic Adolescent CDPPB Treatment Alters Short-Term, but not Long-Term, Glutamatergic Receptor Expression

Sex-specific behavioral impairments produced by neonatal exposure to MK-801 are partially reversed by adolescent CDPPB treatment

Psychomimetic behaviors manifest in adult rodents long after neonatal exposure to the noncompetitive NMDA receptor antagonist MK-801. In the present study, we used this neurodevelopmental model of schizophrenia to evaluate the therapeutic potential of positive allosteric modulation of metabotropic glutamate receptor 5 (mGluR5) during adolescence. To this end, we randomly assigned male and female C57BL6 mouse littermates to one of three treatment groups: (i) neonatal and adolescent saline, (ii) neonatal MK-801 (0.25 mg/kg) and adolescent saline, and (iii) neonatal MK-801 and adolescent CDPPB (10 mg/kg), a positive allosteric modulator of mGluR5. When animals reached adulthood, a wide range of behavioral tests were conducted including sucrose preference, anxiety assessment in the elevated plus maze, and a series of food-reinforced operant procedures meant to assess motor activity, motivation, learning, and attention. Neonatal MK-801 exposure produced profound motor hyperactivity in both sexes and attenuated sucrose preference in males, effects that were reversed by CDPPB. MK-801 produced other deficits such as impaired set shifting or response inhibition deficits that were not reversed by CDPPB. Overall, female mice were more susceptible to MK-801's behavioral effects than males. These findings further support the use of neonatal MK-801 exposure as an animal model of schizophrenia and suggest that CDPPB can reverse the neurodevelopmental progression of some schizophrenia-like behaviors.

Lrrc7 mutant mice model developmental emotional dysregulation that can be alleviated by mGluR5 allosteric modulation

LRRC7 has been identified as a candidate gene for severe childhood emotional dysregulation. Direct experimental evidence for a role of LRRC7 in the disease is needed, as is a better understanding of its impact on neuronal structure and signaling, and hence potential treatment targets. Here, we generated and analyzed an Lrrc7 mutant mouse line. Consistent with a critical role of LRRC7 in emotional regulation, mutant mice had inappropriate juvenile aggressive behavior and significant anxiety-like behavior and social dysfunction in adulthood. The pivotal role of mGluR5 signaling was demonstrated by rescue of behavioral defects with augmentation of mGluR5 receptor activity by 3-Cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl)benzamide (CDPPB). Intra-peritoneal injection of CDPPB alleviated abnormal juvenile behavior, as well as anxiety-like behavior and hypersociability at adulthood. Furthermore, mutant primary neurons had impaired neurite outgrowth which was rescued by CDPPB treatment. In conclusion, Lrrc7 mutant mice provide a valuable tool to model childhood emotional dysregulation and persistent mental health comorbidities. Moreover, our data highlight an important role of LRRC7 in mGluR5 signaling, which is a potential new treatment target for anxiety and social dysfunction.

Perinatal exposure to fluoxetine increases anxiety- and depressive-like behaviours and alters glutamatergic markers in the prefrontal cortex and hippocampus of male adolescent rats: A comparison between Sprague-Dawley rats and the Wistar-Kyoto rat model of depression

BACKGROUND

With approximately 10% of pregnant women prescribed antidepressant drugs for the treatment of depressive disorders, there is growing concern regarding the potential long-term effects of this exposure on offspring. Research is needed in clinically relevant models to determine the effects on offspring behaviour and associated neurobiological systems.

AIM

The aim of this study was to determine the effects of maternal fluoxetine treatment on anxiety-like and depressive-like behaviours in adolescent offspring as well as associated glutamatergic markers, using a clinically relevant rodent model of depression.

METHODS

Wistar-Kyoto (model of innate depression) and Sprague-Dawley rats were treated with fluoxetine (10 mg/kg) from gestational day 0 to postnatal day 14. Male offspring underwent behavioural testing (open field, elevated plus maze, forced swim test) at adolescence followed by quantitative immuno-detection of glutamatergic markers in the prefrontal cortex and ventral hippocampus.

RESULTS

Perinatal fluoxetine exposure exacerbated the anxiety-like and depressive-like phenotype in Wistar-Kyoto offspring and induced an anxiety-like and depressive-like phenotype in Sprague-Dawley offspring. Wistar-Kyoto offspring showed reductions in NMDA receptor NR1, NR2A and NR2B subunits, as well as post-synaptic density 95 (PSD-95) and metabotropic glutamate receptor subtype 1 (mGluR1) in the prefrontal cortex; perinatal fluoxetine exposure further reduced NR1, NR2A, PSD-95 and mGluR1 expression in Wistar-Kyoto as well as Sprague-Dawley offspring. In the ventral hippocampus perinatal fluoxetine exposure reduced PSD-95 and increased metabotropic glutamate receptor subtype 5 (mGluR5) and Homer1b/c in both Sprague-Dawley and Wistar-Kyoto strains.

CONCLUSION

These findings suggest that maternal fluoxetine treatment exacerbates effects of underlying maternal depression on offspring behaviour, which may be mediated through alterations in the glutamatergic system. Further research investigating how to minimise these effects, whilst ensuring optimal treatment for mothers, is essential to move the field forward.