SARS-CoV-2 is a novel infectious contagion leading to COVID-19 disease. The virus has affected the lives of millions of people across the globe with a high mortality rate. It predominantly affects the lung (respiratory system), but it also affects other organs, including the cardiovascular, psychological, and gastrointestinal (GIT) systems. Moreover, elderly and comorbid patients with compromised organ functioning and pre-existing polypharmacy have worsened COVID-19-associated complications. Microbiota (MB) of the lung plays an important role in developing COVID-19. The extent of damage mainly depends on the predominance of opportunistic pathogens and, inversely, with the predominance of advantageous commensals. Changes in the gut MB are associated with a bidirectional shift in the interaction among the gut with a number of vital human organs, which leads to severe disease symptoms. This review focuses on dysbiosis in the gut–lung axis, COVID-19-induced worsening of comorbidities, and the influence of polypharmacy on MB.

Schizophrenia affects millions of people worldwide and is a major challenge for the scientific community. Like most psychotic diseases, it is also considered a complicated mental disorder caused by an imbalance in neurotransmitters. Due to the complexity of neuropathology, it is always a complicated disorder. The lack of proper understanding of the pathophysiology makes the disorder unmanageable in clinical settings. However, due to recent advances in animal models, we hope we can have better therapeutic approaches with more success in clinical settings. Dopamine, glutamate, GABA, and serotonin are the neurotransmitters involved in the pathophysiology of schizophrenia. Various animal models have been put forward based on these neurotransmitters, including pharmacological, neurodevelopmental, and genetic models. Polymorphism of genes such as dysbindin, DICS1, and NRG1 has also been reported in schizophrenia. Hypothesis based on dopamine, glutamate, and serotonin are considered successful models of schizophrenia on which drug therapies have been designed to date. New targets like the orexin system, muscarinic and nicotinic receptors, and cannabinoid receptors have been approached to alleviate the negative and cognitive symptoms. The non-pharmacological models like the post-weaning social isolation model (maternal deprivation), the isolation rearing model etc. have been also developed to mimic the symptoms of schizophrenia and to create and test new approaches of drug therapy which is a breakthrough at present in psychiatric disorders. Different behavioral tests have been evaluated in these specific models. This review will highlight the currently available animal models and behavioral tests in psychic disorders concerning schizophrenia.

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