Haloperidol rescues the schizophrenia-like phenotype in adulthood after rotenone administration in neonatal rats.

Neuropsychiatric disorders are multifactorial disturbances that encompass several hypotheses, including changes in neurodevelopment. It is known that brain development disturbances during early life can predict psychosis in adulthood. As we have previously demonstrated, rotenone, a mitochondrial complex I inhibitor, could induce psychiatric-like behavior in 60-day-old rats after intraperitoneal injections from the 5th to the 11th postnatal day. Because mitochondrial deregulation is related to psychiatric disorders and the establishment of animal models is a high-value preclinical tool, we investigated the responsiveness of the rotenone (Rot)-treated newborn rats to pharmacological agents used in clinical practice, haloperidol (Hal), and methylphenidate (MPD). Taken together, our data show that Rot-treated animals exhibit hyperlocomotion, decreased social interaction, and diminished contextual fear conditioning response at P60, consistent with positive, negative, and cognitive deficits of schizophrenia (SZ), respectively, that were reverted by Hal, but not MPD. Rot-treated rodents also display a prodromal-related phenotype at P35. Overall, our results seem to present a new SZ animal model as a consequence of mitochondrial inhibition during a critical neurodevelopmental period. Therefore, our study is crucial not only to elucidate the relevance of mitochondrial function in the etiology of SZ but also to fulfill the need for new and trustworthy experimentation models and, likewise, provide possibilities to new therapeutic avenues for this burdensome disorder.

Neonatal Rotenone Administration Induces Psychiatric Disorder-Like Behavior and Changes in Mitochondrial Biogenesis and Synaptic Proteins in Adulthood.

Since psychiatric disorders are associated with changes in the development of the nervous system, an energy-dependent mechanism, we investigated whether mitochondrial inhibition during the critical neurodevelopment window in rodents would be able to induce metabolic alterations culminating in psychiatric-like behavior. We treated male Wistar rat puppies (P) with rotenone (Rot), an inhibitor of mitochondrial complex I, from postnatal days 5 to 11 (P5-P11). We demonstrated that at P60 and P120, Rot-treated animals showed hyperlocomotion and deficits in social interaction and aversive contextual memory, features observed in animal models of schizophrenia, autism spectrum disorder, and attention deficit hyperactivity disorder. During adulthood, Rot-treated rodents also presented modifications in CBP and CREB levels in addition to a decrease in mitochondrial biogenesis and Nrf1 expression. Additionally, NFE2L2-activation was not altered in Rot-treated P60 and P120 animals; an upregulation of pNFE2L2/ NFE2L2 was only observed in P12 cortices. Curiously, ATP/ADP levels did not change in all ages evaluated. Rot administration in newborn rodents also promoted modification in Rest and Mecp2 expression, and in synaptic protein levels, named PSD-95, Synaptotagmin-1, and Synaptophysin in the adult rats. Altogether, our data indicate that behavioral abnormalities and changes in synaptic proteins in adulthood induced by neonatal Rot administration might be a result of adjustments in CREB pathways and alterations in mitochondrial biogenesis and Nrf1 expression, rather than a direct deficiency of energy supply, as previously speculated. Consequently, Rot-induced psychiatric-like behavior would be an outcome of alterations in neuronal paths due to mitochondrial deregulation.

Depletion of hypothalamic hypocretin/orexin neurons correlates with impaired memory in a Parkinson's disease animal model.

Parkinson's disease (PD) is a progressive and chronic neurodegenerative disorder characterized by loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and affects multiple neurotransmission systems such as hypocretin/orexin (HO) release and can lead to cognitive and memory deficits. The HO neurons located in lateral hypothalamus/perifornical area (LH/PeF) are involved with consolidation and memory processes. Here we verified the involvement of HO deficit in learning and memory process in an animal model of PD induced by bilateral intra-striatal injections of 6-hydroxydopamine (6-OHDA). The present study performed a working memory test by object recognition task and spatial memory test using the Morris water maze in control and PD-induced animals after depletion of HO neurons. In addition, our results indicate that HO system in degenerative disorders such as PD may modulate the declarative and spatial memory (assessed by object recognition and Morris water maze tests, respectively). A significant reduction of HO neurons in the LH/PeF and HO degeneration process in the hippocampus (CA1 and dentate gyrus areas) were noticed. Our data suggest that the HO system degeneration could be associated to memory dysfunction in PD.