T32. Neonatal Chemical Hypoxia Exposure Causes Neuronal and Behavioral Alterations Related to Schizophrenia in Wistar Rats

Abstract

Background Schizophrenia (SZ) is a complex and debilitating mental disorder that affects approximately 1% of the world population and, according to the World Health Organization, it is one of the top ten causes of disability in developed countries. Neonatal hypoxia is a well-establish risk factor to SZ development, though little is known about the molecular mechanisms involved. Indeed, animals submitted to neonatal gaseous hypoxia show behavioral alteration and neurochemical changes resembling SZ features. However, the effect of chemical hypoxia induced by cobalt chloride (CoCl2) treatment is poorly understood. Remarkably, hypoxia induces an augmentation of adenosinergic system, an effect that seems to be relevant to neurodevelopment. Indeed, attention is being focused to adenosinergic system in the context of SZ. Thus, our goal was to investigate the effect of neonatal CoCl2 administration in distinct neuronal and behavioral parameters related to SZ. Moreover, we evaluated the role of haloperidol, a typical antipsychotic, and caffeine, an adenosinergic antagonist, in this scenario. Methods Wistar rats were treated with CoCl2 (subcutaneous, 60 mg/kg) or saline (NaCl 0.9%) in post-natal day 7 (PND7) – period in which rodent’s brain development is equivalent to human’s in the moment of birth. At PND50 – corresponding to 18 years-old in humans – locomotion, which correlate with SZ positive symptoms, was evaluated. At PND90 – resembling adulthood in humans – social interaction deficit and contextual fear conditioning were analyzed, as indicator of SZ negative symptoms, and cognitive symptoms and diminished emotional processing, respectively. Immediately after, all animals underwent euthanasia and had their brains removed and dissected. HIF-1α and VEGF gene expression were analyzed through RT-qPCR at pre-frontal cortex. Additionally, total neurons and positive-parvalbumin (PV+) cells were labelled at pre-frontal cortex and amygdala through immunofluorescence. Four groups were also assessed to behavioral parameters: i) animals challenged with Haloperidol (ip; 0.1 mg/kg) or saline, 30 minutes before the experiments, at PND50 and PND90, and ii) rats treated with caffeine (sc; 10 mg/kg) or saline (at PND6); experiments were also conducted at PND50 and PND90. Results Our results show that CoCl2 treatment induced hyperlocomotion at PND50, as well as a decrease in social interaction and time of freezing at contextual fear conditioning test at PND90 when compared to control group. CoCl2 treated-rats also showed an increased expression of HIF-1α e VEGF, diminishment in PV+ neurons at pre-frontal cortex and increasing in amygdala in relation to control group. Moreover, haloperidol reversed behavioral deficits induced by CoCl2 treatment in both PND50 and PND90. Interestingly, the previous caffeine exposure also reversed the effect of CoCl2 at PND50 and PND90. Discussion In conclusion, our results indicate that chemical neonatal hypoxia induced behavioral alterations and neuronal changes relevant to SZ, reinforcing the hypoxia participation in the development of this disorder. The abolishment of CoCl2-induced effects after haloperidol reinforces the usage of this model to SZ studies. Importantly, caffeine treatment also warned behavioral modification, strengthening the participation of adenosinergic system in SZ development.