Traumatic brain injury (TBI) is a highly complex multi-factorial disorder. Experimental trauma involves primary and secondary injury cascades that underlie delayed neuronal dysfunction and death. Mitochondrial dysfunction and glutamatergic excitotoxicity are the hallmark mechanisms of damage. Accordingly, a successful pharmacological intervention requires a multi-faceted approach. Guanosine (GUO) is known for its neuromodulator effects in various models of brain pathology, specifically those that involve the glutamatergic system. The aim of the study was to investigate the GUO effects against mitochondrial damage in hippocampus and cortex of rats subjected to TBI, as well as the relationship of this effect with the glutamatergic system. Adult male Wistar rats were subjected to a unilateral moderate fluid percussion brain injury (FPI) and treated 15 min later with GUO (7.5 mg/kg) or vehicle (saline 0.9%). Analyses were performed in hippocampus and cortex 3 h post-trauma and revealed significant mitochondrial dysfunction, characterized by a disrupted membrane potential, unbalanced redox system, decreased mitochondrial viability, and complex I inhibition. Further, disruption of Ca homeostasis and increased mitochondrial swelling was also noted. Our results showed that mitochondrial dysfunction contributed to decreased glutamate uptake and levels of glial glutamate transporters (glutamate transporter 1 and glutamate aspartate transporter), which leads to excitotoxicity. GUO treatment ameliorated mitochondrial damage and glutamatergic dyshomeostasis. Thus, GUO might provide a new efficacious strategy for the treatment acute physiological alterations secondary to TBI.

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Degeneration of the locus coeruleus (LC), the main source of cerebral noradrenaline (NA), has been reported in diverse neurodegenerative diseases, including Parkinson’s diseases (PD). There is increasing evidence indicating the role of NA deficiency in the prefrontal cortex (PFC) and the development of early cognitive impairments in PD. Here, we evaluated whether a selective noradrenergic lesion of LC caused by 6-hydroxydopamine (6-OHDA) may induce memory deficits and neurochemical alterations in the PFC. Adult male Wistar rats received stereotaxic bilateral injections of 6-OHDA (5 μg/2 μl) into the LC, and two stainless-steel guide cannulas were implanted in the PFC. The SHAM group received just vehicle. To induce a selective noradrenergic lesion, animals received nomifensine (10 mg/kg), a dopamine transporter blocker, one hour before surgery. 6-OHDA-lesioned rats displayed impairments of the short- and long-term object recognition memory associated to reduced content of tyrosine hydroxylase in the LC. Neurochemical analysis revealed an altered mitochondrial membrane potential in LC. Regarding the PFC, an increased ROS production, cell membrane damage, and mitochondrial membrane potential disruption were observed. Remarkably, bilateral NA (1 μg/0.2 μl) infusion into the PFC restored the recognition memory deficits in LC-lesioned rats. These findings indicate that a selective noradrenergic LC lesion induced by 6-OHDA deregulates a noradrenergic network in the PFC, which could be involved in the early memory impairments observed in nondemented PD patients.

Atorvastatin is a 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor with cholesterol-lowering, anti-inflammatory, and antioxidant properties. Increasing evidence show atorvastatin acts as a protective agent against insults in the central nervous system (CNS). The regular use of statins has been associated with a reduced risk of Parkinson's disease (PD) development. Here, we evaluated early events involved in the neurotoxicity induced by intranasal (i.n.) infusion of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in rats and the potential of atorvastatin to prevent these early toxic events. Male Wistar rats were pretreated orally with atorvastatin (10 mg/kg/day) or vehicle once a day during seven consecutive days. Twenty-four hours after atorvastatin administration, animals received a single bilateral i.n. infusion of MPTP (1 mg/nostril), and 6 h later, the striatum and the hippocampus were collected to evaluate early oxidative stress parameters and inflammatory cytokines. Atorvastatin prevented MPTP-induced increase in reactive species (RS) generation and in glutathione levels in the striatum. Atorvastatin also prevented the reduction in mitochondrial respiratory chain complex I and II activities evoked by MPTP in the striatum. Atorvastatin per se reduced the levels of the cytokines TNF-α and IL-1β, and surprisingly, it reduced IL-10 and nerve growth factor levels in the striatum. However, the anti-inflammatory IL-10 levels increased in the striatum following atorvastatin plus MPTP treatment. These effects were not observed in the hippocampus. Our findings reinforce and extend the notion of the neuroprotective effects of atorvastatin in a PD model and indicate the modulation of oxidative and inflammatory responses as the mechanisms associated with therapeutic action of atorvastatin in PD.

Parkinson's disease (PD) signs and symptoms regularly include tremor. Interestingly, the nucleoside guanosine (GUO) has already proven to be effective in reducing reserpine-induced tremulous jaw movements (TJMs) in rodent models, thus becoming a promising antiparkinsonian drug. Here, we aimed at revealing the mechanism behind GUO antiparkinsonian efficacy by assessing the role of adenosine A 1 and A 2A receptors (A 1 R and A 2A R) on GUO-mediated anti-tremor effects in the reserpinized mouse model of PD. Reserpinized mice showed elevated reactive oxygen species (ROS) production and cellular membrane damage in striatal slices assessed ex vivo and GUO treatment reversed ROS production. Interestingly, while the simultaneous administration of sub-effective doses of GUO (5 mg/kg) and SCH58261 (0.01 mg/kg), an A 2A R antagonist, precluded reserpineinduced TJMs, these were ineffective on reverting ROS production in ex vivo experiments. Importantly, GUO was able to reduce TJM and ROS production in reserpinized mouse lacking the A 2A R, thus suggesting an A 2A R-independent mechanism of GUOmediated effects. Conversely, the administration of DPCPX (0.75 mg/kg), an A 1 R antagonist, completely abolished both GUOmediated anti-tremor effects and blockade of ROS production. Overall, these results indicated that GUO anti-tremor and antioxidant effects in reserpinized mice were A 1 R dependent but A 2A R independent, thus suggesting a differential participation of adenosine receptors in GUO-mediated effects.