A model of increased impulsivity in rats with bilateral parkinsonism treated with Pramipexole

Impulse control disorders (ICD) is a common side effect of the dopaminergic treatment in patients with Parkinson's disease, which is more associated with dopamine agonists than with levodopa. To understand its pathophysiology, reliable animal models are essential. Using the variable delay-to-signal (VDS) paradigm, impulsivity was evaluated in bilateral parkinsonian rats treated with pramipexole (PPX). In this test, rats have to introduce the snout into a nose poke that is signaled by a light (presented at variable delays) triggering the delivery of a food reward after a correct response. Reaching a stable baseline performance, a partial bilateral dopaminergic lesion with 6-OHDA was induced in the dorsolateral striatum (AP: +1mm, L: ±3.4mm, V:-4.7 mm, Bregma). Rats undertook the VDS test under 5 conditions: basal state, 6-OHDA-induced lesion, the effect of two doses of PPX (0,25mg/kg and 3mg/kg; Latin-square design), and the day after the last dose of PPX. Only the acute administration of 3 mg/kg of PPX significantly rised the number of premature responses, indicating an increase of impulsive behavior, in parkinsonian but not in sham rats. Both doses of PPX significantly decreased the accuracy of responding (correct/total number of responses) and increased the incorrect and perseverative (compulsive behavior) responses in both parkinsonian and sham treated groups when compared with saline-treated groups. In conclusion, PPX induced attention deficit (lack of accuracy) as well as compulsive behavior in control and parkinsonian rats, but increased impulsivity only in the parkinsonian animals. This model could constitute a valid tool to investigate the pathophysiology of ICD.

Positive biocompatibility of nanocrystalline glass-like carbon thin films

The interest in carbon nanomaterials with high transparency and electrical conductivity has grown within the last decade in view of a wide variety of applications, including biocompatible sensors, diagnostic devices and bioelectronic implants. The aim of this work is to test the biocompatibility of particular nanometer-thin nanocrystalline glass-like carbon films (NGLC), a disordered structure of graphene flakes joined by carbon matrix (Romero et al., 2016). We used a cell line (SN4741) from substantia nigra dopaminergic cells derived from transgenic mouse embryo cells (Son et al., 1999). Some cells were cultured on top of NGLC films (5, 20 and 80 nm) and other with NGLC nanoflakes (approx. 5-10 mm2) in increasing concentrations: 1, 5, 10, 20 and 50 μg/ml, during 24 h, 3 days and 7 days. Cells growing in normal conditions were defined under culture with DMEM supplemented with 10% FCS, Glucose (0,6%), penicillin-streptomycin (50U/ml) and L-glutamine (2mM) at 5%CO2 humidified atmosphere. Nanoflakes were resuspended in DMEM at the stock concentration (2 g/l). The experiments were conducted in 96 well plates (Corning) using 2500 cells per well. For MTT analysis, the manufacturer recommendations were followed (Roche, MTT kit assay): a positive control with a 10% Triton X-100 treatments (15 minutes) and a negative control without neither Triton X-100 nor NGLC. As apoptosis/necrosis assay we used LIVE/DEAD® Viability/Cytotoxicity Assay Kit (Invitrogen). In a separate experiment, cells were cultured on top of the NGLC films for 7 days. Primary antibodies: anti-synaptophysin (SYP, clone SY38, Chemicon) and goat anti-GIRK2 (G-protein-regulated inward-rectifier potassium channel 2 protein) (Abcom) following protocol for immunofluorescence. WB for proteins detection performed with a polyclonal anti-rabbit proliferating cell nuclear antigen (PCNA). Results demonstrated the biocompatibility with different concentration of NGLC varying the degree of survival from a low concentration (1 mg/ml) in the first 24 h to high concentrations (20-50 g/ml) after 7 days as it is corroborated by the PCNA analysis. Cells cultured on top of the film showed after 7 days axonal-like alignment and edge orientation as well as net-like images. Neuronal functionality was demonstrated to a certain extent through the analysis of coexistence between SYP and GIRK2. In conclusion, this nanomaterial could offer a powerful platform for biomedical applications such as neural tissue engineering