Polymeric alkylpyridinium salts permit intracellular delivery of human Tau in rat hippocampal neurons: requirement of Tau phosphorylation for functional deficits.

Patients suffering from tauopathies including frontotemporal dementia (FTD) and Alzheimer's disease (AD) present with intra-neuronal aggregation of microtubule-associated protein Tau. During the disease process, Tau undergoes excessive phosphorylation, dissociates from microtubules and aggregates into insoluble neurofibrillary tangles (NFTs), accumulating in the soma. While many aspects of the disease pathology have been replicated in transgenic mouse models, a region-specific non-transgenic expression model is missing. Complementing existing models, we here report a novel region-specific approach to modelling Tau pathology. Local co-administration of the pore-former polymeric 1,3-alkylpyridinium salts (Poly-APS) extracted from marine sponges, and synthetic full-length 4R recombinant human Tau (hTau) was performed in vitro and in vivo. At low doses, Poly-APS was non-toxic and cultured cells exposed to Poly-APS (0.5 µg/ml) and hTau (1 µg/ml; ~22 µM) had normal input resistance, resting-state membrane potentials and Ca(2+) transients induced either by glutamate or KCl, as did cells exposed to a low concentration of the phosphatase inhibitor Okadaic acid (OA; 1 nM, 24 h). Combined hTau loading and phosphatase inhibition resulted in a collapse of the membrane potential, suppressed excitation and diminished glutamate and KCl-stimulated Ca(2+) transients. Stereotaxic infusions of Poly-APS (0.005 µg/ml) and hTau (1 µg/ml) bilaterally into the dorsal hippocampus at multiple sites resulted in hTau loading of neurons in rats. A separate cohort received an additional 7-day minipump infusion of OA (1.2 nM) intrahippocampally. When tested 2 weeks after surgery, rats treated with Poly-APS+hTau+OA presented with subtle learning deficits, but were also impaired in cognitive flexibility and recall. Hippocampal plasticity recorded from slices ex vivo was diminished in Poly-APS+hTau+OA subjects, but not in other treatment groups. Histological sections confirmed the intracellular accumulation of hTau in CA1 pyramidal cells and along their processes; phosphorylated Tau was present only within somata. This study demonstrates that cognitive, physiological and pathological symptoms reminiscent of tauopathies can be induced following non-mutant hTau delivery into CA1 in rats, but functional consequences hinge on increased Tau phosphorylation. Collectively, these data validate a novel model of locally infused recombinant hTau protein as an inducer of Tau pathology in the hippocampus of normal rats; future studies will provide insights into the pathological spread and maturation of Tau pathology.

Comparison of automated home-cage monitoring systems: emphasis on feeding behaviour, activity and spatial learning following pharmacological interventions.

BACKGROUND: Different automated systems have been developed to facilitate long-term and continuous assessment of behaviours including locomotor activity, feeding behaviour and circadian activity. NEW METHOD: This study assessed the effectiveness of three different observation systems as methods for determining strain and pharmacological induced differences in locomotor activity, feeding behaviour and spatial learning. The effect of the CB1 antagonist AM251 on feeding behaviour was determined in the PhenoMaster and PhenoTyper. Next, effects of cholinergic (scopolamine) and glutamatergic (Phenylcyclidine, PCP) receptor antagonism and dopaminergic agonism (apomorphine) on activity were assessed in the PhenoTyper and IntelliCage. Finally, the IntelliCage was utilised to determine differences in activity and spatial learning of C57BL/6 and DBA/2 mouse strains following pharmacological intervention. RESULTS: AM251 induced a suppression of food intake, feeding behaviour and a reduction in body weight in both the PhenoTyper and PhenoMaster. Apomorphine reduced activity in both the PhenoTyper and IntelliCage. Whereas, decreased activity was evident with PCP in the PhenoTyper, but not IntelliCage and Scopolamine induced a trend towards elevated levels of activity in the IntelliCage but not PhenoTyper. Strain differences in activity and spatial learning were also evident, with increased corner visits and drug induced impairments only observed with C57BL/6 mice. COMPARISON WITH EXISTING METHOD: The automated home cage observation systems determined similar drug and strain effects on behaviour to those observed using traditional methods. CONCLUSIONS: All three observation systems reported drug-induced changes in behaviour however, they differ in their application of spatial learning tasks and utilisation of single versus group housed recordings.

Scopolamine and MK801-induced working memory deficits in rats are not reversed by CBD-rich cannabis extracts.

Smoking marijuana causes working and short-term memory deficits, an effect that is mediated by cannabinoid receptor (CB1) activation in the brain. While this may be due to the main psychoactive constituent Delta9-tetrahydrocannabinol (Delta9-THC), plant extracts also contain other cannabinoid and terpenoid compounds with unknown properties. Towards this end, we have recently shown that high concentrations of plant extracts rich in cannabidiol (CBD) can reverse working memory deficits induced by Delta9-THC which is a remaining contaminant of this extract [Fadda P, Robinson L, Fratta W, Pertwee RG, Riedel G. Differential effects of THC- and CBD-rich cannabis-extracts on working memory in rats. Neuropahrmacology 2004;47:1170-9]. Since this effect was dose-dependent and indicative of memory enhancing qualities of the CBD-rich extract, this prompted a wider investigation into the effects of CBD on other forms of amnesia in order to determine the mechanism of action and to reveal its potency against anticholinergic and antiglutamatergic agents. We employed a spatial delayed matching to position task in the open-field water maze. Both scopolamine (0.2 mg/kg i.p.) and dizocilpine (MK801: 0.1mg/kg i.p.) impaired working memory at delays of 30 s and 4 h. Two doses of CBD-rich extracts (5 and 10 mg/kg), which did not affect working memory when given alone, were unable to reverse these deficits when co-administered with scopolamine or MK801. These data suggest that reversal of working memory deficits by CBD-rich extracts are specific to the cannabinoid system and do not compensate for acutely induced cholinergic or glutamatergic receptor hypoactivity.