Medial prefrontal cortex lesions in mice do not impair effort-based decision making.

The function of the medial prefrontal cortex has previously been determined in the rat to play an important role in effort-based decision making and this, along with functions of other areas, has been assumed largely, to hold true in all rodents. In this study, we attempted to replicate this result in mice and to develop a model for effort-based decision making that could be useful for the study of neurological conditions. Mice were trained on a cost-benefit T-maze paradigm, whereby they chose between a low reward with little effort needed to obtain it or a higher reward, which required increased effort. Following training, the medial prefrontal cortex was lesioned. After surgery, contrary to earlier published rat studies, the performance of the mice did not change. In previous studies, prefrontal cortex lesioned rats chose the low effort/low reward option, but lesioned mice continued to select the high reward/high effort option. However, the other results are in line with previous mouse studies in both the extent of pathology and anxiety-like behaviour. These results illustrate a difference in the functioning of the prefrontal cortex between rats and mice and offer a word of caution on the interpretation of data from studies that employ different species

Allopregnanolone preclinical acute pharmacokinetic and pharmacodynamic studies to predict tolerability and efficacy for Alzheimer's disease.

To develop allopregnanolone as a therapeutic for Alzheimer's disease, we investigated multiple formulations and routes of administration in translationally relevant animal models of both sexes. Subcutaneous, topical (transdermal and intranasal), intramuscular, and intravenous allopregnanolone were bolus-administered. Pharmacokinetic analyses of intravenous allopregnanolone in rabbit and mouse indicated that peak plasma and brain levels (3-fold brain/plasma ratios) at 5min were sufficient to activate neuroregenerative responses at sub-sedative doses. Slow-release subcutaneous suspension of allopregnanolone displayed 5-fold brain/plasma ratio at Cmax at 30min. At therapeutic doses by either subcutaneous or intravenous routes, allopregnanolone mouse plasma levels ranged between 34-51ng/ml by 30min, comparable to published endogenous human level in the third trimester of pregnancy. Exposure to subcutaneous, topical, intramuscular, and intravenous allopregnanolone, at safe and tolerable doses, increased hippocampal markers of neurogenesis including BrdU and PCNA in young 3xTgAD and aged wildtype mice. Intravenous allopregnanolone transiently and robustly phosphorylated CREB within 5min and increased levels of neuronal differentiation transcription factor NeuroD within 4h. Neurogenic efficacy was achieved with allopregnanolone brain exposure of 300-500hr*ng/g. Formulations were tested to determine the no observable adverse effect level (NOAEL) and maximally tolerated doses (MTD) in male and female rats by sedation behavior time course. Sex differences were apparent, males exhibited ≥40% more sedation time compared to females. Allopregnanolone formulated in sulfobutyl-ether-beta-cyclodextrin at optimized complexation ratio maximized allopregnanolone delivery and neurogenic efficacy. To establish the NOAEL and MTD for Allo-induced sedation using a once-per-week intravenous regenerative treatment regimen: In female rats the NOAEL was 0.5mg/kg and MTD 2mg/kg. The predicted MTD in human female is 0.37mg/kg. In male rats the NOAEL and MTD were less than those determined for female. Outcomes of these PK/PD studies predict a safe and efficacious dose range for initial clinical trials of allopregnanolone for Alzheimer's disease. These findings have translational relevance to multiple neurodegenerative conditions

Safety, tolerability, and pharmacokinetics of allopregnanolone as a regenerative therapeutic for Alzheimer's disease: A single and multiple ascending dose phase 1b/2a clinical trial

IntroductionAllopregnanolone is an endogenous neurosteroid with the potential to be a novel regenerative therapeutic for Alzheimer's disease (AD). Foundations of mechanistic understanding and well-established preclinical safety efficacy make it a viable candidate.MethodsA randomized, double-blinded, placebo-controlled, single and multiple ascending dose trial was conducted. Intravenous allopregnanolone or placebo was administered once-per-week for 12 weeks with a 1-month follow-up. Participants with early AD (mild cognitive impairment due to AD or mild AD), a Mini-Mental State Examination score of 20-26 inclusive, and age ≥55 years were randomized (6:2 to three allopregnanolone dosing cohorts or one placebo cohort). Primary endpoint was safety and tolerability. Secondary endpoints included pharmacokinetic (PK) parameters and maximally tolerated dose (MTD). Exploratory endpoints included cognitive and imaging biomarkers.ResultsA total of 24 participants completed the trial. Allopregnanolone was safe and well tolerated in all study participants. No differences were observed between treatment arms in the occurrence and severity of adverse events (AE). Most common AE were mild to moderate in severity and included rash (n = 4 [22%]) and fatigue (n = 3 [17%]). A single non-serious AE, dizziness, was attributable to treatment. There was one serious AE not related to treatment. Pharmacokinetics indicated a predictable linear dose-response in plasma concentration of allopregnanolone after intravenous administration over 30 minutes. The maximum plasma concentrations for the 2 mg, 4 mg, 6 mg, and 10 mg dosages were 14.53 ng/mL (+/-7.31), 42.05 ng/mL (+/-14.55), 60.07 ng/mL (+/-12.8), and 137.48 ng/mL (+/-38.69), respectively. The MTD was established based on evidence of allopregnanolone-induced mild sedation at the highest doses; a sex difference in the threshold for sedation was observed (males 10 mg; females 14 mg). No adverse outcomes on cognition or magnetic resonance imaging-based imaging outcomes were evident.ConclusionsAllopregnanolone was well tolerated and safe across all doses in persons with early AD. Safety, MTD, and PK profiles support advancement of allopregnanolone as a regenerative therapeutic for AD to a phase 2 efficacy trial.Trial registrationClinicalTrials.gov-NCT02221622

Medial prefrontal cortex lesions in mice do not impair effort-based decision making.

The function of the medial prefrontal cortex has previously been determined in the rat to play an important role in effort-based decision making and this, along with functions of other areas, has been assumed largely, to hold true in all rodents. In this study, we attempted to replicate this result in mice and to develop a model for effort-based decision making that could be useful for the study of neurological conditions. Mice were trained on a cost-benefit T-maze paradigm, whereby they chose between a low reward with little effort needed to obtain it or a higher reward, which required increased effort. Following training, the medial prefrontal cortex was lesioned. After surgery, contrary to earlier published rat studies, the performance of the mice did not change. In previous studies, prefrontal cortex lesioned rats chose the low effort/low reward option, but lesioned mice continued to select the high reward/high effort option. However, the other results are in line with previous mouse studies in both the extent of pathology and anxiety-like behaviour. These results illustrate a difference in the functioning of the prefrontal cortex between rats and mice and offer a word of caution on the interpretation of data from studies that employ different species.</p

Transforming Growth Factor-β Signaling Alters Substrate Permeability and Tight Junction Protein Expression at the Blood-Brain Barrier during Inflammatory Pain

Our laboratory has shown that peripheral inflammatory pain induced by λ-carrageenan (CIP) can increase blood–brain barrier (BBB) permeability and alter tight junction (TJ) protein expression leading to changes in BBB functional integrity. However, the intracellular signaling mechanisms involved in this pathophysiologic response have not been elucidated. Transforming growth factor (TGF)-β signaling pathways are known to regulate vascular integrity and permeability. Therefore, we examined the function of TGF-β signaling at the BBB in rats subjected to CIP. During CIP, serum TGF-β1 and protein expression of the TGF-β receptor activin receptor-like kinase-5 (ALK5) were reduced. Brain permeability to (14)C-sucrose was increased and expression of TJ proteins (i.e., claudin-5, occludin, zonula occluden (ZO-1)) were also altered after 3 h CIP. Pharmacological inhibition of ALK5 with the selective inhibitor SB431542 further enhanced brain uptake of (14)C-sucrose, increased TJ protein expression (i.e., claudin-3, claudin-5, occludin, ZO-1), and decreased nuclear expression of TGF-β/ALK5 signaling molecules (i.e., Smad2, Smad3), which suggests a role for TGF-β/ALK5 signaling in the regulation of BBB integrity. Interestingly, administration of exogenous TGF-β1 before CIP activated the TGF-β/ALK5 pathway and reduced BBB permeability to (14)C-sucrose. Taken together, our data show that TGF-β/ALK5 signaling is, in part, involved in the regulation of BBB functional integrity