Translational Pharmacology of PRAX-944, a Novel T-Type Calcium Channel Blocker in Development for the Treatment of Essential Tremor

Background

Essential tremor is the most common movement disorder with clear unmet need. Mounting evidence indicates tremor is caused by increased neuronal burst firing and oscillations in cerebello-thalamo-cortical circuitry and may be dependent on T-type calcium channel activity. T-type calcium channels regulate sigma band electroencephalogram (EEG) power during non-rapid eye movement sleep, representing a potential biomarker of channel activity. PRAX-944 is a novel T-type calcium channel blocker in development for essential tremor.

Objectives

Using a rat tremor model and sigma-band EEG power, we assessed pharmacodynamically-active doses of PRAX-944 and their translation into clinically tolerated doses in healthy participants, informing dose selection for future efficacy trials.

Methods

Harmaline-induced tremor and spontaneous locomotor activity were used to assess PRAX-944 efficacy and tolerability, respectively, in rats. Sigma-power was used as a translational biomarker of T-type calcium channel blockade in rats and, subsequently, in a phase 1 trial assessing pharmacologic activity and tolerability in healthy participants.

Results

In rats, PRAX-944 dose-dependently reduced tremor by 50% and 72% at 1 and 3 mg/kg doses, respectively, without locomotor side effects. These doses also reduced sigma-power by ~30% to 50% in rats. In healthy participants, sigma-power was similarly reduced by 34% to 50% at 10 to 100 mg, with no further reduction at 120 mg. All doses were well tolerated.

Conclusions

In rats, PRAX-944 reduced sigma-power at concentrations that reduced tremor without locomotor side effects. In healthy participants, comparable reductions in sigma-power indicate that robust T-type calcium channel blockade was achieved at well-tolerated doses that may hold promise for reducing tremor in patients with essential tremor. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

     

Clonazepam in a Focal-Motor Monkey Model: Efficacy, Tolerance, Toxicity, Withdrawal, and Management

Since the clinical data have been equivocal in regard to the effects of clonazepam (CZP) in focal-motor seizures, an alumina gel monkey model was used to evaluate quantitatively its efficacy with respect to this seizure category. The insolubility of CZP and its short biological half-life in monkey necessitated its evaluation in the model via constant-rate intravenous administration in a solution of polyethylene glycol 400 (PEG). Two groups of monkeys were given CZP in PEG (N = 6) or a PEG solution alone as a control compound (N = 5) for 6 weeks; these treatments were bordered at both ends by 3 weeks of treatment with saline only in order to establish a baseline. CZP was administered at a concentration sufficient to achieve a plasma level of 30 ng/ml in drug step I (3 weeks) and at least double that level in drug step II (3 weeks). As a solute for CZP, and when given by itself, PEG was always administered at a concentration of 35%. The results indicate that CZP is effective for focal-motor seizures and secondarily generalized tonic-clonic seizures, particularly when its concentration in plasma is higher than 60 ng/ml. Withdrawal seizures were evident on cessation of CZP administration. CZP appears to be a useful broad-spectrum anticonvulsant when managed carefully. An unexpected finding was the irreversibility of the pharmacological effect of PEG. Cessation of PEG administration significantly reduced seizure frequency in subsequent weeks to a level below the initial baseline level.     

Facilitation by estradiol of midbrain and pontine unit responses to vaginal and somatosensory stimulation in the squirrel monkey (Saimiri sciureus).

In six female squirrel monkeys anesthetized with a chloralose-urethane mixture, single midbrain and pontine units were tested for their responsiveness to somatosensory, vaginal, and rectal stimulation. Three monkeys (two ovariectomized, one intact) were given a series of estradiol injections that produced full cornification of vaginal smears. The other three animals, all ovariectomized, received only the oil vehicle and their smears remained uncornified throughout. Single-unit activity was sampled from comparable regions in both groups of monkeys. Units responding to tactile stimuli tended to have large receptive fields, and in the estrogen-treated monkeys they comprised a larger proportion of the sample than in the untreated monkeys (89 and 49%, respectively). Similarly, a greater proportion of the units responded to vaginal stimulation (65%) in the estrogen-treated animals than in those receiving the oil vehicle alone (40%). In contrast to the effect of estradiol treatment on neuronal responsiveness to vaginal and tactile cutaneous stimulation, units responding to nociceptive stimulation of the foot were found with equal frequency (48%) in both groups of monkeys. The finding that unit responses to tactile stimuli occurred with a greater frequency in estrogen-treated monkeys is consistent with results previously reported for midbrain and pontine units is estrous and anestrous cats. Unlike the cat, however, in the squirrel monkey there was no indication that the sizes of the peripheral receptive fields were altered by estradiol treatment.     

丁咯地尔抑制NE和GIu引起的单个脑细胞游离钙增高

目的：研究丁咯地尔对去甲肾上腺素（ＮＥ）和谷氨酸（Ｇｌｕ）引起大鼠单个脑细胞内游离钙增高的影响。方法：应用ＡＲ－ＣＭ－ＭＩＣ阳离子测定系统测量细胞内游离钙（［Ｃａ２＋］１）．结果：细胞外钙为 １．３ ｍｍｏｌ·Ｌ－１,丁咯地尔 ０．ｌ,ｌ．０,１０．０μｍｏｌ·Ｌ－１对细胞静息［Ｃａ２＋］．无明显影响,对ＮＥ诱导的［Ｃａ２＋］增高明显抑制,对Ｇｌｕ 诱导的［Ｃａ２＋］ 增高具有一定的抑制作用。结论：丁咯地尔能抑制ＮＥ和Ｇｌｕ 引起的单个脑细胞游离钙增高。     

The effects of hyperglycemia on ischemic cell change and reactive neuronal change in neonatal rat brain following transient forebrain ischemia

To examine the effects of hyperglycemia on a transient ischemia in the neonatal brain, neuropathological and biochemical evaluations were performed. In 10-day-old rats, brain ischemia was induced by permanent occlusion of the right external and internal carotid and subclavian arteries and the clamping of the left external and internal carotid arteries for 2h. The peritoneal injection of a 50% glucose solution (0.10 ml/15 g weight) 5 min before the induction of brain ischemia increased the plasma glucose concentration to 20-25 mmol/l during ischemia. It preserved brain tissue glucose levels at 1h of ischemia in the glucose-treated group, while tissue glucose was exhausted in the saline-injected group. Tissue lactate concentrations increased slightly at the end of the ischemic insult (6.7 mmol/kg) in the saline-injected group and remarkably (18.7 mmol/kg) in the glucose-treated group. Two distinct forms of ischemic neuronal change were found in this study: ischemic cell change and reactive neuronal change. A quantitative neuropathological assessment indicated that hyperglycemia significantly reduced the volume of ischemic cell change in the neocortex from 85% to 33%, but not that of reactive neuronal change (from 5.5% to 2.4%). These results indicated that hyperglycemia attenuated ischemic cell change, but not reactive neuronal change, in the neonatal rat brain and suggested that it reduced ischemic cell change probably because of reserved brain glucose.     

The EEG Consistency Index as a Psycho-Physiological Marker of ADHD and Methylphenidate Response: Replication of Results

ABSTRACT

The current study replicates the design and findings of earlier studies examining an EEG measure called the Consistency Index (CI) as a physiological measure of ADHD (Cox et al., 1998; Cox, Merkel, Kovatchev, & Seward, 2000; Kovatchev et al., 2001) and medication response (Merkel et al., 2000). Six males diagnosed with ADHD between the ages of 16 and 19 were examined in this study. The average CI for participants while off of medication was 26%, indicative of ADHD (CI < 40% strong likelihood of ADHD). These CI readings changed significantly when the participants were on therapeutic dosages of methylphenidate. Five of six participants demonstrated a CI > 50%, which is similar to the CI of an individual with no ADHD (Cox et al., 1998, 2000; Kovatchev et al., 2001). Overall, the average CI when on an effective dose of methyl-phenidate was 57% (CI > 50% strong likelihood of no ADHD). These changes in overall CI were statistically significant (p < 0.05) and demonstrate exciting possibilities for the utility of the CI as a physiological marker of ADHD.     

Association of Combined MRI, Interictal EEG, and Ictal EEG Results with Outcome and Pathology After Temporal Lobectomy

Summary: Purpose: Magnetic resonance imaging, interictal scalp EEG, and ictal scalp EEG each have been shown to localize the primaly epileptic region in most patients with mesial-basal temporal lobe epilepsy (MBTLE), but the association of surgical outcome and pathology with each combination of these test results is not known. Methods: We reviewed the MRI, interictal scalp EEG, and ictal scalp EEG results of 90 consecutive patients with MBTLE. Twelve patients were excluded from the analysis because inconclusive bitemporal intracranial EEG results precluded anterior temporal lobectomy (ATL); none had concordant MRI and interictal scalp EEG results. We compared all combinations of presurgical MRI, interictal EEG, and ictal EEG results to seizure outcome and tissue pathology in the 78 patients who underwent an ATL. Results: Forty-eight (61%) patients had concordant lateral-ized MRI and interictal EEG temporal lobe abnormalities, with no discordant ictal EEG results; 77% of these patients were seizure-free after ATL. Concordance of MRI and interictal EEG abnormalities correlated with seizure cessation (p < 0.05), compared to all combinations with discordant or nonlateralizing MRI and interictal EEG results. Mesial temporal sclerosis (MTS) was confirmed pathologically in about 80% of both groups (p = 0.5). Outcome in patients with concordant MRI and ictal EEG with nonlateralizing interictal EEG was significantly worse than combinations with concordant MRI and interictal EEG (p < 0.02). Conclusions: Compared to other combinations of test results, concordance of MRI and interictal EEG is most closely associated with surgical outcome in MBTLE. However, most selected patients have pathologic confirmation of MTS regardless of test results or outcome. This information may be useful for planning the presurgical evaluation of patients with medically intractable MBTLE.     

Lomerizine,a Ca2+ Channel Blocker,Protects against Neuronal Degeneration within the Visual Center of the Brain after Retinal Damage in Mice

The purpose of this study was to determine whether lomerizine, a Ca²⁺ channel blocker, protects against neuronal degeneration within the dorsal lateral geniculate nucleus (dLGN) and superior colliculus (SC) after the induction of retinal damage by intravitreal injection of N‐methyl‐d ‐aspartate (NMDA) in mice. NMDA (20 mM/2 μL) was injected into the vitreous body of the left eye in mice (DAY 0). Lomerizine at 30 mg/kg, p.o. was administered daily from immediately after the injection of NMDA (DAY 0) to 90 days after (DAY 90). To investigate the neuroprotective effects of lomerizine, the retina, dLGN, and SC were examined using histochemistry and immunohistochemistry. Lomerizine reduced the retinal damage induced by NMDA and partially prevented the transsynaptic neuronal degeneration within dLGN and SC on the contralateral side. Moreover, lomerizine reduced the intravitreal NMDA induced decrease in the light‐induced expression of c‐Fos in the contralateral dLGN (used in this study to evaluate residual vision). These results indicate that lomerizine affords some protection against transsynaptic neuronal degeneration within the visual center of the mouse brain.     

Brain connectivity and high functioning autism: a promising path of research that needs refined models, methodological convergence, and stronger behavioral links

Here we review findings from studies investigating functional and structural brain connectivity in high functioning individuals with autism spectrum disorders (ASDs). The dominant theory regarding brain connectivity in people with ASD is that there is long distance under-connectivity and local over-connectivity of the frontal cortex. Consistent with this theory, long-range cortico-cortical functional and structural connectivity appears to be weaker in people with ASD than in controls. However, in contrast to the theory, there is less evidence for local over-connectivity of the frontal cortex. Moreover, some patterns of abnormal functional connectivity in ASD are not captured by current theoretical models. Taken together, empirical findings measuring different forms of connectivity demonstrate complex patterns of abnormal connectivity in people with ASD. The frequently suggested pattern of long-range under-connectivity and local over-connectivity is in need of refinement.     

Inhibition of platelet aggregation and antagonism of vasopressin-induced ECG changes in primates by a carboprostacyclin analogue, ZK 36374

A chemically stable carboprostacyclin analogue, ZK 36374 has been compared with two other prostacyclin derivatives with respect to ADP-induced in vitro aggregation of baboon and human platelets and ex vivo platelet aggregation in the baboon. ZK 36374 was also tested on the systemic arterial blood pressure of the baboon and against vasopressin-induced ECG changes in primates. Compared to the other two compounds, ZK 36374 displayed enhanced anti-platelet aggregating activity; there was dissociation between this property and its hypotensive potency. ZK 36374 antagonized the vasopressin-induced ECG changes. These results indicate that ZK 36374 possesses therapeutic potential in vascular disease including that affecting the coronary vessels.     

Neuroprotective Effect of Resveratrol on Acute Brain Ischemia Reperfusion Injury by Measuring Annexin V,p53, Bcl-2 Levels in Rats

BackgroundCerebral ischemia is as a result of insufficient cerebral blood flow for cerebral metabolic functions. Resveratrol is a natural phytoalexin that can be extracted from grape''s skin and had potent role in treating the cerebral ischemia. Apoptosis, a genetically programmed cellular event which occurs after ischemia and leads to biochemical and morphological changes in cells. There are some useful markers for apoptosis like Bcl-2, bax, and p53. The last reports, researchers verify the apoptosis with early markers like Annexin V.MethodsWe preferred in this experimental study a model of global cerebral infarction which was induced by bilateral common carotid artery occlusion method. Rats were randomly divided into 4 groups : sham, ischemia-reperfusion (I/R), I/R plus 20 mg/kg resveratrol and I/R plus 40 mg/kg resveratrol. Statistical analysis was performed using Sigmastat 3.5 ve IBM SPSS Statistics 20. We considered a result significant when p<0.001.ResultsAfter administration of resveratrol, Bcl-2 and Annexin levels were significantly increased (p<0.001). Depending on the dose of resveratrol, Bcl2 levels increased, p53 levels decreased but Annexin V did not effected. P53 levels were significantly increased in ishemia group, so apoptosis is higher compared to other groups.ConclusionIn the acute period, Annexin V levels misleading us because the apoptotic cell counts could not reach a certain level. Therefore we should support our results with bcl-2 and p53.     

Brain endothelial cell production of a neuroprotective cytokine, interleukin-6, in response to noxious stimuli

Brain endothelial cells (BECs), specialized cells of the blood–brain barrier (BBB), are ideally positioned to monitor and respond to events in the periphery. The present study examined their potential role in transducing immune signals to the brain and in responding to noxious stimuli. BECs were isolated from rhesus monkeys at 3 age points (fetal/neonatal, adult, and very old animals). Cells were then challenged in vitro with either an immune stimulus (interleukin-1β (IL-1β), or lipopolysaccharide (LPS)) or an oxidative challenge (hypoxia). BECs released interleukin-6 (IL-6), which is known to have neurotrophic and neuroprotective functions. Furthermore, higher amounts of IL-6 were released in both baseline and stimulated conditions by BECs derived from aged animals. This research indicates a pathway whereby immune signals may be communicated to the CNS and has revealed one way that the BBB may protect neuronal survival under challenge conditions.     

毛柳苷在缺血性脑损伤中对白介素4诱导蛋白1表达和小胶质细胞激活及表型的影响

目的 探讨毛柳苷在缺血性脑损伤后对白介素4诱导蛋白1(interleukin-4 induced protein 1,IL4I1)表达及小胶质细胞极化的影响.方法 38只雄性C57BL/6J小鼠随机分为假手术组(4只)、毛柳苷组(17只)和生理盐水组(17只).通过线栓法制作大脑中动脉缺血再灌注模型(缺血60?min拔...