Levetiracetam Pharmacokinetics and Brain Uptake in a Lateral Fluid Percussion Injury Rat Model.

Post-traumatic epilepsy (PTE) occurs in some patients after moderate/severe traumatic brain injury (TBI). Although there are no approved therapies to prevent epileptogenesis, levetiracetam (LEV) is commonly given for seizure prophylaxis due to its good safety profile. This led us to study LEV as part of the Epilepsy Bioinformatics Study for Antiepileptogenic Therapy (EpiBioS4Rx) Project. The objective of this work is to characterize the pharmacokinetics (PK) and brain uptake of LEV in naïve control rats and in the lateral fluid percussion injury (LFPI) rat model of TBI after either single intraperitoneal doses or a loading dose followed by a 7-day subcutaneous infusion. Sprague-Dawley rats were used as controls and for the LFPI model induced at the left parietal region using injury parameters optimized for moderate/severe TBI. Naïve and LFPI rats received either a bolus injection (intraperitoneal) or a bolus injection followed by subcutaneous infusion over 7 days. Blood and parietal cortical samples were collected at specified time points throughout the study. LEV concentrations in plasma and brain were measured using validated high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) methods. Noncompartmental analysis and a naive-pooled compartmental PK modeling approach were used. Brain-to-plasma ratios ranged from 0.54 to 1.4 to 1. LEV concentrations were well fit by one-compartment, first-order absorption PK models with a clearance of 112 ml/h per kg and volume of distribution of 293 ml/kg. The single-dose pharmacokinetic data were used to guide dose selection for the longer-term studies, and target drug exposures were confirmed. Obtaining LEV PK information early in the screening phase allowed us to guide optimal treatment protocols in EpiBioS4Rx. SIGNIFICANCE STATEMENT: The characterization of levetiracetam pharmacokinetics and brain uptake in an animal model of post-traumatic epilepsy is essential to identify target concentrations and guide optimal treatment for future studies.

Early preclinical plasma protein biomarkers of brain trauma are influenced by early seizures and levetiracetam.

OBJECTIVE: We used the lateral fluid percussion injury (LFPI) model of moderate-to-severe traumatic brain injury (TBI) to identify early plasma biomarkers predicting injury, early post-traumatic seizures or neuromotor functional recovery (neuroscores), considering the effect of levetiracetam, which is commonly given after severe TBI. METHODS: Adult male Sprague-Dawley rats underwent left parietal LFPI, received levetiracetam (200 mg/kg bolus, 200 mg/kg/day subcutaneously for 7 days [7d]) or vehicle post-LFPI, and were continuously video-EEG recorded (n = 14/group). Sham (craniotomy only, n = 6), and naïve controls (n = 10) were also used. Neuroscores and plasma collection were done at 2d or 7d post-LFPI or equivalent timepoints in sham/naïve. Plasma protein biomarker levels were determined by reverse phase protein microarray and classified according to injury severity (LFPI vs. sham/control), levetiracetam treatment, early seizures, and 2d-to-7d neuroscore recovery, using machine learning. RESULTS: Low 2d plasma levels of Thr231 -phosphorylated tau protein (pTAU-Thr231 ) and S100B combined (ROC AUC = 0.7790) predicted prior craniotomy surgery (diagnostic biomarker). Levetiracetam-treated LFPI rats were differentiated from vehicle treated by the 2d-HMGB1, 2d-pTAU-Thr231 , and 2d-UCHL1 plasma levels combined (ROC AUC = 0.9394) (pharmacodynamic biomarker). Levetiracetam prevented the seizure effects on two biomarkers that predicted early seizures only among vehicle-treated LFPI rats: pTAU-Thr231 (ROC AUC = 1) and UCHL1 (ROC AUC = 0.8333) (prognostic biomarker of early seizures among vehicle-treated LFPI rats). Levetiracetam-resistant early seizures were predicted by high 2d-IFNγ plasma levels (ROC AUC = 0.8750) (response biomarker). 2d-to-7d neuroscore recovery was best predicted by higher 2d-S100B, lower 2d-HMGB1, and 2d-to-7d increase in HMGB1 or decrease in TNF (P < 0.05) (prognostic biomarkers). SIGNIFICANCE: Antiseizure medications and early seizures need to be considered in the interpretation of early post-traumatic biomarkers.

In search of antiepileptogenic treatments for post-traumatic epilepsy.

Post-traumatic epilepsy (PTE) is diagnosed in 20% of individuals with acquired epilepsy, and can impact significantly the quality of life due to the seizures and other functional or cognitive and behavioral outcomes of the traumatic brain injury (TBI) and PTE. There is no available antiepileptogenic or disease modifying treatment for PTE. Animal models of TBI and PTE have been developed, offering useful insights on the value of inflammatory, neurodegenerative pathways, hemorrhages and iron accumulation, calcium channels and other target pathways that could be used for treatment development. Most of the existing preclinical studies test efficacy towards pathologies of functional recovery after TBI, while a few studies are emerging testing the effects towards induced or spontaneous seizures. Here we review the existing preclinical trials testing new candidate treatments for TBI sequelae and PTE, and discuss future directions for efforts aiming at developing antiepileptogenic and disease-modifying treatments.

Cannabidiol effects on prepulse inhibition in nonhuman primates.

Prepulse inhibition (PPI) of acoustic startle reflex is a well-established behavior paradigm to measure sensorimotor gating deficits. PPI is disrupted in several neuropsychiatric disorders, including schizophrenia. PPI tests can be used to screen new drugs for treatment of such disorders. In this review, we discuss how PPI paradigm can help in screening the therapeutic effects of cannabidiol (CBD). We look into recent literature about CBD effects on PPI response in animal models, especially in nonhuman primates. CBD has been shown to modify PPI in N-methyl d-aspartate receptor antagonist models for schizophrenia, both in rodents and in nonhuman primates. These results show CBD as a potential drug for the treatment of neurologic disorders that present alterations in sensorimotor system, such as schizophrenia. Moreover, the PPI paradigm seems to be a useful and relative simple paradigm to test the efficacy of CBD as a potential therapeutic drug.

Cannabidiol Affects MK-801-Induced Changes in the PPI Learned Response of Capuchin Monkeys (Sapajus spp.).

There are several lines of evidence indicating a possible therapeutic action of cannabidiol (CBD) in schizophrenia treatment. Studies with rodents have demonstrated that CBD reverses MK-801 effects in prepulse inhibition (PPI) disruption, which may indicate that CBD acts by improving sensorimotor gating deficits. In the present study, we investigated the effects of CBD on a PPI learned response of capuchin monkeys (Sapajus spp.). A total of seven monkeys were employed in this study. In Experiment 1, we evaluated the CBD (doses of 15, 30, 60 mg/kg, i.p.) effects on PPI. In Experiment 2, the effects of sub-chronic MK-801 (0.02 mg/kg, i.m.) on PPI were challenged by a CBD pre-treatment. No changes in PPI response were observed after CBD-alone administration. However, MK-801 increased the PPI response of our animals. CBD pre-treatment blocked the PPI increase induced by MK-801. Our findings suggest that CBD's reversal of the MK-801 effects on PPI is unlikely to stem from a direct involvement on sensorimotor mechanisms, but may possibly reflect its anxiolytic properties.

Sensorimotor gating impairments induced by MK-801 treatment may be reduced by tolerance effect and by familiarization in monkeys.

Dizocilpine (MK-801) is a non-competitive NMDA antagonist that induces schizophreniclike effects. It is therefore widely used in experimental models of schizophrenia including prepulse inhibition (PPI) impairments in rodents. Nevertheless, MK-801 has never been tested in monkeys on a PPI paradigm. In order to evaluate MK-801 effects on monkeys' PPI, we tested eight capuchin monkeys (Sapajus spp.) using three different doses of MK-801 (0.01; 0.02; 0.03 mg/kg). Results show PPI impairment in acute administration of the highest dose (0.03 mg/kg). PPI impairment induced by MK-801 was reversed by re-exposure to the PPI test throughout treatment trials, in contrast with rodent studies. These results indicate that tolerance effect and familiarization with PPI test may reduce the sensorimotor gating deficits induced by MK-801 in monkeys, suggesting a drug-training interaction.

Whole-body prepulse inhibition protocol to test sensorymotor gating mechanisms in monkeys.

Prepulse inhibition (PPI) is the decrease of startle reflex amplitude when a slight stimulus is previously generated. This paradigm may provide valuable information about sensorimotor gating functionality. Here we aimed at determining the inhibited and uninhibited startle response of capuchin monkeys (Sapajus spp.), and to evaluate the role of the superior colliculus in PPI. Capuchin monkeys were tested in a whole-body protocol, to determine the best startle amplitude and interstimuli interval. Additionally we tested two subjects with bilateral superior colliculus damage in this protocol. Results show that 115 dB auditory pulse has induced the best startle response. In contrast to reports in other species, no habituation to the auditory stimuli was observed here in capuchins. Also, startle reflex inhibition was optimal after 120 msec interstimuli interval. Finally, there was a downward tendency of percentage inhibition in superior colliculus-lesioned monkeys. Our data provides the possibility of further studies with whole-body protocol in capuchin monkeys and reinforces the importance of the superior colliculus in PPI.

A role for the superior colliculus in the modulation of threat responsiveness in primates: toward the ontogenesis of the social brain.

Defense and social mechanisms in primates seem to share, at least in infancy, common neural substrata.Among these, recent research has implicated the primate superior colliculus (SC) on tasks involving visual detection and recognition of threatening stimuli, such as snakes and faces with emotional expressions. There is also evidence that both kinds of stimuli share specific characteristics and command special attention in the primate visual system. The present review focuses on the role of the SC in these seemingly overlapping functions.We present social behavioral data from capuchin monkeys in which the bilateral lesion of the SC induced a transitory impairment of social behaviors. The findings presented here are compared with previous studies, our own and others, on social behaviors and threat detection. We argue that, although the SC may participate in both systems,its role is more prominent in the detection/recognition of threat. Social interactions more likely depend on larger and more complex neural systems, where the SC may play a key role in early infancy. The implications of these recent findings are discussed under an evolutionary perspective.

Color vision in the black howler monkey (Alouatta caraya).

Electrophysiological and molecular genetic studies have shown that howler monkeys (Alouatta) are unique among all studied platyrrhines: they have the potential to display trichromatic color vision among males and females. This study examined the color discrimination abilities of four howler monkeys (Alouatta caraya) through a series of tasks involving a behavioral paradigm of discrimination learning. The animals were maintained and housed as a group in the Zoological Gardens of Brasília and were tested in their own home cages. Stimuli consisting of pairs of Munsell color chips were presented in random brightness values to assure that discriminations were based on color rather than brightness cues. All the animals (three males, one female) successfully discriminated all the stimulus pairs, including those that would be expected to be difficult for a dichromatic monkey. These results are consistent with the earlier predictions suggesting that howler monkeys are routinely trichromatic.