Phenobarbital administration directed against kindled seizures delays functional recovery following brain insult

Elucidating opportunities and pitfalls in the treatment of experimental traumatic brain injury to optimize and facilitate clinical translation

The aim of this review is to discuss the research presented in a symposium entitled "Current progress in characterizing therapeutic strategies and challenges in experimental CNS injury" which was presented at the 2016 International Behavioral Neuroscience Society annual meeting. Herein we discuss diffuse and focal traumatic brain injury (TBI) and ensuing chronic behavioral deficits as well as potential rehabilitative approaches. We also discuss the effects of stress on executive function after TBI as well as the response of the endocrine system and regulatory feedback mechanisms. The role of the endocannabinoids after CNS injury is also discussed. Finally, we conclude with a discussion of antipsychotic and antiepileptic drugs, which are provided to control TBI-induced agitation and seizures, respectively. The review consists predominantly of published data.

Biologic and plastic effects of experimental traumatic brain injury treatment paradigms and their relevance to clinical rehabilitation

Neuroplastic changes, whether induced by traumatic brain injury (TBI) or therapeutic interventions, alter neurobehavioral outcome. Here we present several treatment strategies that have been evaluated by using experimental TBI models and discuss potential mechanisms of action (ie, plasticity) and how such changes affect function.

Post-Traumatic Neural Depression and Neurobehavioral Recovery after Brain Injury

There are an estimated 2 million traumatic brain injuries (TBIs) each year in the United States, making the yearly incidence eight times greater than that of breast cancer and 34 times greater than HIV/AIDS. Still, it remains a "silent epidemic" because TBI results in persistent neurobehavioral impairment, without necessarily imparting a physical scar. The present review is a comparative analysis of TBI research, both basic and applied, outlining the evidence that at least one component of the brain's innate response to insult (e.g., post-traumatic neural depression) is sufficiently well understood to be the target of additional clinical studies and therapeutic strategy development.

Temporal Lobe Epileptogenesis and Epilepsy in the Developing Brain: Bridging the Gap Between the Laboratory and the Clinic. Progression, But in What Direction?

The origins of human mesial temporal lobe epilepsy and hippocampal sclerosis are still not well understood. Hippocampal sclerosis and temporal lobe epileptogenesis involve a series of pathologies including hippocampal neuronal loss and gliosis, axonal reorganization, and maybe hippocampal neoneurogenesis. However, the causality of these events is unclear as well as their relation to the factors that may precipitate epileptogenesis. Significant differences between temporal lobe epileptogenesis in the adult and immature brain may require differential approaches. Hereditary factors also may participate in some cases of hippocampal sclerosis. The key point is to identify the significance of these age-dependent changes and to design preventive treatments. Novel strategies for the prevention and treatment of mesial temporal lobe epilepsy and hippocampal sclerosis may include rational use of neuroprotective agents, hormonotherapy, immunizations, and immunotherapy.

Amphetamines and related drugs in motor recovery after stroke

Studies in laboratory animals indicate that the rate and extent of functional recovery after focal brain injury can be modulated by drugs affecting specific central neurotransmitters. Preliminary clinical studies suggest that similar drug effects may occur in humans recovering from stroke. Combined with principles derived from the laboratory, these clinical studies provide important insights to guide the rational design of trials aimed at determining the clinical use of this approach to improving poststroke recovery.

Vigabatrin directed against kindled seizures following cortical insult: impact on epileptogenesis and somatosensory recovery

The anticonvulsant drug vigabatrin has not been found to be detrimental to the recovery process when administered following focal cortical insult. This finding is in contrast to the negative postinjury consequences of other anticonvulsant drugs (e.g., phenobarbital and diazepam) with more direct activation of the GABA/benzodiazepine receptor complex. Moreover, phenobarbital directed against kindled seizures affects functional recovery more adversely than either the drug or subconvulsive seizures alone. The purpose of the present study was to determine whether vigabatrin (150, 200, and 250 mg/kg) directed against kindled seizures would impact recovery from lesion-induced somatosensory deficits. Vigabatrin was coupled with daily electrical kindling of the amygdala during the first week after a unilateral anteromedial cortex (AMC) lesion. Somatosensory recovery was assessed using bilateral tactile stimulation tests. Animals receiving the highest dose of vigabatrin prior to electrical kindling (250 mg/kg vigabatrin/kindled) remained significantly impaired even after two months of testing relative to vehicle/kindled, kindled/250 mg/kg vigabatrin, which received vigabatrin after electrical kindling, and the 150, 200, and 250 mg/kg vigabatrin/nonkindled groups (p < 0.0001). In contrast, neither vigabatrin (at any of the doses tested) nor subconvulsive kindled seizures impacted the recovery process (p > 0.05) when administered alone (i.e., without the drug + seizure interaction). These data add to the accumulating experimental and clinical evidence suggesting that the neurobehavioral consequences of the interaction between anticonvulsant drugs and subclinical seizures after brain insult are detrimental to functional recovery.

The temporal patterns of c-Fos and basic fibroblast growth factor expression following a unilateral anteromedial cortex lesion

Following a unilateral anteromedial cortex lesion, a critical period of 12 h to 6 days exists during which the recovery process is exquisitely vulnerable to manipulation. Certain anti-convulsant drugs, as well as convulsive seizures impede recovery when administered during, but not after, the critical period. The mechanisms underlying these behavioral phenomena have not been delineated. Thus, the present study was designed to determine potential mechanisms underlying and responsible for the critical period. To this end, we measured the immunoreactivity of two important markers of the post-injury response cascade, c-Fos and bFGF, at designated times after a unilateral anteromedial cortex lesion. These temporal patterns of expression in the perilesional cortex and ipsilateral dorsal striatum were mapped onto functional recovery patterns. Within the critical period, c-Fos was dramatically elevated through 48 h after the lesion, while bFGF peaked later, on day 6. Upregulation of these markers preceded recovery from somatosensory deficits, which was most dramatic after post-operative day 9 and complete by day 23. Early post-lesion expression of c-Fos may contribute to lesion-induced bFGF expression, which through its neurotrophic properties could be responsible for subsequent functional recovery. Gaining a similar understanding of the critical period following human traumatic brain injury could be an important first step toward improved treatment strategies and neurobehavioral outcome.

Distinctive amygdala kindled seizures differentially affect neurobehavioral recovery and lesion-induced basic fibroblast growth factor (bFGF) expression

The differing effects of partial seizures on neurobehavioral recovery following anteromedial cortex (AMC) injury in rats have previously been reported. Specifically, convulsive Stage 1 seizures evoked ipsilateral to the lesion during the 6-day post-lesion critical period delayed recovery, while non-convulsive Stage 0 seizures were neutral. The present study was designed to elaborate on that research by examining several potential mechanisms for the seizure-associated difference observed in functional outcome. Anesthetized rats sustained unilateral AMC lesions followed by implantation of a stimulating electrode in the amygdala ipsilateral (Expt. 1) or contralateral (Expt. 2) to the lesion. Beginning 48 h after surgery, animals were kindled to evoke Stage 0 or Stage 1 seizure activity during the critical period. Kindling trials and afterdischarge (AD) were controlled to ascertain their role in functional outcome. Recovery from somatosensory deficits was assessed over a two-month period. The results revealed that (i) Stage 0 seizures did not impact recovery regardless of whether initiated ipsilateral or contralateral to the lesion, (ii) Stage 1 seizures prevented recovery only when initiated in the ipsilateral hemisphere during the post-lesion critical period, and (iii) the detrimental effect of Stage 1 seizures appears to be independent of the number of kindling trials provided and cumulative AD. Thus, to determine why Stage 1 seizures evoked in the hemisphere ipsilateral to the lesion impeded recovery, a separate group of animals (Expt. 3) were kindled accordingly and processed for c-Fos and basic fibroblast growth factor (bFGF) immunohistochemistry. It was hypothesized that Stage 1 seizures evoked in the injured hemisphere prevent recovery by blocking lesion-induced bFGF expression in structures shown to be important for recovery after cortex lesions (e.g., striatum). The results confirmed our hypothesis and suggest that the seizure-associated inhibition of lesion-induced bFGF may alter the growth factor-mediated plasticity necessary for functional recovery.