WONOEP appraisal: Biomarkers of epilepsy-associated comorbidities.

Neurologic and psychiatric comorbidities are common in patients with epilepsy. Diagnostic, predictive, and pharmacodynamic biomarkers of such comorbidities do not exist. They may share pathogenetic mechanisms with epileptogenesis/ictogenesis, and as such are an unmet clinical need. The objectives of the subgroup on biomarkers of comorbidities at the XIII Workshop on the Neurobiology of Epilepsy (WONOEP) were to present the state-of-the-art recent research findings in the field that highlighting potential biomarkers for comorbidities in epilepsy. We review recent progress in the field, including molecular, imaging, and genetic biomarkers of comorbidities as discussed during the WONOEP meeting on August 31-September 4, 2015, in Heybeliada Island (Istanbul, Turkey). We further highlight new directions and concepts from studies on comorbidities and potential new biomarkers for the prediction, diagnosis, and treatment of epilepsy-associated comorbidities. The activation of various molecular signaling pathways such as the "Janus Kinase/Signal Transducer and Activator of Transcription," "mammalian Target of Rapamycin," and oxidative stress have been shown to correlate with the presence and severity of subsequent cognitive abnormalities. Furthermore, dysfunction in serotonergic transmission, hyperactivity of the hypothalamic-pituitary-adrenocortical axis, the role of the inflammatory cytokines, and the contributions of genetic factors have all recently been regarded as relevant for understanding epilepsy-associated depression and cognitive deficits. Recent evidence supports the utility of imaging studies as potential biomarkers. The role of such biomarker may be far beyond the diagnosis of comorbidities, as accumulating clinical data indicate that comorbidities can predict epilepsy outcomes. Future research is required to reveal whether molecular changes in specific signaling pathways or advanced imaging techniques could be detected in the clinical settings and correlate with epilepsy-associated comorbidities. A reliable biomarker will allow a more accurate diagnosis and improved treatment of epilepsy-associated comorbidities.

The pathways connecting the hippocampal formation, the thalamic reuniens nucleus and the thalamic reticular nucleus in the rat.

Most dorsal thalamic nuclei send axons to specific areas of the neocortex and to specific sectors of the thalamic reticular nucleus; the neocortex then sends reciprocal connections back to the same thalamic nucleus, directly as well indirectly through a relay in the thalamic reticular nucleus. This can be regarded as a 'canonical' circuit of the sensory thalamus. For the pathways that link the thalamus and the hippocampal formation, only a few comparable connections have been described. The reuniens nucleus of the thalamus sends some of its major cortical efferents to the hippocampal formation. The present study shows that cells of the hippocampal formation as well as cells in the reuniens nucleus are retrogradely labelled following injections of horseradish peroxidase or fluoro-gold into the rostral part of the thalamic reticular nucleus in the rat. Within the hippocampal formation, labelled neurons were localized in the subiculum, predominantly on the ipsilateral side, with fewer neurons labelled contralaterally. Labelled neurons were seen in the hippocampal formation and nucleus reuniens only after injections made in the rostral thalamic reticular nucleus (1.6-1.8 mm caudal to bregma). In addition, the present study confirmed the presence of afferent connections to the rostral thalamic reticular nucleus from cortical (cingulate, orbital and infralimbic, retrosplenial and frontal), midline thalamic (paraventricular, anteromedial, centromedial and mediodorsal thalamic nuclei) and brainstem structures (substantia nigra pars reticularis, ventral tegmental area, periaqueductal grey, superior vestibular and pontine reticular nuclei). These results demonstrate a potential for the thalamo-hippocampal circuitry to influence the functional roles of the thalamic reticular nucleus, and show that thalamo-hippocampal connections resemble the circuitry that links the sensory thalamus and neocortex.

Prediction of cyclosporine A blood levels: an application of the adaptive-network-based fuzzy inference system (ANFIS) in assisting drug therapy.

OBJECTIVE: Therapeutic drug monitoring (TDM) is a procedure in which the levels of drugs are assayed in various body fluids with the aim of individualizing the dose of critical drugs, such as cyclosporine A. Cyclosporine A assays are performed in blood. METHODS: We proposed the use of the Takagi and Sugeno-type "adaptive-network-based fuzzy inference system" (ANFIS) to predict the concentration of cyclosporine A in blood samples taken from renal transplantation patients. We implemented the ANFIS model using TDM data collected from 138 patients and 20 input parameters. Input parameters for the model consisted of concurrent use of drugs, blood levels, sampling time, age, gender, and dosing intervals. RESULTS: Fuzzy modeling produced eight rules. The developed ANFIS model exhibited a root mean square error (RMSE) of 0.045 with respect to the training data and an error of 0.057 with respect to the checking data in the MATLAB: environment. CONCLUSION: ANFIS can effectively assist physicians in choosing best therapeutic drug dose in the clinical setting.

Extracellular hypothalamic gamma-aminobutyric acid (GABA) and L-glutamic acid concentrations in response to bicuculline in a genetic absence epilepsy rat model.

The posterior part of the hypothalamus plays a vital role in the homeostatic processes of the internal environment, including blood pressure and heart rate regulation, by means of gamma-aminobutyric acid (GABA)ergic and glutamatergic neurotransmission. In this study we measured the extracellular levels of GABA and L-glutamic acid in the dorsomedial hypothalamic nucleus (DMH) and posterior hypothalamus (PH), following intracerebroventricular (i.c.v.) administration of bicuculline, a GABA(A)-receptor antagonist, in genetic absence epileptic rats from Strasbourg (GAERS), where heart rate, blood pressure, and EEG recordings were also collected simultaneously. The i.c.v. injection of bicuculline (0.3 nmol) produced no response in non-epileptic Wistar rats but caused an increase in mean arterial pressure in GAERS (P<0.01). Microdialysis experiments showed that L-glutamic acid increased in the DMH in GAERS after bicuculline administration (P<0.01). Additionally, extracellular GABA concentration decreased in the PH (P<0.05). Bicuculline suppressed the spike-and-wave discharges, the characteristic sign of absence seizures. All these results suggest that the bicuculline-induced blood pressure response is accompanied by changes in L-glutamic acid levels in the DMH and GABA levels in the PH, indicating a bicuculline hypersensitivity in the DMH and PH of GAERS that may make the GAERS display an altered mode of central cardiovascular regulation. These results suggest that the circuits affected in GAERS are not only restricted to the regions responsible for seizure generation but also present in the hypothalamus.

The effects of ethosuximide on amino acids in genetic absence epilepsy rat model.

Genetic absence epilepsy rats from Strasbourg (GAERS), a selectively inbred strain of Wistar rats, has been validated as an experimental model for human absence epilepsy. In this model, systemic administration of ethosuximide (ETX) was shown to reduce the spike and wave discharges (SWD). In this study, gamma-aminobutyric acid (GABA) and L-glutamic acid levels in response to ETX injections (i.p., 100 mg/kg) were measured in the microdialysis samples collected from the ventrolateral thalamus (VLT) and the primary motor cortex (M1) area of Wistar rats and GAERS by using HPLC with fluorescent detection. Throughout the microdialysis procedure, continuous EEG recording was performed where ETX was shown to suppress the SWD activity. We demonstrated increased basal GABA levels in the M1 and VLT of GAERS, and ETX treatment did not produce any effect on higher GABA levels in the VLT, but suppressed the increased GABA levels significantly in the M1 of GAERS. All these findings denote the importance of corticothalamic circuitry and the role of increased GABA tonus in primary motor cortex and thalamus of GAERS. The primary motor cortex also seems to be involved in the SWD activity and ETX exerts, at least partially, its neurotransmitter effects through it.