New anticonvulsant candidates prevent P-glycoprotein (P-gp) overexpression in a pharmacoresistant seizure model in mice.

Despite the approval of a considerable number of last generation antiepileptic drugs (AEDs) (only in the last decade, six drugs have gained Food and Drug Administration approval), the global figures of seizure control have seemingly not improved, and available AED can still be regarded as symptomatic treatments. Fresh thinking in AEDs drug discovery, including the development of drugs with novel mechanisms of action, is required to achieve truly innovative antiepileptic medications. The transporter hypothesis proposes that inadequate penetration of AEDs across the blood-brain barrier, caused by increased expression of efflux transporters such as P-glycoprotein (P-gp), contributes to drug-resistant epilepsy. Neuroinflammation due to high levels of glutamate has been identified as one of the causes of P-gp upregulation, and several studies in animal models of epilepsy suggest that antiinflammatory drugs might prevent P-gp overexpression and, thus, avoid the development of refractory epilepsy. We have applied ligand-based in silico screening to select compounds that exert dual anticonvulsant and antiinflammatory effects. Five of the hits were tested in animal models of seizure, with protective effects. Later, two of them (sebacic acid (SA) and gamma-decanolactone) were submitted to the recently described MP23 model of drug-resistant seizures. All in all, SA displayed the best profile, showing activity in the maximal electroshock seizure (MES) and pentylenetetrazol (PTZ) seizure models, and reversing resistance to phenytoin (PHT) and decreasing the P-gp upregulation in the MP23 model. Furthermore, pretreatment with SA in the pilocarpine status epilepticus (SE) model resulted in decreased histamine release in comparison with nontreated animals. This is the first report of the use of the MP23 model to screen for novel anticonvulsant compounds that may avoid the development of P-gp-related drug resistance.

3-Mercaptopropionic acid-induced repetitive seizures increase GluN2A expression in rat hippocampus: a potential neuroprotective role of cyclopentyladenosine.

The N-methyl-D-aspartate receptor (NMDAR) is involved in synaptic plasticity, learning, memory, and neurological diseases like epilepsy and it is the major mediator of excitotoxicity. Functional NMDARs in the mature brain are heteromeric complexes composed of different subunits: GluN1 and GluN2. There are four different GluN2 subunits (A-D) and each of them critically determines the pharmacological and electrophysiological properties of NMDARs. GluN1 is ubiquitously expressed in the central nervous system while the highest GluN2A expression is in the hippocampus. Adenosine, an endogenous anticonvulsant, is a neuromodulator with a critical role in the regulation of neuronal activity, mediating its effect on specific receptors, among which adenosine A1 receptor is highly expressed in the hippocampus. In the present work hippocampal GluN2A expression after the convulsant drug 3-mercaptopropionic acid (MP) induced seizures and the effect of cyclopentyladenosine (CPA) given alone or prior to MP (CPA + MP) in an acute or repetitive experimental model was studied. CPA administered to rats for one or 4 days increases seizure threshold induced by MP. After one administration of MP, no significant difference in GluN2A expression was observed in CPA and CPA + MP by Western blot, although immunohistochemistry revealed an increase in CA2/3 area. However, repetitive MP administration during 4 days showed a significant increase of GluN2A expression, and the repetitive administration of CPA 30 min prior to MP caused a significant decrease of GluN2A expression with respect to MP treatment, returning to control levels. These results show that GluN2A subunit is involved in repetitive MP-induced seizures, while CPA administration displays a protective effect against it.

Towards Automated Assessment of Frailty Status Using a Wrist-Worn Device.

Wearable sensors potentially enable monitoring the user's physical activity in daily life. Therefore, they are particularly appealing for the evaluation of older subjects in their environment, to capture early signs of frailty and mobility-related problems. This study explores the use of body-worn accelerometers for automated assessment of frailty during walking activity. Experiments involved 34 volunteers aged 70+, who were initially screened by geriatricians for the presence of frailty according to Fried's criteria. After screening, the volunteers were asked to walk 60 m at preferred speed, while wearing two accelerometers, one positioned on the lower back and the other on the wrist. Sensor-derived signals were analyzed independently to compare the ability of the two signals (wrist vs. lower back) in frailty status assessment. A gait detection technique was applied to identify segments made of four gait cycles. These segments were then used as input to compute 25 features in time and time-frequency domains, the latter by means of the Wavelet Transform. Finally, five machine learning models were trained and evaluated to classify subjects as robust or non-robust (i.e., pre-frail or frail). Gaussian naive Bayes applied to the features derived from the wrist sensor signal identified non-robust subjects with 91% sensitivity and 82% specificity, compared to 87% sensitivity and 64% specificity achieved with the lower back sensor. Results demonstrate that a wrist-worn accelerometer provides valuable information for the recognition of frailty in older adults, and could represent an effective tool to enable automated and unobtrusive assessment of frailty.

Adenosine A2A Receptor: A New Neuroprotective Target in Light-Induced Retinal Degeneration.

Continuous illumination induces the degeneration of photoreceptors. This animal model of light-induced retinal degeneration resembles many characteristics of human degenerative diseases of the outer retina, such as age-related macular degeneration. This work aimed to evaluate the potential neuroprotective effect of the modulation of adenosine A2A receptor in the model of light-induced retinal degeneration. Sprague-Dawley rats were intravitreally injected in the right eye with either CGS 21680, an adenosine A2A receptor agonist, or SCH 58261, an adenosine A2A receptor antagonist. Contralateral eyes were injected with respective vehicles as control. Then, rats were subjected to continuous illumination (12,000 lux) for 24 h. Retinas were processed by glial fibrillary acidic protein (GFAP) immunohistochemistry, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) technique, Western blotting (WB), and quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Another group of rats was subjected to functional studies by electroretinography. Animals treated with CGS21680 showed a significant increase of apoptotic nuclei in the outer nuclear layer and a significant increase of GFAP immunoreactive area of the retinas but did not alter WB nor electroretinography results. qRT-PCR showed that CGS 21680 significantly increased the expression of interleukin-1ß. On the opposite, SCH 58261 significantly decreased apoptotic nuclei in the outer nuclear layer and GFAP immunoreactive area of the retinas. It also significantly decreased GFAP and activated caspase-3 levels as measured by WB and preserved retinal function, as treated eyes showed significantly greater amplitudes of a- and b-waves and oscillatory potentials. qRT-PCR revealed that SCH 58261 significantly decreased the expression of tumor necrosis factor-α. These results show that the blockade of the A2A receptor before the start of the pathogenic process is neuroprotective, as it prevents light-induced retinal damage. The use of A2A receptor antagonists deserves to be evaluated in retinal degenerative diseases.

CB1 Cannabinoid Receptor is a Target for Neuroprotection in Light Induced Retinal Degeneration.

In the last few years, an increasing interest in the neuroprotective effect of cannabinoids has taken place. The aim of the present work was to study the effects of modulating cannabinoid receptor 1 (CB1) in the context of light induced retinal degeneration (LIRD), using an animal model that resembles many characteristics of human age-related macular degeneration (AMD) and other degenerative diseases of the outer retina. Sprague Dawley rats (n = 28) were intravitreally injected in the right eye with either a CB1 agonist (ACEA), or an antagonist (AM251). Contralateral eyes were injected with respective vehicles as controls. Then, rats were subjected to continuous illumination (12,000 lux) for 24 h. Retinas from 28 animals were processed by GFAP-immunohistochemistry (IHC), TUNEL technique, Western blotting (WB), or qRT-PCR. ACEA-treated retinas showed a significantly lower number of apoptotic nuclei in the outer nuclear layer (ONL), lower levels of activated Caspase-3 by WB, and lower levels of glial reactivity by both GFAP-IHC and WB. qRT-PCR revealed that ACEA significantly decreased the expression of Bcl-2 and CYP1A1. Conversely, AM251-treated retinas showed a higher number of apoptotic nuclei in the ONL, higher levels of activated Caspase-3 by WB, and higher levels of glial reactivity as determined by GFAP-IHC and WB. AM251 increased the expression of Bcl-2, Bad, Bax, Aryl hydrocarbon Receptor (AhR), GFAP, and TNFα. In summary, the stimulation of the CB1 receptor, previous to the start of the pathogenic process, improved the survival of photoreceptors exposed to LIRD. The modulation of CB1 activity may be used as a neuroprotective strategy in retinal degeneration and deserves further studies.

The NMDAR subunit NR2B expression is modified in hippocampus after repetitive seizures.

NMDA receptor is involved in synaptic plasticity, learning, memory and neurological diseases like epilepsia and it is the major mediator of excitotoxicity. NR2B-containing NMDA receptors may be playing a crucial role in epileptic disorders. In the present study the effect of the convulsant drug 3-mercaptopropionic acid (MP) repetitive administration (4-7 days) on the hippocampal NR2B subunit was studied. A significant decrease in NR2B in the whole hippocampus was observed after MP4 with a tendency to recover to normal values in MP7 by western blot assay. Immunohistochemical studies showed a decrease in several CA1 and CA2/3 strata (21-73%). MP7 showed a reversion of the drop observed at 4 days in stratum oriens, pyramidal cell layer in CA1, CA2/3 and CA1 stratum radiatum. A significant fall in the lacunosum molecular layer of both areas and stratum radiatum of CA2/3 was observed. The immunostaining in MP4 showed a decrease in the granulare layer from dentate gyrus (20%), in hillus (71%) and subicullum (63%) as compared with control and these decreases were similar at MP7 values. Results showed decreases in NR2B subunit expression in different areas following repeated MP-induce seizures, suggesting that NR2B expression is altered depending on the diverse hippocampal input and output signals of each region that could be differently involved in modulating MP-induced hyperactivity.

Differential hippocampal pharmacokinetics of phenobarbital and carbamazepine in repetitive seizures induced by 3-mercaptopropionic acid.

Previous evidence has shown that chronic 3-mercaptopropionic acid (MP) administration induced brain P-glycoprotein (P-gp) overexpression altering target site accumulation of phenytoin. The aim of the present work was to assess the involvement of P-glycoprotein in carbamazepine and phenobarbital hippocampal pharmacokinetics in an experimental model of epilepsy, induced by repetitive MP administration. Seizures were induced in Wistar rats by injection of MP (45 mg kg(-1), i.p.) during 10 days. Control rats (C) were injected with saline solution. In order to monitor extracellular brain antiepileptic levels, a concentric probe was inserted into the hippocampus. Animals were administered with carbamazepine (10 mg kg(-1), i.v.) or phenobarbital (20 mg kg(-1), i.v.) 30 min after intraperitoneal administration of vehicle or nimodipine (2 mg kg(-1)), a well known P-glycoprotein inhibitor. No differences were found in hippocampal concentrations of carbamazepine comparing all groups. In vehicle pre-treated rats, hippocampal phenobarbital concentrations were lower in MP (maximal concentration, C(max): 6.0+/-0.6 microg ml(-1), p<0.05) than in C animals (C(max): 9.4+/-0.9 microg ml(-1)). Control rats pre-treated with nimodipine showed similar results (C(max): 10.7+/-0.6 microg ml(-1)) than those pre-treated with vehicle. Nimodipine pre-treatment in MP rats enhanced hippocampal phenobarbital concentrations (C(max): 10.2+/-1.0 microg ml(-1), p<0.05) as compared with vehicle pre-treatment. Results of our work suggest that P-glycoprotein (P-gp) overexpression by repetitive seizures induced by MP administration does not modify brain bioavailability of carbamazepine. Conversely, hippocampal levels of phenobarbital are reduced in MP rats with regard to non-epileptic rats, suggesting a potential role of P-gp overexpression in pharmacoresistance to phenobarbital.

Adenosine A1 receptor: A neuroprotective target in light induced retinal degeneration.

Light induced retinal degeneration (LIRD) is a useful model that resembles human retinal degenerative diseases. The modulation of adenosine A1 receptor is neuroprotective in different models of retinal injury. The aim of this work was to evaluate the potential neuroprotective effect of the modulation of A1 receptor in LIRD. The eyes of rats intravitreally injected with N6-cyclopentyladenosine (CPA), an A1 agonist, which were later subjected to continuous illumination (CI) for 24 h, showed retinas with a lower number of apoptotic nuclei and a decrease of Glial Fibrillary Acidic Protein (GFAP) immunoreactive area than controls. Lower levels of activated Caspase 3 and GFAP were demonstrated by Western Blot (WB) in treated animals. Also a decrease of iNOS, TNFα and GFAP mRNA was demonstrated by RT-PCR. A decrease of Iba 1+/MHC-II+ reactive microglial cells was shown by immunohistochemistry. Electroretinograms (ERG) showed higher amplitudes of a-wave, b-wave and oscillatory potentials after CI compared to controls. Conversely, the eyes of rats intravitreally injected with dipropylcyclopentylxanthine (DPCPX), an A1 antagonist, and subjected to CI for 24 h, showed retinas with a higher number of apoptotic nuclei and an increase of GFAP immunoreactive area compared to controls. Also, higher levels of activated Caspase 3 and GFAP were demonstrated by Western Blot. The mRNA levels of iNOS, nNOS and inflammatory cytokines (IL-1ß and TNFα) were not modified by DPCPX treatment. An increase of Iba 1+/MHC-II+ reactive microglial cells was shown by immunohistochemistry. ERG showed that the amplitudes of a-wave, b-wave, and oscillatory potentials after CI were similar to control values. A single pharmacological intervention prior illumination stress was able to swing retinal fate in opposite directions: CPA was neuroprotective, while DPCPX worsened retinal damage. In summary, A1 receptor agonism is a plausible neuroprotective strategy in LIRD.

The expression of adenosine receptors changes throughout light induced retinal degeneration in the rat.

The modulation of adenosine receptors, A1 (A1R) and A2A (A2AR), is neuroprotective in different models of retinal injury. In order to understand the processes underlying retinal degeneration, we studied the expression of adenosine receptors in the retinas of control and continuously illuminated (CI) rats by qRT-PCR, Western blot (WB) and immunohistochemistry (IHC). Significant increases of A1R, A2AR, and A2BR mRNAs at 1, 5, and 7 days of CI (P < 0.0001) were observed by qRT-PCR. Also, a significant increase of A3R mRNA was detected after 5 and 7 days of CI. WB studies showed a significant rise of A1R on day 1 of CI and on days 5 and 7 (P < 0.0001), while A2AR increase was seen from 2 days of CI on (P < 0.001). After 1 day of CI, A1R immunoreactivity (A1R-IR) increased in ganglion cell layer, inner nuclear layer, and in both the outer and inner plexiform layers. After 2 days of CI, the A1R-IR went back to control levels. After 5 days of CI, a second rise in A1R, which persisted until 7 days of CI, was measured (P < 0.0001). A significant rise of A2aR immunoreactivity was also observed at day 2 of CI at GCL and INL and subsided at days 5 and 7 (P < 0.0001). The observed up-regulation of A1R after 1 day of CI, corresponds with the peak of oxidative stress; while the rise of A2aR at day 2 of CI, coincides with the massive apoptosis of photoreceptors. We postulate that an early modulation of adenosine receptors could delay or prevent the degeneration of photoreceptors.

Nimodipine restores the altered hippocampal phenytoin pharmacokinetics in a refractory epileptic model.

The present work was undertaken to examine the central pharmacokinetics of phenytoin (PHT) in an experimental model of epilepsy, induced by administration of 3-mercaptopropionic acid (MP), and possible participation of P-glycoprotein in this model of epilepsy. Repeated seizures were induced in male Wistar rats by injection of 3-MP (45 mg kg(-1), i.p.) during 10 days. Control rats (C) were injected with saline solution. In order to monitor extracellular PHT levels, either a shunt microdialysis probe or a concentric probe was inserted into carotid artery or hippocampus, respectively. All animals were administered with PHT (30 mg kg(-1), i.v.) 30 min after intraperitoneal administration of vehicle (V) or nimodipine (NIMO, 2 mg kg(-1)). No differences were found in PHT plasma levels comparing all experimental groups. In pre-treated rats with V, hippocampal PHT concentrations were lower in MP (maximal concentration, C(max): 2.7+/-0.3 microg ml(-1), p<0.05 versus C rats) than in C animals (C(max): 5.3+/-0.9 microg ml(-1)). Control rats pre-treated with NIMO showed similar results (C(max): 4.5+/-0.8 microg ml(-1)) than those pre-treated with V. NIMO pre-treatment of MP rats showed higher PHT concentrations (C(max): 6.8+/-1.0 microg ml(-1), p<0.05) when compared with V pre-treated MP group. Our results indicate that central pharmacokinetics of PHT is altered in MP epileptic rats. The effect of NIMO on hippocampal concentrations of PHT suggests that P-glycoprotein has a role in reduced central bioavailability of PHT in our epileptic refractory model.

New model of pharmacoresistant seizures induced by 3-mercaptopropionic acid in mice.

About 30% of the patients with epilepsy do not respond to clinically established anticonvulsants, despite having effective concentrations of the antiepileptic drug in plasma. Therefore, new preclinical models of epilepsy are needed to identify more efficacious treatments. We describe here a new drug-resistant seizure model in mice to be used at the early stages of pre-clinical trials. This model consists in inducing daily generalized seizures for 23 consecutive days by administration of 3-mercaptopropionic acid (MP). As a result, 100% of animals become resistant to phenytoin and 80% to phenobarbital. Such resistance is strongly associated with the overexpression of P-glycoprotein (Pgp), observed in cerebral cortex, hippocampus and striatum while resistance to Pgp nonsubstrate drugs such as carbamazepine, diazepam and levetiracetam is not observed. This model could be useful for screening novel anticonvulsant drugs with a potential effect on pharmacoresistant seizures treatment.

ABC transporters during epilepsy and mechanisms underlying multidrug resistance in refractory epilepsy.

It is estimated 20-25% of the epileptic patients fails to achieve good control with the different antiepileptic drugs (AEDs) treatments, developing refractory epilepsy (RE). Discovered first in cancer, the activity of P-glycoprotein (P-gp) and others ABC transporters as multidrug-resistance-associated proteins (MRPs) and breast cancer resistant protein (BCRP) are directly related with the refractoriness. We have observed the overexpression of these all transporters in the brain of patients with RE, and according with other authors, all these data suggests an active drug efflux from brain. Both constitutive and seizure induced brain P-gp overexpression was also suggested. As confirmation of these clinical evidences, different models of experimental epilepsy have demonstrated P-gp overexpression on blood brain barrier (BBB) and brain parenchyma cells, as astrocytes and neurons. In our model, early P-pg detection in vessel-related cells and later additional P-gp detection in neurons, correlated with the gradual loss of protective effect of phenytoin. The progressive neuronal P-gp expression, depending on intensity and time-constancy of seizure-injury, was in agreement with the development of "P-gp-positive seizure-axis" proposed by Kwan & Brodie, who also showed that the development of RE directly correlated with the number and frequency of seizures before initiation of drug therapy. P-gp expression in excretory organs suggests that P-gp have a central role in drug elimination. Persistent low levels of AEDs in plasma and P-gp brain overexpression in several RE pediatric patients were reported. We also observed in adult RE patients, an increased liver clearance of 99mTc-hexakis-2-methoxyisobutylisonitrile (99mTc-MIBI) (a P-gp substrate), and the surgically treated cases showed P-gp brain overexpression. These results suggest the systemic hyperactivity of P-gp in RE patients, including brain P-gp over-expression should be suspected when persistent subtherapeutic levels of AEDs in plasma are detected. P-gp neuronal expression described in both clinical and experimental reports indicates that additional mechanisms could be operative from seizure-affected P-gp-positive neurons, due to AEDs targets are expressed at membrane level. An alternative mechanism was demonstrated in P-gp-expressed cells that exhibit lower membrane potential (Deltapsi(0)=-10 to -20) compared to normal physiological Deltapsi(0) of -60 mV. Under this situation and irrespective to the P-gp pharmacoresistant property or type of drug treatment selected, P-gp-expressed neurons could increase their sensitivity to new seizures perhaps as an epileptogenic mechanism. The understanding of properties of these ABC transporters can offer new tools for better selection of more effective preventive or therapeutic strategies and avoid the invasive surgical treatments for RE.

Differential expression of cerebellar metabotropic glutamate receptors mGLUR2/3 and mGLUR4a after the administration of a convulsant drug and the adenosine analogue cyclopentyladenosine.

Metabotropic glutamate receptors (mGluR) play a role in synaptic transmission, neuronal modulation and plasticity but their action in epileptic activity is still controversial. On the other hand adenosine acts as a neuromodulator with endogenous anticonvulsive properties. Since cerebellum from epileptic patients has shown neuronal damage, sometimes associated with Purkinje cells loss, we have explored the effect of repetitive seizures on two types of mGluR in the cerebellum. Seizures were induced by the convulsant drug 3-mercaptopropionic acid (MP) and the effect of the adenosine analogue cyclopentyladenosine (CPA) alone or before MP administration (CPA+MP) were also evaluated. The expression of the receptors subtypes 2/3 (mGluR2/3) and 4a (mGluR4a) was assessed by immunocitochemistry. Granular cell layer was labeled with mGluR2/3 antibody and increased immunoreactivity was observed after MP (60%), CPA (53%) and CPA + MP (85%) treatments. Control cerebellum slices showed mGluR4a reactivity around Purkinje cells, while MP, CPA and CPA+MP treatment decreased this immunostaining. Repetitive administration of MP and CPA induces an increased cerebellar mGluR2/3 and a decreased mGluR4a immunostaining, suggesting a distinct participation of both receptors that may be related to the type of cell involved. A protective action and /or an apoptotic effect may not be discarded. CPA repetitive administration although increase seizure latency, cannot prevent seizure activity.

Astrocytic response in hippocampus and cerebral cortex in an experimental epilepsy model.

Astrocytes are very sensitive to alterations in the brain environment and respond showing a phenomenon known as astroglial reaction. S100beta is an astroglial derived neurotrophic factor, seems to be involved in neuroplasticity. The aim of this work was to study the astrocytic response in rat hippocampus and cerebral cortex after repetitive seizures induced by 3-mercaptopropionic acid (MP) administration. Immunocytochemical studies were performed to analyze GFAP and S100beta expression. Both studied areas showed hypertrophied astrocytes with enlarged processes and increased soma size. Astrocyte hyperplasia was observed only in the cerebral cortex. A significant decrease in the astrocytic S100beta immunostaining occurs after MP treatment. These results indicate that MP administration induces an astroglial reaction with reduced intracellular S100beta level. The observed reduction in astroglial S100beta could be related to the release of this factor to the extracellular space, where it may produce neurotrophic or deleterious effects accordingly to the concentration achieved. The mechanism of this remains to be elucidated.

Neuronal and glial expression of the multidrug resistance gene product in an experimental epilepsy model.

1. Failure of anticonvulsive drugs to prevent seizures is a common complication of epilepsy treatment known as drug-refractory epilepsy but their causes are not well understood. It is hypothesized that the multidrug resistance P-glycoprotein (Pgp-170), the product of the MDR-1 gene that is normally expressed in several excretory tissues including the blood brain barrier, may be participating in the refractory epilepsy. 2. Using two monoclonal antibodies against Pgp-170, we investigated the expression and cellular distribution of this protein in the rat brain during experimentally induced epilepsy. Repeated seizures were induced in male Wistar rats by daily administration of 3-mercaptopropionic acid (MP) 45 mg/kg i.p. for either 4 days (MP-4) or 7 days (MP-7). Control rats received an equivalent volume of vehicle. One day after the last injection, rats were sacrificed and brains were processed for immunohistochemistry for Pgp-170. As it was previously described, Pgp-170 immunostaining was observed in some brain capillary endothelial cells of animals from control group. 3. Increased Pgp-170 immunoreactivity was detected in MP-treated animals. Besides the Pgp-170 expressed in blood vessels, neuronal, and glial immunostaining was detected in hippocampus, striatum, and cerebral cortex of MP-treated rats. Pgp-170 immunolabeled neurons and glial cells were observed in a nonhomogeneous distribution. MP-4 animals presented a very prominent Pgp-170 immunostaining in the capillary endothelium, surrounding astrocytes and some neighboring neurons while MP-7 group showed increased neuronal labeling. 4. Our results demonstrate a selective increase in Pgp-170 immunoreactivity in the brain capillary endothelial cells, astrocytes, and neurons during repetitive MP-induced seizures. 5. The role for this Pgp-170 overexpression in endothelium and astrocytes as a clearance mechanism in the refractory epilepsy, and the consequences of neuronal Pgp-170 expression remain to be disclosed.

Citrate Synthase ande lactate dehydrogenase activities in rat cerebral cortex following the administration of the convulsants bicuculline and 3-mercaptopropionic acid

La administración intraperitoneal de bicuculina (Bic) y ácido 3-mercaptopropiónico (MP) produce convulsiones generalizadas en animales de laboratorio. En este trabajo se estudió el efecto de estos convulsivantes sobre la actividad de la lactato deshidrogenasa y de citrato sintasa de corteza cerebral de rata. La Bic se administró en dosis de1.0 mg/Kg (subconvulsiva) y 7.5 mg/Kg (convulsiva) y el MP en dosis de 150 mg/Kg (convulsiva). La actividad de lactato deshidrogenasa en fracciones solubre y particulada de corteza cerebral no se modificó por la administración de Bic o MP. La actividad de citrato sintasa en homogeneizados de corteza cerebral aumentó alrededor del 40% por la administración de Bic en dosis subconvulsiva y convulsiva; un aumento semejante se encontró por la administración de MP. No se encontró modificación en la actividad de la enzima hepática, sugiriendo especificidad de tejido. La mayor actividad de citrato sintasa en homogeneizados de corteza cerebral encontrada luego de la administración de los convulsivantes se correlaciona con el aumento en los niveles de citrato cerebral descriptos en estados convulsivos