Status epilepticus-induced changes in the subcellular distribution and activity of calcineurin in rat forebrain

This study was performed to determine the effect of prolonged status epilepticus on the activity and subcellular location of a neuronally enriched, calcium-regulated enzyme, calcineurin. Brain fractions isolated from control animals and rats subjected to pilocarpine-induced status epilepticus were subjected to differential centrifugation. Specific subcellular fractions were tested for both calcineurin activity and enzyme content. Significant, status epilepticus-induced increases in calcineurin activity were found in homogenates, nuclear fractions, and crude synaptic membrane-enriched fractions isolated from both cortex and hippocampus. Additionally, significant increases in enzyme levels were observed in crude synaptic fractions as measured by Western analysis. Immunohistochemical studies revealed a status epilepticus-induced increase in calcineurin immunoreactivity in dendritic structures of pyramidal neurons of the hippocampus. The data demonstrate a status epilepticus-induced increase in calcineurin activity and concentration in the postsynaptic region of forebrain pyramidal neurons.

Expression of different isoforms of protein kinase C in the rat hippocampus after pilocarpine-induced status epilepticus with special reference to CA1 area and the dentate gyrus

At 4 h during pilocarpine-induced status epilepticus (DPISE) in rat, protein kinase C (PKC)beta1, PKCbeta2, and PKCgamma were induced at the border between the stratum oriens and alveus (O/A border) of CA1 in the hippocampus. Induced PKCgamma was colocalized with metabotropic glutamate receptor alpha (mGluR alpha). By intracerebroventricular injection of mGluR1alpha antagonists, (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA), PKCbeta1, PKCbeta2, and PKCgamma immunoreactive products decreased dramatically; however, intracerebroventricular injection of saline did not change the expression of PKCbeta1, PKCbeta2, and PKCgamma, suggesting that these three PKC isoforms might be involved in mGluR1alpha-related excitoneurotoxicity. One day after pilocarpine-induced status epilepticus (APISE), PKCdelta was induced in microglial cells. At this time point, both PKCgamma and PKCepsilon immunopositive products decreased in the inner molecular layer of upper blade of the stratum granulosum. At 7-31 days APISE, induced PKCbeta1, PKCdelta, PKCeta, and PKCzeta positive astrocytes were demonstrated in all parts of hippocampus, suggesting that they may be involved in gliosis. By this time, both PKCgamma and PKCepsilon immunopositive products in the inner molecular layer had almost disappeared, suggesting that they may be involved in the inhibition of granule cells by controlling neurotransmitter release presynaptically in the dentate gyrus of normal rats.

Upregulation of gp130 and differential activation of STAT and p42/44 MAPK in the rat hippocampus following kainic acid-induced seizures

We investigated the activation and cellular distribution of two signaling pathways, the signal transducers and activators of transcription (STATs) and mitogen-activated protein kinases (MAPKs) following kainic acid (KA)-induced seizures, in relation to the expression of gp130, a common cytokine signal transducer for the interleukin (IL)-6 family of cytokines. Rapid and short-lasting upregulation of gp130 was observed in the granule cells. This became evident in astrocytes by 3 h, increased progressively to peak at 3 days, and was sustained for 10 days. STATs, including STAT1 and STAT3, and p42/44 MAPK were activated in distinct cellular and spatial distributions within the hippocampus following seizures. A rapid and sustained seizure-induced activation of STAT3 and STAT1, revealed by nuclear STAT3 and STAT1 immunoreactivities, was observed exclusively in reactive astrocytes in the hippocampus, nearly coinciding with the time course of gp130 expression; however, STAT3 activation was greater. In contrast, seizure induced the rapid and transient activation of p42/44 MAPK in a subpopulation of hippocampal neurons and in astrocytes, although with weaker staining intensity. Two signaling pathways involving gp130, STATs and MAPK, were differentially activated in reactive astrocytes after KA injection, indicating that STATs and MAPK may differentially mediate the astroglial reaction in the rat hippocampus after KA-induced seizures.

Expression and activation of caspase 3 following status epilepticus in the rat

It is in dispute whether caspase 3 contributes to status epilepticus (SE)-induced cell loss. We hypothesized that caspase 3-mediated cell death continues beyond the acute phase of SE. We induced SE with either kainic acid or electrical stimulation of the amygdala in Wistar and Sprague-Dawley rats. Caspase 3 immunohistochemistry, Western blot analysis and enzyme activity measurements were used to determine cellular localization and the time course of caspase 3 expression and activation. Immunohistochemistry indicated that caspase 3 protein expression increased following SE, peaking at 16-24 h. Cleavage of procaspase 3 to active fragments (p20-17) was detected 2-7 days after SE. Caspase 3 enzyme activity was elevated at 8 h and further increased up to 19.4-fold at 7 days following SE. Activation of caspase 3 after SE occurred in the hippocampus and the extrahippocampal temporal lobe but not in the thalamus. Caspase 3-immunoreactive cells represented only a minority of degenerating cells as assessed by Fluoro-Jade B and TUNEL staining. Analysis of double-labelled sections indicated that active caspase 3 was located in astrocytes rather than neurons or microglia. There was increased caspase 3 expression in both rat strains, and it was independent of the method used to induce SE. These data demonstrate that caspase 3 contributes to the cell death occurring within the first week after SE, but in only a small proportion of degenerating cells. These results suggest that, contrary to expectations, caspase 3 inhibitors would have only limited benefits in the treatment of SE.

Upregulation of neuronal nitric oxide synthase in in vitro stellate astrocytes and in vivo reactive astrocytes after electrically induced status epilepticus

Neuronal nitric oxide synthase (nNOS) is a constitutively expressed and calcium-dependent enzyme. Despite predominantly expressed in neurons, nNOS has been also found in astrocytes, although at lower expression levels. We have studied the regulation of nNOS expression in cultured rat astrocytes from cortex and spinal cord by Western blotting and immunocytochemistry. nNOS was not detectable in cultured astrocytes grown in serum-containing medium (SCM), but was highly expressed after serum deprivation. Accordingly, calcium-dependent NOS activity and both intracellular nitrite levels and nitrotyrosine immunoreactivity after glutamate stimulation were higher in serum-deprived astrocytes than in cells grown in SCM. Serum deprivation induced a modification of astrocytes morphology, from flat to stellate. nNOS up-regulation was also observed in reactive astrocytes of rat hippocampi after electrically induced status epilepticus, as demonstrated by double-labeling experiments. Thus, nNOS upregulation occurs in both in vitro stellate and in vivo reactive astrocytes, suggesting a possible involvement of glial nNOS in neurological diseases characterized by reactive gliosis.

Caspase-mediated death of newly formed neurons in the adult rat dentate gyrus following status epilepticus

A large proportion of cells that proliferate in the adult dentate gyrus under normal conditions or in response to brain insults exhibit only short-term survival. Here, we sought to determine which cell death pathways are involved in the degeneration of newly formed neurons in the rat dentate gyrus following 2 h of electrically induced status epilepticus. We investigated the role of three families of cysteine proteases, caspases, calpains, and cathepsins, which can all participate in apoptotic cell death. Status epilepticus increased the number of bromodeoxyuridine (BrdU)-positive proliferated cells in the subgranular zone of the dentate gyrus. At the time of maximum cell proliferation, immunohistochemical analyses revealed protein expression of active caspase-cleaved poly (ADP-ribose) polymerase (PARP) in approximately 66% of the BrdU-positive cells, while none of them expressed cathepsin B or the 150-kDa calpain-produced fodrin breakdown product. To evaluate the importance of cysteine proteases in regulating survival of the newly formed neurons, we administered intracerebroventricular infusions of a caspase inhibitor cocktail (zVAD-fmk, zDEVD-fmk and zLEHD-fmk) over a 2-week period, sufficient to allow for neuronal differentiation, starting 1 week after the epileptic insult. Increased numbers of cells double-labelled with BrdU and neuron-specific nuclear protein (NeuN) marker were detected in the subgranular zone and granule cell layer of the caspase inhibitor-treated rats. Our data indicate that caspase-mediated cell death pathways are active in progenitor cell progeny generated by status epilepticus and compromise survival during neuronal differentiation.

Status Epilepticus Induces Changes in the Expression and Localization of Endogenous Palmitoyl-Protein Thioesterase 1

Kainic acid (KA)-induced experimental epilepsy, a model of excitotoxicity, leads to selective neuronal death and synaptic restructuring. We used this model to investigate the effects of neuronal hyperactivation on palmitoyl-protein thioesterase 1 (PPT1), the deficiency of which causes drastic neurodegeneration. Immunological stainings showed that epileptic seizures in adult rats led to a progressive and remarkable increase of PPT1 in limbic areas of the brain. Within 1 week, the maximal expression was observed in CA3 and CA1 pyramidal neurons of the hippocampus. In the surviving pyramidal neurons, PPT1 localized in vesicular structures in cell soma and neuritic extensions. After seizures, colocalization of PPT1 with synaptic membrane marker (NMDAR2B) was enhanced. Further, synaptic fractionation revealed that after seizures PPT1 was readily observed on the presynaptic side of synaptic junction. These data suggest that PPT1 may protect neurons from excitotoxicity and have a role in synaptic plasticity.

Alterations in cytochrome c oxidase activity and energy metabolites in response to kainic acid-induced status epilepticus

The effects of kainic acid (KA)-induced limbic seizures have been investigated on cytochrome c oxidase (COx) activity, COx subunit IV mRNA abundance, ATP and phosphocreatine (PCr) levels in amygdala, hippocampus and frontal cortex of rat brain. Rats were killed either 1 h, three days or seven days after the onset of status epilepticus (SE) by CO2 and decapitation for the assay of COx activity and by head-focused microwave for the determination of ATP and PCr. Within 1 h COx activity and COx subunit IV mRNA increased in all brain areas tested between 120% and 130% of control activity, followed by a significant reduction from control, in amygdala and hippocampus on day three and seven, respectively. In amygdala, ATP and PCr levels were reduced to 44% and 49% of control 1 h after seizures. No significant recovery was seen on day three or seven. Pretreatment of rats with the spin trapping agent N-tert-butyl-alpha-phenylnitrone (PBN, 200 mg kg(-1), i.p.) 30 min before KA administration had no effect on SE, but protected COx activity and attenuated changes in energy metabolites. Pretreatment for three days with the endogenous antioxidant vitamin E (Vit-E, 100 mg/kg, i.p.) had an even greater protective effect than PBN. Both pretreatment regimens attenuated KA-induced neurodegenerative changes, as assessed by histology and prevention of the decrease of COx subunit IV mRNA and COx activity in hippocampus and amygdala, otherwise seen following KA-treatment alone. These findings suggest a close relationship between SE-induced neuronal injury and deficits in energy metabolism due to mitochondrial dysfunction.

A significant increase in both basal and maximal calcineurin activity in the rat pilocarpine model of status epilepticus

This study focused on the effects of status epilepticus on the activity of calcineurin, a neuronally enriched, calcium-dependent phosphatase. Calcineurin is an important modulator of many neuronal processes, including learning and memory, induction of apoptosis, receptor function and neuronal excitability. Therefore, a status epilepticus-induced alteration of the activity of this important phosphatase would have significant physiological implications. Status epilepticus was induced by pilocarpine injection and allowed to continue for 60 min. Brain region homogenates were then assayed for calcineurin activity by dephosphorylation of p-nitrophenol phosphate. A significant status epilepticus-dependent increase in both basal and Mn(2+)-dependent calcineurin activity was observed in homogenates isolated from the cortex and hippocampus, but not the cerebellum. This increase was resistant to 150 nM okadaic acid, but sensitive to 50 microM okadaic acid. The increase in basal activity was also resistant to 100 microM sodium orthovanadate. Both maximal dephosphorylation rate and substrate affinity were increased following status epilepticus. However, the increase in calcineurin activity was not found to be due to an increase in calcineurin enzyme levels. Finally, increase in calcineurin activity was found to be NMDA-receptor activation dependent. The data demonstrate that status epilepticus resulted in a significant increase in both basal and maximal calcineurin activity.

Chronic inhibition of Ca(2+)/calmodulin kinase II activity in the pilocarpine model of epilepsy

The development of symptomatic epilepsy is a model of long-term plasticity changes in the central nervous system. The rat pilocarpine model of epilepsy was utilized to study persistent alterations in calcium/calmodulin-dependent kinase II (CaM kinase II) activity associated with epileptogenesis. CaM kinase II-dependent substrate phosphorylation and autophosphorylation were significantly inhibited for up to 6 weeks following epileptogenesis in both the cortex and hippocampus, but not in the cerebellum. The net decrease in CaM kinase II autophosphorylation and substrate phosphorylation was shown to be due to decreased kinase activity and not due to increased phosphatase activity. The inhibition in CaM kinase II activity and the development of epilepsy were blocked by pretreating seizure rats with MK-801 indicating that the long-lasting decrease in CaM kinase II activity was dependent on N-methyl-D-aspartate receptor activation. In addition, the inhibition of CaM kinase II activity was associated in time and regional localization with the development of spontaneous recurrent seizure activity. The decrease in enzyme activity was not attributed to a decrease in the alpha or beta kinase subunit protein expression level. Thus, the significant inhibition of the enzyme occurred without changes in kinase protein expression, suggesting a long-lasting, post-translational modification of the enzyme. This is the first published report of a persistent, post-translational alteration of CaM kinase II activity in a model of epilepsy characterized by spontaneous recurrent seizure activity.

Nitric oxide synthase immunoreactivity in the rat hippocampus after status epilepticus induced by perforant pathway stimulation

Nitric oxide has recently been implicated in mediation of neuronal excitotoxicity and damage. This study aimed at elucidating the changes in the expression of neuronal isoform of nitric oxide synthase (nNOS) in the hippocampus after status epilepticus induced by perforant pathway stimulation. nNOS-immunoreactivity (nNOS-ir) and neuronal damage, assessed by silver staining, were evaluated separately in different hippocampal subfields 2 weeks after induction of status epilepticus. Perforant pathway stimulation resulted in an increase in the number of nNOS-immunoreactive neurons in the stratum radiatum of the CA1 and CA3 subfields of the hippocampus proper, and the hilus of the dentate gyrus. The morphology and distribution of the nNOS-ir neurons resembled that of interneurons. No correlation of the number of nNOS-ir neurons to the neuronal damage score was observed. Our results suggest that status epilepticus provokes a de novo expression of nNOS protein, and the nNOS expressing neurons may be selectively resistant to epileptic brain injury.

Status epilepticus results in an N-methyl-D-aspartate receptor-dependent inhibition of Ca2+/calmodulin-dependent kinase II activity in the rat

Status epilepticus is a major medical emergency that results in significant alteration of neuronal function. Status epilepticus involves seizure activity recurring frequently enough to induce a sustained alteration in brain function. This study was initiated to investigate how status epilepticus affects the activity of calcium and calmodulin-dependent kinase II in the brain. Calcium and calmodulin-dependent kinase II is a neuronally enriched signal transducing system involved in the regulation of neurotransmitter synthesis and release, cytoskeletal function, gene transcription, neurotransmitter receptor function and neuronal excitability. Therefore, alteration of this signal transduction system would have significant physiological effects. Status epilepticus was induced in rats by pilocarpine injection, allowed to progress for 60 min and terminated by repeated diazepam injections. Animals were killed at specific time-points and examined for calcium and calmodulin-dependent kinase II activity. Calcium and calmodulin-dependent kinase II activity was significantly reduced in cerebral cortex and hippocampal homogenates obtained from status epilepticus rats when compared with control animals. Once established, the status epilepticus-induced inhibition of calcium and calmodulin-dependent kinase II activity was observed at all time-points tested following the termination of seizure activity. However, calcium and calmodulin-dependent kinase II activity was not significantly decreased in thalamus and cerebellar homogenates. In addition, status epilepticus-induced inhibition of calcium and calmodulin-dependent kinase II activity was dependent upon activation of N-methyl-D-aspartate subtype of glutamatergic receptors. Thus, status epilepticus induced a significant inhibition of calcium and calmodulin-dependent kinase II activity that involves N-methyl-D-aspartate receptor activation. The data support the hypothesis that inhibition of calcium and calmodulin-dependent kinase II activity may be involved in the alteration of neuronal function following status epilepticus.

Changes in NADPH-diaphorase positivity induced by status epilepticus in allocortical structures of the immature rat brain

The distribution and time course of changes of nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) positivity were studied in immature rats (12 and 25 days old) surviving motor status epilepticus (SE) induced by a high dose of pilocarpine. Motor SE characterized by continuous convulsions was interrupted after 2 h by an injection of clonazepam (0.5 mg/kg or 1 mg/kg in 12- and 25-day-old rats, respectively) in order to reduce mortality. Correlation between electroencephalographic and behavioral seizure activity was confirmed using animals with electrodes implanted bilaterally in the hippocampus and sensorimotor cortex. Brains were examined 2, 6, 13, and 21 days after motor SE using NADPH-diaphorase histochemistry. Two types of changes were found in both age groups: (a) decrease of NADPH-d positivity occurred in both neuropil and cell bodies in piriform, periamygdalar, and entorhinal cortices; and (b) NADPH-d positivity was induced in the cell bodies in the hippocampal fields CA1/2, CA3, and dentate gyrus. These changes were more intense in animals surviving SE at postnatal day 25 than in younger age group, and they peaked 2 days after SE. The changes observed after SE disappeared quickly in 12-day-old rat pups, where only moderate changes could be observed in piriform, periamygdalar, and entorhinal cortices 6 days after SE, whereas the changes in the histochemical positivity persisted in older animals even 21 days after SE.

Mitogen-activated protein kinase is increased in the limbic structures of the rat brain during the early stages of status epilepticus

Systemic administration of pilocarpine (PILO) in adult rat produces acute limbic seizures leading to status epilepticus. Recent studies have shown the activation of mitogen-activated protein kinase (MAPK) cascades during experimentally induced seizures. MAPK activation may be triggered by glutamatergic stimulation and may play a key role in signal transduction pathways. In the present study, immunocytochemistry was used to analyze the spatiotemporal distribution pattern of the MAPK protein and its active form (A-MAPK) following PILO-induced status epilepticus. MAPK and A-MAPK immunoreactivities exhibited different patterns of distribution in the brain of normal and epileptic rats. The saline-treated rats, as well as the animals that received PILO but did not evolve to status epilepticus, showed a weak but selective MAPK immunoreactivity, detected in the hippocampal pyramidal neurons, dentate gyrus, hilus, CA3, CA1, and entorhinal, piriform, and cingulate cortices. A-MAPK immunoreactivity was instead observed only in neurites of the CA3 and hilus and in cells of the entorhinal and piriform cortices. In PILO-treated rats, between 30 and 60 min after status epilepticus there was an increase of the immunoreactivity to both antibodies, which were differently distributed throughout several structures of the limbic system. The immunostaining showed a slight decrease after 5 h of status epilepticus. However, MAPK and A-MAPK immunopositivities decreased markedly after 12 h of status epilepticus, returning almost to the basal expression. These findings are consistent with a spatial and time-dependent MAPK expression in selected limbic structures, and its activation could represent an initial trigger for neuronal modifications that may take part in the mechanism underlying acute epileptogenesis and in long-lasting neuropathological changes of the PILO model of epilepsy.

Serum neuron-specific enolase is a marker for neuronal damage following status epilepticus in the rat

We determined the serum concentrations of neuron-specific enolase (s-NSE) in rat pups of 1, 2, 3, and 4 weeks of age and in adult rats that were subjected to lithium-pilocarpine status epilepticus (SE). Damage to brain regions was rated on a scale of 0 (no damage) to 5 (> 50% cell loss). Rat pups of 1-2 weeks of age had a higher baseline s-NSE than the adults. Following SE, 1 week old rat pups had no elevation of s-NSE and no histologic evidence of damage. At older ages the increases in NSE ranged from 18.9 +/- 0.8 ng/ml in the 2 week old (vs. 11.5 +/- 0.5 control) to 35.8 +/- 2.1 ng/ml in the 3 week old (vs. 12.1 +/- 0.8 control). In the adult rats s-NSE increased from 5.4 +/- 0.4 in the control animals to 30.4 +/- 1.3 after SE. The different brain regions examined had distinctive ontogenic profiles for SE-induced damage. Elevation of s-NSE after SE correlated with overall histologic evidence for damage.

Reduced cortical ecto-ATPase activity in rat brains during prolonged status epilepticus induced by sequential administration of lithium and pilocarpine

Considerable evidence indicates that ATP, acting intracellularly of as a neurotransmitter, can influence nerve cell physiology in a variety of ways. Defects in the functioning of ATP-metabolizing enzymes could therefore lead to disturbances in neurotransmission and creation of sustained neuronal discharges characteristic of status epilepticus. In this study we investigated synaptosomal ATPase changes in rat brains during lithium/pilocarpine-induced status epilepticus. After 2 h of continuous electroencephalographic spiking, both Mg(2+)- and Ca(2+)-dependent ecto-ATPases were significantly decreased in freshly prepared synaptosomal preparations from the status rats. The intracellularly acting Ca2+Mg(2+)-ATPase (Ca-pump) was also decreased, but no changes occurred in synaptosomal Na+K(+)-ATPase activity. The difference between ecto-ATPase activities of the control and status rat brains was not affected by repeated freezing-thawing and lengthy storage. Possible involvement of reduced synaptosomal divalent cation-dependent ATPases in the pathophysiology of status epilepticus is discussed.

Neuron-specific enolase, a marker of acute neuronal injury, is increased in complex partial status epilepticus

PURPOSE

To determine whether complex partial status epilepticus (CPSE) causes brain injury in humans. Serum neuron-specific enolase (s-NSE) is an accepted marker of acute brain injury, and increases in s-NSE have been correlated with the duration and outcome of generalized convulsive status epilepticus. s-NSE levels in CPSE are unknown. Increase in s-NSE in CPSE would provide new information about the degree of brain injury in CPSE and would help confirm that CPSE is a medical emergency.

METHODS

This was a pilot prospective study of serial levels of s-NSE and outcome in CPSE. Eight patients with confirmed CPSE and no acute neurologic deficit were identified prospectively. Results were compared with those of normal and epileptic control groups, and outcome was assessed at hospital discharge or at 7 days with the Glasgow Oucome Scale (GOS).

RESULTS

The mean peak s-NSE was 21.81 ng/ml, which for the 8 patients with CPSE was four times higher than that of normal controls (mean s-NSE = 5.36 SD = 1.66, p = 0.0003) and epileptic controls (mean s-NSE = 4.61 SD = 1.74, p. = 0.001).

CONCLUSION

The increase in s-NSE provides new evidence that CPSE causes brain injury in humans.

Recurrent reversible rhabdomyolysis associated with hyperthermia and status epilepticus

A 6-year-old boy developed rhabdomyolysis following hyperthermia and status epilepticus with a diagnosis of severe myoclonic epilepsy of infancy. At 2 and 3 years of age, he had similar episodes. Each time he recovered completely in 3-4 weeks with conservative management, in spite of renal insufficiency and marked liver dysfunction. Several cases of recurrent myoglobinuria after intense exercise of generalized tonic-clonic convulsions were reported to have genetic errors of carbohydrate or lipid metabolism of muscle. In our patient, however, the activity of these enzymes was found to be normal. This indicates that status epilepticus may cause recurrent rhabdomyolysis in subjects with normal glycolytic and lipolytic enzyme activity.

Loss of type II calcium/calmodulin-dependent kinase activity correlates with stages of development of electrographic seizures in status epilepticus in rat

Understanding the molecular basis of altered neuronal excitability in epilepsy is a major challenge in neuroscience research. The present study suggests an inverse correlation between changes in neuronal excitability in status epilepticus and the activity of type II multifunctional calcium/calmodulin-dependent kinase II (CaM kinase II), a major Ca(2+)-signal transducing system in brain. 'Continuous' hippocampal stimulation (CHS), a new model of non-convulsive limbic status epilepticus (SE), mimics the progression of electrographic changes characteristic in human SE and allows for quantitation of post-stimulus seizure severity. In the present study, hippocampus and anterior neocortex from CHS-stimulated rats and paired surgical controls were assayed for CaM kinase II activity by incorporation of radiolabeled phosphate from [gamma-32P]ATP into the 50-kDa subunit of the kinase itself (autophosphorylation). In all instances, CHS induced sustained interictal bursting and/or electrographic seizures. Decreased CaM kinase II activity was seen in all preparations from electrically stimulated hippocampus. CaM kinase II activity in CHS animals was diminished by 37% relative to controls (P less than 0.01; Student's paired t-test). The progressive intensity of the EEG discharges correlated directly with the decrement of CaM kinase II activity (P less than 0.05; Spearman's rank correlation test, n = 5). This is the first report of a dynamic modulation of a biochemical system that has been implicated in neuronal excitability in coordination with the characterized developmental stages of SE.

Decreased calmodulin kinase activity after status epilepticus

Status epilepticus was induced in paralyzed, ventilated rats using bicuculline and was maintained for 50 to 120 minutes. Cerebral cortex, hippocampus, and cerebellum were assayed for calmodulin kinase II activity in vitro using [gamma-32P]ATP and polyacrylamide gel electrophoresis. Seizures resulted in a 3.2 fold decrease in calmodulin kinase activity in crude synaptic membranes of cortex and in a 8.2 fold decrease in hippocampal membranes. Cytosolic calmodulin kinase activity was slightly increased in rats in status epilepticus but statistical significance was not reached. Status epilepticus did not affect calcium/calmodulin-dependent kinase activity in cerebellar membranes or cytosol. These data suggest that intense firing associated with continuous seizure activity decreases calmodulin kinase activity in cortical and hippocampal synaptic membranes, which may result in altered neuronal excitability.

Etomidate: a selective adrenocortical 11 beta-hydroxylase inhibitor

To investigate the adrenocortical suppression caused by the anesthetic etomidate, plasma levels of progesterone (P), 17-hydroxyprogesterone (17-OHP), 11-deoxycorticosterone (DOC), corticosterone (B), aldosterone (Aldo), 11-deoxycortisol (S), cortisol (F), and cortisone (E) were measured simultaneously before and after a short-term ACTH stimulation test in a 6.5-year-old boy whose convulsions could be kept under control only with constant etomidate infusions. During etomidate therapy, plasma levels of DOC and S were extremely elevated, the progestins P and 17-OHP were slightly elevated, whereas B and Aldo were in the lower normal range, and F and E were markedly decreased. A short-term ACTH stimulation test during etomidate infusion gave a blunted response of B, Aldo, F and E, whereas the level of DOC remained high and S even further increased. P and 17-OHP showed a positive response to ACTH. The ratios of B/DOC and F/S, which reflect adrenocortical 11 beta-hydroxylase activity, were extremely decreased during etomidate and did not change after ACTH stimulation. In contrast, the ratios of DOC/P and S/17-OHP, which reflect 21-hydroxylase activity, were elevated and remained elevated after ACTH stimulation. After discontinuation of etomidate therapy, all the baseline steroid levels were somewhat elevated, but responded normally to ACTH. These results demonstrate that etomidate causes a specific and reversible blockade of the 11 beta-hydroxylation of adrenal steroid synthesis.