Levels of catechols in epileptogenic and nonepileptogenic regions of the human brain

The impact of epilepsy on the quality of life of patients with meningioma: A systematic review

Quality of life (QoL) is regarded as an important outcome measure in meningioma, and studies have investigated the role of various clinical and demographic factors. Epilepsy is known to impair quality of life but the impact of epilepsy on quality of life in a meningioma population is not well defined. The aim of this systematic review is to identify and summarise the current literature on meningioma, epilepsy and quality of life. A PubMed search was performed that identified 162 articles. Only 4 articles relevant to meningioma, epilepsy and QoL were found and each were analysed in terms of design, data, findings and conclusions. Each article was different in terms of study population, aims and outcome measure, but all suggest that epilepsy has an impact on quality of life. Anti-epileptic drugs, uncontrolled seizures and cognitive dysfunction may be particularly significant. The identified articles were weakened by small sample size, short follow-up, a lack of recorded epilepsy variables and the use of quality of life measures that are either too specific or not validated. Future studies are warranted to improve understanding in this topic, aid clinical decisions and improve QoL in these patients.

Seizure-associated Takotsubo cardiomyopathy

Takotsubo cardiomyopathy is characterized by chest pain, dyspnea, electrocardiographic changes resembling an acute coronary syndrome, and transient wall-motion abnormalities without identifiable coronary culprit lesion explaining the wall-motion abnormality. Takotsubo cardiomyopathy occurs frequently after emotional or physical stress. Seizures have been reported as triggers of takotsubo cardiomyopathy. It is unknown if seizure-associated takotsubo cardiomyopathy differs from takotsubo cardiomyopathy associated with other triggers. Seizure-associated takotsubo cardiomyopathy cases from the literature were compared with takotsubo cardiomyopathy series comprising 30 or more patients. Thirty-six seizure-associated takotsubo cardiomyopathy cases (6 male, mean-age 61.5 years) were found. Seizure-type were tonic-clonic (n = 13), generalized (n = 5), status epilepticus (n = 6), grand mal (n = 2), or not reported (n = 13). Twelve patients had a history of epilepsy, in 15 patients takotsubo cardiomyopathy-associated seizure was the first or the information was not given (n = 9). In 17 patients takotsubo cardiomyopathy occurred immediately after the seizure, in 9 patients 1-72 h postictally, and in 10 patients, the interval was not reported. In 20 patients neurologic disorders were reported and in 14 psychiatric disorders were reported. There were medical comorbidities in 17 patients, arterial hypertension (n = 11), hyponatremia (n = 2), and cancer (n = 2). Compared with 974 patients reported in takotsubo cardiomyopathy -series, patients with seizure-associated takotsubo cardiomyopathy were younger (61.5 vs. 68.5 years, p < 0.0001), more frequently males (17 vs. 9%, p = 0.004), had less frequent chest pain (6 vs.76%, p < 0.005), more frequent cardiogenic shock (25 vs. 8%, p = 0.003), and more frequent recurrency (14 vs. 3%, p = 0.004). Seizure-associated takotsubo cardiomyopathy manifests frequently as sudden hemodynamic deterioration, which could result in death in the absence of adequate help. Probably some cases of sudden unexpected death in epilepsy are attributable to takotsubo cardiomyopathy.

Macroprolactinomas and epilepsy

OBJECTIVE

To assess the prevalence and characteristics of epilepsy in patients with macroprolactinomas. Secondly, to report the response to dopamine agonist (DA) therapy.

PATIENTS

A case note analysis of all patients with a diagnosis of macroprolactinoma attending a neuroendocrine clinic between 1996 and 2006. Those with epilepsy at diagnosis of macroprolactinoma were examined in detail.

RESULTS

There were 64 patients with macroprolactinoma and 29 of these had tumours with suprasellar extension compressing/invading the optic apparatus and/or surrounding brain structures. Six of these 29 patients (four men), had a history of seizures at the time of diagnosis, five of whom had features suggestive of temporal lobe epilepsy. None of the other 35 patients had epilepsy. All six patients with epilepsy had invasive prolactinomas on cranial imaging and marked hyperprolactinaemia (median prolactin 369 000 mU/l, range 28 000 to > 750 000). Seizures had been present for a median of 2 years (range 1-23 years) before the diagnosis of macroprolactinoma. A rapid reduction in seizure frequency occurred in all patients with initiation of DA therapy. Four have been seizure-free between 18 months to 15 years despite only small reductions in tumour size.

CONCLUSIONS

Invasive macroprolactinomas can commonly be associated with epilepsy, particularly of temporal lobe origin. It is essential to enquire about epileptic symptoms, as the seizure disorder may have been undiagnosed/untreated for years. DA therapy can reduce ictal frequency and the doses of anti-epileptic drugs. Complete freedom from epilepsy can also occur.

A case of takotsubo cardiomyopathy associated with epileptic seizure: reversible left ventricular wall motion abnormality and ST-segment elevation

A 59-year-old woman was admitted for consciousness disturbance. She had a history of endocranial operation for astrocytoma. Her electrocardiogram showed ST-segment elevation indicative of acute myocardial infarction. Emergency coronary angiography showed normal coronary arteries, whereas left ventriculography showed extensive severe hypokinesis in the anteroseptal and apical segments. Electroencephalography showed slow sharp wave activity from the left frontal lobe to the temporal lobe, and she was diagnosed as having status epilepticus. This is a rare case of takotsubo cardiomyopathy associated with epileptic seizure. Acute myocardial ischemia caused by impaired coronary microcirculation induced by abnormal catecholamine release is a possible cause of cardiac wall motion abnormality, as in our case.

Epilepsy-induced microarchitectural changes in the brain

Our understanding of the pathogenesis of the neuropathology of epilepsy has been challenged by a need to separate the "lesions" that cause epilepsy from the "lesions" that are produced by the epilepsy. Significant clinical, genetic, pathologic, and experimental studies of Ammon horn sclerosis (AHS) suggest that AHS is the result and cause of seizures. The data support the idea that seizures cause alterations in cell numbers, cell shape, and organization of neuronal circuitry, thus setting up an identifiable seizure-genic focus. As such, AHS represents a slowly progressive lesion and a search for the cause of the initiating seizure has led to the identification of ion channel mutations. In this report, the neuropathology of other conditions associated with intractable epilepsy is considered, suggesting that in them similar epilepsy-produced alterations in microarchitecture can be observed. The idea is important to define the optimum time for epilepsy surgery and the underlying etiology of these seizure-genic lesions.

Brain tumor and seizures: pathophysiology and its implications for treatment revisited

Seizures affect approximately 50% of patients with primary and metastatic brain tumors. Partial seizures have the highest incidence, followed by secondarily generalized, depending on histologic subtype, location, and tumor extent. The underlying pathophysiologic mechanisms of tumor-associated seizures are poorly understood and include theories of altered peritumoral amino acids, regional metabolism, pH, neuronal or glial enzyme and protein expression, as well as immunologic activity. An involvement of changed distribution and function of N-methyl-d-aspartate subclass of glutamate receptors also has been suggested. The often unpredictable responses to seizures after surgical tumor removal add substantial evidence that multiple factors are involved. The therapy of tumor-related seizures is far from perfect. Several factors contribute to these treatment difficulties, such as tumor growth and drug interactions; however, one of the main reasons for poor seizure control may result from the insufficient or even absent influence of the currently available antiepileptic drugs (AEDs) on most of the pathophysiologic mechanisms of tumor-related seizures. Studies are needed to elucidate more clearly the pathophysiologic mechanisms of tumor-related seizures and to identify and develop the optimal AEDs.

The role of catecholamines in seizure susceptibility: new results using genetically engineered mice

The catecholamines norepinephrine and dopamine are abundant in the CNS, and modulate neuronal excitability via G-protein-coupled receptor signaling. This review covers the history of research concerning the role of catecholamines in modulating seizure susceptibility in animal models of epilepsy. Traditionally, most work on this topic has been anatomical, pharmacological, or physiological in nature. However, the recent advances in transgenic and knockout mouse technology provide new tools to study catecholamines and their roles in seizure susceptibility. New results from genetically engineered mice with altered catecholamine signaling, as well as possibilities for future experiments, are discussed.

Biogenic amines in the human neocortex in patients with neocortical and mesial temporal lobe epilepsy: identification with in situ microvoltammetry

Biogenic amines in well defined subtypes of human temporal lobe epilepsy (TLE) have not been well characterized. Specimens from five patients with neocortical TLE (NTLE) and nine with mesial TLE (MTLE) were immediately placed in Ringer's lactate; stearate indicator microelectrodes were placed in temporal gray matter, Ag/AgCl reference microelectrodes and auxiliary microelectrodes were placed 3-7 mm contralaterally to the indicator microelectrode. Dopamine (DA), ascorbic acid (AA), norepinephrine (NE) and serotonin (5-HT) were identified by their characteristic oxidative potentials in vitro. Four of five patients with NTLE had NE depletion in temporal neocortex while eight of nine patients with MTLE had high concentrations of NE (chi-square P<0.01). Significant concentrations of DA were present in the temporal lobes of three of five NTLE patients but in only one of the nine MTLE patients (chi-square P<0.05). 5-HT was present in the neocortex of both NTLE and MTLE patients in similar concentrations. AA was found in the neocortex of one NTLE patient. These data support an association between NE depletion and NTLE. The relative NE deficiency along with the consistent presence of DA in NTLE patients suggest an impairment in the catecholamine pathway. The presence of AA, a co-factor in NE synthesis, in the neocortex of one NTLE patient may also be related since AA is a cofactor in NE synthesis.

Monoamine neurotransmitters in resected hippocampal subparcellations from neocortical and mesial temporal lobe epilepsy patients: in situ microvoltammetric studies

It is known that epilepsy patients diagnosed with neocortical temporal lobe epilepsy (NTLE), differ from those diagnosed with mesial temporal lobe epilepsy (MTLE), e.g., in hippocampal (HPC) pathology. In the present studies, we tested the hypothesis that NTLE and MTLE subtypes of human epilepsy might differ in regards to their HPC monoamine neurochemistry. Monoamine neurotransmitters were studied in separate signals and within s with semiderivative microvoltammetry, used in combination with stearate indicator, Ag-AgCl reference and stainless steel auxiliary microelectrodes. Anterior HPC specimens from the patients' epileptogenic zone, defined by electrocorticography, were resected neurosurgically from 13 consecutive patients with intractable temporal lobe epilepsy. Four patients were diagnosed with NTLE and nine with MTLE. The criteria for the diagnosis of NTLE versus MTLE was absence versus presence of HPC sclerosis, respectively, based on MRI examination of resected tissue. In addition, NTLE patients demonstrated seizure onset in anterolateral temporal neocortex on electroencephalography (EEG). HPC subparcellations studied were: (a) Granular Cells of the Dentate Gyrus (DG), (b) Polymorphic Layer of DG and (c) Pyramidal Layer: subfields, CA1 and CA2. Dopamine (DA), serotonin (5-HT), norepinephrine (NE) and ascorbic acid (AA) (co-factor in DA to NE synthesis), exhibited separate and characteristic half-wave potentials in millivolts. Each half-wave potential, i.e., the potential at which maximum current was generated, was experimentally established in vitro. Concentrations of neurotransmitters found in HPC subparcellations were interpolated from calibration curves derived in vitro from electrochemical detection of monoamines and AA in saline phosphate buffer. Significant differences between subtypes in concentration of monoamines were analyzed by the Mann Whitney rank sum test and those differences in probability distribution of monoamines were analyzed by the Fisher Exact test; in each case, P<0.01 was the criteria selected for determining statistical significance. DA concentrations were higher in NTLE compared with MTLE in each HPC subparcellation [P=0.037, 0.024 and 0.007, respectively (P<0.01)] and DA occurred more frequently in NTLE in the Pyramidal Layer [P=0.077 (P<0.01)]. AA was present in one NTLE patient. NE concentrations were higher in MTLE vs. NTLE in each subparcellation [P=0.012, 0.067 and 0.07, respectively (P<0.01)] and NE occurred more frequently in MTLE in Granular Cells of DG and Pyramidal Layer [P=0.052 and 0.014, respectively (P<0.01)]. In MTLE, NE concentrations in the CA1 subfield of the Pyramidal Layer were decreased vs. the CA2 subfield [P=0.063 (P<0.01)]. Serotonin was found in every HPC subparcellation of each subtype but 5-HT concentrations were higher in NTLE vs. MTLE in the Granular Cells of DG and the Pyramidal Layer (CA1 subfield) [P=0.076 and 0.095, respectively (P<0.01)]. Thus, this preliminary study showed that marked differences in HPC monoamine neurochemistry occurred in NTLE patients as compared with MTLE patients.

Cortical catecholamine changes and seizures induced by 4-aminopyridine in awake rats, studied with a dual microdialysis-electrical recording technique

We describe a rotatory electrical device that permits the simultaneous microdialysis and electroencephalographic (EEG) recording, by means of bipolar electrodes attached to the microdialysis probe, in two brain regions of awake rats. Using this device, we have found that the microdialysis infusion of 4-aminopyridine (4-AP) in the motor cerebral cortex produces intense behavioral convulsions and EEG seizures in both the infused and the contralateral cortex. This convulsant action is accompanied by a remarkable increase of extracellular dopamine (about 15-fold), norepinephrine (2.4-fold) and vanillylmandelic acid (1.8-fold) concentration in the infused cortex. Delayed increases of these amines were observed also in the contralateral cortex. The results suggest that 4-AP induces the release of catecholamines either through a direct effect on nerve endings or as a consequence of seizures.

Heterogeneous distribution of polyamines in temporal lobe epilepsy

Polyamine contents were determined in human temporal lobe epilepsy. In the seven patients studied, stereoelectroencephalography (SEEG) located the epileptogenic focus in Ammon's horn and neuropathological findings were limited to hippocampal gliosis and sclerosis. Each polyamine exhibited a specific regional distribution. The most important variations were observed for spermidine and spermine while putrescine levels varied less. The regional variation was predominant in middle > posterior > anterior parts of the temporal lobe. Spermine contents and the spermidine/spermine (SPD/SPM) index varied especially in the middle and posterior parts of the hippocampus. Metabolic SPD/SPM index and spermidine levels were found to be drastically increased in almost all limbic parts when compared to neocortical regions. The opposite was observed for spermine. The heterogeneous distribution of polyamines was compared to abnormal electrical activities recorded by SEEG: SPD/SPM index and spermidine levels were sharply increased in seizure onset areas and high levels of spermine were detected in temporal cortex propagation areas. The presently reported heterogeneity of polyamine contents might contribute to modulate differentially the local control of excitability in human temporal epilepsy.

Three-dimensional mapping of norepinephrine and serotonin in human thalamus

Detailed quantitative information on catecholamines and 5-hydroxytryptamine (serotonin) in the human thalamus is much needed because of increasing interest in norepinephrine and serotonin as modulators of thalamic behavioral state control and overall information processing. This study provides three-dimensional distribution patterns of these monoamines in postmortem thalami from 13 normal subjects (no known neurological or psychiatric histories). The patterns come from a relatively fine-grained grid mapping procedure on successive coronal sections. Samples were analyzed by high performance liquid chromatography with electrochemical detection. The highest endogenous concentrations of norepinephrine are found in a ventromedial core that includes a number of the medial and intralaminar sub-nuclei but extends only slightly into the sensory regions of the lateral tier. The posterior portion of the thalamus, the pulvinar, contains low levels of norepinephrine. The distribution of 5-hydroxytryptamine is quite similar to that of norepinephrine in the rostral two-thirds of thalamus; however, in the pulvinar region, levels of serotonin are considerably increased and differ markedly between individual thalami. The study provides the first definitive mapping of serotonin levels in human thalamus. Consistent with many animal studies, there is no evidence for major dopaminergic innervation of human thalamus. By emphasizing the pattern distribution of the monoamines rather than the absolute values, it can be shown that the ambiguities of postmortem degradation frequently associated with biochemical assays are largely avoided. The terminal field distribution of norepinephrine is an essentially constant neurochemical signature in all thalami examined. The utility of the biochemical grid mapping procedure may be especially significant in terms of matching with data from functional neuroimaging techniques.

Monoamines and their metabolites in cerebrospinal fluid and temporal cortex of epileptic patients

The involvement of monoamines in the initiation or maintenance of epileptic phenomena has been extensively studied in cerebral tissues and in cerebrospinal fluid. The present work was undertaken to study monoamines and their metabolites in human spiking and non-spiking temporal cortex excised from patients with complex partial seizures unresponsive to available anticonvulsants. The same substances were also analyzed by HPLC-ED in cerebrospinal fluid obtained 24 h before the surgical procedure and compared with those from patients with chronic headache and normal neurological evaluation. The results show increased 5-HT, 5-HIAA and HVA levels in spiking compared with non-spiking cortex. Cerebrospinal fluid levels of 5-HIAA and HVA are concomitantly increased in epileptic compared with headache patients.

The role of dopamine in epilepsy

The clinical benefits of dopamine agonists in the management of epilepsy can be traced back over a century, whilst the introduction of neuroleptics into psychiatry practice 40 years ago witnessed the emergence of fits as a side effect of dopamine receptor blockade. Epidemiologists noticed a reciprocal relationship between the supposed dopaminergic overactivity syndrome of schizophrenia and epilepsy, which came to be regarded as a dopamine underactivity condition. Early pharmacological studies of epilepsy employed nonselective drugs, that often did not permit dopamine's antiepileptic action to be clearly dissociated from that of other monoamines. Likewise, the biochemical search for genetic abnormalities in brain dopamine function, as predeterminants of spontaneous epilepsy, proved largely inconclusive. The discovery of multiple dopamine receptor families (D1 and D2), mediating opposing influences on neuronal excitability, heralded a new era of dopamine-epilepsy research. The traditional anticonvulsant action of dopamine was attributed to D2 receptor stimulation in the forebrain, while the advent of selective D1 agonists with proconvulsant properties revealed for the first time that dopamine could also lower the seizure threshold from the midbrain. Whilst there is no immediate prospect of developing D2 agonists or D1 antagonists as clinically useful antiepileptics, there is a growing awareness that seizures might be precipitated as a consequence of treating other neurological disorders with D2 antagonists (schizophrenia) or D1 agonists (parkinsonism).

Effect of chronic administration of phenytoin on regional monoamine levels in rat brain

Phenytoin (DPH) is a widely used anticonvulsant drug but a conclusive mode of action is not yet clear. This study was undertaken to assess the effects of chronic administration of DPH on monoamine levels. DPH (50 mg/kg body weight) was administered to adult male Wistar rats by intraperitoneal injections for 45 days and the regional brain levels of norepinephrine (NE), dopamine (DA) and serotonin (5-HT) were assayed using high performance liquid chromatographic (HPLC) method. The experimental rats revealed no behavioral deficits of any kind nor body and brain weight deficits were observed. Increased NE levels were observed after DPH administration in motor cortex (P < 0.05), striatum-accumbens (P < 0.01) and hippocampus (P < 0.01), whereas, NE level was decreased in brain stem (P < 0.05). DA levels were increased in striatum-accumbens (P < 0.05), hypothalamus (P < 0.001) and cerebellum (P < 0.001) but decreased in brainstem (P < 0.01). In DPH treated rats, 5-HT levels were increased in motor cortex (P < 0.001) but decreased in cerebellum (P < 0.001) when compared to control group of rats. The present study suggest that chronic administration of DPH induces alterations in monoamine levels in specific brain regions. DPH seems to mediate its anticonvulsant action by selectively altering the monoamine levels in different brain regions.

Neurochemical and morphological changes associated with human epilepsy

To date a multitude of studies into the morphology and neurochemistry of human epilepsy have been undertaken with variable, and often inconsistent, results. This review summarises these studies on a range of neurotransmitters, neuromodulators, neuropeptides and their receptors. In addition to this, novel changes in cell viability and sprouting have been identified and are discussed. Whether the alterations observed are a result of the seizures or are a contributory factor is unclear. However, it may be that following an initial insult (such as febrile convulsions, status epilepticus or head injury) secondary processes occur both of an anticonvulsant nature in an attempt to compensate for seizure activity, and in a kindling type of fashion, resulting in an increased susceptibility to seizures, leading to future seizures. Many of the alterations documented in this study probably represent one or both of these processes. Clearly no single chemical abnormality or morphological alteration is going to explain the clinically diverse disorder of epilepsy. However, by drawing together the neurochemistry and morphology of epilepsy, we may begin to understand the mechanisms involved in seizure disorders.

MDR1 gene expression in brain of patients with medically intractable epilepsy

Why some patients with seizures are successfully treated with antiepileptic drugs (AEDs) and others prove medically intractable is not known. Inadequate intraparenchymal drug concentration is a possible mechanism of resistance to AEDs. The multiple drug resistance gene (MDR1) encodes P-glycoprotein, an energy-dependent efflux pump that exports planar hydrophobic molecules from the cell. If P-glycoprotein is expressed in brain of some patients with intractable epilepsy and AEDs are exported by P-glycoprotein, lower intraparenchymal drug concentrations could contribute to lack of drug response in such patients. Eleven of 19 brain specimens removed from patients during operation for intractable epilepsy had MDR1 mRNA levels > 10 times greater than those in normal brain, as determined by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) method. Immunohistochemistry for P-glycoprotein from 14 of the patients showed increased staining in capillary endothelium in samples from epileptic patients as compared with staining in normal brain samples. In epileptic brain specimens with high MDR1 mRNA levels, expression of P-glycoprotein in astrocytes also was identified. Last, steady-state intracellular phenytoin (PHT) concentrations in MDR1 expressing neuroectodermal cells was one fourth that in MDR1-negative cells. MDR1 expression is increased in brain of some patients with medically intractable epilepsy, suggesting that the patients' lack of response to medication may be caused by inadequate accumulation of AED in brain.

The anticonvulsant FCE 26743 is a selective and short-acting MAO-B inhibitor devoid of inducing properties towards cytochrome P450-dependent testosterone hydroxylation in mice and rats

The effects of the potent anticonvulsant FCE 26743 ((S)-2-(4-3-fluorobenzyloxy)benzylamino)propionamide) on monoamine oxidase (MAO) activity were measured in-vitro and ex-vivo using rat tissue homogenates. In-vitro, FCE 26743 showed potent and selective inhibitory properties towards liver MAO-B, with IC50 values about 10(-7) M for MAO-B and higher than 10(-5) M for MAO-A. When determined ex-vivo in brain, the ED50 value for the inhibition of MAO-B was 1.1 mg kg-1 (p.o.) 1 h post-dosing, whereas MAO-A remained virtually unaffected after administration of 60 mg kg-1. Similar effects were seen in liver. Following oral administration of 5 mg kg-1 FCE 26743 to rats, brain MAO-B inhibition was 79% after 1 h and 13% after 24 h, indicating that FCE 26743 behaves as a short-acting MAO-B inhibitor. The ability of FCE 26743 to act as a MAO substrate was assessed in mice by measuring the urinary excretion of alaninamide, a potential metabolite of FCE 26743 which would result from the action of MAO. No alaninamide was detectable in the 0-8 h urines after administration of a 119 mg kg-1 dose, suggesting that FCE 26743 is not, or only to a small degree, a substrate of MAO. The effects of FCE 26743 on cytochrome P450 enzymes involved in testosterone hydroxylation were determined in rats after repeated administration. No induction of the cytochrome P450 system was noted.

Altered patterns of catecholaminergic fibers in focal cortical dysplasia in two patients with partial seizures

We present the histologic study of two patients who underwent cerebral cortex resection for partial seizures linked with cortical dysplasia. The distinction of areas of seizure origin from areas of seizure propagation was made according to stereoelectroencephalographic criteria. Samples of epileptogenic tissue were studied by using cytoarchitectonic and immunohistochemical stainings. We mapped the catecholaminergic afferents by employing antisera directed against tyrosine hydroxylase and dopamine-beta-hydroxylase enzymes. The epileptic activity was correlated with the underlying patterns of cytoarchitectonic and immunohistochemical changes. The neuropathological features were focal and consisted of large neurons dispersed through all but the first cortical layer (associated in one case to giant glial cells), of variable disturbance of lamination, of neuronal ectopia in the white matter and of moderate proliferation of small glial cells. Areas of seizure onset coincided with that of dysplastic zones. Both laminar distribution and density of catecholaminergic fibers were altered in the dysplastic cortices (area of seizure onset) and there was an increase in the density of tyrosine hydroxylase-immunoreactive fibers in the surrounding areas of seizure propagation. Our results indicate that these developmental epileptogenic lesions were associated with abnormal neuronal circuitry. They provide evidence at the structural level of the increase in tyrosine hydroxylase activity previously reported in spiking areas of human epileptogenic cerebral cortex and they suggest that catecholamines may contribute toward limiting seizure activity propagation.

Alterations in monoamine levels in discrete regions of rat brain after chronic administration of carbamazepine

Carbamazepine (25 mg/kg body weight) was administered intraperitoneally to adult male Wistar rats for 45 days and norepinephrine (NE), dopamine (DA) and serotonin (5-HT) levels were simultaneously assayed in discrete brain regions by high performance liquid chromatographic (HPLC) method. Experimental rats displayed no behavioral abnormalities. Body and brain weights were not significantly different from control group of rats. After exposure it was observed that norepinephrine levels were elevated in motor cortex (P < 0.01) and cerebellum (P < 0.05), while dopamine levels were decreased in these two regions (P < 0.001, P < 0.05). However, dopamine levels were increased in hippocampus (P < 0.01). Serotonin levels were significantly decreased in motor cortex (P < 0.001) and hypothalamus (P < 0.001) but increased in striatum-accumbens (P < 0.001) and brainstem (P < 0.001). These results suggest that carbamazepine may mediate its anticonvulsant effect by differential alterations of monoamine levels in discrete brain regions particularly in motor cortex and cerebellum.

Can our knowledge of monoamine oxidase (MAO) help in the design of better MAO inhibitors?

This paper presents a rapid overview of the mechanism by which monoamine oxidase (MAO) catalyzes the deamination of its substrates, and highlights the stereoselective nature of the active site of the enzyme. With the help of a few selected examples it is also discussed which structural factors are thought to have a preponderant influence on the affinity and selectivity of molecules towards the active site of either form of MAO. From the currently available data on the enzyme and its inhibition, it clearly appears that new MAO inhibitors, of whatever type, could be easily designed by structural modulation of molecules already found to have MAO inhibitory properties. As to whether better MAO inhibitors could be envisaged, it is suggested that MAO inhibition might be advantageously combined with other pharmacological properties for the treatment of pathological conditions, such as stroke and epilepsy, to the occurrence of which MAO activity might contribute. The rationale of this approach is presented.

Compensatory function of central dopaminergic system for suppressing psychic seizures--repeated plasma homovanillic acid measurement in refractory temporal lobe epilepsy

Repeatedly measured plasma homovanillic acid concentration, as a clinically available index of central dopaminergic activity in a patient with temporal lobe epilepsy during a drug-free period, was significantly correlated with seizure frequency in the week immediately following, but not preceding, blood sampling days. This result suggests a compensatory function of the dopaminergic system in suppressing refractory psychic seizures.

Polyamine metabolism in epileptic cortex

Polyamine (tissue) concentrations have been studied in hippocampus and temporal neocortex from patients with temporal lobe epilepsy. Depth electrode recordings demonstrated hippocampal origin of the seizures, the temporal neocortex being involved during the discharge propagation. Neuropathological examination of excised tissues showed glial proliferation or glioma in Ammon's horn (CA), whereas the temporal neocortex did not exhibit any histological abnormality. Polyamine (putrescine or PUT, spermidine or SPD, spermine or SPM) concentrations were determined on surgical samples from the hippocampus and various areas of temporal neocortex. Human post-mortem tissue from temporal lobe regions was used for controls. In post-mortem controls and temporal neocortex specimens from epileptic patients, polyamine levels were similar (in nmol/g wet weight: PUT = 40-100; SPD = 200-350; SPM = 100-200). In CA, polyamine levels exhibited striking changes: SPD content was significantly increased (350-700 nmol/g) while SPM was lowered (50-100). PUT was only increased in CA invaded by the tumoral process (100-180). Accordingly, a very high SPD/SPM molar ratio in the abnormal CA region was observed, indicating an acceleration of polyamine neosynthesis which is usually related to ornithine decarboxylase induction. Metabolic changes in polyamines appear to be selective of human epileptic hippocampus. A relationship between glial proliferation (gliosis or neoplasia), epileptic firing and polyamines is discussed.

Cerebrospinal fluid and serum levels of dopa, catechols, and monoamine metabolites in patients with epilepsy

We measured CSF and serum concentrations of monoamines and monoamine metabolites in normal control subjects and in patients with partial epilepsy between and less than 2 h after complex partial seizures (CPS) or secondarily generalized tonic-clonic seizures (SGTCs). After SGTCs, concentrations of norepinephrine in CSF were significantly higher (p less than 0.05) than interictal concentrations, concentrations after PSs, and concentrations in control subjects. Serum epinephrine levels also were significantly higher after SGTCs than interictal and control subjects' levels. CSF HVA levels were significantly higher after PSs than interictal or control subjects' levels. CSF concentrations of norepinephrine and its intraneuronal metabolite, dihydroxyphenylglycol, were highly correlated, both interictally and following SGTCs, whereas correlations between serum and CSF levels of these catechols generally were not statistically significant. The results indicate that seizures are associated with release of catecholamines in the central nervous system.

Quantification of mu and non-mu opiate receptors in temporal lobe epilepsy using positron emission tomography

Alterations in a variety of neurotransmitter systems have been identified in experimental models of epilepsy and in brain tissue from patients with intractable temporal lobe seizures. The availability of new high-affinity radioligands permits the study of some neuroreceptors in vivo with positron emission tomography (PET). We previously characterized the in vivo binding of 11C-carfentanil, a potent and selective mu opiate receptor agonist, and described increases in 11C-carfentanil binding in the temporal neocortex of patients with unilateral temporal lobe epilepsy. These studies have been extended to 11C-diprenorphine, which labels mu, kappa, and delta opiate receptor subtypes. Paired measurements of opiate receptor binding were performed with PET using 11C-carfentanil and 11C-diprenorphine in patients with unilateral temporal lobe seizures. Carfentanil binding, reflecting changes in mu opiate receptors, was increased in the temporal neocortex and decreased in the amygdala on the side of the epileptic focus. Diprenorphine binding, reflecting mu as well as non-mu opiate subtypes, was not significantly different among regions in the focus and nonfocus temporal lobes. Regional glucose metabolism, measured using 18F-2-fluoro-2-deoxyglucose, was decreased in the mesial and lateral aspects of the temporal lobe ipsilateral to the epileptogenic focus. The variation in pattern of carfentanil and diprenorphine binding supports a differential regulation of opiate subtypes in unilateral temporal lobe epilepsy.

Synaptosomal ATPase activities in temporal cortex and hippocampal formation of humans with focal epilepsy

Intact nerve endings (synaptosomes) have been isolated from spiking and non-spiking temporal cortex and hippocampus samples from 14 patients immediately after temporal lobectomy for intractable epilepsy. Synaptosomes were also prepared from frozen brain samples of humans with no known neurological diseases. Four adenosine triphosphatase (ATP)-metabolizing enzymes (ecto-ATPase, ecto-adenylate kinase, Na+,K(+)-ATPase and Ca2+,Mg2(+)-ATPase) were assayed in the synaptosomal fractions from the most spiking temporal cortex area (including focus) as well as from various regions of the hippocampus, and compared with enzyme activities of the least spiking or non-spiking temporal cortex of the same patient. Enzyme activities of the epileptic brain samples were also compared with values measured in the corresponding regions of normal brains. Ecto-ATPase activities of epileptic temporal cortex were decreased (approximately 30%) in both comparisons. In contrast to these findings, a substantially increased (in some cases 300%) ecto-ATPase activity was observed in the posterior part of epileptic hippocampus. We suggest that the higher than normal ecto-ATPase activity in this particular hippocampal region is related to the presence of granule cells and their efferent (or afferent) synaptic connections. The synaptosomal ecto-adenylate kinase showed alterations opposite to the changes found for the ecto-ATPase. The intrasynaptosomal ATPase (Na+,K(+)- and Ca2+,Mg2(+)-) were decreased in the epileptic hippocampus-, but not in the temporal cortex samples, in relation to the corresponding normal enzyme activity values. These complex alterations in synaptosomal ATP-metabolizing enzyme activities may be important elements of seizure development and maintenance in human temporal lobe epilepsy.

Tyrosine hydroxylase-immunoreactive neurons in the temporal lobe in complex partial seizures

The anterior mesial portion of the temporal lobe removed from 16 patients who underwent surgery for the treatment of complex partial seizures was found to contain tyrosine hydroxylase-immunoreactive neurons. The distribution of these neurons was correlated with the underlying neuropathological features. Ammon's horn sclerosis was present in 8 patients; a ganglioglioma, in 7 patients; and an infarction in the distribution of the middle cerebral artery, in 1 patient. Tyrosine hydroxylase-immunoreactive neurons were found in Ammon's horn of 6 of the 8 patients with Ammon's horn sclerosis, and in the subiculum and entorhinal cortex of all 8 patients with the same pathology. None of these neurons were found in Ammon's horn of the 7 patients with a ganglioglioma, but were found in the subiculum of 5 of the 7 patients and in entorhinal cortex of all 7 patients. Tyrosine hydroxylase immunoreactivity was also studied in 13 control autopsy specimens. No tyrosine hydroxylase-immunoreactive neurons were found in Ammon's horn or the subiculum of any of the control specimens, but were found in the entorhinal cortex of 6 of the 13 specimens. The tyrosine hydroxylase-immunoreactive neurons in the mesial portion of the temporal lobe of patients with complex partial seizures may contribute to the increased levels of tyrosine hydroxylase found in neurochemical studies of specimens taken at temporal lobectomy.

Levels of biogenic amines, their metabolites, and tyrosine hydroxylase activity in the human epileptic temporal cortex

The levels of serotonin (5-HT), 5 hydroxyindoleacetic acid (5-HIAA), dopamine (DA), homovanillic acid (HVA), norepinephrine (NE), and tyrosine hydroxylase (TH) activity were measured in the focus (spiking) and nonfocus (nonspiking) regions of the temporal neocortex of 20 patients with intractable complex partial seizures. The levels of 5-HT, DA, 5-HIAA, and HVA were higher in the focus when compared to the nonfocus. Values for NE and TH activity were not different when focus and nonfocus were compared. The ratios of metabolite to precursor for 5-HT and DA were not significantly different between the focus and the nonfocus, suggesting that the changes observed were the result of a modification in the synthesis and release of these amines. Such changes in the epileptic focus could be caused by altered transsynaptic regulatory processes, which occur as a result of neuronal loss, gliosis, or neuronal sprouting.

A study of monoamine metabolism in human epilepsy

Fourteen patients with intractable epilepsy underwent surgical resection of their epileptogenic focus. Hippocampal and temporal cortical samples were obtained, and subjected to high performance liquid chromatography with electrochemical detection. Levels of 5-hydroxyindoleacetic acid (5-HIAA) in actively spiking temporal cortex were 0.454 +/- 0.012 ng/mg (mean +/- SEM), contrasting with less actively spiking cortex values of 0.248 +/- 0.042 ng/mg and normal literature values, obtained from post-mortem material, of 0.140 +/- 0.050 ng/mg. Similarly, homovanillic acid (NVA) levels were significantly increased in epileptic tissue compared to normal literature values. Actively spiking cortex values were 0.172 +/- 0.001 pg/mg, less active cortex values were 0.058 +/- 0.012 pg/mg, and literature values were 0.011 +/- 0.002 pg/mg. Although a direct statistical comparison between the data reported here and literature values may not be valid, the findings show a continuum from normal through increasingly active electrode sites, likely reflecting a true biologic phenomena. Similarly, statistically significant increases in 5-HIAA and HVA levels were found in hippocampal tissue, which also showed significantly lower dihydroxyphenylacetic acid levels. We conclude that raised levels of serotonin and dopamine metabolites in actively spiking cortex likely reflect an increase in their turnover, and are an epileptic epiphenomenon. Exaggeration of turnover may represent the "metabolic noise" of epilepsy, rather than a concerted strategy of local or distal neurons to contain an epileptogenic focus.

Animal models of the epilepsies

The study of mechanisms of the epilepsies requires employment of animal models. Choice of a model system depends upon several factors, including the question to be studied, the type of epilepsy to be modelled, familiarity and convenience. Over 50 models are reviewed. Major categories of models are those for simple partial seizures: topical convulsants, acute electrical stimulation, cortically implanted metals, cryogenic injury; for complex partial seizures: kainic acid, tetanus toxin, injections into area tempesta, kindling, rodent hippocampal slice, isolated cell preparations, human neurosurgical tissue; for generalized tonic-clonic seizures: genetically seizure-prone strains of mouse, rat, gerbil, fruitfly and baboon, maximal electroshock seizures, systemic chemical convulsants, metabolic derangements; and for generalized absence seizures: thalamic stimulation, bilateral cortical foci, systemic penicillin, gamma-hydroxy-butyrate, intraventricular opiates, genetic rat models. The lithium-pilocarpine, homocysteine and rapid repetitive stimulation models are most useful in studies of status epilepticus. Key findings learned from each of the models, the model's strengths and weaknesses are detailed. Interpretation of findings from each of these models can be difficult. Do results pertain to the epilepsies or to the particular model under study? How important are species differences? Which clinical seizure type is really being modelled? In a model are behavior or EEG findings only similar superficially to epilepsy, or are the mechanisms comparable? The wealth of preparations available to model the epilepsies underscores the need for unifying themes, and for better understanding of basic mechanisms of the epilepsies.

Adrenergic mediated phosphatidylinositol metabolism is modulated by epileptic discharges in human neocortex

Adrenergic mediated phosphatidylinositol (PI) hydrolysis was measured in tissues obtained from 21 patients immediately following surgery for focal epilepsy. Accumulation of [3H]inositol monophosphate (IP1) was significantly reduced (21%, P less than 0.01) in actively spiking neocortex (n = 15) versus samples from non-spiking regions (n = 9). Epileptic discharges may blunt alpha 1-adrenoceptor stimulated transmembrane signalling in human neocortical epileptic foci.

Transient changes in cortical alpha 1 adrenoceptors and seizure threshold following electroconvulsive seizures in rats

Alpha 1 adrenoceptor density (Bmax) is consistently decreased in actively spiking human cortical epileptic foci. Interpretation of these unique human data is limited because all surgical excisions are completed shortly after a period of active seizure discharge. To determine the temporal profile of seizure-induced changes in cortical alpha 1 adrenoceptors we examined rats primed by 15 daily electroconvulsive seizures (ECS). Since the noradrenergic system has an inhibitory effect on epileptic activity, we also measured the postictal rise in minimal ECS seizure threshold. Animals were sacrificed immediately before or at intervals after the last scheduled seizure. Cortical membranes were assayed using [3H]prazosin as specific radioligand. Repeated ECS produced an increase in the number of cortical alpha 1 sites from 4 to 24 h postictally, but following the last seizure there was a transient 'normalization' of alpha 1 receptor density which persisted for 3 h. The postictal ECS seizure threshold also remained elevated for a 2 h period. Both these transient postictal changes may in part result from activation of the central NA system. Decreased alpha 1 adrenoceptors in surgical specimens of spiking cerebral cortex may also be a secondary response to focal seizure activity.