Adenosine receptor antagonism accounts for the seizure-prolonging effects of aminophylline

Severe amnestic syndrome due to theophylline toxicity

We report a case of severe amnestic syndrome following theophylline overdose. A woman in her early 30s was admitted to hospital where she developed status epilepticus following an intentional overdose of theophylline and lansoprazole. She developed a profound acidosis and required intubation in the intensive care unit. Following extubation the patient was noted to have a severe amnestic syndrome with poor short-term memory. A work-up to exclude infectious, autoimmune and paraneoplastic causes for encephalitis was undertaken. Cerebrospinal fluid analysis was normal and autoimmune encephalitis titres were negative. Initial MRI brain imaging demonstrated hyperintensities of the mesial temporal lobes bilaterally. Follow-up imaging at 4 months identified further interval reduction but persistent hippocampal hyperintensities. Theophylline toxicity with corresponding amnestic syndrome and hippocampal hyperintensities has been rarely reported. We believe this case with persistent abnormal Montreal Cognitive Assessment Score at 12 months correlates with persistent hippocampal abnormalities seen on imaging.

Dihydropyrimidinones Scaffold as a Promising Nucleus for Synthetic Profile and Various Therapeutic Targets: A Review

BACKGROUND

This review elaborates the updated synthetic and pharmacological approaches of a known group of dihydropyrimidinones/thiones from the multi-component reaction like Biginelli reaction, which was named Pietro Biginelli in 1891. This review consists of the reaction of an aromatic aldehyde, urea and ethyl acetoacetate leading to dihydropyrimidinone/thione. Currently, the scientific movement to develop economically viable green methods using compounds that are reusable, non-volatile, easily obtained, etc. Objective: This review covers the recent synthesis and pharmacological advancement of dihydropyrimidinones/ thiones moiety, along with covering the structure-activity relationship of the most potent compounds, which may prove to become better, more efficacious and safer agents. Thus, this review may help the researchers in drug designing and development of new Dihydropyrimidinones entities.

CONCLUSION

This review focuses on the wide application of dihydropyrimidinone/thione review reports the design, synthesis and pharmacological activities of nitrogen-sulphur containing dihydropyrimidinone moiety by using multi-component reaction. Dihydropyrimidinones (DHPM) pharmacophore is an important heterocyclic ring in medicinal chemistry. It is derived from multi-component reactions, "Biginelli reaction" and plays a critical role as anticancer, antioxidant, antimicrobial, anti-inflammatory, anti-HIV-1, antimalarial, anti-inflammatory, antihypertensive and anti-tubercular agents. Exhaustive research has led to its vast biological profile, with a wide range of therapeutic application.

Effect of acute caffeine administration on PTZ-induced seizure threshold in mice: Involvement of adenosine receptors and NO-cGMP signaling pathway

PURPOSE

Caffeine is a non-selective antagonist of A₁ and A_2A adenosine receptors (ARs). In this regard, nitric oxide (NO) is partly involved in the central effects of caffeine. In this study, we examined the effect of acute caffeine administration on pentylenetetrazole (PTZ)-induced seizure threshold by focusing on A₁Rs, A_2ARs, and NO-cGMP signaling pathway.

METHODS

NMRI male mice (25-30 g) received caffeine (5, 50, and 100 mg/kg) alone, whereas 8-CPT (1 and 5 mg/kg, a selective A₁Rs antagonist), SCH-442416 (5 and 10 mg/kg, a selective A_2ARs antagonist) or sildenafil (5 and 10 mg/kg, a phosphodiesterase 5 inhibitor) were administrated alone or as pre-treatment before caffeine. Seizure threshold was assessed by intravenous infusion of PTZ. Nitric oxide metabolites (NOx) were measured with the Griess method.

RESULTS

When administrated alone, caffeine (5 and 50 mg/kg) and 8-CPT (1 and 5 mg/kg) significantly decreased seizure threshold, while 100 mg/kg of caffeine, SCH-442416 or sildenafil did not change it. Only pre-treatment with SCH-442416 (5 and 10 mg/kg) or sildenafil (5 and 10 mg/kg) before 100 mg/kg of caffeine significantly decreased seizure threshold. Moreover, NOx levels significantly decreased following alone administration of caffeine (100 mg/kg) or 8-CPT (5 mg/kg).

CONCLUSION

The results of present study showed that 5 and 50 mg/kg of caffeine had a proconvulsant effect but caffeine at a dose of 100 mg/kg had no effect on seizure threshold. In addition, it seems that the effect caffeine on seizure threshold is partly mediated through ARs or modulation of the NO-cGMP signaling pathway.

Aminophylline Effect on Renal Ischemia-Reperfusion Injury in Mice

BACKGROUND

Aminophylline increases the intracellular concentration of cAMP and exerts an anti-inflammatory effect. The aim of this study was to investigate the effect of aminophylline on renal ischemia-reperfusion (I/R) injury in mice.

METHODS

Thirty C57BL/6 mice were divided into 3 groups. In the sham group (group S, n = 10), only right nephrectomy was performed. In the control group (group C, n = 10), after right nephrectomy, the mice were subjected to 30 minutes of left renal ischemia. In the aminophylline group (group A, n = 10), an intraperitoneal injection of aminophylline (5 mg/kg) was performed before renal ischemia. Twenty-four hours after reperfusion, the mice were euthanized, and plasma and kidney samples were obtained to analyze the serum creatinine, renal histology, and expression levels of nuclear factor-kappa B (NF-kB) and pro-inflammatory cytokines.

RESULTS

The serum creatinine concentration in group C was markedly elevated at 24 hours after reperfusion. Aminophylline treatment significantly reduced serum creatinine, compared with group C. Aminophylline also reduced the histological evidence of renal damage. The expression levels of NF-kB, tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory protein-2 (MIP-2), and intercellular adhesion molecule-1 (ICAM-1) mRNA were significantly increased in group C (P < .001). Group A showed lower expression of NF-kB, TNF-α, MCP-1, MIP-2, and ICAM-1 mRNA than group C (P < .01).

CONCLUSIONS

Aminophylline treatment improved the renal function and indexes of renal inflammation, which suggests that it provided reno-protection against renal I/R injury.

Recent synthetic and medicinal perspectives of dihydropyrimidinones: A review

Dihydropyrimidines are the most important heterocyclic ring systems which play an important role in the synthesis of DNA and RNA. Synthetically they were synthesized using Multi-component reactions like Biginelli reaction and Hantzschdihydropyridine. In the past decades, such Biginelli type dihydropyrimidones have received a considerable amount of attention due to the interesting pharmacological properties associated with this heterocyclic scaffold. In this review, we highlight recent developments in this area, with a focus on the DHPMs, recently developed as anti-inflammatory, anti-HIV, anti-tubercular, antifungal anticancer, antibacterial, antifilarial, antihyperglycemic, antihypertensive, analgesic, anti-convulsant, antioxidant, anti-TRPA1, anti-SARS, and anti-cancer activity and α_1a binding affinity.

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This review is focused on synthetic prospective of dihydropyrimidinones.

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This review is also focused on medicinal prospective of dihydropyrimidinones.

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It includes structure-activity relationship study of different activities.

NTPDase and 5'-nucleotidase activities in synaptosomes of rabbits experimentally infected with BoHV-5

Bovine herpesvirus type 5 (BoHV-5) is the causative agent of herpetic meningoencephalitis in cattle. The purinergic system is described as a modulator of the immune response and neuroinflammation. These functions are related to the extracellular nucleotides concentration. NTPDase and 5'-nucleotidase are enzymes responsible for controlling the extracellular concentration of adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), and adenosine (ADO). The aim of this study is to determinate the ectonucleotidase activity in cortical synaptosomes and synaptosomes from the hippocampus of rabbits experimentally infected with BoHV-5. Rabbits were divided into four groups, two control groups (non-inoculated animals), and two infected groups (inoculated with BoHV-5). The infected groups received 0.5 ml of BoHV-5 suspension with 10(7.5)TCID50 of viral strain SV-507/99, per paranasal sinuses, and the control groups received 0.5 ml of minimum essential media per paranasal sinuses. Animals were submitted to euthanasia on days 7 and 12 post-inoculation (p.i.); cerebral cortex and hippocampus were collected for the synaptosomes isolation and posterior determination of the ectonucleotidase activities. The results showed a decrease (P < 0.05) in ectonucleotidase activity in synaptosomes from the cerebral cortex of infected rabbits, whereas an increased (P < 0.05) ectonucleotidase activity was observed in synaptosomes from the hippocampus. These differences may be related with the heterogeneous distribution of ectonucleotidases in the different brain regions and also with the viral infectivity. Therefore, it is possible to speculate that BoHV-5 replication results in changes in ectonucleotidase activity in the brain, which may contribute to the neurological signs commonly observed in this disease.

Early caffeine exposure: transient and long-term consequences on brain excitability

The influence of pre- and postnatal caffeine treatment on brain excitability during development and adulthood is reviewed. Pre- and postnatal exposure to caffeine induces sex- and age-specific long-term neurochemical alterations in the brain and the behavior of rodents. Because adenosine neuromodulation is closely related to the regulation of brain excitability the increased expression in adenosine receptor system due to neonatal caffeine treatment should cause transient and permanent changes in seizure susceptibility. So far, findings have been focused on primarily developmental changes of the brain adenosine modulatory system and have demonstrated that the alterations are not restricted to a single brain region. Neurobehavioral changes and the anticonvulsant effect of early caffeine exposure are dependent on the caffeine dose, developmental stage of exposure and age of testing. Although outcomes of caffeine treatment are still a matter of debate, our review raise questions concerning the impact of early caffeine treatment on regulation of seizure susceptibility during development and adulthood.

Initial experience using aminophylline to improve renal dysfunction in the pediatric cardiovascular ICU

OBJECTIVE

To determine if aminophylline administration is associated with improved creatinine clearance and greater urine output in children with acute kidney injury in the cardiovascular ICU.

DESIGN

Single-center retrospective cohort study.

SETTING

Pediatric cardiovascular ICU, university-affiliated children's hospital.

PATIENTS

Children with congenital or acquired heart disease in the cardiovascular ICU who received aminophylline to treat oliguric acute kidney injury and fluid overload.

INTERVENTIONS

Patients received aminophylline after consultation with a pediatric nephrologist. Data were collected retrospectively over 7 days to assess if aminophylline was associated with improvement in creatinine clearance, urine output, and fluid overload.

MEASUREMENTS AND MAIN RESULTS

Thirty-one patients received 52 aminophylline courses. Over the 7-day study period, serum creatinine decreased from a mean of 1.13 ± 0.91 to 0.87 ± 0.83 mg/dL (-0.05 mg/dL/d, p < 0.001). A concomitant increase was seen in estimated glomerular filtration rate from a mean of 50.0 ± 30.0 to 70.6 ± 58.1 mL/min/1.73 m (+3.66 mL/min/1.73 m/d, p < 0.001). Average daily urine output increased by 0.22 mL/kg/hr (p < 0.001), and fluid overload decreased on average by 0.42% per day in the 7-day study period (p = 0.005). Although mean furosemide dose increased slightly (0.12 mg/kg/d, p = 0.01), hydrochlorothiazide dosing did not significantly change over the study period. There were no complications related to aminophylline administration.

CONCLUSIONS

Our study suggests that aminophylline therapy may be associated with significantly improved renal excretory function and may augment urine output in children who experience oliguric acute kidney injury in the cardiovascular ICU. Additionally, we did not identify any aminophylline-related side effects in this high-risk cardiac population. Future prospective studies are necessary to confirm the safety profile and to ensure that the beneficial effects are independent of other clinical interventions.

Rolofylline, an adenosine A1-receptor antagonist, in acute heart failure

BACKGROUND

Worsening renal function, which is associated with adverse outcomes, often develops in patients with acute heart failure. Experimental and clinical studies suggest that counterregulatory responses mediated by adenosine may be involved. We tested the hypothesis that the use of rolofylline, an adenosine A1-receptor antagonist, would improve dyspnea, reduce the risk of worsening renal function, and lead to a more favorable clinical course in patients with acute heart failure.

METHODS

We conducted a multicenter, double-blind, placebo-controlled trial involving patients hospitalized for acute heart failure with impaired renal function. Within 24 hours after presentation, 2033 patients were randomly assigned, in a 2:1 ratio, to receive daily intravenous rolofylline (30 mg) or placebo for up to 3 days. The primary end point was treatment success, treatment failure, or no change in the patient's clinical condition; this end point was defined according to survival, heart-failure status, and changes in renal function. Secondary end points were the post-treatment development of persistent renal impairment and the 60-day rate of death or readmission for cardiovascular or renal causes.

RESULTS

Rolofylline, as compared with placebo, did not provide a benefit with respect to the primary end point (odds ratio, 0.92; 95% confidence interval, 0.78 to 1.09; P=0.35). Persistent renal impairment developed in 15.0% of patients in the rolofylline group and in 13.7% of patients in the placebo group (P=0.44). By 60 days, death or readmission for cardiovascular or renal causes had occurred in similar proportions of patients assigned to rolofylline and placebo (30.7% and 31.9%, respectively; P=0.86). Adverse-event rates were similar overall; however, only patients in the rolofylline group had seizures, a known potential adverse effect of A1-receptor antagonists.

CONCLUSIONS

Rolofylline did not have a favorable effect with respect to the primary clinical composite end point, nor did it improve renal function or 60-day outcomes. It does not show promise in the treatment of acute heart failure with renal dysfunction. (Funded by NovaCardia, a subsidiary of Merck; ClinicalTrials.gov numbers, NCT00328692 and NCT00354458.).

Haemodynamic effects of rolofylline in the treatment of patients with heart failure and impaired renal function

AIMS

The direct effects of adenosine A1 receptor antagonists on haemodynamic parameters in patients with acute heart failure (HF) remain largely unknown.

METHODS AND RESULTS

We evaluated the haemodynamic effects of the AA(1)RA rolofylline in 59 HF patients with concomitant renal impairment (estimated creatinine clearance 20-80 mL/min). Placebo or rolofylline 30 mg was administered as a 4 h infusion followed by intravenous (i.v.) loop diuretic administration. Haemodynamic measurements were carried out hourly up to 8 h post-dosing by pulmonary artery catheterization. Urine output, fractional excretion of sodium, potassium, urea, and uric acid, and blood urea nitrogen (BUN) and creatinine levels were also measured. In both groups, the changes from baseline in all haemodynamic indices except mean pulmonary artery pressure (PAP) were not clinically significant. Mean [95% confidence interval (CI)] PAP showed a placebo-adjusted decrease with rolofylline of -1.5 (-4.1, 1.1)mmHg at Hour 4 and -3.5 mmHg (95% CI: -6.2, -0.2) at Hour 8. There was a significant increase with rolofylline in diuresis [placebo-corrected mean (95% CI) change of 68 (20, 116)mL/h at Hour 2-4 and 103 (21, 185)mL/h at Hour 4-8] and in fractional excretion of sodium, potassium, and uric acid. Placebo-corrected changes in plasma levels of creatinine and BUN with rolofylline were non-significant.

CONCLUSION

Single administration of rolofylline in patients with HF and impaired renal function produced a slight decrease in mean PAP and consistently increased diuresis and natriuresis without compromising renal function, both before and after administration of i.v. loop diuretics.

Anticonvulsant action of 2-chloroadenosine against pentetrazol-induced seizures in immature rats is due to activation of A1 adenosine receptors

Potentiation of adenosinergic inhibitory modulation is one of possible strategies to develop new antiepileptic drugs. Nonspecific receptor agonist 2-chloroadenosine was tested against pentetrazol-induced convulsions in immature (7, 12, 18 and 25 days old) and adult rats. Doses of 1-15 mg/kg i.p. suppressed tonic phase of generalized tonic-clonic seizures (GTCS) in the two youngest groups, whereas GTCS were abolished in older rats. Minimal clonic seizures in 18-day and older rats were suppressed by high doses of 2-chloroadenosine. The role of A1 and A2A adenosine receptors was studied in 12- and 25-day-old rats. Action of an agonist of A1 receptors CCPA is similar to that of 2-chloroadenosine. An agonist of A2A receptors CGS 21680 exhibits an anticonvulsant action only in the dose-inducing catalepsy; an A2A antagonist ZM 241385 moderately suppressed tonic phase of GTCS only in 12-day-old animals. Anticonvulsant action of adenosine agonists is due to their effects on A1 receptors.

Effects of early postnatal caffeine exposure on seizure susceptibility of rats are age- and model-dependent

Repeated caffeine treatment during early postnatal period led to a decreased sensitivity to convulsant action of drugs interfering with inhibitory systems. To know if it is a general effect we studied convulsant action of agonists of glutamate receptors N-methyl-d-aspartate (NMDA) and kainic acid (KA). Early (the first day after the last injection) and delayed (at postnatal day (P) 25) consequences of daily administration of caffeine at P7-P11 or P13-P17 days were studied. Two doses (one submaximal and one supramaximal) of either drug were chosen for each age group on the basis of our older data demonstrating decreasing sensitivity during postnatal development. Both early and delayed proconvulsant effects of submaximal doses of either agonist were observed in P7-P11 groups, early effect was markedly expressed; the effects of the supramaximal doses were not affected. The other administration group (P13-P17) also exhibited an increased sensitivity to convulsant action but delayed effects were more pronounced than early consequences especially with supramaximal doses of both agonists. In contrast to a decreased sensitivity to drugs suppressing inhibitory systems, seizures induced by glutamate receptor agonists are potentiated in caffeine-treated immature rats. Timing of caffeine administration and interval between the last exposure and testing play an important role.

Evidence for the involvement of the adenosine A(2A) receptor in the lowered susceptibility to pentylenetetrazol-induced seizures produced in mice by long-term treatment with caffeine

Long-term caffeine intake has been reported to decrease the susceptibility to convulsants in mice. Occurrence of seizures following long-term oral administration of caffeine (0.3g/l) was investigated using adenosine A(2A) receptor knockout (A(2A)R KO) and control (A(2A)R WT) mice. Clonic seizures induced by acute pentylenetetrazol (PTZ, 50mg/kg i.p.) were significantly attenuated in adenosine A(2A)R KO mice drinking only water and reduced by a 14-day caffeine treatment in adenosine A(2A)R WT mice. In addition we showed a protecting effect of a 21-day caffeine treatment in A(2A)R WT mice against kindled seizures induced by PTZ in an increasing dose schedule. Summing up, these protective effects against PTZ-induced seizures occurring when adenosine A(2A)R is absent or chronically blocked by a relevant dose of caffeine may be related to a decreased neuronal excitability.

Effects of postnatal caffeine exposure on seizure susceptibility in developing rats

Postnatal caffeine treatment of rats can influence brain excitability during development. To study the mechanism involved in the alterations of seizure susceptibility, we used an animal model that corresponds to the infants treated with caffeine for apnea of prematurity. Seizure susceptibility to four convulsant drugs (pentetrazol, picrotoxin, bicuculline and aminophylline) was assessed in 12- and 25-day-old rats exposed to caffeine at a daily dose of 10 and/or 20 mg/kg s.c. at postnatal days 7-11. Our results demonstrated that the changes in generalized tonic-clonic seizures (GTCS) are more expressed than changes in minimal clonic seizures. There are marked differences among individual convulsants with the highest sensitivity of aminophylline-induced seizures and nearly complete resistance of bicuculline-induced seizures. The changes in individual models are age specific: aminophylline- and picrotoxin-induced seizures are more affected in 12- than in 25-day-old rats whereas PTZ-induced seizures are more changed by early postnatal caffeine exposure in 25- than in 12-day-old animal. Taken together, repeated caffeine treatment from postnatal day 7 to 11 reduces the seizure susceptibility during development and this reduction is also model specific.

Effect of acute versus chronic theophylline administration on acute restraint stress-induced increase of pentylenetetrazol seizure threshold in mice

Various stressful paradigms were found to induce anticonvulsant effects in different seizure models. Methylxanthines, such as theophylline might contribute to the reduction of restraint-induced stress. Therefore, in this study the influence of acute restraint stress on pentylenetetrazol (PTZ) seizure thresholds as well as the effect of acute and chronic theophylline pretreatment on stress-induced modulation of the seizure threshold were assessed in mice. The onset of the three consecutive seizure phases: myoclonic twitch (MTW), generalized clonus (GNCL) and tonic hind limb extension (THE) was delayed after exposure to a 2 h restraint stress by 34%, 23% and 24%, respectively. In nonstressed mice, acute theophylline injection (100 mg/kg, i.p.) decreased the threshold only for THE. However, in stressed animals, the pretreatment with the methylxanthine significantly enhanced the dose of the convulsant producing the same seizure phase. In nonstressed mice, long-term theophylline treatment (50 mg/kg, twice daily for 14 days) increased PTZ threshold for all three seizure phases. In contrast, in chronically treated with theophylline mice exposed to restraint stress, significant decrease in the PTZ threshold for all seizure phases compared to control stressed animals have been observed. These results suggest that, depending on the treatment regimen (acute versus chronic), theophylline specifically and differentially modulates the anticonvulsant effect of restraint stress in mice.

Consequences of Prolonged Caffeine Administration and Its Withdrawal on Pilocarpine- and Kainate-induced Seizures in Rats

PURPOSE

To investigate the consequences of caffeine consumption on epileptic seizures, we used the pilocarpine and the kainate models of epilepsy. We hypothesized that prolonged caffeine consumption or its withdrawal would alter adenosine levels and hence alter seizure susceptibility.

METHODS

We administered a 0.1% caffeine solution in the drinking water of adult male Wistar rats over a 2-week period. We challenged another group of animals with the same doses of pilocarpine or kainate 12 h after the withdrawal of the same caffeine-administration protocol.

RESULTS

This did not alter the threshold for the induction of seizures by a subconvulsant dose of pilocarpine (200 mg/kg, i.p.) or kainic acid (8 mg/kg, i.p.). Similarly, challenging another group of animals with the same doses of pilocarpine or kainate 12 h after the withdrawal of the same caffeine-administration protocol did not lead to any significant changes in seizures.

CONCLUSIONS

With the pilocarpine model of epilepsy, we were not able to find any significant difference in seizure profile that could stem from either caffeine administration or its withdrawal. Despite the extensive laboratory evidence on the convulsant properties of xanthine derivatives in animal models of epilepsy, such strong evidence is lacking in clinical settings. Our current findings with the administration of caffeine at doses similar to those of daily life both support and confirm the clinical experience.

Toluene exposure increases aminophylline-induced seizure susceptibility in mice

The effects of toluene on the sensitivity to seizures induced by aminophylline were investigated. Mice were pretreated with an ip injection of corn oil or toluene (100-500 mg/kg) followed by a timed intravenous infusion of aminophylline at various time intervals to assess the seizure thresholds and lethal doses. Toluene increased seizure susceptibility to aminophylline in a dose- and time-dependent manner. Toluene-induced enhancement of seizure susceptibility to aminophylline occurred as early as 30 min and persisted for at least 3 days after a single administration of toluene (500 mg/kg). Treatment of benzaldehyde, one of toluene's metabolites, also showed an increase in the susceptibility to aminophylline. The enhancing effect was also observed in caffeine-induced seizures 1 h, but not 1 day after toluene treatment. These results suggest that individuals with toluene exposure may increase the risk for convulsive and even lethal complications associated with the therapeutic use of aminophylline.

Prolonged low-dose caffeine exposure protects against hippocampal damage but not against the occurrence of epilepsy in the lithium-pilocarpine model in the rat

PURPOSE

Acute caffeine exposure has proconvulsant effects and worsens epileptic and ischemic neuronal damage. Surprisingly, prolonged caffeine exposure decreases the susceptibility to seizures and the extent of ischemic damage. We explored whether the exposure to a low long-term dose of caffeine could protect the brain from neuronal damage and epileptogenesis in the lithium-pilocarpine model of temporal lobe epilepsy.

METHODS

Rats received either plain tap water or water containing caffeine (0.3 g/L) for 15 days before the induction of status epilepticus (SE) by lithium-pilocarpine and for 7 days after SE. The extent of neuronal damage was assessed in the hippocampus and piriform and entorhinal cortices in brain sections stained with thionine and obtained from animals killed 7 days after SE. The latency to spontaneous recurrent seizures was controlled by video monitoring.

RESULTS

Caffeine treatment induced a marked, almost total neuroprotection in CA1 and a very limited protection in the hilus of the dentate gyrus, whereas damage in layers III-IV of the piriform cortex was slightly worsened by the treatment. All rats, whether they received caffeine or plain tap water, became epileptic after the same latency (17-19 days).

CONCLUSIONS

Thus these data extend the neuroprotective effects of low long-term caffeine exposure to epileptic damage and confirm that the sole protection of the Ammon's horn has no influence on the genesis of spontaneous recurrent seizures in this model.

Changes of cortical epileptic afterdischarges under the influence of convulsant drugs

Convulsant drugs picrotoxin (0.5 and/or 1 mg/kg, intraperitoneal (i.p.)) and pentylenetetrazol (10 and/or 20 mg/kg, i.p.) were used to compromise GABAergic inhibition, caffeine (75 and/or 150 mg/kg, i.p.) to antagonize adenosinergic system to study the role of inhibition in cortical epileptic afterdischarges. Rats with implanted cortical stimulation and registration electrodes were stimulated four times at 10-min intervals, drugs were injected between the first and second stimulation. Four different phenomena were evaluated: movements directly bound to stimulation were intensified by all three drugs, i.e., excitability of the cerebral cortex was increased. Incidence of two types of afterdischarges (spike-and-wave rhythm and "limbic" type) was not changed by any drug, i.e., the transition of epileptic activity into limbic structures was not increased. Afterdischarges were most efficiently prolonged by caffeine, i.e., caffeine probably interferes with mechanism(s) arresting cortical afterdischarges. The intensity of clonic seizures accompanying spike-and-wave afterdischarges, i.e., spread of epileptic activity into the motor system was only transiently increased by picrotoxin, the effects of caffeine did not reach the level of statistical significance. Our results indicate various mechanisms and diverse role of the two inhibitory systems in generation of evaluated phenomena.

Effect of theophylline and trimethobenzamide when given during kainate-induced status epilepticus: an improved histopathologic rat model of human hippocampal sclerosis

PURPOSE

The most common pathology in temporal lobe epilepsy (TLE) is hippocampal sclerosis. It is controversial whether status epilepticus (SE) or prolonged seizures plus secondary cerebral injuries are pathogenic mechanisms of hippocampal sclerosis. This study addressed this question in rat models of TLE.

METHODS

Hippocampal neuron densities and supragranular mossy fiber sprouting were determined in adult rats subjected to systemic kainate-induced SE (KA-only) and KA-induced SE followed 75 minutes later by theophylline (KA/Theo) or trimethobenzamide (KA/Tri). These drugs probably decrease seizure-induced cerebral hyperemia or hypertension.

RESULTS

Compared with controls and KA-only rats, KA/Tri and KA/Theo rats showed decreased CA3b and CA1 neuron densities (i.e., greater Sommer's sector injury). In addition, KA/Tri rats showed that increased trimethobenzamide dosages were associated with decreased hilar, CA3c, CA3b, CA1, and subiculum neuron densities. There were no significant differences in supragranular mossy fiber sprouting between KA-only, KA/Tri, and KA/Theo rats.

CONCLUSIONS

Pharmacologic manipulations during KA-induced SE are associated with differences in hippocampal pathology, especially in Sommer's sector, and the final pattern of damage and axon sprouting shows histopathologic similarities to that in patients with hippocampal sclerosis. Our findings support the hypothesis that secondary physiologic insults during SE that are likely to decrease seizure-induced cerebral hyperemia and hypertension may generate greater hippocampal neuronal injury compared with SE alone, and this may be a pathogenic mechanism of human hippocampal sclerosis in patients with TLE.

Proconvulsant effect of aminophylline on cortical epileptic afterdischarges varies during ontogeny

Effect of aminophylline on epileptic afterdischarges (ADs) induced repeatedly by rhythmic electrical stimulation of sensorimotor cortical area was studied in rat pups 12, 18 and 25 days old. The proconvulsant effect of aminophylline (50 and/or 100 mg/kg i.p.) was more expressed in 12- and 18-day-old rats than in the oldest group. In 12-day-old rat pups there was an enormous increase of transition of the spike-and-wave type of ADs into the second, limbic type, a situation observed only exceptionally under control conditions. A prolongation of ADs was related to this transition (limbic ADs are always longer than spike-and-wave ones). Eighteen-day-old rats exhibit this transition less frequently but a marked prolongation of spike-and-wave ADs was recorded in a part of these animals forming a pattern of status lasting some tens of minutes. Aminophylline led only to a transient prolongation of spike-and-wave ADs in the oldest group. The transition into the limbic type of ADs was seen in this age group only exceptionally what is in contrast to age-matched controls in which this transition is common. The effect of aminophylline on cortical ADs which is most marked in the youngest group changes qualitatively during postnatal development.

Lethal seizures predicted after aminophylline therapy in cocaine abusers

Mice with a history of chronic (10 days), but not acute, treatment with a non-convulsant dose of cocaine showed increased sensitivity (P<0.001) to the toxic effects of aminophylline (seizures, lethality) relative to controls even days after the cessation of cocaine treatment. The present finding suggests that individuals with a history of cocaine use may be at increased risk for convulsive and lethal complications associated with the therapeutic use of aminophylline.

Widespread expression of ecto-apyrase (CD39) in the central nervous system

We have shown that ecto-apyrase protein is expressed in primary neurons and astrocytes in cell culture (T.-F. Wang, P.A. Rosenberg, G. Guidotti, 1997. Mol. Brain Res. 1997, 47: 295-302). Here we present immunohistochemical studies showing that ecto-apyrase protein is widely distributed in rat brain, as it is present in neurons of the cerebral cortex, hippocampus and cerebellum as well as in glial cells and endothelial cells. Ecto-apyrase is enriched in brain postsynaptic density membrane fractions and is localized in proximity to synaptophysin, the marker of synaptic vesicles. These results together with the observation that P2 purinergic receptors are present throughout the brain suggest that ecto-apyrase is involved in regulating synaptic transmission mediated by extracellular ATP.

Therapeutic doses of theophylline exert proconvulsant effects in developing mice

We studied the effect of therapeutic doses of theophylline on electrically-induced convulsions in developing mice. A theophylline dose as small as 3 mg/kg increased seizure susceptibility of 21-day-old mice, but not of 42-day-old mice. These findings were consistent with clinical reports that theophylline at the therapeutic blood concentrations occasionally induced convulsions in children. The age-dependent proconvulsant effect of theophylline was well inhibited by phenobarbital (PB), dose-dependently, but not by other well-established antiepileptic drugs (AEDs). PB may be a good choice of AED in patients with bronchial asthma and seizure disorders, if PB is indicative for their seizure types. The proconvulsant effect of theophylline in 21-day-old mice was counteracted by not only an adenosine A1 agonist, but also an NMDA antagonist and a histamine H3 antagonist. Several studies have established that the proconvulsant effect of theophylline intoxication is mainly due to the blockade of adenosine A1 receptors. The present findings suggested that the proconvulsant properties of therapeutic doses of theophylline in developing period were different from those of theophylline intoxication. Combination of therapeutic doses of theophylline and centrally-acting histamine H1 antagonists showed proconvulsant effects even in 42-day-old mice, suggesting that peripherally acting histamine H1 antagonists, such as astemizole, evastine and epinastine, were much safer than centrally acting histamine H1 antagonists for patients with both allergy and seizure history.

Characterization of brain ecto-apyrase: evidence for only one ecto-apyrase (CD39) gene

A rat brain cDNA coding for ecto-(Ca,Mg)-apyrase activity was isolated using human CD39 cDNA and functionally expressed in COS-7 cells. The gene codes for a protein with high similarity to human (75% identity) and murine (90% identity) CD39. It is expressed in primary neurons and astrocytes in cell culture as well as in kidney, liver, muscle and spleen. Southern analysis of the mouse genome suggests that there may be a single copy of the ecto-apyrase gene. Interestingly, the human CD39 gene cytologically co-localizes with the susceptibility gene involved in human partial epilepsy with audiogenic symptoms; such a coincidence is consistent with reports on the deficiency of ecto-apyrase activity in the brains of humans with temporal lobe epilepsy and in those of mice with audiogenic seizures.

Kindled seizures do not affect adenosinergic inhibition of DA or ACh release in rat accumbens or PFC

Epileptic seizures are thought to terminate largely as a result of the extracellular accumulation of the purinergic neuromodulator, adenosine, released by discharging neurons. However, the postictal surge in extracellular adenosine and its widespread inhibitory effects are limited in time to only a few minutes and cannot directly account for increased resistance to seizures and the complex behavioural and motivational effects that may persist for hours or days after a seizure. The present study examined whether kindled seizures might alter the sensitivity or efficacy of inhibitory presynaptic adenosine receptors, and thereby induce more enduring changes in downstream transmitter systems. Rats were kindled in the amygdala of the dominant cerebral hemisphere, contralateral to the preferred direction of rotation, and their brains were removed either 2 h or 28 days after completion of kindling. Inhibition of electrically stimulated release of dopamine (DA) and acetylcholine (ACh) by the A1 adenosine-receptor agonist, R-phenylisopropyladenosine (R-PIA) was then measured in the prefrontal cortex (PFC) and nucleus accumbens. R-PIA (1.0 microM) inhibited [1H]DA release from PFC and nucleus accumbens tissue, and [14C]ACh release from nucleus accumbens tissue, but release was unaffected by prior kindling, regardless of the intervening interval. These results do not support suggestions that DA or ACh might mediate the effects of seizure-induced changes in purinergic inhibitory tone so as to cause long-term shifts in seizure threshold and postictal behavior.

Psychopharmacologic violence associated with cocaine abuse: kindling of a limbic dyscontrol syndrome?

1. An association of cocaine abuse with aggressive or violent behavior arising from direct pharmacologic effects of cocaine is demonstrable in the forensic and clinical literature. 2. The neurobehavioral basis for this association is considered form among known CNS actions of cocaine. A hypothesis is developed concerning the role of pharmacological kindling by cocaine that may sensitize for release of limbic-hypothalamic mechanisms of aggressive behavior, and for a drug-induced dyscontrol syndrome. 3. Parallels are drawn to kindling by electrical stimuli, and to neurophysiological research on mechanisms of aggression. 4. A role of concurrent hyperthermic effects of cocaine is suggested. 5. Potential contributions of cocaine actions on CNS serotonergic, catecholaminergic and/or adenosinergic systems are considered. 6. A likely role of concurrent ethanol ingestion to enhance the manifestation of cocaine-associated violence is recognized. 7. Pharmacological challenges, lidocaine or caffeine, are suggested as a means of detecting lowered thresholds of limbic excitability as a consequence of repeated cocaine exposures.

Loss of A1 adenosine receptors in human temporal lobe epilepsy

Using quantitative receptor autoradiographic methods we have examined A1 adenosine receptors, adenosine uptake sites, benzodiazepine receptors, NMDA, AMPA, and kainic acid receptors in temporal lobes removed from patients suffering from complex partial seizures and in normal control post-mortem temporal cortex. Binding to A1 adenosine receptors and NMDA receptors was reduced in epileptic temporal cortex, while the other neurochemical parameters were unchanged. The reason for this A1 receptor loss is unclear as it occurred in both idiopathic and symptomatic cases and thus may be a consequence rather than an initial cause of seizures. However, because adenosine is a powerful anticonvulsant substance, loss of anticonvulsant A1 receptors may contribute to the human epileptic condition. It is also possible that the observed differences in A1 binding are due to autopsy vs. biopsy changes in the levels of A1 adenosine receptors.

Adenosine in acute theophylline intoxication

Although it appears that adenosine would be theoretically useful in the emergent therapy of theophylline toxicity, published clinical data supporting the efficacy and safety of using adenosine for such a situation are currently lacking. The use of adenosine also is not without some risk. In addition, the use of adenosine infusions can be relatively expensive. Until more clinical evidence can be obtained, the routine use of adenosine in the treatment of acute theophylline ingestion cannot be recommended.

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.

Calcium channel blockers improve hypoxia/hypoglycemia-induced impairment of rat hippocampal 2-deoxyglucose uptake in vitro after ethanol withdrawal

The aim of the present study was to determine whether calcium channel antagonists attenuated hypoxia/hypoglycemia- or glutamate-induced reduction in 2-deoxyglucose (2-DG) uptake of hippocampal slices obtained from ethanol withdrawal rats. Ethanol withdrawal significantly potentiated the hypoxia/hypoglycemia- and glutamate-induced reductions in 2-DG uptake of hippocampal slices. Both nifedipine and flunarizine exhibited attenuating effects on ethanol withdrawal-induced potentiation of impairment of 2-DG uptake caused by hypoxia/hypoglycemia or glutamate. Hypoxia/hypoglycemia-induced deficit of 2-DG uptake was prevented by ethanol, but chronic consumption of ethanol resulted in the development of tolerance to neuroprotective effect. These findings suggest that the increased sensitivity of neurons to ischemic damage by ischemia may involve in the increased activity of calcium channels in the hippocampus.

Amnesic syndrome after theophylline associated seizures: iatrogenic brain injury

Two patients developed a disabling amnesic syndrome after seizures associated with oral theophylline treatment. Such seizures are more likely in the elderly, in the presence of pre-existing neurological disease, and when theophylline is given with certain antibiotics and cimetidine. The mechanism of neuronal injury may be by the excessive release of endogenous excitotoxic glutamate.

Effect of an adenosine antagonist and an adenosine agonist on status entry and severity in a model of limbic status epilepticus

Adenosine is an endogenous neuromodulator that suppresses excitatory neurotransmission. We postulated that adenosine-mediated mechanisms resist status epilepticus (SE) entry and limit SE severity. In the first experiment rats were given an adenosine agonist (2-chloroadenosine), an adenosine antagonist (aminophylline), or saline vehicle, prior to SE induction with pulsed-train current delivered to amygdala in successive 5-min current-on sessions. Saline-treated animals entered limbic SE, with predominantly exploratory behavior, after 6.0 +/- 0.9 current-on sessions. Aminophylline increased major convulsive activity during stimulation and resulted in entry into convulsive SE after only 2.1 +/- 0.1 sessions. 2-Chloroadenosine, in contrast, suppressed major convulsive activity during stimulation, and blocked (in 3/7) or delayed (4/7) SE entry, with successes requiring 12.8 +/- 0.9 stimulation sessions. In a second experiment, animals already in exploratory SE were administered a single injection of saline vehicle, aminophylline, or 2-chloroadenosine. Aminophylline converted exploratory SE into lethally severe convulsive SE. 2-Chloroadenosine suppressed SE behaviorally and electrographically, and protected recipients from the seizure-associated cerebral damage seen in saline-administered SE controls. These results support the hypothesis that endogenous adenosine mechanisms resist SE entry, modulate the severity of ongoing SE, and limit the anatomic spread of seizure activity.

Autoradiographic analysis of serotonin receptors and transporter in kindled rat brain

While serotonin (5-HT) has been shown to be anticonvulsant in several types of experimentally induced seizures, 5-HT receptor binding has not been investigated in the kindling model of epilepsy. The present study examined the effects of amygdala kindling on two 5-HT receptor subtypes and on the 5-HT transporter in rat brain. Kindling induced a persistent bilateral increase in 5-HT1A binding in the dentate gyrus, while 5-HT1B receptors increased only in a delayed fashion. Binding to the 5-HT transporter was transiently decreased in dentate gyrus. In cerebral cortex, binding of the three ligands was unchanged. Alterations in 5-HT receptors and the 5-HT transporter may endogenously modulate kindled seizures. Additionally, autoradiography of adenosine A1 receptors revealed no change for these receptors in any brain region.

Differential effects of various xanthines on pentylenetetrazole-induced seizures in rats: an EEG and behavioural study

The present study deals with the EEG (electroencephalogram) and behavioural effects of a subconvulsant dose (30 mg/kg i.p.) of pentylenetetrazole in freely moving rats pretreated (100 mg/kg p.o., 1 h before pentylenetetrazole) with two classic (theophylline and caffeine) and two new (enprofylline and isbufylline) xanthines. In rats treated with vehicle, pentylenetetrazole caused a slight desynchronization of the EEG, characterized by periods of 'wave discharges', and 'spike-and-wave discharge complexes'. In rats pretreated with xanthines (theophylline or caffeine) pentylenetetrazole produced a dramatic increase in ictal seizures with the appearance of continuous spikes; concomitantly animals experienced myoclonic jerks (100%) and in some cases (ca. 20%) the animals died. In contrast, in enprofylline-pretreated rats, pentylenetetrazole induced only brief periods of wave discharges and spike-and-wave discharge complexes whose duration was significantly reduced compared to that of controls, although these discharges were associated with mild epileptic behaviour. When isbufylline-pretreated rats were challenged with pentylenetetrazole, the EEG was characterized by a short run of wave discharges (whose duration was shorter than that of other groups). No enprofylline- or isbufylline-treated rats developed seizures or died. In conclusion, only xanthines with strong adenosine A1 receptor antagonism (theophylline and caffeine) markedly enhance the EEG and behavioural effects of a subconvulsive dose of pentylenetetrazole. The present experimental approach could be used to evaluate the pro-convulsive potential of new xanthine derivatives.

Unilateral brain damage after prolonged hemiconvulsions in the elderly associated with theophylline administration

The brains of 14 elderly patients who died after status epilepticus were examined pathologically. Three of the 14 patients showed unilateral brain damage which corresponded to the side of the seizures, and the lesions were thought to be caused by seizures. In these three and two other patients, no causative lesion related to the seizures was found. In these five patients, status epilepticus occurred during theophylline therapy and thus the seizures in these five patients were assumed to be induced by theophylline. In the three patients with unilateral brain damage, the damage was seen in the hippocampus, amygdala and thalamus in two patients, while in the third, the whole hemisphere was damaged, including the hippocampus, amygdala, thalamus, basal ganglia and cerebral cortex. The distribution of pathological changes within the thalamus was described. It is suggested that the thalamus was primarily affected by seizures, rather than by secondary degeneration from the cortex.

In vivo studies on the mechanism of action of the broad spectrum anticonvulsant loreclezole

In animal models of epilepsy the anticonvulsant profile of loreclezole resembles that of barbiturates and benzodiazepines. We examined whether the increase in seizure threshold to pentylenetetrazole infusion produced by 10 mg/kg of loreclezole, pentobarbital or diazepam could be reversed by a spectrum of benzodiazepine partial inverse to full inverse agonists (FG-7142 beta-carboline carboxylate, CGS-8216, Ro-15-4513 and DMCM) or by a benzodiazepine neutral antagonist (Ro-15-1788). The doses of the benzodiazepine inverse agonists were chosen to produce a 20-40% decrease in seizure threshold. The seizure threshold increase produced by loreclezole and pentobarbital was reduced by all the benzodiazepine inverse agonists and potentiated by Ro-15-1788. Diazepam was antagonized by the benzodiazepine inverse agonists and by the neutral antagonist. The generality of this finding was examined in amygdala-kindled rats. The decrease in the duration of forepaw clonus and the reduction in behavioural stage34 produced by loreclezole, pentobarbital and diazepam was reversed by CGS-8216. Ro-15-1788, which itself showed anticonvulsant effects in this model, antagonized the effects of diazepam, but not loreclezole or pentobarbital. Thus loreclezole behaves more like a barbiturate than a benzodiazepine in these two in vivo models. This suggests a possible mechanism of action of loreclezole at a neuromodulatory site within the GABAA receptor complex, which is unlikely to be a benzodiazepine receptor.