Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0036572 (seizures)
 80,221 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Adenosine has been proposed as a metabolic factor involved in the regulation of cerebral blood flow. The evidence in support of this hypothesis, presented in this review, includes information on the adenosine receptors associated with cerebral blood vessels, the synthesis and metabolism of adenosine, and the release of adenosine from the brain. Adenosine dilates cerebral blood vessels, acting at an A2 receptor. The critical evidence implicating an involvement of adenosine in cerebrovascular regulation is derived from experiments with adenosine antagonists and potentiators. The antagonists include methylxanthine adenosine receptor antagonists and the enzyme adenosine deaminase. Potentiators include transport inhibitors, enzyme inhibitors, and adenosine precursors. Adenosine has been implicated in vascular regulation during hypoxia/ischemia, hypercapnia, seizures, severe hypotension, and hypoglycemia. Adenosine possesses a number of properties that can be used to minimize neuronal degeneration during cerebral insults, such as ischemia, including vasodilatation, reduction of excitatory transmitter release, reduction of membrane calcium permeability, inhibition of platelets, and neutrophil aggregation. Several recent studies have demonstrated that manipulation of central adenosine tone can alter the extent of cerebral ischemic damage, indicating a potential new therapeutic approach for the treatment of stroke.
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PMID:Adenosine in the control of the cerebral circulation. 270 69

Dilazep (i.p.), a coronary vasodilator and an uptake inhibitor of adenosine, dose dependently potentiated acute ethanol-induced motor incoordination in mice. In view of peripheral cardiovascular depressive effects of dilazep, the effect of i.c.v. dilazep (25, 50 and 75 micrograms), and its metabolites, 1,4-bis(3-hydroxypropyl)perhydro-1,4-diazepine (BHPD) (15, 31 and 62 micrograms) and 1-[3-(3,4,5-trimethoxybenzoyloxy)propyl]perhydro-1,4-diazepine (TBPD) (62 and 125 micrograms) on ethanol-induced motor incoordination was studied. Dose-related potentiation of ethanol-induced motor incoordination was noted with dilazep and its metabolites. Whereas dilazep (i.p.) produced no apparent central nervous system (CNS) effects, by i.c.v. route, it caused CNS excitation including tonic-clonic seizures. Adenosine uptake inhibition, Ca2+ entry blockade or direct activation of adenosine receptors was ruled out as the possible mechanism of seizures because dipyridamole, verapamil or N6-(2-phenylisopropyl)-adenosine (R-PIA) administered i.c.v., while potentiating ethanol (i.p.)-induced motor incoordination did not produce seizures. The CNS excitation was minimal with BHPD and none with TBPD. Theophylline pretreatment partially blocked potentiation of ethanol-induced motor incoordination by dilazep and BHPD and not by TBPD. The data suggest dilazep-induced potentiation of ethanol-induced motor incoordination is partially due to central adenosine receptor mechanism and partly due to other yet unknown mechanism(s) and further supported our earlier reports about adenosine involvement in the CNS effects of ethanol. The data also suggest that dilazep (i.c.v.)-induced seizures are due to mechanism(s) other than adenosine uptake inhibition, Ca2+ entry blockade or direct adenosine receptor activation.
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PMID:Central nervous system effects and behavioral interactions with ethanol of centrally administered dilazep and its metabolites in mice. 275 78

The convulsant properties of xanthine amine congener (XAC, 8-(4-(2-aminoethyl)-aminocarboxylmethyloxy)phenyl-1,3-dipropylxant hine) are compared to those of caffeine. Male Swiss albino mice were infused with convulsants through a lateral tail vein. Convulsion thresholds (i.e. the amount of convulsants required to elicit convulsions) of 39.8 +/- 2.0 mg/kg (n = 10) and 109.8 +/- 2.3 mg/kg (n = 10) were calculated for XAC and caffeine respectively. Pretreatment of animals with the adenosine receptor agonists 2-chloroadenosine, N6-cyclohexyladenosine or 5'-N-ethylcarboxamido-adenosine (1 mg/kg, i.p., 20 minutes prior to infusion) significantly decreased the seizure threshold of both XAC and caffeine. The adenosine uptake blockers, 6-nitrobenzylthioinosine or dipyridamole (0.25 mg/kg, i.p., 20 minutes prior to infusion) did not significantly affect the seizure threshold to either XAC or caffeine. The benzodiazepine agonist diazepam (5 mg/kg, i.p., 20 minutes prior to infusion) significantly increased the seizure threshold to both XAC (p less than 0.05) and caffeine (p less than 0.01), whereas the benzodiazepine antagonist Ro 15-1788 (10 mg/kg, i.p., 20 minutes prior to infusion) significantly increased the seizure threshold to caffeine (p less than 0.01), but not XAC. The results suggest that actions at benzodiazepine receptors may be a tenable hypothesis to explain the convulsant actions of caffeine, but not those of XAC.
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PMID:Potent convulsant actions of the adenosine receptor antagonist, xanthine amine congener (XAC). 277 59

The effects of various metabolically-stable analogs of adenosine on the threshold for seizures in rats was determined by measuring the dose of pentylenetetrazol (PTZ), infused through a tail vein, required to elicit a myoclonic jerk. The adenosine receptor agonists, 2-chloroadenosine (2-ClAdo), cyclohexyladenosine (CHA) and L- and D-phenylisopropyladenosine (L- and D-PIA), all produced dose-dependent elevations of the seizure threshold for pentylenetetrazol in rats. L-Phenylisopropyl-adenosine was the most potent analog of adenosine tested with a dose as small as 5 micrograms/kg (i.v.) producing a 23% increase in seizure threshold for pentylenetetrazol. The rank order of the potency of adenosine agonists in increasing the seizure threshold was L-PIA greater than 2-ClAdo greater than CHA greater than D-PIA, with L-PIA being 79 times more potent than D-PIA. In contrast to these effects, the adenosine receptor antagonist, theophylline, elicited a proconvulsant effect in doses from 15 to 60 mg/kg (i.p.). The effect of theophylline in reducing seizure threshold for pentylenetetrazol peaked at 30 mg/kg, a dose which reduced the seizure threshold by approx. 27%. Support for the involvement of recognition sites for adenosine in the observed modulation of seizure threshold was provided by the antagonism of the elevation of the seizure threshold for pentylenetetrazol induced by 2-ClAdo, by pretreatment with theophylline (5 mg/kg, i.v.). These findings provide support for the idea that endogenous adenosine may function as a regulator of seizure susceptibility.
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PMID:Purinergic modulation of the seizure threshold for pentylenetetrazol in the rat. 301 16

The effects of 2-chloroadenosine (2-CLA), a metabolically stable analog of adenosine, and aminophylline, an adenosine receptor antagonist, on seizures produced by pilocarpine (PILO) were examined in rats. The effects of 2-CLA on amygdaloid and hippocampal kindled seimres were also examined. In the animals pretreated with aminophylline (25-100 mg/kg), a non-convulsant dose of PILO (100 mg/kg) resulted in severe motor limbic seizures which rapidly evolved to status epilepticus. 2-CLA (5-10 mg/kg) blocked the appearance of behavioral and EEG seizures produced by a convulsant dose of PILO (380 mg/kg) and completely blocked the evolution of hippocampal and amygdaloid kindled seizures. The results indicate that purinergic mechanisms are involved in the modulation of seizure threshold within the limbic system.
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PMID:Anticonvulsant role of adenosine. 350 33

This study explored the anticonvulsant effects of adenosine analogs at the focus of seizures kindled from various brain structures. Chemitrodes were implanted in the amygdala (AM), hippocampus (HIPP), or caudate nucleus (CN) of Long-Evans rats and electrically stimulated once daily until fully generalized seizures appeared (i.e., kindled). Once kindled, various doses (0.001-0.5 microgram/0.5 microliter) of the adenosine analogs, L-phenylisopropyladenosine (L-PIA), N-ethylcarboximidoadenosine (NECA) or vehicle were injected into the seizure focus 5 min prior to electrical stimulation. The afterdischarge (AD) and behavioral seizure stages were measured. L-PIA had potent anticonvulsant effects when injected directly into the kindled seizure focus in the AM, HIPP, or CN. NECA effects were statistically significant only in CN-kindled seizures. The regional differences in efficacy of the two adenosine analogs suggest that L-PIA, an A1 adenosine subtype agonist, may exert its effects through A1 adenosine receptors in the AM, HIPP, and CN, where A1 binding has been demonstrated, whereas NECA, an A2 adenosine receptor agonist, may only be maximally effective in the CN where A2 adenosine binding sites are located.
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PMID:Differential effects of adenosine analogs on amygdala, hippocampus, and caudate nucleus kindled seizures. 369 15

Carbamazepine, a drug effective in pain, seizure, and affective disorders, was screened for its ability to interact with a variety of neurotransmitter and neuromodulator binding sites on brain membranes. The most potent effect was observed on adenosine antagonist ( [3H]DPX) binding to the adenosine receptor (KI = 3.5 +/- 0.4 microM) followed by adenosine agonist ( [3H]CHA) binding (KI = 24.5 +/- 3.6 microM). Lower potency effects were observed on benzodiazepine receptors, and no inhibition was seen in a variety of other systems. The inhibition of adenosine receptor binding by carbamazepine was competitive. No correlation was observed between the potency of a series of carbamazepine analogs as inhibitors of either ( [3H]DPX, [3H]CHA or [3H]diazepam binding and their ability to inhibit electroshock-induced convulsions, suggesting that the anticonvulsant properties of these agents are not mediated by the adenosine receptor, but raising the possibility that other clinical effects of carbamazepine may relate to its ability to act at the adenosine receptor.
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PMID:Specific and potent interactions of carbamazepine with brain adenosine receptors. 631 50

The behavioral and physiological effects of L-phenylisopropyladenosine, cyclohexyladenosine and 2-chloroadenosine were examined in mice and rats. These analogs of adenosine are agonists which bind with high affinity to putative central A1 receptors in vitro. Relatively low doses of these drugs administered i.p. produced marked sedation and hypothermia; higher doses resulted in an almost complete cessation of spontaneous motor activity as well as some ataxia. These analogs also antagonized seizures elicited by a variety of convulsants with different mechanisms of action. The differences observed in the anticonvulsant potencies of the analogs suggest that these effects are not produced by the interaction of these drugs with a single class of adenosine receptor. In particular, 2-chloroadenosine and cyclohexyladenosine appear to be more related to each other pharmacologically than to L-phenylisopropyladenosine. Because some of the anticonvulsant actions of L-phenylisopropyladenosine are not reversed by the adenosine antagonist theophylline, and are not shared by the other analogs, these may reflect actions mediated by other, perhaps nonpurinergic receptors. Although benzodiazepines also have sedative, hypothermic and anticonvulsant properties, responses to benzodiazepines can be clearly dissociated from responses to the adenosine agonists.
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PMID:Sedative and anticonvulsant effects of adenosine analogs in mouse and rat. 705 24

Theophylline, that is a potent adenosine receptor antagonist, and enprofylline (3-propylxanthine), that seems to lack antagonism of neuronal depressant effects of adenosine, have been tested for convulsive activity in three animal species. In urethane-anaesthetized guinea-pigs theophylline produced massive generalized convulsions. Enprofylline was without any seizure activity but produced about the same changes as theophylline in heart rate, blood pressure, respiratory rate (less marked) and blood gas status. The lethal infused dose of enprofylline ws about twice as large as that of theophylline. This should be compared with the observation that enprofylline is about 5 times more potent than theophylline as a bronchodilator. Also in conscious guniea-pigs, mice and cats enprofylline was shown to be devoid of theophylline-like seizure activity. The CNS-stimulant effects of lethal doses of theophylline progressed until death occurred. The major behavioral effects of lethal doses of enprofylline in contrast were inhibition of activity and sedation. It is suggested that lack of seizure-activity reflects inability of enprofylline to antagonize neuronal depressant effects of endogenous adenosine.
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PMID:Seizure activity in animals given enprofylline and theophylline, two xanthines with partly different mechanisms of action. 713 50

The effect of chronic administration of the adenosine A1 receptor agonist N6-cyclopentyladenosine (CPA) and the adenosine A1 antagonist 8-cyclopentyl-1,3-dipropylxanthine (CPX) on N-methyl-D-aspartate (NMDA)-evoked seizures was studied in C57BL/6 mice (20/group). Animals were injected i.p. for 9 days with either 1.0 mg/kg CPA or 1.0 mg/kg CPX followed by 2 injection-free days (the washout period) and subsequent administration of a single dose of 60 mg/kg NMDA. As in our previous study, this dose of NMDA caused clonic/tonic seizures resulting in high (60%) mortality within 3 h after injection of the drug. Despite insignificant changes in seizure latency, chronic pretreatment with CPA increased the incidence of clonic/tonic episodes and end-point mortality. Conversely; chronic exposure to CPX completely eliminated clonic/tonic episodes, significantly increased average survival time, and reduced end-point mortality (P < 0.05). The results indicate that chronic treatment with adenosine A1 receptor antagonist may protect against NMDA-evoked seizures to the same degree as previously observed following a single, acute exposure to CPA. Since the density of adenosine receptor binding sites was unchanged after chronic treatment with either CPX or CPA, it is likely that the mechanism behind the observed protection may rest at the level of second messenger systems coupled to adenosine A1 receptors.
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PMID:Chronic adenosine A1 receptor agonist and antagonist: effect on receptor density and N-methyl-D-aspartate induced seizures in mice. 801 54


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