n(6)-cyclohexyladenosine and Ischemic-Attack--Transient

Emergence of slow EEG rhythms within the delta frequency band following an ischemic insult of the brain has long been considered a marker of irreversible anatomical damage. Here we investigated whether ischemic adenosine release and subsequent functional inhibition via the adenosine A(1) receptor (A(1)R) contributes to post-ischemic delta activity.. Rats were subjected to episodes of non-injuring transient global cerebral ischemia (GCI) under chloral hydrate anesthesia.. We found that a GCI lasting only 10s was enough to induce a brief discharge of rhythmic delta activity (RDA) with a peak frequency just below 1 Hz quantified as an increase by twofold of the 0.5-1.5 Hz spectral power. This post-ischemic RDA did not occur following administration of the A(1)R antagonist 8-cyclopentyl-1,3-dipropylxanthine. Nevertheless, a similar RDA could be induced in rats not subjected to GCI, by systemic administration of the A(1)R agonist N(6)-cyclopentyladenosine.. Our data suggest that A(1)R activation at levels that occur following cerebral ischemia underlies the transient post-ischemic RDA.. It is likely that the functional, thus potentially reversible, synaptic disconnection by A(1)R activation promotes slow oscillations in the cortical networks. This should be accounted for in the interpretation of early post-ischemic EEG delta activity.

Topics: Adenosine; Adenosine A1 Receptor Antagonists; Animals; Delta Rhythm; Disease Models, Animal; Electrocardiography; Electroencephalography; Heart Rate; Ischemic Attack, Transient; Male; Rats; Rats, Wistar; Receptor, Adenosine A1; Statistics, Nonparametric; Theophylline; Xanthines

Chronological changes of adenosine A1 receptor binding of the rat brain were determined by in vitro [3H]cyclohexyladenosine (CHA) autoradiography after 90 min of middle cerebral artery (MCA) occlusion and after such occlusion followed by different periods of recirculation. One day after the ischaemia, [3H]CHA binding sites decreased significantly in the cerebral cortex (p < 0.05) and lateral segment of the caudate putamen (p < 0.01), both supplied by the occluded MCA; thereafter, the binding sites decreased progressively in those ischaemic foci. On the contrary, there was no alteration on day 1, but 3 days after ischaemic insult, a significant decrease of [3H]CHA binding sites was first detected in the ipsilateral thalamus and the substantia nigra, both areas which had not been directly affected by the original ischaemic insult. This post-ischaemic delayed phenomenon observed in the thalamus and the substantia nigra developed concurrently with 45Ca accumulation, which was studied in our previous study. Based on the present study, alteration of adenosine A1 receptor binding activities is involved not only in the ischaemic foci, but also in the remote areas associated neuroanatomically with the ischaemic foci. We suggest that multi-focal post-ischaemic alterations of adenosine A1 binding activities may exacerbate clinical symptoms of patients at a chronic stage of stroke.

Topics: Adenosine; Animals; Autoradiography; Brain; Cerebrovascular Disorders; Humans; Ischemic Attack, Transient; Male; Organ Specificity; Rats; Rats, Wistar; Receptors, Purinergic P1; Reference Values; Substantia Nigra; Thalamus; Time Factors; Tritium

1. Receptor autoradiographic and histological techniques were used to investigate long-term changes in the gerbil brain following transient cerebral ischaemia. 2. Transient ischaemia was induced for 3 min and 10 min, and the animals were allowed to survive for 8 months. 3. Histological examination revealed that 3 min ischaemia caused neuronal damage and mild shrinkage only in the hippocampal CA1 sector. Ten minutes of ischaemia produced severe neuronal damage in the striatum and the hippocampal CA1 and CA3 sectors. Considerable shrinkage was seen in the hippocampus; the dentate gyrus, however, was not damaged. 4. Three minutes of ischaemia produced changes in the binding of [3H]-quinuclidinylbenzilate ([3H]-QNB), [3H]-muscimol, and [3H]-MK-801 in various brain regions, as determined autoradiographically. In contrast, [3H]-cyclohexladenosine ([3H]-CHA) and [3H]-PN200-110 ([3H]-isradipine) binding in the brain was unaltered. 5. Ten minutes of ischaemia resulted in a major loss of neurotransmitter receptors, especially in the hippocampus. The substantia nigra showed a significant reduction in [3H]-CHA binding, whereas the striatum, which was morphologically damaged, showed no significant changes in any of the neurotransmitter receptors examined. 6. The results demonstrated that long-term survival after transient cerebral ischaemia produced alterations in neurotransmitter receptors, especially in the hippocampal formation, where considerable shrinkage was noted. These results also suggest that the hippocampal damage was not static, but progressive.

Topics: Adenosine; Animals; Autoradiography; Binding Sites; Brain; Dizocilpine Maleate; Gerbillinae; Hippocampus; Ischemic Attack, Transient; Isradipine; Male; Muscimol; Neurons; Quinuclidinyl Benzilate; Receptors, Neurotransmitter

Changes in second messenger and neurotransmitter system receptor ligand binding induced by transient forebrain ischemia were studied in the gerbil hippocampus. The animals were allowed variable periods of recovery ranging from 2 h to 7 days after 5-min bilateral carotid artery occlusion. The binding of second messenger systems ([3H]inositol 1,4,5-trisphosphate ([3H]IP3)to inositol 1,4,5-triphosphate, [3H]forskolin to adenylate cyclase and [3H]phorbol 12,13-dibutylate to protein kinase C) and neurotransmitter receptor systems ([3H]PN200-110 to L-type calcium channels. [3H]N6-cyclohexyl-adenosine to adenosine A1 and [3H]quinuclidinyl benzilate to muscarinic cholinergic receptor) were assayed using quantitative autoradiography. In the CA1 subfield, 2 h after ischemia, [3H]IP3, [3H]forskolin, and [3H]quinuclidinyl benzilate binding activities significantly decreased by 25, 17 and 13%, respectively, though no morphological abnormalities were obvious. Six hours after ischemia, the [3H]phorbol 12,13-dibutylate binding activity in the stratum oriens of the CA1 subfield increased by 15%. One day after ischemia, [3H]PN200-110 binding activity in this subfield decreased by 26%, and 7 days after ischemia, [3H]phorbol 12,13-dibutylate and [3H]N6-cyclohexyl-adenosine receptor binding activities decreased in this subfield. In particular, at 7 days after ischemia, [3H]IP3 binding activity in the CA1 subfield showed a complete decline. In the CA3 subfield, [3H]PN200-110 binding activity decreased 2 days after ischemia, and [3H]IP3 and [3H]N6-cyclohexyl-adenosine binding activities decreased 7 days after ischemia. In the dentate gyrus, the structure of which remained histologically intact after ischemic insult, [3H]IP3 and [3H]forskolin binding activities decreased 7 days after ischemia. In contrast, the [3H]phorbol 12,13-dibutylate binding activity increased in the molecular layer of the dentate gyrus 7 days after ischemia. These results indicate that marked alteration of intracellular signal transduction precedes neuronal damage in the hippocampal CA1 subfield and that the histologically intact CA3 and dentate gyrus also shows modulated neuronal transmission after ischemia.

Topics: Adenosine; Adenylyl Cyclases; Animals; Autoradiography; Calcium Channel Blockers; Calcium Channels; Cerebral Cortex; Colforsin; Gerbillinae; Hippocampus; Inositol 1,4,5-Trisphosphate; Inositol 1,4,5-Trisphosphate Receptors; Ischemic Attack, Transient; Isradipine; Male; Neurons; Organ Specificity; Oxadiazoles; Phorbol 12,13-Dibutyrate; Protein Kinase C; Pyramidal Tracts; Quinuclidinyl Benzilate; Receptors, Cell Surface; Receptors, Cytoplasmic and Nuclear; Receptors, Muscarinic; Receptors, Purinergic; Second Messenger Systems; Time Factors; Tritium

We performed receptor autoradiography to determine sequential alterations in the binding of muscarinic cholinergic and adenosine A1 receptors and of a voltage dependent L-type calcium channel blocker 1 h-1 month after transient cerebral ischemia in the gerbil brain. [3H]Quinuclidinyl benzilate (QNB), [3H]cyclohexyladenosine (CHA) and [3H]PN200-110 were used to label muscarinic and adenosine A1 receptors and L-type calcium channels, respectively. Transient ischemia was induced for 10 min. [3H]QNB and [3H]CHA binding showed no significant alteration in selectively vulnerable areas at an early stage (1-24 h) of recirculation. However, the dentate molecular layer which was resistant to ischemia revealed a significant decrease in the [3H]CHA binding sites 24 h after ischemia. Thereafter, the [3H]QNB and [3H]CHA binding showed significant reduction in most of selectively vulnerable areas. Marked reduction was especially found in the dorsolateral part of striatum and the hippocampal CA1 sector which was the most vulnerable to ischemia. In contrast, [3H]PN200-110 binding showed a transient elevation in the hippocampal CA1 sector, the dentate molecular layer and the thalamus 1 h of recirculation. However, the striatum and neocortex revealed no alteration in the [3H]PN200-110 binding. Thereafter, the reduction in the [3H]PN200-110 binding was seen only in the dorsolateral part of the striatum and the hippocampal CA1 sector. The results suggest that transient cerebral ischemia can cause the alterations in the binding of muscarinic cholinergic and adenosine A1 receptors and of L-type calcium channel blocker in most of selectively vulnerable areas.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine; Animals; Autoradiography; Brain; Calcium Channel Blockers; Calcium Channels; Dihydropyridines; Gerbillinae; Ischemic Attack, Transient; Isradipine; Male; Organ Specificity; Quinuclidinyl Benzilate; Receptors, Muscarinic; Receptors, Nicotinic; Receptors, Purinergic; Time Factors; Tritium

The protective roles of Ca2+ channel blockers against ischemic hippocampal damage are still debated. We used autoradiography to study postischemic L-type Ca2+ channels (1,4-dihydropyridine Ca2+ channel blocker binding), adenosine A1 receptors, and muscarinic cholinergic receptors in the rat hippocampus using [3H]PN200-110 (PN), [3H]cyclohexyladenosine (CHA), and [3H]quinuclidinyl benzilate (QNB), respectively, in 49 rats subjected to 20 minutes of forebrain ischemia. The rats were decapitated after 1 (n = 7), 3 (n = 7), 6 (n = 8), 12 (n = 7), 24 (n = 6), 48 (n = 6), or 168 (n = 8) hours of recirculation; eight control rats were sham-operated but experienced no cerebral ischemia. Reduced receptor binding preceding the delayed death of CA1 pyramidal cells was first observed in the stratum oriens of the CA1 subfield. Significant reductions in [3H]PN, [3H]CHA, and [3H]QNB bindings of this stratum compared with control were noticed after 3 (35%, p less than 0.01), 12 (31%, p less than 0.01), and 1 (10%, p less than 0.05) hours of recirculation, respectively. By 168 hours after ischemia (when the populations of CA1 pyramidal cells were depleted) all strata in the CA1 subfield had lost most of their receptor sites, and [3H]PN, [3H]CHA, and [3H]QNB bindings in the stratum oriens were decreased to 23%, 30%, and 63% of control (p less than 0.01). Although [3H]PN binding in the CA3 subfield did not change significantly during 168 hours after ischemia, the histologically intact dentate gyrus exhibited a 31% loss of binding sites compared with control (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine; Animals; Autoradiography; Binding Sites; Calcium Channel Blockers; Hippocampus; Ischemic Attack, Transient; Isradipine; Male; Oxadiazoles; Quinuclidinyl Benzilate; Rats; Rats, Inbred Strains; Receptors, Muscarinic; Receptors, Purinergic; Time Factors; Tissue Distribution

The effects of an i.p. administration of cyclohexyladenosine (CHA) have been examined upon ischemic brain damage in gerbils. Ischemia was induced for 20 min by occlusion of both carotid arteries, and CHA was administered 5 min after recirculation at a dose of 2 mg/kg. Animals were sacrificed either 1, 3 or 6 days after ischemia and their brains were used for examination of cell morphology and quantitative autoradiography. In animals subject to ischemia, the deterioration of the laminar organization of the hippocampus was associated with a significant decrease in adenosine A1-receptors (labeled with [3H]CHA), G-protein (labeled with [3H]forskolin). The treatment with CHA considerably improved the morphological preservation of cells in the CA1 region of the hippocampus and prevented the reduction in the specific binding of all radioligands. Adenosine, its analogues and other substances modulating adenosine receptors may thus provide new therapeutic approaches to the treatment of ischemia-induced brain injury.

Topics: Adenosine; Adenylyl Cyclases; Animals; Colforsin; Gerbillinae; GTP-Binding Proteins; Hippocampus; In Vitro Techniques; Ischemic Attack, Transient; Male; Receptors, Purinergic

The effect of postischemically injected cyclohexyl adenosine has been studied in gerbils. The animals were subjected to 30 min of bilateral carotid occlusion. Fifteen minutes after ischemia, one group of gerbils received a cerebroventricular injection of 251 of 0.5 M solution of cyclohexyl adenosine. The second group of ischemic animals was injected with the vehicle. After injections, the animals were randomly divided into two groups. Survival of one group of animals was monitored for 10 days. The second group was killed 5 days after ischemia, and the brains were used for a qualitative and quantitative histological evaluation. At the end of the 10-day monitoring period, 53% of the cyclohexyl adenosine-injected and 10% of the vehicle-injected ischemic animals were still alive (P less than 0.01, logrank test). Morphological preservation of the hippocampus and striatum was considerably improved in the cyclohexyl adenosine-treated animals (P less than 0.001, Student's t test). The nature of the protective effect of cyclohexyl adenosine is unknown, but it is suggested that reduction of neurotoxic excitatory amino acid release may be involved.

Topics: Adenosine; Animals; Cell Survival; Cerebral Cortex; Corpus Striatum; Gerbillinae; Hippocampus; Ischemic Attack, Transient; Male

Transient brain ischemia results in a selective destruction of cell bodies within the hippocampus and cortex. This cellular destruction appears to be mediated through a release of endogenous exictatory amino acids following the ischemic episode, since the neurotoxic effects of ischemia can be attenuated by compounds that have antagonist activity at N-methyl-D-aspartate (NMDA) receptors. In the present study, the protective effects of a novel NMDA receptor antagonist, CGS 19755, were further evaluated by using quantitative autoradiography to characterize adenosine A1, NMDA, PCP, and benzodiazepine receptors in ischemic gerbil brain. Bilateral carotid artery occlusion (20 minutes) resulted in marked decreases (30-60%) in adenosine A1, NMDA, and PCP, but not benzodiazepine, receptors in gerbil forebrain. Postischemic treatment with CGS 19755 was found to completely block the ischemia-induced decreases in brain adenosine and NMDA receptors. [3H]TCP binding in ischemic gerbil brain was also elevated by CGS 19755 treatment; significant differences remained, however, between the CGS 19755-treated and control gerbils. These results indicate that transient brain ischemia produces significant and selective alterations in gerbil forebrain receptor systems. The observed decreases in radioligand binding are probably reflective of an ischemia-induced destruction of forebrain structures. However, there is some evidence that transient ischemia can also cause long-term changes in the affinity of some receptor systems. The postischemic efficacy of CGS 19755 appears to be due to its ability to block the neurotoxic effects of transient ischemia.

Topics: Adenosine; Animals; Autoradiography; Female; Flunitrazepam; Gerbillinae; Image Processing, Computer-Assisted; Ischemic Attack, Transient; Pipecolic Acids; Piperazines; Piperidines; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter; Receptors, Phencyclidine

The cellular localization of adenosine A1 receptors in the CA1 region of the rat hippocampus was investigated using radioligand binding and lesioning methods in a quantitative autoradiographic study. Kainic acid injection reduced [3H]cyclohexyladenosine binding in the CA3 region by 40% and in the CA1 region by 30%. Transient cerebral ischemia reduced [3H]cyclohexyladenosine binding in the CA1 region by 50%, while no change was measured in the CA3 region. These findings suggest that adenosine A1 receptors are located presynaptically on axon terminals of CA3 pyramidal cells and postsynaptically on the dendrites of CA1 pyramidal cells in the CA1 region of rat hippocampus.

Topics: Adenosine; Animals; Autoradiography; Hippocampus; Ischemic Attack, Transient; Kainic Acid; Male; Pyramidal Tracts; Rats; Rats, Inbred Strains; Receptors, Purinergic; Synapses; Tritium