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PubMed2006

Diagnostics and characterisation of preocclusive stenoses and occlusions of the internal carotid artery with B-flow.

The purpose was to evaluate whether B-flow can improve the ultrasonographic diagnosis of preocclusive stenosis and occlusion of the internal carotid artery (ICA) compared with colour-coded Doppler and power Doppler. Ninety patients with occlusions or preocclusive stenoses of the ICA suspected by Doppler sonography were examined with B-flow in comparison with colour-coded Doppler sonography (CCDS), power Doppler (PD) and intra-arterial digital subtraction angiography (DSA). Intrastenotic flow detection and lengths of stenoses were the main criteria. Ulcerated plaques found by surgery in 42/90 patients were compared by ultrasonography (US). Diagnosis of ICA occlusion with CCDS, PD and B-flow was correct in all 42 cases. A preocclusive ICA stenosis in DSA was detected correctly in all 48/48 cases (100%) for B-flow, in 44/48 (92%) for PD and in 39/48 (81%) for CCDS. Surgical findings showed in 17/42 cases ulcerated plaques; 15/17 (89%) of these cases were detected with B-flow, 12/17 (71%) with PD, 10/17 (59%) with CCDS, and 8/17 (47%) with DSA. With B-flow the extent of stenosis was appraised more precisely than with PD and CCDS (P<0.0001). In conclusion, B-flow is a reliable method for preocclusive stenosis of the ICA with less intrastenotic flow artefacts. B-flow facilitates the characterization of plaque morphologies.

Aged↗
PubMed1987

Monitoring of subcortical and cortical somatosensory evoked potentials during carotid endarterectomy: comparison with stump pressure levels.

Monitoring of multichannel somatosensory evoked potentials (SEPs) has been performed in 40 cases of carotid endarterectomy (CEA). SEPs were obtained after median nerve stimulation at wrist, recording from 2nd cervical and from the scalp parietal (ipsi- and contralateral) and central (contralateral) positions. The reduction of CBF due to clamping of the carotid artery provoked SEP abnormalities in 10 of the 40 cases. None of the 30 patients with unmodified SEPs developed post-surgical neurological sequelae. SEP alterations were characterized exclusively by amplitude decrements and latency increases of the cortical components, the subcortical ones being unaffected. In 5 of these patients, SEPs returned to normal values before the end of the intervention and no neurological deficit was observed on awakening. In the remaining 5 cases SEPs retained their abnormalities and patients developed post-surgery neurological sequelae (4 immediately, 1 the day after). SEP alterations affected parietal and central components to a similar extent; however, in a few cases cerebral blood flow deficits provoked by carotid clamping modified differently the central P22 and the parietal N20-P25 waves. Comparisons with stump (back) pressure in the carotid artery revealed a higher sensitivity of the SEP technique in detecting vascularization problems due to carotid clamping. The time course of the appearance of SEP abnormalities seems to discriminate alterations secondary to collateral revascularization from those determined by embolization.

Adult↗
PubMed1996

Characterization of dopamine receptors mediating inhibition of excitatory synaptic transmission in the rat hippocampal slice.

1. The effect of dopamine (DA) on the excitatory synaptic transmission was studied in the CA1 neurons of rat hippocampal slices using intracellular recording technique. 2. Depolarizing excitatory postsynaptic potentials (EPSPs) were evoked by stimulation of the Schaffer collateral-commissural pathway. Superfusion of DA (0.03-1 microM) reversibly decreased the EPSP in a concentration-dependent manner and with an estimated IC50 of 0.3 microM. The sensitivity of postsynaptic neurons to the glutamate-receptor agonists, alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid or N-methyl-D-aspartate was unchanged by DA (0.3 microM) pretreatment. In addition, DA (0.3 microM) increased the magnitude of paired-pulse facilitation, a phenomenon attributed to an increase in the amount of transmitter released in response to the second stimulus. 3. The reduction of DA (0.3 microM) on the EPSP was antagonized by sulpiride (1-10 nM), a selective D2-receptor antagonist. However, D1-receptor antagonist, SKF-83566 (1-10 microM), did not significantly affect the reduction of DA (0.3 microM) on the EPSP. 4. (+/-)-2-(N-Phenylethyl-N-propyl)amino-5-hydroxytetralin (1 microM), an agonist of D2 receptor, mimicked the inhibitory effect of DA on the EPSP. However, neither the D1-receptor agonist SKF-38393 (1 microM) nor the D3-receptor agonist (PD-128,907 (1 microM) affected the EPSP. 5. Incubation of hippocampal slices with pertussis toxin (PTX, 5 micrograms/ml) for 12 h prevented the reduction of EPSP induced by DA (0.3 microM). 6. Rp-adenosine-3',5'-cyclic monophosphothioate (25 microM), a potent inhibitor of protein kinase A (PKA), alone decreased the amplitude of EPSP below baseline values and prevented the subsequent reduction by DA (0.3 microM). 7. These results indicate that DA at a low concentration (< or = 0.3 microM) reduces the excitatory response of hippocampal CA1 neurons after synaptic stimulation via the activation of presynaptic D2 receptors. The presynaptic action of DA is mediated by a PTX-sensitive Gi-proteins-coupled to PKA pathway.

Animals↗
PubMed1983

Myocardial lactate metabolism during pacing induced angina pectoris.

Myocardial lactate metabolism was studied in 20 patients with coronary heart disease during and immediately after slight angina pectoris induced by atrial pacing. Myocardial lactate extraction ratio (MLE) decreased from 0.27 +/- 0.03 (SEM) before angina to 0.01 +/- 0.06 during angina, and further to -0.32 +/- 0.11 at 15 sec after pacing. Lactate production was found to occur in eight patients during pacing and 13 patients after pacing. Cardiac venous flow was measured by thermodilution in eight of these patients. 'Net ischaemic lactate efflux' increased by 23 +/- 4 mumol/min 15 sec after pacing, whereas 'lactate uptake in non-ischaemic regions' diminished by 11 +/- 2 mumol/min. Lactate production 15 min after pacing was revealed in all patients with subtotal stenosis of the left anterior descending coronary artery (LAD), whereas it was less frequently observed in patients with occluded LAD and collaterals to the post-stenotic area. Increased washout of metabolites from the ischaemic myocardium during the early recovery period is the main reason for the rather high sensitivity of ischaemia detection by this procedure. This permits shorter pacing periods and less pain than in earlier studies. Both MLE and electrocardiographic changes were equally reproducible after 20 and 45 min recovery period.

Angina Pectoris↗
PubMed1996

[Comparison between two diagnostic methods of computer's mathematic model and clinical diagnosis on TCM syndromes of rheumatoid arthritis].

Based on the test result of 14 trace elements in hair of 163 cases of rheumatoid arthritis, we used one of the methods of the computer's mathematic model, DYNAMIC to assign the patients to five groups among multidimensional space. Then, another method, M-DEC was used to diagnose it back on one plane. The result was compared with that by the usual clinical diagnosis, also five groups were obtained, the group of Deficiency of both Liver and Kidney, syndrome of intermingled Cold with Heat, Deficiency of Qi and Yin, syndrome of Dampness-Heat stagnating in collaterals and syndrome of Phlegm-Dampness stagnating in collaterals. And Kappa was 0.77, greater than 0.6. It displayed the consistency in observation of these two methods, which was shown reliable. After that, we have detected the sensitivity of the syndrome diagnosis by computer's mathematic model method, the result was 96.67% and the specificity of that was 95.15%. So we consider this method could give us an objective judgment on TCM syndromes of rheumatoid arthritis.

Adult↗
PubMed2006

Cut-off value of coronary flow velocity reserve by transthoracic Doppler echocardiography for the assessment of significant donor left anterior descending artery stenosis in patients with spontaneously visible collaterals.

We evaluated the influence of collateral circulation on a donor left anterior descending artery and an appropriate cut-off value of coronary flow velocity reserve for the diagnosis of significant donor left anterior descending artery stenosis. Measurement of coronary flow velocity reserve by transthoracic Doppler echocardiography provides noninvasive assessment of significant left anterior descending artery stenosis. The cut-off value of coronary flow velocity reserve for the diagnosis of significant donor left anterior descending artery stenosis has not been well studied. We retrospectively examined 64 patients who had no significant left anterior descending artery stenosis and who had other coronary artery stenosis. Seventeen patients had collaterals from the left anterior descending artery (group A) and 47 patients did not have collaterals (group B). We prospectively examined 23 consecutive patients who had collaterals from the left anterior descending artery to other coronary arteries. Eight patients had a significant donor left anterior descending artery stenosis. Coronary flow velocity reserve assessment was performed by transthoracic Doppler echocardiography in the 2 protocols. Coronary flow velocity at baseline in group A was significantly higher than that in group B. Coronary flow velocity reserve in group A was significantly lower than that in group B (2.6 +/- 0.8 vs 3.2 +/- 0.9, p < 0.05). Coronary flow velocity during hyperemia and coronary flow velocity reserve were significantly lower in patients with significant stenosis. A cut-off value of 2.0 of coronary flow velocity reserve had a sensitivity of 88% and a specificity of 93% for the diagnosis of significant donor left anterior descending artery stenosis. In conclusion, coronary flow velocity reserve of a donor left anterior descending artery was decreased by the presence of collaterals. However, a cut-off value < 2.0 was appropriate for the diagnosis of significant donor left anterior descending artery stenosis in a population that included patients with collaterals.

Blood Flow Velocity↗
PubMed1991

Transcranial Doppler sonography: collateral pathways in internal carotid artery obstructions.

Fifty-four patients with stenoses and occlusions of the extracranial internal carotid artery (ICA) demonstrated by intravenous digital subtraction angiography (IVDSA) were studied by extracranial duplex and transcranial Doppler. Two hundred healthy volunteers served as control group. Intracranial collateralization was demonstrated in 32 patients with ICA stenoses greater than 80% and occlusions. Twelve patients with unilateral and 8 patients with bilateral ICA obstructions greater than 80% showed collateral supply via the anterior (ACA) and/or posterior cerebral artery (PCA). In 5 cases of unilateral ICA occlusion and in 7 patients with bilateral ICA stenoses greater than 80% and occlusions, the ophthalmic artery and ACA and/or PCA served as collateral vessels. Five patients with ICA occlusions showed leptomeningeal anastomoses in the region of the postocclusive middle cerebral artery (MCA). All 54 patients showed normal time-mean flow velocity in the post-obstructive MCA. In unilateral ICA stenoses greater than 80% and occlusions, the pulsatility index in the ipsilateral MCA was reduced in comparison with the contralateral side, indicating that this parameter is more sensitive to hemodynamic effects of ICA obstructions than time-mean velocity.

Angiography, Digital Subtraction↗
PubMed2005

Role of contrast-enhanced MR venography in the preoperative evaluation of parasagittal meningiomas.

Parasagittal meningiomas (PSM) may pose a difficult surgical challenge since venous patency and collateral anastomoses have to be clearly defined for correct surgical planning. The aim of this study was to assess the diagnostic value of contrast-enhanced (CE) magnetic resonance venography (MRV) in the preoperative evaluation of venous infiltration and collateral venous anastomoses in patients with PSM. CE-MRV was compared with phase-contrast (PC) magnetic resonance (MR) angiography, conventional angiography (when available), and surgery as a reference. Twenty-three patients undergoing surgery for meningiomas located adjacent to the superior sagittal sinus were prospectively evaluated. All the patients underwent both conventional MR examination and MRV. This was performed by means of PC and CE techniques. Both sets of angiograms (CE and PC) were evaluated by two expert neuroradiologists to assess (1) patency of the sinus (patent/occluded), (2) the extent of occlusion (in centimeters), and (3) the number of collateral anastomoses close to the insertion of the meningioma. Eight patients underwent digital subtraction angiography (DSA). All patients were operated on, and intraoperative findings were taken as the gold standard to evaluate the diagnostic value of MRA techniques. PC-MRV showed a flow void inside the sinus compatible with its occlusion in 15 cases, whereas CE-MRV showed the sinus to be occluded in five cases. CE-MRV data were confirmed by surgery, showing five patients to have an occlusion of the superior sagittal sinus. The PC-MRV sensitivity was thus 100% with a specificity of 50%. In those cases in which both MRV techniques documented occlusion of the sinus, the extent of occlusion was overestimated by PC compared with CE and surgery. CE-MRV depicted 87% of collateral venous anastomoses close to the meningioma as subsequently confirmed by surgery, while PC showed 58%. In the preoperative planning for patients with meningiomas located close to a venous sinus, CE-MRV provides additional and more reliable information concerning venous infiltration and the presence of collateral anastomoses compared with PC sequences.

Adult↗
PubMed1975

[Nonocclusive mesenteric vascular disease following atrio-ventricular block and pacemaker treatment. Gangrene of small and large bowel with occlusion of inferieor mesenteric artery (author's transl)].

A case of nonocclusive mesenteric vascular disease consequential to a low cardiac output syndrome in a patient with a temporary pacemaker is reported. Preexisting occlusion of the inferior mesenteric artery resulted in a total gangrene of small and large bowel. Experimental findings suggest that this occlusion could have resulted in a compensatory increase of blood flow in the superior mesenteric artery. The possibility is discussed that the preexisting necessary increase of superior mesenteric blood flow could be followed by equally increased sensitivity of regional organic systems in non-occlusive mesenteric vascular disease.

Abdomen, Acute↗
PubMed1984

Ultrasonographic study of portal venous system in portal hypertension and after portosystemic shunt operations.

One hundred sixty patients with portal hypertension were examined by means of ultrasonography in order to evaluate the sensitivity of this technique in the diagnosis of intrahepatic portal hypertension and in the detection of portal vein thrombosis. Thirty-eight of these patients were selected for a portosystemic shunt and were reexamined after operation to assess the value of ultrasonography as a screening test for the patency of surgical portosystemic shunts. In patients with intrahepatic portal hypertension the main ultrasonographic findings observed were dilatation of the portal trunk of more than 1.3 cm (56.6% of cases), patency and dilatation of the umbilical vein (5.8%), presence of intra-abdominal collateral vessels (11.6%), splenomegaly with dilatation of splenic vein radicles at the hilus (91.3%), and disappearance of normal caliber variations during respiration in splenic or mesenteric veins (78.5% and 88.4%, respectively). The disappearance of normal caliber variations proved a highly specific and sensitive finding. Partial or total occlusion of the portal trunk was observed at ultrasonography in 19 of 21 (90.5%) patients with portal vein thrombosis. Surgical portosystemic shunts were displayed in 28 of 37 patients (75.7%). Ultrasonography seems to be the most important noninvasive tool in the diagnosis of portal hypertension. In patients selected for surgical portosystemic shunts ultrasonography supplies morphologic data regarding liver parenchyma and abdominal vascular anatomy, and it should be performed as a routine screening test for assessment of surgical shunt patency.

Humans↗
PubMed1978

Recognition of splenic vein occlusion.

Radiologic findings and medical records of 27 patients with angiographic documentation of splenic vein occlusion were reviewed. The most common causes were pancreatic carcinoma, pancreatitis, and malignant lymphoma. Radiographic findings which suggest splenic vein occlusion are gastric varices without esophageal varices and collateral veins in the left upper abdomen during the vascular phase of rapid sequence pyelography. Additional features may be associated with the underlying disease, such as pancreatic calcification and upper abdominal mass lesions. The diagnosis is usually confirmed by high dose celiac or splenic angiography. Examination of the stomach with barium for the detection of gastric varices is more sensitive than has been previusly recognized; features which suggest them are described. Isolated gastric varices may be a clue to isolated splenic vein occlusion and its underlying causes.

Adult↗
PubMedDate not supplied

Dielectric spectrogram for instantaneous evaluation of ischemic injury of the liver.

Electrical properties of tissues sensitively reflect structural and physiologic changes. The authors examined the use of a dielectric spectrogram for instantaneous evaluation of ischemic injury of the liver. Wistar rats, which had enough collateral circulation for portal bypass with subcutaneous transposition of the spleen, were used. Four ischemic periods (15, 30, 60, and 120 min) were examined and followed by reflow. Permittivity and conductivity were measured at 39 frequency points in the 20 Hz-1 MHz range using an LCR meter system. They were then expressed in a loss tangent (LT) plot to clear their behavior. The maximum LT value (max-LT) and the minimum LT value (min-LT) of the normal liver were 3.98 +/- 0.28 and 2.98 +/- 0.22, and appeared in 15-20 kHz and 150-300 kHz, respectively. During the first 30 min after ischemia, max-LT decreased to 3.25 +/- 0.14 (p < 0.005) and its range shifted to 0.3-0.6 kHz, and min-LT decreased to 1.35 +/- 0.06 (p < 0.001) without shifting of range. Max-LT then decreased gradually and min-LT began to increase. After reflow, max-LT increased and higher max-LT was observed in the longer ischemic cases. Max-LT at 1 hr after reflow correlated negatively with recovery rate of bile flow at that time (y = -0.238x + 1.84, r2 = 0.82). Additionally, the difference between max-LT and min-LT at just before reflow (dif-LT) showed a significant correlation coefficient with recovery rate of bile flow at 1 hr after reflow (y = 2.22x -3.32, r2 = 0.92).

Animals↗
PubMed1982

[Responses of pyramidal tract neurons and cortico-rubral neurons to stimulation of different lateral hypothalamic structures in the cat].

Extracellular responses of pyramidal tract, corticorubral and nonidentified neurons of pericruciate cortex to electrical stimulation of lateral hypothalamus and cutaneous stimulation of all limbs were studied in cats anaesthetized with chloraloze. Responses to hypothalamic stimulation were found in 73%, 55% and 79% of cells respectively. A number of pyramidal tract neurons and nonidentified cells responded to hypothalamic stimulation monosynaptically. On the other hand the latency of corticorubral neuronal responses were longer, less stable and were considered to be polysynaptic. Some cortical neurons responded to stimulation of more than one part of the hypothalamus. Pyramidal tract and cortico-rubral neurons with axon collaterals directed to hypothalamus were identified. Some nonidentified neurons responded to hypothalamic stimulation antidromically and were considered to be corticohypothalamic neurons. It was shown that most of cortical neurons sensitive to hypothalamic stimulation responded also to cutaneous stimulation of more than one limb and had wide bilateral receptive fields.

Animals↗
PubMed1987

Angiographic morphology and intraluminal coronary artery thrombus in patients with angina pectoris: clinical correlations.

A prospective study was conducted in 104 consecutive patients who underwent coronary angiography for the evaluation of angina pectoris. 50 patients experienced unstable symptoms, while the rest of them were stable. Coronary lesions reducing the luminal diameter by at least 50% were compared between both groups according to localization, grade, length, type and collateralization. Eccentric irregular lesions (EIL) appeared more frequently in the unstable group of patients (27% vs 3%, P less than 0.01), while the incidence of concentric lesions was higher in stable group (45% vs 26%, P less than 0.02). There was no significant difference in localization, grade, length, or collateralization. EIL were most frequently identified as spontaneous AP producing lesions (55%, P less than 0.001) in 29 patients in the unstable group. Spontaneous angina was associated in 86% with EIL, occlusions, or filling defects--all of these lesions might contain occlusive or nonocclusive thrombi. EIL with a narrow neck appeared on angiograms earlier than EIL with a wall irregularity. We conclude that EIL is a sensitive and very specific angiographic marker of unstable AP. The morphologic details of EIL may help one to choose appropriate therapy.

Angina Pectoris↗
PubMed1995

Ulnar collateral ligament: differentiation of displaced and nondisplaced tears with US and MR imaging.

PURPOSE: To compare the usefulness of ultrasound (US) and magnetic resonance (MR) imaging in the differentiation of displaced and nondisplaced tears of the ulnar collateral ligament (UCL). MATERIALS AND METHODS: Seventeen patients (eight female and nine male, aged 14-70 years) with clinically diagnosed tears underwent examination with US and MR imaging. T1-weighted, spin-echo (SE) and T2-weighted, turbo SE sequences were used. MR and US findings were compared with those of surgery. Normal UCLs in 21 volunteers were also examined with MR imaging. RESULTS: The results of US were correct in 15 patients, but displaced and nondisplaced ruptures were misinterpreted in two patients (sensitivity, 88%; specificity, 83% for displaced, 91% for nondisplaced). Sensitivity and specificity were both 100% for MR imaging. The T2-weighted sequence was more useful because the normal UCL is rarely homogeneously hypointense. CONCLUSION: MR imaging is better than US, but both methods are useful in the evaluation of the torn UCL.

Adolescent↗
PubMed1996

Dobutamine-induced wall motion abnormalities: correlations with myocardial fractional flow reserve and quantitative coronary angiography.

OBJECTIVES: This study evaluated both the relation between dobutamine-induced wall motion abnormalities and the physiologic and morphologic features of epicardial coronary artery stenoses and the impact of the extent of the area at risk on the sensitivity of dobutamine echocardiography. BACKGROUND: The accuracy of dobutamine echocardiography has traditionally been assessed by comparing results with stenosis geometry. Myocardial fractional flow reserve is a functional index of coronary stenosis severity that takes into account both antero-grade and collateral flow and may therefore be a more appropriate standard for comparison. METHODS: Seventy-five patients with normal left ventricular function, good echocardiographic images and an isolated coronary stenosis underwent, within 6 h, dobutamine echocardiography, quantitative coronary angiography and intracoronary pressure measurements. Myocardial fractional flow reserve was calculated as the ratio of mean hyperemic distal coronary to aortic pressure. RESULTS: The degree of dobutamine-induced dyssynergy correlated significantly with percent diameter stenosis (r = 0.68), area stenosis (r = 0.68) and minimal lumen diameter (r = -0.60) and markedly better with myocardial fractional flow reserve (r = -0.77). However, marked dispersion of the individual data was observed. The sensitivity of dobutamine echocardiography in detecting lesions with a minimal lumen diameter < or = 1 mm and diameter stenosis > or = 50% was 83% and 80%, respectively. All but one patient with a myocardial fractional flow reserve >0.75 had a normal stress test result. Among patients with a myocardial fractional flow reserve < or = 0.75, the sensitivity of dobutamine echocardiography was significantly lower for lesions in vessels with a reference diameter < or = 2.6 mm than for lesions in larger vessels (58% vs. 90%, p = 0.008). CONCLUSIONS: 1) The magnitude of wall motion abnormalities induced by dobutamine infusion correlates with angiographic and, more closely, with functional indexes of stenosis severity, even though a wide scatter is observed. 2) In patients with a functionally significant stenosis, the amount of myocardium at risk is a critical determinant of the accuracy of dobutamine echocardiography.

Coronary Angiography↗
PubMed2000

Adenosine receptor blockade reveals N-methyl-D-aspartate receptor- and voltage-sensitive dendritic spikes in rat hippocampal CA1 pyramidal cells in vitro.

The present study was done to determine the possible effects of endogenous adenosine, present in the extracellular fluid of the hippocampal slice, on pyramidal cells in the CA1 region using intracellular recording techniques. Administration of 5 microM of the adenosine receptor antagonist, 8-sulfophenyltheophylline (n=11), induced a depolarization (2.6+/-0.4 mV, mean+/-S.E.M.) with an increase in input resistance (6.7+/-2.1%) in pyramidal cells, and increased the amplitude of the excitatory postsynaptic potentials elicited by stimulation of Schaffer collateral afferents; 50 microM 8-sulfophenyltheophylline (n=68) produced a similar depolarization (3.4+/-1.7 mV) and an increase in input resistance (26+/-3.0%), but also produced spontaneous, synchronized giant excitatory postsynaptic potentials which could generate bursts of spikes. These effects lasted more than 10 min after washout. In the presence of 20 microM 6-cyano-7-nitro-quinoxaline-2,3-dione, a non-N-methyl-D-aspartate receptor antagonist, and 50 microM D-2-amino-5-phosphonovalerate, an N-methyl-D-aspartate receptor antagonist, 50 microM 8-sulfophenyltheophylline (n=4) induced only depolarization (3.1+/-1.3 mV) and an increase in input resistance (23+/-3.8%). In the presence of 20 microM 6-cyano-7-nitro-quinoxaline-2,3-dione only, 50 microM 8-sulfophenyltheophylline (n=7) induced not only the depolarization with an increase in input resistance, but also the occurrence of small-amplitude (11+/-5.6 mV), fast rising, all-or-none, voltage-sensitive spikes of 2-3 ms duration, which were attributed to a dendritic origin. The latency of these dendritic spikes in response to stimulation of Schaffer collateral afferents lasted up to 21 ms. These dendritic spikes could generate one or more action potentials, depending on the resting membrane potential and the frequency of the dendritic spikes. In the presence of 50 microM 8-sulfophenyltheophylline plus 20 microM 6-cyano-7-nitro-quinoxaline-2,3-dione, 50 microM D-2-amino-5-phosphonovalerate blocked the spontaneous dendritic spikes (n=4). In the presence of 5 microM 8-sulfophenyltheophylline, 200 microM N-methyl-D-aspartate (n=5) increased the occurrence of dendritic spikes. These data indicate that adenosine present in the extracellular fluid of the hippocampal slice tonically inhibits not only (S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate-mediated synaptic transmission, but also voltage- and N-methyl-D-aspartate receptor-sensitive dendritic spikes. Endogenous adenosine acting on adenosine A(1) receptors is thus visualized as a control to prevent the genesis of synchronized giant excitatory postsynaptic potentials. In our experiments, blockade of this tonic activation of adenosine receptors appears to have altered the origins of action potentials and led to epileptiform firing in CA1 pyramidal cells.

Action Potentials↗