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991.
Francis M. Sessler Robert D. Mouradian Jung-Tung Cheng Hermes H. Yeh Weimin Liu Barry D. Waterhouse 《Brain research》1989,499(1)
Previous in vivo studies from our laboratory have consistently shown that iontophoretically applied norepinephrine (NE) can potentiate γ-aminobutyric acid (GABA)-induced depressant responses of cerebrocortical, cerebellar and hypothalamic neurons. Additional experiments have further suggested that this noradrenergic facilitating action is specific for GABA and results from the activation of a β-type adrenoceptor. The goal of the present studies was to determine if the cAMP second messenger system might also be a component of the mechanism responsible for this NE modulatory action on GABA-mediated inhibition. In one set of in vitro experiments, we examined cerebellar neuronal responses to GABA before, during and after iontophoretic application of NE, 8-bromo3′,5′-cylic AMP (BcAMP) or 3-isobutyl-1-methyl xanthine (IBMX) or bath application of forskolin (10–30 μM). In a second group of in vivo studies, extracellularly recorded responses of individual cerebellar Purkinje (P) cells to iontophoretic pulses of GABA or β-alanine were examined before, during and after NE or BcAMP microiontophoresis. In 20 of 25 cerebellar cells recorded from tissue slices, iontophoretically applied NE markedly enhanced responses to GABA in a manner similar to that observed previously in vivo. In these in vitro preprarations, bath application of forskolin was also capable of potentiating GABA-induced inhibition in each of 4 cases tested whereas dideoxy-forskolin was not. Iontophoretic application of IBMX further enhanced the facilitating effects of NE on GABA-induced inhibition in 10 of 11 cases tested. Furthermore, under in vitro conditions, BcAMP augmented inhibitory responses to GABA in all cerebellar neurons tested. In the intact rat brain, iontophoretic administration of BcAMP caused a marked NE-like augmentation of P-cell responses to GABA in 73% of the cells tested. As with NE, BcAMP was ineffective in enhancing P-cell inhibitory responses to β-alanine, an agent which like GABA causes hyperpolarization, by increasing Cl− conductance. In summary, these results indicate that a membrane permeant analog of cAMP, a phosphodiesterase inhibitor and an agent which directly activates adenyl cyclase can mimic the previously observed GABA-potentiating actions of NE. Thus, these findings provide further support for the contention that noradrenergic enhancement of GABA inhibition results from a cascade of transmembrane events which includes β-receptor activation, adenyl cyclase stimulation and increased intracellular production of cAMP. 相似文献
992.
A modified anterior interhemispheric approach for clipping aneurysms of the anterior communicating artery is described. This approach is preferred on anatomical grounds because the anterior circle of Willis can be fully visualized with minimal manipulation of the frontal lobes and anterior cerebral arteries. The advantages of this approach are minimal traction, reduced operative time, and preservation of the olfactory nerve. 相似文献
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En-Lin Yeh Yi-Shiung Yeh 《European journal of nuclear medicine and molecular imaging》1981,6(2):69-71
The ejection fractions measured with the radionuclide method are usually lower than those measured with the X-ray contrast method in our hospitals. One of the reasons for this may be that the photon attenuation by the cardiac blood pool and soft tissue is greater for the larger end-diastolic ventricle than that for the end-systolic ventricle. Mathematically, the error due to photon attenuation in radionuclide ejection fraction study is calculated to be about 5 percentage points. Clinically, if 5 percentage points are added to the ejection fractions measured by the radionuclide method, the results would correlate better with the studies by the X-ray contrast method. The correction factors for photon attenuation may also be applied in calculation of the residual urinary bladder volume. 相似文献
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A method of ultrasound directed needle puncture using a clamp and a guide block is described. It eliminates the need for an aspiration biopsy transducer and has proved to be simple, accurate, and inexpensive. 相似文献
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We studied the systemic and renal acid-base response of monkeys during ten weeks of immobilization. By three weeks of immobilization, arterial pH and bicarbonate concentrations were elevated (chronic metabolic alkalosis). Net urinary acid excretion increased in immobilized animals. Urinary bicarbonate excretion decreased during the first three weeks of immobilization, and then returned to control levels. Sustained increases in urinary ammonium excretion were seen throughout the time duration of immobilization. Neither potassium depletion nor hypokalemia was observed. Most parameters returned promptly to the normal range during the first week of recovery. Factors tentatively associated with changes in acid-base status of monkeys include contraction of extracellular fluid volume, retention of bicarbonate, increased acid excretion, and possible participation of extrarenal buffers. 相似文献
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