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111.
Previous studies suggest a reduced dopaminergic function in subjects with the A1 (minor) allele of the D2 dopamine receptor (DRD2) gene. To explore influences on visuospatial ability as a function of the DRD2 gene, 182 alcohol- and other drug-naive sons (age 10–14) of active alcoholic, recovered alcoholic, and nonalcoholic fathers were administered a visuospatial task (Benton's Judgment of Line Orientation Test) which makes minimal motoric/verbal demands. Visuospatial scores were lower for boys with the A1 allele and for sons of active alcoholics. A1-allele boys made more errors than A2 boys on all 11 of the template lines, with the effect being largest for the rightmost presentations. In contrast, the effect of family history for alcoholism was strongest on both right and left midquadrant presentations. Moreover, separate analyses of the two types of errors produced allele but not family history of alcoholism effects when the two lines were misjudged as farther apart than they actually were and family history but not allele effects where the two lines were misjudged as closer together. These results suggest that polymorphism of the DRD2 gene and family history of alcoholism are dissociable determinants of visuospatial ability and that visuospatial defects previously observed in alcoholics may, in part, be antecedent to their drinking behavior. 相似文献
112.
Leonards U Ibanez V Giannakopoulos P 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2002,146(2):172-183
Aging is accompanied by increasing difficulty in working memory associated with the temporary storage and processing of goal-relevant information. Face recognition plays a preponderant role in human behavior, and one might therefore suggest that working memory for faces is spared from age-related decline compared to socially less important visual stimulus material. To test this hypothesis, we performed working memory (n-back) tasks with two different visual stimulus types, namely faces and doors, and compared them to tasks with primarily verbal material, namely letters. Age-related reaction time slowing was comparable for all three stimulus types, supporting hypotheses on general cognitive and motor slowing. In contrast, performance substantially declined with age for faces and doors, but little for letters. Working memory for faces resulted in significantly better performance than that for doors and was more sensitive to on-line manipulation errors such as the temporal order. All together, our results show that even though face perception might play a specific role in visual processing, visual working memory for faces undergoes the same age-related decline as it does for socially less relevant visual material. Moreover, these results suggest that working memory decline cannot be solely explained by increasing vulnerability in prefrontal cortex related to executive functioning, but indicate an age-related decrease in a visual short-term buffer, possibly located in the temporal cortex. 相似文献
113.
Membrane currents of guinea-pig ventricular myocytes were recorded using the whole-cell voltage clamp method. The epinephrine-induced increase in Ca2+ current (2.9±0.5 times control) was reduced (1.8 ±0.3 times) by replacing Na+ with Li+ in the bathing solution. In addition, 0.5 M epinephrine increased a time-independent membrane conductance in the Na+ external solution, having a reversal potential of –19 ±3 mV (epinephrine-induced current). In the Li+ external solution, however, 0.5 M epinephrine failed to induce the epinephrine-induced current. The findings are consistent with the reported Li+ inhibition of GTP-binding protein and/or adenylate cyclase. 相似文献
114.
Stanley G. Rane George G. Holz IV Kathleen Dunlap 《Pflügers Archiv : European journal of physiology》1987,409(4-5):361-366
Dihydropyridine (DHP) calcium channel antagonists, which inhibit the slowly inactivating or L-type cardiac calcium (Ca) current, have been shown to be ineffective in blocking45Ca influx and Ca-dependent secretion in a number of neuronal preparations. In the studies reported here, however, the antagonist DHP nifedipine inhibited both the L-type Ca current and potassium-evoked substance P (SP) release from embryonic chick dorsal root ganglion (DRG) neurons. These results suggest that, in DRG neurons. Ca entry through L-type channels is critical to the control of secretion. The inhibition of Ca current by nifedipine was both voltage and time-dependent, significant effects being observed only on currents evoked from relatively positive holding potentials maintained for several seconds. As expected from these results, nifedipine failed to inhibit L-type Ca current underlying the brief plateau phase of the action potential generated from the cell's normal resting potential; likewise, no significant effect of the drug was observed on action potential-stimulated SP release evoked by electrical field stimulation. The results of this work are discussed in terms of an assessment of the role of L-type Ca channels in neurosecretion.This work was supported by United States Public Health Service Grant NS16483 (KD) and by a USPHS Postdoctoral Fellowship (SGR) 相似文献
115.
Stéphane Genet Raymond T. Kado 《Pflügers Archiv : European journal of physiology》1997,434(5):559-567
The contribution of the Na/K ATPase (pump) current to the polarization of the Purkinje cell has been studied using slices
of the rat cerebellum by blocking the pump with dihydro-ouabain (DHO) while recording the membrane potential with microelectrodes
in the somata. From our recordings, it appeared that blocking the pump depolarized the Purkinje cells more rapidly than might
be expected from shifts in Na+ and K+ concentrations, suggesting the removal of a hyperpolarizing current. Application of DHO, in the presence of tetrodotoxin (TTX),
led to calcium spike firing and plateau-like discharges suggesting activation of voltage-dependent calcium channels in the
dendrites. Adding 2 mM Co2+ to the medium did not prevent the depolarizations. Removing calcium from the bathing medium containing 2 mM Co2+ blocked the spiking activity but DHO application still produced a depolarization. Experiments to measure the current inhibited
by DHO indicated that the Na/K pump supplies a constant current of 240 pA. Substitution of the sodium with choline produced
a hyperpolarization, during which DHO had no effect on the membrane potential. Substitution of the sodium with lithium produced
only a slowly developing depolarization. It is concluded that in the cerebellar Purkinje cell, a continuous sodium ion influx
activates the pumps which produce a current that directly contributes to the membrane polarization. Possible pathways for
this sodium influx are discussed.
Received: 3 April 1997 / Received after revision and accepted: 12 May 1997 相似文献
116.
A. S. Amin A. O. Verkerk Z. A. Bhuiyan A. A. M. Wilde H. L. Tan 《Acta physiologica (Oxford, England)》2005,185(4):291-301
Aim: Brugada syndrome is an inherited cardiac disease with an increased risk of sudden cardiac death. Thus far Brugada syndrome has been linked only to mutations in SCN5A, the gene encoding the α‐subunit of cardiac Na+ channel. In this study, a novel SCN5A gene mutation (D1714G) is reported, which has been found in a 57‐year‐old male patient. Since the mutation is located in a segment of the ion‐conducting pore of the cardiac Na+ channel, which putatively determines ion selectivity, it may affect ion selectivity properties. Methods: HEK‐293 cells were transfected with wild‐type (WT) or D1714G α‐subunit and β‐subunit cDNA. Whole‐cell configuration of the patch‐clamp technique was used to study biophysical properties at room temperature (21 °C) and physiological temperature (36 °C). This study represents the first measurements of human Na+ channel kinetics at 36 °C. Ion selectivity, current density, and gating properties of WT and D1714G channel were studied. Results: D1714G channel yielded nearly 80% reduction of Na+ current density at 21 and 36 °C. At both temperatures, no significant changes were observed in V1/2 values and slope factors for voltage‐dependent activation and inactivation. At 36 °C, but not at 21 °C, D1714G channel exhibited more slow inactivation compared with WT channel. Ion selectivity properties were not affected by the mutation at both temperatures, as assessed by either current or permeability ratio. Conclusion: This study shows no changes in ion selectivity properties of D1714G channel. However, the profoundly decreased current density associated with the D1714G mutation may explain the Brugada syndrome phenotype in our patient. 相似文献
117.
Brighina F Piazza A Daniele O Fierro B 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2002,145(2):177-181
Recent studies showed hyperexcitability of the occipital cortex in subjects affected by migraine with aura. It has been shown that 1 Hz repetitive transcranial magnetic stimulation (rTMS) reduces excitability of visual cortex in normal subjects. The aim of the study was to investigate the effects of low frequency (1 Hz) rTMS on visual cortical excitability by measuring changes in phosphene threshold (PT) in subjects with migraine with aura. Thirteen patients with migraine with aura and 15 healthy controls were examined. Using a standardized transcranial magnetic stimulation protocol of the occipital cortex, we assessed the PT (the lowest magnetic stimulation intensity at which subjects just perceived phosphenes) before and after a 1-Hz rTMS train delivered at PT intensity for 15 min. The difference in the proportion of subjects reporting phosphenes in migrainer and control groups was significant (migrainers: 100% vs controls 47%; P<0.05), and 1 Hz rTMS over the occipital cortex led to a significantly increased visual cortex excitability expressed as a decrease in PT in subjects affected by migraine with aura. Conversely, after a 1-Hz TMS train normal subjects showed increased PT values, which suggests a decreased visual cortex excitability. Our findings confirm that the visual cortex is hyperexcitable in migrainers and suggest a failure of inhibitory circuits, which are unable to be upregulated by low frequency rTMS. 相似文献
118.
We have proposed a theory in which pathways ascending from the brainstem reticular formation control sensory centers in the dorsal thalamus and neocortex. We assumed that the sensory messages received at a given level are transformed by a stochastic process, called Alopex, in a way which maximizes responses in central feature analyzers. Perception is seen as a process involving a close cyclic interaction between brainstem and sensory relays. We discuss the specific case of visual information flow and the proposed modification of visual images at the level of the dorsal lateral geniculate nucleus (dLGN). Computer simulations of a simple model, representing the dLGN and reafferent control emanating from the reticular formation, show that sensory features are effectively enhanced and--in the absence of sensory input--quasi-sensory features may be generated by feedback of a simple scalar variable that is formed by the non-linear superposition of the responses of any number of feature analyzers. The model proposes a specific mechanism for such processes as visual imagery, hallucinations, and dreaming, and provides a framework for further studies into the nature of cognitive brain functions. 相似文献
119.
A rapidly inactivating Ca2+-dependent K+ current in pheochromocytoma cells (PC12) of the rat 总被引:13,自引:0,他引:13
The membrane electrical properties of undifferentiated pheochromocytoma cells of the rat (PC12) were studied using both current-and voltage-clamp techniques with the use of low-resistance blunt-tipped micropipettes (patch electrodes). In the presence of tetrodotoxin (TTX, 2–3 M), a spike-like wave form with a prominent after-hyperpolarization (AHP) was recorded following brief (< 10 ms) depolarizing current pulses. The inorganic divalent cations, Cd2+ (0.5 mM), Mn2+ (4mM), and 0 mM Ca2+/4 mM Mg2+ solution prolonged the duration, attenuated the AHP, slowed the rate of repolarization, and slightly enhanced the amplitude of this wave form. A rapidly inactivating outward current was recorded in over 70% of the cells under voltage-clamp conditions. This transient current was elicited at about ±30 mV, and was blocked by tetraethylammonium (5 mM), inorganic divalent cations (Cd2+, 0.5 mM; Mn2+, 4 mM; Ba2+, 3 mM), and removal of Ca2+ (0 mM Ca2+/4 mM Mg2+) from the local perfusion medium. In addition, 4-aminopyridine (5 mM), which blocks the transient outward K+ current IA in a variety of excitable cells, did not have any appreciable effect on this rapidly inactivating current. Moreover, it was possible to elicit the current at a holding potential of ±40 mV. The reversal potential of this current was ±90 mV, and shifted positively when extracellular K+ concentrations were elevated. It is concluded that PC12 cells have a rapidly inactivating Ca2+ -dependent K+ current. A possible explanation for the transient nature of this current may be the presence of an effective intracellular Ca2+ buffering (uptake or extrusion) system. 相似文献
120.
Jan Schmeller Michael Wessolly Elena Mairinger Sabrina Borchert Thomas Hager Thomas Mairinger Kurt Werner Schmid Jeremias Wohlschlaeger Robert F.H. Walter Fabian D. Mairinger 《Pathology, research and practice》2019,215(2):381-386