摘要:

AbstractThe addition of glutamate to the bathing medium increased the average firing rate of cerebellar rat Purkinje cellsin vitro.At concentrations lower than 10−6M, there was no deviation from controls in the firing pattern or rate that was detectable. At 10−3Mglutamate, the amplitude of the action potentials was gradually decreased until all activity was abolished. The action of glutamate was rapid in onset and reversible. Glycine produced sustained depression of firing at concentrations higher than 10−3M.This inhibition was strychnine‐insensitive and considered nonspecific. Strychnine, on the other hand, exerted an excitatory influence on Purkinje cells when applied at low concentrations (10−8to 10−6M). The firing became more irregular and complex discharges appeared. Higher concentrations of strychnine (>10−5M) inhibited the spontaneous activity. The effect of strychnine was partly reversible. The data suggest that low concentrations of strychnine lower the threshold for inputs at excitatory as well as inhibi

ISSN:0022-3034    

DOI:10.1002/neu.480070203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractFive enzymes concerned with the metabolism of adenine derivatives were assayed in seven regions of the rat brain. A region which included the hypothalamus had the highest AMP deaminase and adenosine deaminase activities, while its 5'‐nucleotidase activities were relatively low. The enzymes named and also the uptake of [14C]adenine by incubated tissue samples were more active with hypothalamic than with neocortical tissues. On superfusion with glucose‐bicarbonate saline after assimilating [14C]adenine, the hypothalamic tissues released about 0.2% of their14C content per minute. This release was increased fourfold with electrical excitation but the presence of 0.25 μUMtetrodotoxin prevented most of this increase. The compounds released during superfusion and electrical stimulation were preponderantly hypoxanthine, inosine, and adenosine, with only small amounts of adenine nucleotides. The output of all these compounds increased during the period of stimulation and also the proportion of adenine nucleotides increased when stimulation was carried out in the presence of tetrodotoxin. The output of the nucleotides and adenosine increased more promptly when stimulated than did that of the other compounds named. The results are discussed in terms of the metabolic roles of the enzymes concerned, and in relation to whether the enzymes are acting on intracellular or extracellular substr

ISSN:0022-3034    

DOI:10.1002/neu.480070204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractThe single pass clearance of glycine from the cerebral capillary bed was measured in the rabbit with the indicator diffusion method. It was shown that glycine was extracted to the same degree as fructose (ca. 07). The concentration of glycine injected into the carotid artery was varied some 700‐fold without significantly affecting the clearance of this amino acid in transit through the brain. Cross inhibition of the unidirectional movement of glycine was not demonstrable. These present results and most previous studies suggest that this putative neurotransmitter does not cross the blood‐brain barrier by a carrier mediated proc

ISSN:0022-3034    

DOI:10.1002/neu.480070205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractThe protein, β‐bungarotoxin, a presynaptic neurotoxin isolated from the venom of the snakeBungarus multicinctus, is known to inhibit mitochondrial function. Within 30 min after adding the toxin to a rat diaphragmphrenic nerve preparation, the quantal content increased tenfold and the frequency of miniature endplate potentials increased fourfold. No increase in miniature endplate potential frequency was seen in the absence of extracellular calcium. Since mitochondria may be involved in regulating intracellular calcium levels, the rate at which the transmitter release is turned off was studied by measuring delayed release in the presence and absence of toxin. Delayed release is elevated about eightfold by the toxin. If delayed release is due to residual calcium, as has been hypothesized, these data may be explained if the toxin does not alter the amount of calcium which enters the terminal, but rather the rate at which that calcium is removed. Alternatively, a calcium‐dependent modification of the release process itself might be produced.The eventual reduction in transmitter output did not appear to result from depletion of the terminal of releaseable packets of transmitter, but does require extracellular cal

ISSN:0022-3034    

DOI:10.1002/neu.480070206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractThe potential waves evoked in the caudate nucleus (CN) of cats by stimulation of the cerebral neocortex were stereotactically recorded. The head and the body of the caudate nucleus were systematically explored. Stimulation of the ipsilateral sigmoid gyrus and the orbitofrontal cortex evoked waves with the largest amplitude in the CN. Smaller potentials were evoked from the ipsilateral ectosylvian and suprasylvian gyri and from the sigmoid gyrus on the contralateral side. Antidromic conduction from the caudate nucleus to the cortex demonstrated the directness of the corticocaudate pathway. By stimulating the white matter and by making lesions, the corticocaudate pathway was shown to pass, in part, through the subcallosal fasciculus and, in part, through the internal capsule. Corticocaudate connections were shown to be separate from the fibers of the corticospinal tract. A staggered and extensively overlapping topographic progression of the corticocaudate projections was demonstrable along the antero‐posterior axis, but was less evident in the medio‐lateral direction. It was concluded that the intranuclear distribution of functional synaptic connections must be more profusely branched than was suspected from anatomical d

ISSN:0022-3034    

DOI:10.1002/neu.480070207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractIn cultures of dissociated chick sympathetic ganglia, retrograde (somatopetal) movement of concanavalin A receptors in the axolemma can be observed directly. Such movement was visualized by using concanavalin A coated red blood cells (ConA‐RBCs) as membrane markers. Forty‐eight percent of all ConA‐RBCs which bound to sympathetic nerve fibers moved somatopetally at rates ranging from 11‐84 μ/hr with a mean and standard error of 49 ± 6 μ/hr (n= 18). On nongrowing nerve fibers, the ConA‐ RBCs within 60 μ of the cell body showed retrograde movement, while on elongating neurites only those markers within 30 μ showed such movement. The rate of retrograde ConA‐RBC movement appeared to increase with distance from the cell soma. The binding of ConA‐RBCs to sympathetic neurites was specific for concanavalin A receptors since pretreatment with either concanavalin A or α‐methylglucopyranoside prevented this binding. Untreated polystyrene beads (1.1 μ) which bound nonspecifically to the neurite membrane also showed retrograde movement. These beads moved somatopetally at rates similar to those of the ConA‐RBCs but did so regardless of their initial distance from the soma. These data suggest that retrograde movement of surface elements might be a general property of cultured

ISSN:0022-3034    

DOI:10.1002/neu.480070208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractThe movements of spherical particles in the range of 0.3 to 0.8 μm diameter within neurities of cultured embryonic mouse spinal cord fragments were observed and recorded by means of Nomarski optics and time‐lapse photocinematography at high power. Particulate movements were measured by projecting the motion pictures onto a calibrated screen and recording the distances moved with time of linearly moving particles and making note of the direction (toward or away from the neuron soma) of movement. In all, 128 particles were measured in six cultures. These measurements were taken away from the neuron soma near the periphery of the neurites. Eighty‐three particles were noted to be moving toward the neuron at a mean velocity of 1.03 ± 0.38 (SD) μm/sec while 45 anterograde moving particles were noted to move at 1.07 ± 0.62 (SD) μm/sec. Statistical analysis of these velocities revealed no significant difference between them. Particles which were elongated and probably represented mitochondria moved more sluggishly and could not be measured accurately by the techniques employed. It appeared the spherical particles moving in a retrograde direction originated at the neurite tip apparently by pinocytosis. There was a suggestion that anterograde flow and retrograde flow may have been affected unequally by factors which develop in the observation chamber over a period of 2 hr or more. The most likely factor responsible was probably

ISSN:0022-3034    

DOI:10.1002/neu.480070209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480070210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480070202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY