摘要:

AbstractThe soma but not the axon of the giant neuron, R2, ofAplysiacan generate an all‐or‐none Ca spike in Na‐free or TTX‐containing medium (Junge and Miller, 1974). Extracellular axonal recordings made at several distances from the soma provide evidence that the transition in ability to fire a spike in Na‐free medium occurs within the first 250 μm of the axon. Application of 25 mMTEA‐Br to the bathing medium causes a more than tenfold increase in the duration of the somatic action potential. The duration of the axonal action potential in TEA decreases with distance from the soma. At distances greater than 3 mm from the soma this concentration of TEA causes little or no increase in the duration of the axon spike. The effect of 25 mMTEA on both the soma and proximal axon is blocked reversibly by 30 mMCoCl2or 1 mMCdCl2. The duration of the somatic action potential in TEA increases with an increase in Ca concentration of the bath. At a constant concentration of Na, the voltage level of the somatic plateau increases with Ca concentration in the manner predicted for a Ca electrode. In the presence of 11 mMCa2+the potential of the plateau is relatively insensitive to Na concentration. The TEA plateau in R2 reveals a prolonged voltage‐dependent permeability to Ca. The duration of the plateau may indicate the degree of Ca activation

ISSN:0022-3034    

DOI:10.1002/neu.480080502

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

年代:1977

数据来源: WILEY

摘要:

AbstractA method has been developed for the long‐term culture of dissociated adult mouse dorsal root ganglia (DRG). Of critical importance to the success of this technique was a three‐hour incubation in collagenase which softened the DRG and permitted gentle dissociation. The morphological and electrophysiological features of the dissociated adult DRG were similar to those observed in previous studies of immature (i.e., embryonic and newborn) DRG in culture and also to those of adult DRGin situ.With regard to electrophysiological work, the adult DRG neurons are superior to embryonic and newborn neurons because of their larger size and greatly increased survival in culture (no degeneration for first six days, and thereafter a relatively slow decrease). The adult neurons regenerated nerve fibers to an extent comparable to that of immature neurons. Therefore, the adult DRG cultures might be useful to study factors influencing regeneration in the adult mammalian nervous system. The adult cultures might also be useful to investigate factors influencing the aging proc

ISSN:0022-3034    

DOI:10.1002/neu.480080503

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe role of the electrosensory inputs in postural control was examined in the weakly electric fishEigenmannia virescens.These fish exhibit tonic postural tilt in response to a tilted plexiglas substrate in both transverse and longitudinal planes (rolling and head‐up pitching responses, respectively), but not to electrically “transparent” agar substrate. The fish's pitching and rolling responses were abolished when the electrosensory inputs from the trunk were bilaterally eliminated even though the fish's visual and mechanosensory lateral‐line systems remained intact. Unilateral lesion abolished the rolling response but not the pitching response. These results demonstrate the functional role of the electrosensory system in postural control, in addition to its known role in social communication and in object location, and the underlying neuronal mechanism is di

ISSN:0022-3034    

DOI:10.1002/neu.480080504

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

年代:1977

数据来源: WILEY

摘要:

AbstractFast axonal transport of [3H]protein has been examined in bullfrog primary afferent neurons incubated in media supplemented with divalent cations that can act as agonists or antagonists of calcium ions. Incubation in calcium‐free medium (CFM) had no effect on therateof transport, but reduced theamountof transported [3H]protein by 40–60% relative to transport in the contralateral preparation maintained in normal medium. Preparations incubated in CFM supplemented with 1.8 mMSrCl2(equimolar to the CaCl2concentration in normal medium) carried out transport at control levels. Incubation conditions in which primary afferent somata were exposed to the Sr2+‐medium while nerve trunks were maintained in CFM also supported normal transport. By contrast, selective exposure of nerve trunks to Sr2+‐medium, and somata to CFM resulted in a reduced level of transport similar to that observed when the whole preparation was incubated in CFM. The depression of transport resulting from incubation in CFM was shown to be reversible when preparations were transferred from CFM to either Sr2+‐supplemented CFM or to normal medium. By contrast to the effects of Sr2+, Ba2+(up to 18 mM) did not substitute for Ca2+in the transport process. When normal medium was supplemented with calciumantagonist cations, the amount of transport was depressed (Co2+>Mn2+>>Mg2+), with no concomitant effect on the rate of transport. Results of studies with Co2+, as well as those with Sr2+, suggest that a major locus of action of these cations is within the neuronal soma at a step subsequent to protein synthesis, and prior to the onset of protein translocation via the transport system. Thus, it is inferred that these divalent cations affect a calcium‐dependent step that occurs during the initiation phase of fast axona

ISSN:0022-3034    

DOI:10.1002/neu.480080505

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

年代:1977

数据来源: WILEY

摘要:

AbstractUsing organized nervous system tissue cultures of embryonic mouse spinal cord, time‐lapse motion pictures of intra‐axonal particle movements were made using Nomarski optics. The paths of 272 particles were followed and analyzed using digital computer methods. Particles had a bidirectional saltatory motility with net anterograde and retrograde velocities which were shown to be the same (about 1 micron per second). When anterograde moving and retrograde moving particles were analyzed separately for anterograde and retrograde saltations, the velocities of saltations in the direction of net movement were found to be 1.5 times greater than saltations against the direction of net movement. These differences were statistically significant. In addition, it was shown that there were regions within the axon where variations in particle motion were similar from particle to particle as they passed, and that more disturbed motion was found to occur near intra‐axonal objects which were judged to be mitochondria. No decrease of particle velocity was noted in regions away from mitochondria nor was an increase in velocity noted near them. Computer‐drawn particle plots illustrate the various facets of particle

ISSN:0022-3034    

DOI:10.1002/neu.480080506

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe release of acetylcholinesterase from neurons was studied using cultured chick‐embryo spinal‐cord cells. Cells dissociated from 12‐day‐old chick‐embryo spinal cords were grown in culture for 10–12 days. Numerous well differentiated spinal neurons were found after 7–10 days in culture. Acetylcholinesterase activity per dish increased by 60‐fold from days 2–12. Acetylcholinesterase was released into the surrounding media by the cells when they were incubated either in the standard culture medium or the serum‐free medium. Acetylcholinesterase release was significantly reduced when protein synthesis and microtubules were disrupted by cycloheximide and colchicine, respectively. Histochemical localization of acetylcholinesterase indicated that the synthesis and release of acetylcholinesterase are attributable to neurons. Cultured chick‐embryo brain and neuroblastoma cells also released acetylcholinesterase into the media. These results are discussed with regard to possible physiological roles for acetylcholinesterase s

ISSN:0022-3034    

DOI:10.1002/neu.480080507

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe responses of the widespread common inhibitory motor neuron (CI) to tactile stimulation of the cercus and the abdomen and electrical stimulation of the cercal nerve and the abdominal connectives are investigated. Tactile stimulation produces high frequency (>500 impulses/s) spike discharge in CI with the onset of CI activity preceding the discharge of the excitatory motor neurons. Electrical stimulation of the connectives demonstrates a monosynaptic connection between at least one intermediate sized fiber (conduction velocity = 3.7 m/s) in the abdominal connective and the ipsilateral CIs in the meso‐ and metathoracic ganglia. Electrical stimulation of the cercal nerve suggests a disynaptic path from cercal nerve to CI. Arguments are presented for a cercal afferent‐to‐CI reflex and the possible functional role of early excitation of CI is disc

ISSN:0022-3034    

DOI:10.1002/neu.480080508

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

年代:1977

数据来源: WILEY

摘要:

AbstractExperiments were performed on chronically denervated frog sartorius muscles to determine the permeability of the acetylcholine‐activated channels to organic cations. The membrane voltage response to bath‐applied acetylcholine was measured with the moving electrode when the muscles were bathed in normal Ringer and in Ringer in which all of the Na+had been replaced with an organic cation. The magnitude of the maximum voltage response was used to estimate the permeability of the channel to the organic cation. These results were compared with those which have been reported for innervated frog sartorius muscles (Maeno, Edwards, and Anraku, 1977). It is concluded that the permeability to a wide range of organic cations is virtually identical for the extrajunctional channels which develop following denervation and the channels which are localized at the junctional region of innervated musc

ISSN:0022-3034    

DOI:10.1002/neu.480080509

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

年代:1977

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480080510

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

年代:1977

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480080501

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

年代:1977

数据来源: WILEY