摘要:

AbstractThe axonal branching pattern of the two cerebral giant neurones (CGCs) ofLymnaea stagnaliswas studied with intrasomatically applied horseradish peroxidase. The cells are symmetrical. Each CGC projects to the ipsilateral n. labialis medius and n. arteriae labialis, the subcerebral commissure, and to all ipsi‐ and contralateral buccal nerves. The contralateral buccal nerves are reached via the ipsilateral cerebro‐buccal connective and the buccal commissure. The CGC fire action potentials 1:1 in a driver‐follower relationship. Each cell is capable of both driving and following. The relationship depends on the membrane potentials of the somata. In driving CGC spikes are initiated in a cerebral spike trigger zone located near the soma. In following cells spikes are initiated in a distal zone located in the buccal ganglia. The buccal zone is only affected by the partner CGC. CGC are synchronized by three coupling mechanisms: mutual excitatory chemical synapses, electrotonic coupling, and common input. The chemical and electrotonic connections are located in the buccal ganglia. All spikes are relayed to the partner cell via the chemical synapses. The electrotonic coupling improves the efficiency of the chemical synapses. The dual connection selectively synchronizes the CGC‐axonal spikes from each side of the buccal mass. Common excitatory input affects the cerebral spike trigger zones and can initiate simultaneous spikes in both cells. This results in bilateral synchrony of spikes in the CGC‐axons in both the buccal and the l

ISSN:0022-3034    

DOI:10.1002/neu.480120502

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe ovulation hormone‐producing caudo‐dorsal cells (CDC) ofLymnaea stagnalishave three states of excitability (active, inhibited, and resting), which are related to the egg‐laying cycle. Active state CDC produce a firing pattern of prolonged spiking activity (1 spike/2 s), which in the animal occurs shortly before egg laying. In preparations it is evoked as an afterdischarge upon repetitive stimulation of CDC. The afterdischarge is not synaptically driven, but rests on a pacemaking mechanism. CDC are silent in the inhibited and resting states, which follow egg laying. In these states the membrane potential is mainly dependent on [K+]0. In the active state the ratio of the K+, Na+, and Ca2+permeabilities has changed considerably, probably resulting from an increased permeability to Na+and Ca2+. The firing rate in the afterdischarge is dependent on the membrane potential, which is confirmed experimentally by varying [K+]0.[Na+]0and [Ca2+]0directly influence the firing rate. Firing stops in Na+‐free saline, but is enhanced by Ca2+‐free or high‐Mg2+saline. TTX does not affect firing. Relatively high concentrations of Co2+and La3+(2 × 10−3M) strongly inhibit CDC. Regular firing can be changed into bursting by various means, such as high K+or addition of 1 mMBa2+. Bursting normally occurs at the beginning of the afterdischarge. Postburst hyperpolarizations are reduced in Ca2+‐free saline and by low Co2+(10−4‐5 10−4M). Active CDC are driven by a pacemaking mechanism constituted by a voltage‐dependent Na+/Ca2+channel and a Ca2+‐dependent K+channel, thus resembling that of bursting pacemakers. The pacemaking mechanism is inactive in the r

ISSN:0022-3034    

DOI:10.1002/neu.480120503

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

年代:1981

数据来源: WILEY

摘要:

AbstractAn examination of the pattern of outflow of radioactivity in sciatic nerves was made at times from 1 to 82 days in the rat and up to 132 days in the cat after injecting the L5 and L7 dorsal root ganglia, respectively, with3H‐leucine. Slow waves moving at a rate of 1–2 mm/day were looked for on the basis of their reported presence in the motor fibers of the rat. A consistent pattern of slow waves was not seen in the cat or rat sensory fibers of the sciatic nerves nor was evidence of a slow wave found in the cat dorsal columns. Irregularities in the pattern of outflow which at times appeared as “waves” did so in an irregular fashion, a pattern inconsistent with a steady progression of slow waves in the fibers. The decrease of radioactivity appearing first near the ganglia helps create the impression of a wave along with irregular decreases in the overall levels of radioactivity with time. The results were explained on the basis of the unitary hypothesis. The labeled components are considered to be moved down the fiber by the fast transport mechanism, those components dropping off locally in the fibers early on, constituting the slow wave. As those components turn over locally in the various organelles of fiber and are further redistributed, they may at times give rise to what appears a

ISSN:0022-3034    

DOI:10.1002/neu.480120504

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

年代:1981

数据来源: WILEY

摘要:

AbstractNeurons ofAplysia californicaare naturally pigmented and the pigment accumulates with age. In the present study the pigment was examined in the same neuron fromAplysiaof three postmetamorphic ages: young, sexually mature, and old. The large central neuron, R2, was examined by light and electron microscopy to determine if the pigment possessed properties similar to lipofuscin pigment seen in aging mammalian neurons. We used the same microscopic techniques that demonstrate the presence of lipofuscin in mammalian neurons. Light microscopic studies demonstrated a regional correlation between autofluorescence, staining with Sudan Black, and the naturally occurring pigment in old R2s. Electron microscopic studies revealed the presence of large vacuolated and lamellated membrane‐bound bodies in the peripheral cytoplasm of old R2s, similar to those found in mammalian neurons. The bodies were located in the same region in which autofluorescence and Sudan Black staining were observed. Although the naturally occurring pigment accumulates with age, it acquires characteristics of lipofuscin pigment in the neurons of older sexually mature animals. The presence of these pigment characteristics can be used as an index of aging inAplysianeurons as they are in mammalian neuron

ISSN:0022-3034    

DOI:10.1002/neu.480120505

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe gill withdrawal reflex (GWR) to direct gill stimulation was studied in sexually matureAplysiaand in those older by at least two months. The GWR threshold in oldAplysiawas five‐ to sevenfold higher than that in mature animals. In the habituation paradigm, the GWR amplitude decremented rapidly to zero in old animals whereas in mature animals it persisted for at least ten trials. The GWR could not be dishabituated in old animals. The GWR is an age‐dependent behavior in that parieto‐visceral ganglion suppression of the GWR appears to increase with age. Also the electrophysiological properties of two neurons in the parieto‐visceral ganglion were compared in the two age groups: L7a neuron which dishabituates the GWR in mature and not in old animals; and R2which manifests cytological changes with age. In old animals L7′s input resistance was lower, the time constant was increased, and the size of the psp evoked by gill stimulation was smaller than those of mature L7s. Similar membrane changes with age were measured in R2. Soma size of L7was approximately the same in the two age groups as was that of R2. The physiological parameters of neurons of known function continue to change during postmetamorphic life

ISSN:0022-3034    

DOI:10.1002/neu.480120506

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

年代:1981

数据来源: WILEY

摘要:

Abstract32P‐ATP was injected into the L5dorsal root ganglion and axoplasmic transport of the phosphorylated MA proteins 2, microtubule‐associated proteins 2, was observed. After the injection of32P‐ATP, the nerve was dissected out at prescribed time intervals and sliced into 5‐mm pieces. Each segment was electrophoresed on an SDS‐polyacrylamide slab gel and subjected to autoradiography. A protein of 310,000 dalton was transported at a velocity of 6.6‐10.6 mm/day in the axon with the electrophoretic mobility identical to that of MA proteins 2, one of the key components associated with the m

ISSN:0022-3034    

DOI:10.1002/neu.480120507

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe transport of labeled proteins from the hypothalamus to the neurohypophysis following35S‐methionine injection into the rat supraoptic nucleus was studied using a unique approach adapted for the study of short‐axon systems. Multiple‐rate components comparable to those found in other neuronal systems were demonstrated. Neurosecretory vesicle‐containing proteins (e.g., neurophysins) were transported at fast rates (≥ 120 mm/day), whereas the cytoskeletal protein, actin, moved principally in the slow component of transport. Two‐dimensional gel electrophoresis was used to analyze the diverse patterns of labeled proteins found in the various rate components of axonal transport in

ISSN:0022-3034    

DOI:10.1002/neu.480120508

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

年代:1981

数据来源: WILEY

摘要:

AbstractIn this study it was found that several agents which elevate cAMP levels in cells also increase dramatically the quantity of transmitter released from crayfish excitatory nerve terminals in response to a stimulus. With respect to time course and magnitude, the increase produced by one of these agents, the cyclic nucleotide phosphodiesterase inhibitor Squibb 20,009 (SQ 20,009), is unlike any reported for such a drug at a synapse. Additionally, SQ 20,009 potentiated the facilitation of transmitter release produced by serotonin (5‐HT) at this synapse. These results establish a possible role for cAMP in the control and modulation of transmitter release at the crayfish neuromuscular junction (NMJ). They further suggest that 5‐HT functions here by activation of a presynaptically located adenylate cycl

ISSN:0022-3034    

DOI:10.1002/neu.480120509

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe nature and role of the depolarizing afterpotentials (DAPs) of buccal motoneurons ofTritonia diomedeawere examined. Neuron B5 exhibits a DAP whose ionic dependence and modifiability by TEA and 4‐AP suggest a similarity to the DAP previously described in pleural pacemaker neurons. Reduction of the DAP severely reduces the ability of these neurons to generate bursts of action potentials. Certain other motoneurons (B1 and B6) are reexcited by a slow DAP (SDAP) which appears to be of synaptic origin. It is concluded that DAPs, which are dependent upon motoneuron activity, contribute to the synthesis of motor output by the buccal ganglio

ISSN:0022-3034    

DOI:10.1002/neu.480120510

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

年代:1981

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480120501

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

年代:1981

数据来源: WILEY