摘要:

AbstractEgg‐laying inLymnaeais characterized by the stereotyped egg‐laying behavior (ELB), composed of foot contractions and shell movements. Egg‐laying can be induced by a clean water stimulus, that triggers a discharge of the neuroendocrine caudo‐dorsal cells (CDCs), which release the ovulation hormone into the blood. A part of the behavior is lost when egg‐laying is triggered by hormone injection, indicating that during natural stimulus‐induced or spontaneous egg‐laying this part (the first phase) may be controlled by neuronal events in the CNS triggered by (a) factor(s) not released to the blood. The authors have identified an unpaired neuron, the ring neuron, that is excited during anin vitroafterdischarge of the CDCs, and which, by its numerous axonal branches in the pedal ganglia, modulates motorneurons of the columellar muscle, which controls shell movements. These motorneurons, identified as such in reduced preparations by 1 for 1 muscle potentials and elements in the connecting nerve, all receive either excitatory or inhibitory input from the ring neuron, as well as from an unknown neuron which has common input of the ring neuron and the motorneurons. The action of the CDCs on the ring neuron cannot be mimicked by the ovulation hormone, and we therefore conclude that the first part of the ELB is probably caused by a nonhormonal local action of the CDCs on the ring neuron and possibly the common

ISSN:0022-3034    

DOI:10.1002/neu.480160102

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

年代:1985

数据来源: WILEY

摘要:

AbstractOvulation in the pond snailLymnaea stagnalisis controlled by the neuroendocrine caudo‐dorsal cells (CDCs) in the cerebral ganglia, which release an ovulation hormone during a period of impulse activity. Firing of the single RN in the right cerebral ganglion hyperpolarizes the CDCs. This hyperpolarization is caused by the opening of potassium channels in the axons that connect both the CDC clusters. By this action, that presumably is mediated by axonal branches of the RN in the intercerebral commissure closely associated with these CDC axons, the RN decouples both the CDC clusters. Although the RN has negative feedback on the CDC, it does not control afterdischarge characteristics. The authors suggest that the RN, next to the egg‐laying behavior, is involved in another behavior, not compatible with ovulation. Male reproductive activity is presented as a possible candidate for such behav

ISSN:0022-3034    

DOI:10.1002/neu.480160103

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe morphology of two pairs of identified peptidergic neurons (B11 and B12) located in the buccal ganglia ofTritonia diomedeawas described. Both pairs of neurons contained a large quantity of a small cardioactive peptide (SCP) in their somata. One of the pairs (B11), the large dorsal white cells, contained ACh in their somata along with SCP.Both pairs of cells appeared white in live preparations under epi‐illumination. Each B11 and B12 was a unipolar neuron and sent its major axonal branch through the ipsilateral gastro‐esophageal nerve to the gut. In addition, B12 sent a small branch to the contralateral buccal ganglion.A characteristic feature of both neuron pairs was their vesicular content. Three types of vesicles were observed in B11. Vesicles with electron‐lucent core (LCV) and electron‐dense core (DCV) were found in the somata. The axon hillock and the beginning of axon contained vesicles with variable electron dense core (VDCV) in addition to LCV and DCV. The ratio of DCV: LCV: VDCV changed from 5:95:0 for the perinuclear cytoplasm to 8:55:37 for the beginning of axon. The average maximum diameters were 97 ± 23 nm for DCV, 103 ± 32 nm for LCV and 106 ± 29 nm for VDCV.B12 somata contained DCV (average maximum diameter 100 ± 26 nm), LCV (109 ± 23 nm) and elliptical vesicles with eccentric electron‐opaque core

ISSN:0022-3034    

DOI:10.1002/neu.480160104

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

年代:1985

数据来源: WILEY

摘要:

AbstractSwimming inAequoreais controlled by a network of electrically coupled neurons (swim motorneurons) located in the inner nerve ring. The network is made up of the largest neurons in the ring, up to 22 μm in diameter. Intracellular recordings from swim motorneurons reveal slow membrane potential oscillations and a superimposed barrage of synaptic “noise.” The synaptic noise, but not the slow oscillations, is eliminated in seawater containing an elevated Mg++concentration. The swim motorneurons produce a rapid burst of two to eight action potentials preceding each contraction of the subumbrella. Spontaneous bursting persists in high‐Mg++seawater. Injected ramp currents indicated a “bursty” character of the swim motorneurons as suprathreshold depolarizations produced repetitive bursting with an increasing burst frequency with increased depolarization. Hyperpolarizing currents locally blocked spiking in swim motorneurons.Intercellular coupling was demonstrated with Lucifer Yellow injection and dual electrode recordings. In dye fills, only the large neurons of the inner nerve ring were dye‐coupled.Two pieces of evidence suggest that swim motorneurons activate the overlying epithelial cells via chemical synapses. First, direct synaptic connections have been noted in ultrastructural examination of the inner nerve ring region. Second, dual recordings from a swim motorneuron and an epithelial cell reveal a 1:1 correspondence between neuron spikes and epithelial synaptic potentials. The synaptic potentials occur with a latency as short as 3 ms which is constant in any one recording session. The results suggest that the swim motorneuron network ofAequoreanot only performs a motorneuron function, but also serves as the pattern generator for swimm

ISSN:0022-3034    

DOI:10.1002/neu.480160105

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

年代:1985

数据来源: WILEY

摘要:

AbstractAcetylcholine (ACh) causes contraction ofAplysiabuccal muscles E1 and I5, and serotonin (5‐hydroxytryptamine, 5‐HT) enhances ACh‐elicited contractions of these muscles. Possible roles of calcium influx in mediating these responses were examined by studying influx of45Ca++. 5‐HT increased calcium influx into both I5 and E1. Maximal influx occurred at 10−6M5‐HT and the increased influx could be sustained in the presence of 5‐HT for at least 10 min. ACh also caused calcium influx, and calcium influx increased approximately in proportion to log[ACh] from 10−5Mto 10−3MACh. 5‐HT and ACh probably bring about calcium influx by different mechanisms since the effect of ACh was additive to a maximal 5‐HT response, and 10−4M hexamethonium bromide inhibited the increased influx caused by ACh but did not affect influx caused by 5‐HT. Cyclic AMP analogues and forskolin neither caused an increase in calcium influx nor an increase in the influx caused by ACh. The data support a model in which ACh‐elicited contractions of I5 and E1 are due primarily to calcium entry across the extracellular membrane, and 5‐HT can “load” an intracellular site by a mechanism different from that activated by ACh. The data do not support a role for cyclic AMP in mediating th

ISSN:0022-3034    

DOI:10.1002/neu.480160106

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

年代:1985

数据来源: WILEY

摘要:

AbstractTwo criteria were developed to identify symmetrical synapses in the tentacle ganglion of the snailAchatina fulica. First, the concentration of electron lucent vesicles within 20 nm of one membrane had to be less than three times the concentration at the opposed membrane. Second, paramembranous densities had to be present in both cells, as unanimously judged by three independent observers. Nine synapses (27% of sample) satisfied both criteria. It is suggested that these synapses transmit chemically in two directions.

ISSN:0022-3034    

DOI:10.1002/neu.480160107

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

年代:1985

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480160108

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

年代:1985

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480160109

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

年代:1985

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480160110

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

年代:1985

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480160101

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

年代:1985

数据来源: WILEY