摘要:

AbstractThe serotonin (5‐hydroxytryptamine, 5‐HT) content of tissue compartments in the medicinal leech,Hirudo medicinalis, was measured by means of highpressure liquid chromatography coupled with electrochemical detection (HPLC–EC). Each segmental ganglion contains 21.3 ± 2.9 (9) pmol 5‐HT [X ± SEM (N)]. The pharynx contains 7.1 ± 1.1 (9) pmol 5‐HT/mg wet weight; the salivary glands 3.2 ± 0.9 (10), ventral body wall 2.0 ± 0.2 (11), and vasofibrous tissue 1.2 ± 0.2 (11). The blood of hungry leeches contains 8.7 ± 1.9 (7) nM5‐HT while that of well‐fed leeches is 2.2 ± 0.4 (6) nM.Leeches were injected with the cytotoxic analog of serotonin, 5,7‐dihydroxytryptamine (5,7‐DHT) producing selective lesions of the peripherally projecting serotonin‐containing neurons, and which in turn abolished their feeding behavior. The serotonin content of the pharynx and ganglia of these toxin‐treated leeches were lowered significantly. The serotonin levels within the body wall and salivary glands were not altered significantly by the toxin treatment, but the levels within the vasofibrous tissue and bloo

ISSN:0022-3034    

DOI:10.1002/neu.480150502

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

年代:1984

数据来源: WILEY

摘要:

AbstractAcetylcholine has been suggested as a neurotransmitter released in theAplysiagill by peripheral afferents of central neurons and by peripheral neurons within the gill. The perfused gill, isolated from the abdominal ganglion, was examined. At concentrations greater than 1 μM, acetylcholine elicited a slowly developing tonic contraction of the afferent vein that reversed upon washout. This effect was observed on both quiescent and active preparations. At concentrations less than 1 μM, acetylcholine perfusion resulted in a reduction of gill tone. The excitatory effect of acetylcholine was reduced 80 and 60% by the cholinergic antagonists atropine and hexamethonium, respectively. The acetylcholine‐evoked contraction was potentiated 2.5‐fold when curare was coinfused. Carbachol did not mimic the excitatory effects of acetylcholine. At all concentrations examined (1–100 μM), carbachol infusion reduced baseline tension, the amplitude of spontaneous contractions and contractions evoked by FMRFamide and dopamine. Contractions evoked by perfusion ofp‐chlorophenylthiocyclic AMP were greatly reduced when carbachol was added to the perfusate. Further addition of curare reversibly blocked carbachol inhibition of the cyclic AMP%evoked contractions. These finding suggest that excitatory and inhibitory cholinergic receptors are involved in the regulation of gill contractile behavior by ace

ISSN:0022-3034    

DOI:10.1002/neu.480150503

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

年代:1984

数据来源: WILEY

摘要:

AbstractSpreading depression (SD) in the chick retina is completely suppressed by 10 mMMgCl2in the bathing solution (Mg‐sensitive SD). However, after increasing the KCl concentration in the Mg solution to values between 10 and 20 mMthe retina can again exhibit SDs (Mg‐insensitive SD). It has been postulated that the Mg‐sensitive SD is a glutamatergic phenomenon. This is supported by the effect of four gl(utamate)‐antagonists—L‐proline, glutamic acid diethyl ester (GDEE),D‐α‐aminoadipate (D‐AA), and 2‐amino‐4‐phosphonobutyrate (APB)—which all suppressed this type of SD. It was suggested that this effect is due to competitive binding of glutamate involved in the Mg‐sensitive SD and the gl‐antagonist to glutamate receptors. The suppression of SD could be reversed by washing the preparation in a physiologic salt solution. The gl‐antagonists in relatively high concentrations had a cytotoxic effect which, when severe, suppressed SD and prevented the recovery of this phenomenon by washing the compound out of the tissue.The compounds examined had, in addition to their gl‐antagonistic properties, a gl‐agonistic effect, which was postulated to enhance the Na+permeability of neural membranes resulting in a release of K+into the extracellular space. In preparations bathed in 10 mMMgCl2(which suppresses Mg‐sensitive SDs) the four compounds investigated promoted Mg‐insensitive SDs supposedly when the extracellular K+concentration

ISSN:0022-3034    

DOI:10.1002/neu.480150504

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe gastric system of the lobster stomatogastric ganglion has previously been thought to include no neurons capable of endogenous bursting. We describe conditions under which one of the motorneurons, the CP cell, can burst endogenously in a free‐running manner in the absence of other phasic network activity. Isolated preparations of the foregut nervous system were used, and the CP bursting was either spontaneous or was activated by continuous stimulation of an input nerve.Three criteria were applied to establish the endogenous nature of such burst generation in CP: absence of phasic input, reset of the bursting pattern by pulses of current in a characteristic phase‐dependent manner, and modulation of burst rate by sustained injected current. (1) The firing of other cells which are known to be related synaptically to CP was monitored in nerve records. These other cells were either silent or fired only tonically. Cross‐correlograms showed that CP bursting was not ascribable to phasic activity in these other network cells. (2) A depolarizing current pulse of sufficient strength injected intracellularly between bursts triggered a burst prematurely and reset the subsequent rhythm. A hyperpolarizing pulse during a burst terminated it and reset the subsequent rhythm. Reset behavior was similar to that described for other endogenous bursters. (3) Application of a positive‐going ramp current initially caused an increase in burst rate, as described for other endogenous bursters. However, further depolarization caused a slower burst rate due to lengthening of the individual bursts, although mean firing frequency continued to increase throughout the range tested.Such free‐running endogenous repetitive bursting appeared to result from the CP's ability to produce slow regenerative depolarizations (“plateau potentials”). When bursting was present, so was the plateau property, as determined by I–V analysis and by the ability of brief current pulses to trigger and terminate bursts. The previous inability to observe endogenous bursting in preparations with central input removed may be due to the usual absence of the plateau property in su

ISSN:0022-3034    

DOI:10.1002/neu.480150505

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

年代:1984

数据来源: WILEY

摘要:

AbstractIn spiders, retrograde cobalt staining was used to clarify the distribution and detailed innervation of the three types of proprioceptors in the tibiometatarsal leg joint: internal joint receptors, lyriform slit sense organs, and cuticular spines and hairs. The axons of all these receptors run in just two lateral, ascending nerves, which had previously been associated only with the internal receptors. Each nerve contains several hundred axons ranging in diameter from 0.1 μm to ca. 10 μm. Each slit of the four tibial lyriform organs is innervated by two bipolar sensory neurons. The lateral nerves are entirely sensory and run just beneath the cuticle, a convenient site for electrophysiological recording. We demonstrate simultaneous nerve and muscle recordings from intact spiders; these, in combination with selective sensory ablations, show that a resistance reflex in the flexor metatarsi muscles is elicited by internal joint‐receptor un

ISSN:0022-3034    

DOI:10.1002/neu.480150506

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe fast axoplasmic transport of labeled proteins was studied in cats showing hindlimb paralysis 4–7 weeks after a single oral dose of tullidora (Karwinskia humboldtiana) toxins. The isotope (3H‐leucine) was injected into the spinal ganglion and the contralateral spinal cord of the seventh lumbar segment in order to study transport in sensory and motor fibers.The axoplasmic transport in motor fibers of the sciatic nerve was clearly altered in tullidora‐treated cats. The majority of these animals showed a gradual decline of radioactivity from the cord to the periphery instead of the clear‐cut wave front always seen in normal cats. An apparent wave was seen in three treated cats but the wave peak was behind the normal position and the slope of the wave front was reduced. While the rate of transport indicated by the farthest extent of the foot of the slope was not in all cases significantly changed, the results all indicated a hindered transport by the reduced slope front in the distal segments of the motor axons. In contrast, the axoplasmic transport appeared normal in the sensory fibers of all but one tullidora‐treated cat.Light and electron microscopy of medial gastrocnemius and sural (cutaneous) nerves revealed axonal constrictions and axolemal irregularities associated with organelle retention after tullidora treatment. Also, some mitochondria appeared swollen. These changes were more frequent and intense in the motor nerve fibers than in the cutaneous ner

ISSN:0022-3034    

DOI:10.1002/neu.480150507

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

年代:1984

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480150501

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

年代:1984

数据来源: WILEY