scholarly journals Habituation of swimming activity in the medicinal leech

1985 ◽  
Vol 116 (1) ◽  
pp. 169-188
Author(s):  
E. A. Debski ◽  
W. O. Friesen
Keyword(s):  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Body Wall ◽  
Spontaneous Recovery ◽  
Medicinal Leech ◽  
The Body ◽  
Swimming Activity ◽  
Stimulus Generalization ◽  
Anterior Segments ◽  
Stimulation Of

Tactile stimulation (light stroking) of a body wall flap attached to the ventral nerve cord of the medicinal leech evokes episodes of swimming activity. This swimming response undergoes habituation, involving changes in swim initiation and swim maintenance. Repeated stimulation of the body wall flap evoked swimming activity between three and 39 times before this response failed. During repetitive stimulation, the length of swim episodes decreased by about 50%. The number of swim episodes which could be elicited was not correlated with swim episode length. Following habituation, swim initiation showed significant spontaneous recovery, but swim episode length returned only to 60% of control values. In preparations where spontaneous recovery was followed by rehabituation, the number of swim episodes elicited declined with each habituation-recovery sequence. Additional stimulation immediately following habituation trials had a dual effect: recovery of the swimming response was delayed, but the lengths of swim episodes following spontaneous recovery were increased. Pinching the body wall flap immediately restored the swimming response in an habituated preparation. Swim initiation habituated more rapidly during stimulation of anterior body wall flaps than during stimulation of mid-body or posterior flaps. However, swim length was independent of this regional variation in swim responsiveness. The number of swim episodes elicited by stimulation of body wall flaps attached to posterior or anterior segments depended upon whether this segment was stimulated before or after other flaps. In contrast, in mid-body segments there was no evidence for such stimulus generalization. The lengths of swim episodes elicited during sequential stimulation of several body wall flaps were independent of the stimulation sequence. We propose that separate processes control swim initiation and swim maintenance. These processes must be repeated in most, if not all, of the segmental ganglia of the leech ventral nerve cord.

scholarly journals MUSCLE TENSION AND REFLEXES IN THE EARTHWORM

1923 ◽  
Vol 5 (3) ◽  
pp. 327-333 ◽  
Author(s):  
A. R. Moore
Keyword(s):  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Body Wall ◽  
Muscle Tension ◽  
Posterior Part ◽  
The Body ◽  
Entire Length ◽  
Sensory Cells ◽  
Ventral Region ◽  
Anterior Segments

1. By the use of preparations of earthworm in which the cutaneous receptors have been anesthetized with a solution of M/8 MgCl2, it is shown that peristalsis can be initiated by tension alone. 2. The receptors of the tension reflex are the intermyal sensory cells of the ventral region of the body wall. 3. It is concluded that Straub obtained the tension reflex because his preparations contained the intermyal receptors; Budington was unable to observe the tension reflex in any preparation from which the intermyal receptors had been removed. 4. Intermyal receptors are the receptors of the following reaction: Passive unilateral tension of the posterior part of an earthworm induces active homolateral tension of the musculature of the anterior segments, and results in the course of progress being brought into line with the enforced orientation of the tail. This reaction is termed the homostrophic reflex. 5. The receptors for the reaction are distributed throughout the entire length of the worm, the effectors are limited to the anterior 15 to 20 segments. The impulse is conducted by the ventral nerve cord. 6. The interaction of the homostrophic reflex and tropisms is considered.

scholarly journals Mutations Affecting Nerve Attachment of Caenorhabditis elegans

Genetics ◽  
2001 ◽  
Vol 157 (4) ◽  
pp. 1611-1622 ◽  
Author(s):  
Go Shioi ◽  
Michinari Shoji ◽  
Masashi Nakamura ◽  
Takeshi Ishihara ◽  
Isao Katsura ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Body Wall ◽  
The Body ◽  
Genetic Loci ◽  
Muscle Attachment ◽  
C Elegans ◽  
Ventral Cord ◽  
Excretory Canal

Abstract Using a pan-neuronal GFP marker, a morphological screen was performed to detect Caenorhabditis elegans larval lethal mutants with severely disorganized major nerve cords. We recovered and characterized 21 mutants that displayed displacement or detachment of the ventral nerve cord from the body wall (Ven: ventral cord abnormal). Six mutations defined three novel genetic loci: ven-1, ven-2, and ven-3. Fifteen mutations proved to be alleles of previously identified muscle attachment/positioning genes, mup-4, mua-1, mua-5, and mua-6. All the mutants also displayed muscle attachment/positioning defects characteristic of mua/mup mutants. The pan-neuronal GFP marker also revealed that mutants of other mua/mup loci, such as mup-1, mup-2, and mua-2, exhibited the Ven defect. The hypodermis, the excretory canal, and the gonad were morphologically abnormal in some of the mutants. The pleiotropic nature of the defects indicates that ven and mua/mup genes are required generally for the maintenance of attachment of tissues to the body wall in C. elegans.

Physiology of Water Motion Detection in the Medicinal Leech

1981 ◽  
Vol 92 (1) ◽  
pp. 255-275
Author(s):  
W. OTTO FRIESEN
Keyword(s):  
Neuronal Activity ◽  
Water Waves ◽  
Nerve Cord ◽  
Action Potentials ◽  
Ventral Nerve Cord ◽  
Body Wall ◽  
Medicinal Leech ◽  
Afferent Input ◽  
Excitatory Input ◽  
Simultaneous Action

1. Neuronal activity resulting from stimulation by water waves occurs in ventral nerve cord-body wall preparations of the medicinal leech, Hirudo medicinalis. In segmental nerves, this activity consists of afferent compound action potentials with graded amplitudes resulting from simultaneous action potentials in many small sensory axons. Afferent input impinging on one segmental ganglion activates neuronal activity along much of the ventral nerve cord. 2. Previously identified tactile mechanoreceptors are insensitive to low-amplitude wave stimulation. Touch-cell impulse activity can be evoked by moderate or strong wave stimulation, but these impulses appear to arise near the cell body, not from the peripheral receptor endings. 3. The transduction sites for wave stimulation are localized at or very near the segmental sensilla. Because of their location and modality the receptors were named ‘sensillar movement receptors’ (SMR). 4. S cells (Rohde's fibre) receive suprathreshold excitatory input during SMR activation without concomitant activity in the tactile mechanoreceptors. 5. The annulus erector motor neurones contralateral to the afferent SMR inflow are inhibited by SMR activation. This inhibition is also observed in ganglia adjacent to the ganglion receiving the afferent input and provides a neuronal basis for reflexive smoothing of the leech body wall. 6. Two neurones in the anterior median packet of segmental ganglia receive powerful synaptic input during SMR activation. One, cell 202, receives 10 mV excitatory potentials while the other, cell 201, receives 10 mV inhibitory potentials.

Role of central interneurons in habituation of swimming activity in the medicinal leech

1986 ◽  
Vol 55 (5) ◽  
pp. 977-994 ◽  
Author(s):  
E. A. Debski ◽  
W. O. Friesen
Keyword(s):  
Tactile Stimulation ◽  
Body Wall ◽  
The Body ◽  
Swimming Activity ◽  
Cycle Period ◽  
Direct Stimulation ◽  
Impulse Frequency ◽  
Neuronal Mechanisms ◽  
Intracellular Stimulation ◽  
Stimulation Of

Swimming activity evoked by light tactile stimulation of a body wall flap in dissected leech preparations undergoes habituation (5). In this study, we examine the activity of several interneurons (cell 204, cell 205, the S cell, and cell 208) during habituation trials to study further the neuronal mechanisms that mediate this decline in responsiveness. Light tactile stimulation of the leech body wall evoked initially a marked excitatory response in cell 204 homologs (segmental swim-initiating neurons) that preceded the initiation of swimming activity. This response decreased over the course of repeated stimulus trials; however, no marked decline in cell 204 activity accompanied the cessation of swim initiation. A similar activity pattern was observed in cell 205. Thus the habituation of swimming activity to stroking of the body wall is not due solely to reduced input to cell 204 and cell 205. The early activity of cell 204 was not correlated to the duration of subsequent swim episodes. However, the impulse frequency of cell 204 during swim episodes was negatively correlated to the period of swim cycles. This correlation between cell 204 activity and cycle period occurred both within individual episodes as well as between trials in a habituation series. Direct stimulation of cell 204 with current pulses evoked swimming activity reliably for an average of 72 trials. Therefore, habituation that results from stroking the body wall (which occurs after approximately 6 trials) is not mediated by plasticity in the connections between cell 204 and the swim oscillator. The S cell fired repeatedly in response to light tactile stimulation. This response declined with repeated trials. Intense intracellular stimulation of the S cell was sufficient to initiate swimming activity in some preparations. The magnitude and duration of the excitation required to initiate swimming by this means were far greater, however, than that which occurred during stroking the body wall. The response of cell 208 (a swim oscillator cell) to body wall stimulation during habituation trials was variable; usually an initial hyperpolarization was followed by some depolarization. No aspect of this response correlated with the onset of habituation. Our results are consistent with the idea that cell 204 and cell 205 are part of the pathway that mediates swimming activity in response to light tactile stimulation of the leech body wall, and that habituation occurs, in part, as the result of reduced sensory input to this cell.(ABSTRACT TRUNCATED AT 400 WORDS)

Neuronal control of swimming in the medicinal leech. IV. Identification of a network of oscillatory interneurones

1978 ◽  
Vol 75 (1) ◽  
pp. 25-43
Author(s):  
W. O. Friesen ◽  
M. Poon ◽  
G. S. Stent
Keyword(s):  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Body Wave ◽  
Medicinal Leech ◽  
The Body ◽  
Cycle Period ◽  
Neuronal Control ◽  
Swimming Movement ◽  
Analogue Models ◽  
Motor Neurones

Four oscillatory interneurones that appear to be the principal components of the central swim oscillator of Hirudo medicinalis have been identified on each side of the segmental ganglia of the ventral nerve cord. During ‘swimming’ episodes of an isolated nerve cord preparation each interneurone undergoes a polarization rhythm that is phase-locked with the impulse burst rhythm of the motor neurones known to drive the swimming movement. Passage of current into any of the interneurones can shift the phase of the swim rhythm. One of the interneurones projects its axon rearward to posterior ganglia and the other three project their axons frontward to anterior ganglia. The oscillatory interneurones are connected both intra- and interganglionically to form a topologically complex intersegmental network of concatenated ring circuits that possess the feature of recurrent cyclic inhibition. Theoretical analysis and electronic analogue models show that the network is inherently oscillatory and can produce both a cycle period and intra- and intersegmental phase relations of its elements that are appropriate for generating the body wave of the swimming movement.

Initiation, Maintenance and Modulation of Swimming in the Medicinal Leech by the Activity of a Single Neurone

1978 ◽  
Vol 77 (1) ◽  
pp. 71-88 ◽  
Author(s):  
JAMS C. WEEKS ◽  
WILLIAM B. KRISTAN JR.
Keyword(s):  
Horseradish Peroxidase ◽  
Nerve Cord ◽  
Tactile Stimulation ◽  
Medicinal Leech ◽  
Swimming Activity ◽  
Cycle Period ◽  
Impulse Frequency ◽  
Contraction Phase ◽  
Pattern Characteristic ◽  
Stimulation Of

A neurone (designated cell 204) has been identified in the segmental ganglia of the leech which, when stimulated intracellularly in isolated nerve cords, reliably initiates and maintains the neuronal activity pattern characteristic of swimming. In a minimally dissected leech, cell 204 activity results in normal swimming movements. Cell 204 is an unpaired, intersegmental interneurone which is present in most, if not all, of the segmental ganglia. Horseradish peroxidase injections indicate that cell 204 has extensive arborizations in its own ganglion and sends an axon both anteriorly and posteriorly via Faivre's Nerve. Cell 204 is normally quiescent, but during swimming activity becomes depolarized and produces impulse bursts in the ventral contraction phase of its own segment. Such activity is observed in every cell 204 in the nerve cord and is independent of the stimulus used to evoke the swimming episode. Activity in any cell 204 is sufficient for initiation and maintenance of swimming activity, whereas activity in any two of them is not necessary for swimming. During swimming activity, imposed increases in the impulse frequency of any cell 204 cause a decrease in the swim cycle period of the entire nerve cord. Tactile stimulation of the skin, which is an effective method of eliciting swimming episodes, excites cell 204. Our findings indicate that cell 204 may activate swimming in the intact leech.

scholarly journals Physiological characterisation of antennal mechanosensory descending interneurons in an insect (Gryllus bimaculatus, Gryllus campestris) brain

2001 ◽  
Vol 204 (13) ◽  
pp. 2265-2275 ◽  
Author(s):  
Michael Gebhardt ◽  
Hans-Willi Honegger
Keyword(s):  
Electrical Stimulation ◽  
Experimental Evidence ◽  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Sensory Nerves ◽  
Gryllus Bimaculatus ◽  
Central Origin ◽  
Gryllus Campestris ◽  
Descending Interneurons ◽  
Stimulation Of

SUMMARY We investigated five different descending brain interneurons with dendritic arborizations in the deutocerebrum in the crickets Gryllus bimaculatus and G. campestris. These interneurones convey specific antennal mechanosensory information to the ventral nerve cord and all responded to forced antennal movements. These interneurones coded for velocity and showed preferences for distinct sectors of the total range of antennal movements. Their axons descended into the posterior connective either ipsilateral or contalateral to the cell body. Electrical stimulation of sensory nerves indicated that the interneurons received input from different afferents of the two antennal base segments. One interneuron had a particularly large axon with a conduction velocity of 4.4ms−1. This was the only one of the five interneurons that also received visual input. Its activity was reduced during voluntary antennal movements. The reduction in activity occurred even after de-efferentation of the antenna, indicating that it had a central origin. Although we do not have experimental evidence for behavioural roles for the descending antennal mechanosensory interneurons, the properties described here suggest an involvement in the perception of objects in the path of the cricket.

Mechanoreceptors, Photoreceptors and Rapid Conduction Pathways in the Leech, Hirudo Medicinalis

1969 ◽  
Vol 50 (1) ◽  
pp. 129-140 ◽  
Author(s):  
M. S. LAVERACK
Keyword(s):  
Nerve Cord ◽  
Body Wall ◽  
The Body ◽  
Nerve Fibres ◽  
Peripheral Stimulation ◽  
Conducting Pathway ◽  
Transmission Of Information ◽  
Rapid Transmission ◽  
The Right ◽  
Light Flashes

1. Mechanoreceptors in the body wall of the leech Hirudo are stimulated by deformation of the animal's surface. They respond at all frequencies of stimulation up to about 50-60 Hz. 2. Light flashes, from a microscope lamp or an electronic flash source, are also a potent means of peripheral stimulation. 3. After peripheral stimulation impulses can be recorded in a fast central pathway. This pathway conducts equally well in the posterior to anterior and in the opposite directions. 4. Interference with either the right or left connective linking any two segmental ganglia does not interrupt the rapid conduction of these impulses. 5. Severance of the median connective or Faivre's nerve interrupts conduction. This seems to implicate at least one, and possibly more, of the nerve fibres of this median connective in the rapid transmission of information from the extremities of the body. 6. A slower conducting pathway also exists in the nerve cord.

scholarly journals Ingestive behaviour and physiology of the medicinal leech

1988 ◽  
Vol 137 (1) ◽  
pp. 513-527 ◽  
Author(s):  
C. M. Lent ◽  
K. H. Fliegner ◽  
E. Freedman ◽  
M. H. Dickinson
Keyword(s):  
Body Wall ◽  
Initial Rate ◽  
Medicinal Leech ◽  
The Body ◽  
Meal Size ◽  
Blood Sucking ◽  
Animal Size ◽  
Ingestive Behaviour ◽  
Blood Meals ◽  
Blood Meal Size

Ingestion lasts 25 min in Hirudo medicinalis and is characterized by pharyngeal peristalsis which fills the crop. This peristalsis has an initial rate of 2.4 Hz which decays smoothly to 1.2 Hz at termination of ingestion. During ingestion, the leech body wall undergoes peristalsis which appears to aid in filling the crop diverticula. Body peristalsis begins at a rate of 10 min-1 and decreases linearly to 2 min-1 at termination. The body also undergoes dorsoventral flexions when blood flow is occluded. Blood meal size increases slightly with leech size: 8.4 g for 1-g leeches and 9.7 g for 2-g leeches. However, relative meal size decreases markedly with increasing animal size; from 8.15 times body mass for 1-g to 4.80 times for 2-g leeches. When intact leeches were exposed to micromolar concentrations of serotonin, there was an increase in the rate of pharyngeal peristalsis and the size of the blood meals. Leeches excrete the plasma from their ingested blood meals. Excretion is activated during ingestion, which increases feeding efficiency by increasing the proportion of blood cells in the ingestate. Excretion continues for 4–6 days following ingestion, removing all the remaining plasma from the ingestate. Leech ingestion comprises stereotyped muscular movements, secretion of saliva and excretion of plasma. A strikingly similar feeding physiology is seen in the blood-sucking insect Rhodnius, and we suggest that efficient sanguivory may require the convergent evolution of similar ingestive mechanisms.

Visual and Multimodal Interneurones in the Ventral Nerve Cord of the Cockroach, Periplaneta Americana

1973 ◽  
Vol 59 (3) ◽  
pp. 675-696
Author(s):  
R. J. COOTER
Keyword(s):  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Tactile Stimulation ◽  
Periplaneta Americana ◽  
Compound Eye ◽  
Visual Stimulation ◽  
Contralateral Stimulation ◽  
Thoracic Nerve ◽  
General Properties ◽  
Stimulation Of

1. Visual and multimodal units were recorded from the thoracic nerve cord of the cockroach, Periplaneta americana, using glass microelectrodes. 2. Compound-eye units could be classified as ON-, OFF- or ON-OFF-units according to their response to visual stimulation. Some were multimodal, firing to both visual and tactile stimulation of the antennae. 3. Although some units were found to be either fired by ipsilateral or by contralateral stimulation only, others were fired by both types of stimulation, often in different ways. 4. Ocellar units were invariably OFF-units, mainly phasic, but one type showed tonic dark-firing in addition to the phasic OFF-burst. 5. The general properties of cockroach visual units are discussed and compared with those reported by other workers for different insects.

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