Excitability of nerve-free hydra

Campbell, Richard D.; Josephson, Robert K.; Schwab, W.; Rushforth, Norman B.

doi:10.1038/262388a0

Cited by 68 publications

(58 citation statements)

References 13 publications

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“…Extracellular studies have provided detailed descriptions of electrical signals but could not link them to a particular cell type. In fact, whether rhythmic potentials and longitudinal contraction bursts are conducted by neurons or by the muscle/epithelial cells is still under debate [10,20,21], and surgical isolations indicate that they can propagate along both axes of the epithelium [8]. Also, extracellular recordings, which could be more akin to electromyograms, can be disrupted by the motion of the animal [9], and therefore cannot be carried out in certain types of behavior.…”

Section: Introductionmentioning

confidence: 99%

Non-overlapping Neural Networks in Hydra vulgaris

2017

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Summary To understand the emergent properties of neural circuits it would be ideal to record the activity of every neuron in a behaving animal and decode how it relates to behavior. We have achieved this with the cnidarian Hydra vulgaris, using calcium imaging of genetically engineered animals to measure the activity of essentially all of its neurons. While the nervous system of Hydra is traditionally described as a simple nerve net, we surprisingly find instead a series of functional networks that are anatomically non-overlapping and are associated with specific behaviors. Three major functional networks extend through the entire animal and are activated selectively during longitudinal contractions, elongations in response to light and radial contractions, while an additional network is located near the hypostome and is active during nodding. These results demonstrate the functional sophistication of apparently simple nerve nets, and the potential of Hydra and other basal metazoans as a model system for neural circuit studies.

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Section: Introductionmentioning

confidence: 99%

Non-overlapping Neural Networks in Hydra vulgaris

2017

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“…This behavior has been termed a contraction burst and is accompanied by large electrical signals1718. Removal of nerve cells from Hydra tissue4 completely eliminated spontaneous contraction bursts in the body column. Such nerve-free polyps were nearly motionless for hours.…”

Section: Resultsmentioning

confidence: 99%

“…Such nerve-free polyps were nearly motionless for hours. Nevertheless, such polyps still responded to strong mechanical stimulation (pinching with forceps) with propagation of electrical signals and coordinated contraction of the body column4. Thus contraction of the body column is regulated at two levels: (1) epitheliomuscle cells are connected by gap junctions and can propagate an electrical signal mediating contraction in response to exogenous stimuli and (2) spontaneous initiation of epitheliomuscle cell contraction is controlled by the nervous system, since it is absent in nerve-free animals.…”

Section: Resultsmentioning

confidence: 99%

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Innexin gap junctions in nerve cells coordinate spontaneous contractile behavior in Hydra polyps

Takaku

Hwang

Wolf

et al. 2014

Sci Rep

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Nerve cells and spontaneous coordinated behavior first appeared near the base of animal evolution in the common ancestor of cnidarians and bilaterians. Experiments on the cnidarian Hydra have demonstrated that nerve cells are essential for this behavior, although nerve cells in Hydra are organized in a diffuse network and do not form ganglia. Here we show that the gap junction protein innexin-2 is expressed in a small group of nerve cells in the lower body column of Hydra and that an anti-innexin-2 antibody binds to gap junctions in the same region. Treatment of live animals with innexin-2 antibody eliminates gap junction staining and reduces spontaneous body column contractions. We conclude that a small subset of nerve cells, connected by gap junctions and capable of synchronous firing, act as a pacemaker to coordinate the contraction of the body column in the absence of ganglia.

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“…A few animals have excitable epithelia in addition to excitable neurons--epithelia which can conduct signals over wide areas without decrement. Epithelial or neuroid conduction has been demonstrated in hydrozoan coelenterates (Mackie, 1965(Mackie, , 1976Mackie and Passano, 1968;Spencer, a,b, 1975Spencer, , 1978Campbell et al, 1976), in larval amphibians (Roberts, 1969(Roberts, , 1971(Roberts, , 1975Roberts and Stirling, 1971;Spencer, 1974 b), in tunicates (Gait and Mackie, 197 I;Bone and Mackie, 1975;Mackie and Bone, 1976), and in molluscs (Kater et al, 1978). Epithelial conduction probably occurs as well in ctenophores (Horridge, 1965;Tamm, 1973) and in anthozoan coelenterates (McFarlane, 1969(McFarlane, , 1974Shehon and McFarlane, 1976).…”

Section: Introductionmentioning

confidence: 99%

Electrical properties of an excitable epithelium.

Josephson¹,

Schwab²

1979

The Journal of General Physiology

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The exumbrellar epithelium of the hydromedusa, Euphysajaponica, is composed of a single layer of broad (70 #m), thin (1-2 #m) cells which are joined by gap junctions and simple appositions. Although the epithelium lacks nerves, it is excitable; electrically stimulating the epithelium initiates a propagated action potential. The average resting potential of the epithelial cells is -46 inV. The action potential, recorded with an intracellular electrode, is an all-or-nothing, positive, overshooting spike. The epithelial cells are electrically coupled. The passive electrical properties of the epithelium were determined from the decrement in membrane hyperpolarization with distance from an intraceUular, positive current source. The two-dimensional space constant of the epithelium is 1.3 mm, the internal longitudinal resistivity of the cytoplasm and intercellular junctions is 196 ~:m, and the resistivity of both apical and basal cell membranes is greater than 23 k~cm 2. Although the membrane resistivity is high, the transverse resistivity of the epithelium is quite low (7.5 ~:m2), indicating that the epithelium is leaky with a large, transverse, paracellular shunt.

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Excitability of nerve-free hydra

Cited by 68 publications

References 13 publications

Non-overlapping Neural Networks in Hydra vulgaris

Non-overlapping Neural Networks in Hydra vulgaris

Innexin gap junctions in nerve cells coordinate spontaneous contractile behavior in Hydra polyps

Electrical properties of an excitable epithelium.

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