<i>In vivo</i> responses of paired giant mechanoreceptor neurons in <i>Aplysia</i> abdominal ganglion

Cobbs, J. S.; Pinsker, H. M.

doi:10.1002/neu.480090508

Cited by 6 publications

(8 citation statements)

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“…Aplysia (Cobbs and Pinsker, 1978;Jahan-Parwar et al, 1983;Weiss et al, 1986b,c). The RM cell groups, which consist of moderately sized nonpigmented cells, appear to represent a distinct class of mechanosensory cells that differ in a number of respects from previously described sensory neuron clusters: (1) the responses of RM neurons exhibit very rapid sensory adaptation, (2) they are electrically coupled to one another, (3) they synthesize the SCPs, and (4) they do not exhibit sensorin-A-like immunoreactivity.…”

Section: Discussionmentioning

confidence: 99%

A population of SCP-containing neurons in the buccal ganglion of Aplysia are radula mechanoafferents and receive excitation of central origin

et al. 1994

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The rostral cluster of SCP-immunoreactive cells, originally identified in each buccal hemiganglion of juvenile Aplysia, was examined in mature specimens. Immunohistochemical and dye-fill experiments showed that each rostral cluster consists of approximately 40 cells. Although these neurons exhibit heterogeneity of size and shape, all cells project an axon into the radula nerve. Tracing of dye-filled cells showed that they project to the layer of tissue that lines the inner surface of the food-grasping portion of the chitinous radula. This tissue contains SCP- immunoreactive nerve fibers and varicosities in regions corresponding to the projections of dye-filled neurons. Several observations indicate that rostral cluster neurons transduce tactile stimuli applied to the radula surface: (1) each cell responds to touch of a circumscribed receptive field with a rapidly adapting burst of action potentials, (2) the evoked spikes arise abruptly from the resting potential without prepotentials, and (3) the responses persist when central and peripheral synaptic transmission is blocked in high Mg2+, low Ca2+ artificial seawater solutions. These cells, designated radula mechanoafferent (RM) neurons, do not respond to chemical stimuli including NaCl, glutamate, and seaweed extract. The highest density of receptive fields is found on the posterodorsal edges of the radula halves, areas most directly involved in grasping food. The RM neurons are electrically coupled cells, with coupling coefficients ranging from 0.006 to 0.22. They fire phasically during buccal motor programs, even in the absence of peripheral feedback from the radula or other portions of the buccal mass. In radiolabeling studies the RM cells were found to synthesize authentic SCPA and SCPB. Sensorin-A, a peptide that is localized to other Aplysia mechanoafferent neurons, was not detected immunohistochemically in these cells.

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Section: Discussionmentioning

confidence: 99%

A population of SCP-containing neurons in the buccal ganglion of Aplysia are radula mechanoafferents and receive excitation of central origin

et al. 1994

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“…In addition, it is activated by external mechanoafferent stimulation applied to the perioral zone. While C2 has a number of properties in common with other mechanoreceptors of invertebrates (Audesirk and Audesirk, 1980a, b;Byrne et al, 1974;Cobbs and Pinsker, 1978;Getting, 1976;Rosen et al, 1982) the overall constellation of properties of this cell distinguishes it from other receptor neurons in Aplysia and other invertebrates. For example, several types of sensory as well as motor neurons that exhibit branch block have been described (Dorsett and Sigger, 198 1;Haydon and Winlow, 1982;Spira et al, 1976;Spray et al, 1980a, b;Van Essen, 1973;Yau, 1976), but, unlike C2, these neurons are not blocked when first activated.…”

Section: Discussionmentioning

confidence: 99%

Sensory function and gating of histaminergic neuron C2 in Aplysia

Weiss¹,

Chiel²,

Kupfermann³

1986

J. Neurosci.

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This paper explores the possible sensory function of the identified histaminergic neuron C2. Mechanical stimulation of a narrow region around the mouth of the animal (perioral zone) elicits brief depolarizing potentials in C2. Extracellular recordings from the peripheral axons of C2 indicate that the depolarizing potentials are due to action potentials that are conveyed from the periphery but do not invade the cell body, since they fail at a region with a low safety factor within the cerebral ganglion. These blocked axonal spikes (A-spikes) function as if they were excitatory synaptic inputs to C2, since the synaptic output of C2 does not occur unless the A-spikes succeed in evoking full action potentials in the soma (or an electrically close initial segment) of C2. Furthermore, like synaptic potentials, the A-spikes exhibit temporal and spatial summation, and facilitation. C2 receives both tonic and phasic inhibitory synaptic potentials, which can decrease the summation of A-spikes and thereby alter the frequency-filtering properties of C2 or block its synaptic output. Thus, C2 appears to be an unusual proprioceptive afferent that has a high degree of integrative function and may provide critical gating that is dependent on a variety of external and internal conditions.

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“…Although peripheral nerves in Aplysia contain numerous large axons (e.g. Coggeshall, 1967), no neurons have yet been described in the CNS (Byrne et al, 1974;Cobbs and Pinsker, 1978;Dubuc and Castellucci, 1991;Hickie, 1994) or periphery (Bailey et al, 1979;Frost et al, 1997) with properties expected of rapidly conducting siphon mechanoafferents.…”

Section: 1997)' (A) Examples Of Responses Of An Le Cell Gill Motomentioning

confidence: 98%

Functions of the LE sensory neurons inAplysia

Walters

Cohen

1997

Invertebrate Neuroscience

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Mechanosensory neurons which innervate the siphon and have their cell bodies in the LE cluster of the abdominal ganglion of Aplysia have revealed many cellular and molecular processes that may play general roles in learning and memory. It was initially suggested that these cells are largely responsible for triggering the gill-withdrawal reflex evoked by weak siphon stimulation, and that most of this effect is mediated by their monosynaptic connections to gill motor neurons. This implied a simple link between plasticity at these synapses and modifications of the reflex during learning. We review more recent studies from several laboratories showing that the LE cells are not activated by very weak tactile stimuli that elicit the gill-withdrawal reflex, and that an unidentified population of siphon sensory neurons has lower mechanosensory thresholds and produces shorter latency responses. Furthermore, the direct connections between LE cells and gill motor neurons make a minor contribution when the reflex is elicited in pinned siphon preparations by light stimuli that weakly activate the LE cells. Because weak mechanical stimulation of the unrestrained siphon causes little or no LE cell activation, it is unlikely that, under natural conditions, sensitization or conditioning of reflex responses elicited by light siphon touch depends upon plasticity of LE cell synapses onto either motor or interneurons. The LE cells appear to function as nociceptors because they are tuned to noxious stimuli and, like mammalian nociceptors, show peripheral sensitization following nociceptive activation. This sensitization and the profound activity-dependent potentiation of LE synapses indicate that LE cell contributions to defensive reflexes should be largest during and after intense activation of the LE cells by noxious stimulation (with the LE cell plasticity contributing to long-lasting memory of peripheral injury). The LE sensory neurons offer special opportunities for direct tests of this and other hypotheses about specific mnemonic functions of fundamental mechanisms of neural plasticity.

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In vivo responses of paired giant mechanoreceptor neurons in Aplysia abdominal ganglion

Cited by 6 publications

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A population of SCP-containing neurons in the buccal ganglion of Aplysia are radula mechanoafferents and receive excitation of central origin

A population of SCP-containing neurons in the buccal ganglion of Aplysia are radula mechanoafferents and receive excitation of central origin

Sensory function and gating of histaminergic neuron C2 in Aplysia

Functions of the LE sensory neurons inAplysia

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