AMPA/kainate and NMDA-like glutamate receptors at the chromatophore neuromuscular junction of the squid: role in synaptic transmission and skin patterning

Publication Type:Journal Article
Year of Publication:2003
Authors:P. A. Lima, Nardi, G., Brown, E. R.
Journal:European Journal of Neuroscience
Volume:17
Pagination:507-516
Date Published:Feb
Type of Article:Article
ISBN Number:0953-816X
Accession Number:WOS:000180899600008
Keywords:Alloteuthis subulata, APLYSIA-CALIFORNICA, BRAIN NEURONS, calcium, D-ASPARTATE RECEPTORS, giant synapse, glutamate, Invertebrate, LONG-TERM POTENTIATION, MOUSE CENTRAL NEURONS, NITRIC-OXIDE SYNTHASE, SENSORIMOTOR SYNAPSES, SENSORY NEURONS, SEPIA-OFFICINALIS, synapse
Abstract:

Glutamate receptor types were examined at the chromatophore synapses of the squids Alloteuthis subulata and Loligo vulgaris, where nerve-induced muscle contraction causes chromatophore expansion. Immunoblotting with antibody raised against a squid AMPA receptor (sGluR) demonstrated that AMPA/kainate receptors are present in squid skin. Application of L-glutamate evoked chromatophore muscle contractions in both ventral and dorsal skins, while NMDA was only active on a subpopulation of dorsal chromatophores. In dorsal skin, neurotransmission was partly blocked by either AMPA/kainate receptor antagonists (CNQX and DNQX) or NMDA receptor antagonists (AP-5 and MK-801) or completely blocked by simultaneous application of both classes of antagonists. In isolated muscle fibres, ionophoretic application of l-glutamate evoked fast inward CNQX- and DNQX-sensitive currents with reversal potentials around +14 mV and a high conductance to Na+ . In fibres from dorsal skin only, a slower outward glutamate-sensitive current appeared at positive holding potentials. At negative potentials, currents were potentiated by glycine or by removing external Mg2+ and were blocked by AP-5 and MK-801. Glutamate caused a fast, followed by a slow, transient increase in cytoplasmic Ca2+. The slow component was increased in amplitude and duration by glycine or by lowering external Mg2+ and decreased by AP-5 and MK-801. In cells from ventral skin, no 'NMDA-like responses' were detected. Thus, while AMPA/kainate receptors mediated fast excitatory synaptic transmission and rapid colour change over the whole skin, activation of both AMPA/kainate and NMDA-like receptors in a subpopulation of dorsal chromatophores prolonged the postsynaptically evoked Ca2+ elevation causing temporally extended colour displays with behavioural significance.

Short Title:Eur. J. Neurosci.Eur. J. Neurosci.
Alternate Journal:Eur. J. Neurosci.
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith