Neurotransmitters of squid chromatophores
Cornwell, J.C.; Messenger, J.B. (1995). Neurotransmitters of squid chromatophores, in: Abbott, N.J. et al. Cephalopod neurobiology: neuroscience studies in squid, octopus and cuttlefish. pp. 369-379
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| Authors | | Top |
- Cornwell, J.C.
- Messenger, J.B.
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| Abstract |
Squid chromatophores expand as a result of the contraction of a set of 15-25 radial muscles set around a sac containing pigment granules. Running along the surface of each radial muscle are excitatory nerve fibres that arise directly from cells lying in the brain. There appear to be no inhibitory fibres. The hypothesis that L-glutamate may be an excitatory transmitter at the neuromuscular junctions on the radial muscles has been confirmed by the application of a series of newly developed specific glutamate receptor agonists to the skin of the small loliginid squid, Alloteuthis subulata. All the non-NMDA receptor agonists tested on Alloteuthis expanded the chromatophores. More importantly, immunohistochemical staining of the skin with antibodies raised against L-glutamate shows that this putative transmitter is endogenous in the radial muscle nerves. Serotonin (5-hydroxytryptamine, 5HT) has long been known to affect the responses of chromatophores to nerve stimulation, and to cause paling of the skin (radial muscle relaxation) when applied topically. Similar effects have now been obtained with 5HT receptor agonists and immunohistochemical staining reveals that 5HT is also endogenous in the radial nerves. It remains to be established whether these two substances co-exist in the same nerve fibres. The mode of action of 5HT is not clear. |
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