User:Alr1129

Cnidarian neuropeptides
Although the morphological 'simplicity', or rather lack of complexity when compared to later diverging organisms (arthropods, mammals, etc.), that cnidarians show might suggest a less complex nerve net, this is not the case. Neurons and synapses found within the cnidarian nervous network operate in the manner as those found in all later diverging animals: fast, overshooting action potentials produced by fast, inactivating sodium (Na+) currents, and fast chemical synapses and within hydrozoans electrical synapses as well.

Within the nerve net of Cnidarians, namely sea anemones (Anthozoa: hexacorallia) and jellyfish (cubozoans, schyphozoans, and hydrozoans thus far) a variety of neuropeptides can be found. These neuropeptides are similar to those found in other organisms such as Caenorhabditis Elegans (roundworm), Mus musculus (house mice), and even Homo sapiens (humans). Cnidarian neuropeptides have been analyzed using techniques such as: immunochytochemistry, histochemistry, biochemistry, molecular biology, behavioral and electrophysiology. Below is a table representation of the cnidarian neuropeptides and the organism in which they have been identified so far:

Key: C=Clear vesicles, D=Dense-cored vesicles. I=immunochytochemistry, H=histochemistry, B=Biochemistry, M=Molecular biology, P=Physiological/Behavioral effects, S=Synaptic localization.

=History= In the 1960s interest in cnidarian electrophysiological studies rose due to the access to large electrical signals from a variety of hydroid tissues. However, this interest was short-lived as the discovery of ‘epithelial conduction’, the finding of epithelial cells in hydroids capable of producing and transmitting electrical signals. This discovery led to the questioning of the electrical signal’s origin. The electrical signal could have been a cause of the neurons, or the epithelial cells, or a combination of the two. The lack of methodology to investigate the ‘epithelial conduction’ origin led to a decline in this field.

In the 1970s however, the discovery of a limited number of preparations that permitted intracellular recordings from neurons and a greatly improved understanding of the cnidarian neuroanatomy led to the re-emergence of interest in this field. The presences of distinct nerve tracts as opposed to the previously thought diffuse nerve nets helped explain the enormous size of the electrical activity recorded. In addition, the introduction of intracellular recording also allowed scientist to begin to investigate and contribute to our understanding of neurobiological principles.