The nervous systems of cnidarians

TY - JOUR

T1 - The nervous systems of cnidarians

AU - Grimmelikhuijzen, C J

AU - Westfall, J A

PY - 1995/1/1

Y1 - 1995/1/1

N2 - Cnidarians have simple nervous systems and it was probably within this group or a closely-related ancestor that nervous systems first evolved. The basic plan of the cnidarian nervous system is that of a nerve net which, at some locations, has condensed to form nerve plexuses, or circular or longitudinal nerve tracts which may be syncytia. At the ultrastructural level, many cnidarian neurons have the combined characteristics of sensory, motor, inter- and neurosecretory neurons and thus appear to be multifunctional. We propose that these multifunctional neurons resemble the ancestors of the more specialized neurons that we find in higher animals today. The primitive nervous system of cnidarians is strongly peptidergic: from a single sea anemone species Anthopleura elegantissima, we have now isolated 16 different novel neuropeptides. These peptides are biologically active and cause inhibitions or contractions in muscle preparations or isolated muscle cells from sea anemones. The various peptides are located in at least six distinct sets of neurons showing that sea anemone neurons have already specialized with respect to their peptide content. Using immuno-electronmicroscopy, we have found that the peptides are located in neuronal dense-cored vesicles associated with both synaptic and non-synaptic release sites. All these data indicate that evolutionarily "old" nervous systems use peptides as transmitters. We have also investigated the biosynthesis of the cnidarian neuropeptides. These neuropeptides are made as large precursor proteins which contain multiple (up to 36) copies of immature neuropeptides. Thus, the biosynthesis of neuropeptides in cnidarians is very efficient and comparable to that of higher invertebrates, such as molluscs and insects, and vertebrates.

AB - Cnidarians have simple nervous systems and it was probably within this group or a closely-related ancestor that nervous systems first evolved. The basic plan of the cnidarian nervous system is that of a nerve net which, at some locations, has condensed to form nerve plexuses, or circular or longitudinal nerve tracts which may be syncytia. At the ultrastructural level, many cnidarian neurons have the combined characteristics of sensory, motor, inter- and neurosecretory neurons and thus appear to be multifunctional. We propose that these multifunctional neurons resemble the ancestors of the more specialized neurons that we find in higher animals today. The primitive nervous system of cnidarians is strongly peptidergic: from a single sea anemone species Anthopleura elegantissima, we have now isolated 16 different novel neuropeptides. These peptides are biologically active and cause inhibitions or contractions in muscle preparations or isolated muscle cells from sea anemones. The various peptides are located in at least six distinct sets of neurons showing that sea anemone neurons have already specialized with respect to their peptide content. Using immuno-electronmicroscopy, we have found that the peptides are located in neuronal dense-cored vesicles associated with both synaptic and non-synaptic release sites. All these data indicate that evolutionarily "old" nervous systems use peptides as transmitters. We have also investigated the biosynthesis of the cnidarian neuropeptides. These neuropeptides are made as large precursor proteins which contain multiple (up to 36) copies of immature neuropeptides. Thus, the biosynthesis of neuropeptides in cnidarians is very efficient and comparable to that of higher invertebrates, such as molluscs and insects, and vertebrates.

KW - Amino Acid Sequence

KW - Animals

KW - Cnidaria

KW - Molecular Sequence Data

KW - Nervous System

KW - Nervous System Physiological Phenomena

KW - Neuropeptides

KW - Sequence Homology, Amino Acid

KW - Species Specificity

KW - Synaptic Transmission

M3 - Journal article

C2 - 7833621

SN - 1023-294X

VL - 72

SP - 7

EP - 24

JO - Experientia

JF - Experientia

ER -