Biomaterial Database

Serial synapses in Aplysia. 1978

K Graubard

Serial synapses occur between small profiles in the neuropil of Aplysia abdominal ganglion. Material was fixed in phosphate buffered OsO4, embedded in epon, and sections were stained with uranyl acetate and lead citrate. A class of synapses had the following characteristics: (1) synaptic vesicles clustered against the presynaptic membrane, (2) a widened extracellular space of about 20 nm containing electron-dense material, (3) straightening of the pre- and postsynaptic membranes, and (4) no postsynaptic membrane specialization. Some density between the presynaptic membrane and the adjacent synaptic vesicles was occasionally observed. Synapses occurred between small profiles in the neuropil (typical profile diameters were 1--3 micrometer). In this sample of approximately 100 synapses, four serial synapses were identified. The serial synaptic profiles were all small. In addition to the finding of serial synapses, 40% of the postsynaptic profiles contained vesicles similar to the synaptic vesicles seen in presynaptic profiles. Serial synapses may be the anatomical substrate of presynaptic inhibition and facilitation and of dishabituation.

UI	MeSH Term	Description	Entries
D005724	Ganglia	Clusters of multipolar neurons surrounded by a capsule of loosely organized CONNECTIVE TISSUE located outside the CENTRAL NERVOUS SYSTEM.
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001048	Aplysia	An opisthobranch mollusk of the order Anaspidea. It is used frequently in studies of nervous system development because of its large identifiable neurons. Aplysiatoxin and its derivatives are not biosynthesized by Aplysia, but acquired by ingestion of Lyngbya (seaweed) species.	Aplysias
D013569	Synapses	Specialized junctions at which a neuron communicates with a target cell. At classical synapses, a neuron's presynaptic terminal releases a chemical transmitter stored in synaptic vesicles which diffuses across a narrow synaptic cleft and activates receptors on the postsynaptic membrane of the target cell. The target may be a dendrite, cell body, or axon of another neuron, or a specialized region of a muscle or secretory cell. Neurons may also communicate via direct electrical coupling with ELECTRICAL SYNAPSES. Several other non-synaptic chemical or electric signal transmitting processes occur via extracellular mediated interactions.	Synapse