Biomaterial Database

Morphogenesis and synaptogenesis of the zebrafish Mauthner neuron. 1981

C B Kimmel, and S K Sessions, and R J Kimmel

The shape of the Mauthner neuron (M-neuron) and the distribution of its afferent synapses were studied between days 2 and 6 after fertilization in the zebrafish Brachydanio rerio. This interval is just after the outgrowth of M-dendrites begins, and during this time the M-cell acquires its definitive shape. The M-cell has two large invariant dendrites: The lateral dendrite terminates in the sensory neuropil of the acoustico-lateral area, and th ventral dendrite terminates in the neuropil of the motor tegmentum. Fine dendrites are present, and mostly arise from three regions; from the terminus of each major dendrite and from the ventral surface of the perikaryon. The number and position of fine dendrites within each of these sets is variable, even among animals from a single isogenic clone. M-cells with improper numbers or positions of large dendrites were never encountered, even early in development. This suggests that their outgrowth is a highly directed process. Large numbers of afferent synapses are formed on the M-cell during the time of dendrite outgrowth. By day 6 there is a mosaic pattern of morphologically distinctive terminals that is similar to the pattern of the adult goldfish M-cell. Identified categories of terminals include (1) myelinated club endings, on the distal part of the lateral dendrite, (2) boutons, on the dendrites and perikaryon, (3) unmyelinated club endings, on the dorsomedial portion of the perikaryon adjacent to the axon cap, and (4) spiral fiber terminals within the axon cap. The nonrandom nature of the input may be ascertained by observing the distribution of electrotonic or gap junctions on the cell surface. These are frequently encountered on the initial segment of the axon (spiral fiber terminals), ventral dendrite and ventral perikaryon (boutons), and distal lateral dendrite (myelinated club endings). Gap junctions are only rarely observed on the dorsal surface of the cell, although this region, like others of the cell, receives large numbers of chemical synaptic contacts. This pattern is similar at all stages studied, which suggests that no large rearrangements in synaptic contacts occur during this developmental period. We discuss these observations in relation to the hypothesis that patterned dendritic growth of the M-cell is directed by synaptic interactions with the afferents.

UI	MeSH Term	Description	Entries
D007814	Larva	Wormlike or grublike stage, following the egg in the life cycle of insects, worms, and other metamorphosing animals.	Maggots,Tadpoles,Larvae,Maggot,Tadpole
D008526	Medulla Oblongata	The lower portion of the BRAIN STEM. It is inferior to the PONS and anterior to the CEREBELLUM. Medulla oblongata serves as a relay station between the brain and the spinal cord, and contains centers for regulating respiratory, vasomotor, cardiac, and reflex activities.	Accessory Cuneate Nucleus,Ambiguous Nucleus,Arcuate Nucleus of the Medulla,Arcuate Nucleus-1,External Cuneate Nucleus,Lateral Cuneate Nucleus,Nucleus Ambiguus,Ambiguus, Nucleus,Arcuate Nucleus 1,Arcuate Nucleus-1s,Cuneate Nucleus, Accessory,Cuneate Nucleus, External,Cuneate Nucleus, Lateral,Medulla Oblongatas,Nucleus, Accessory Cuneate,Nucleus, Ambiguous,Nucleus, External Cuneate,Nucleus, Lateral Cuneate
D008854	Microscopy, Electron	Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.	Electron Microscopy
D009413	Nerve Fibers, Myelinated	A class of nerve fibers as defined by their structure, specifically the nerve sheath arrangement. The AXONS of the myelinated nerve fibers are completely encased in a MYELIN SHEATH. They are fibers of relatively large and varied diameters. Their NEURAL CONDUCTION rates are faster than those of the unmyelinated nerve fibers (NERVE FIBERS, UNMYELINATED). Myelinated nerve fibers are present in somatic and autonomic nerves.	A Fibers,B Fibers,Fiber, Myelinated Nerve,Fibers, Myelinated Nerve,Myelinated Nerve Fiber,Myelinated Nerve Fibers,Nerve Fiber, Myelinated
D009474	Neurons	The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.	Nerve Cells,Cell, Nerve,Cells, Nerve,Nerve Cell,Neuron
D001921	Brain	The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM.	Encephalon
D002454	Cell Differentiation	Progressive restriction of the developmental potential and increasing specialization of function that leads to the formation of specialized cells, tissues, and organs.	Differentiation, Cell,Cell Differentiations,Differentiations, Cell
D003712	Dendrites	Extensions of the nerve cell body. They are short and branched and receive stimuli from other NEURONS.	Dendrite
D005399	Fishes	A group of cold-blooded, aquatic vertebrates having gills, fins, a cartilaginous or bony endoskeleton, and elongated bodies covered with scales.
D000344	Afferent Pathways	Nerve structures through which impulses are conducted from a peripheral part toward a nerve center.	Afferent Pathway,Pathway, Afferent,Pathways, Afferent