Fine structure of the synaptic endings on the Mauthner cell of the goldfish

Abstract

This study has investigated the fine structure of the Mauthner cell of the goldfish. The animals were divided into three groups of three fish and each group was perfused with one of the following fixatives: osmium tetroxide, glutaraldehyde, or formaldehyde. Large myelinated club endings and smallvesicle boutons (SVBs) are found on the distal part of the lateral dendrite. The club endings have the structure of the mixed synapse and contain large, round synaptic vesicles. The SVBs, appearing as small boutons, show the structural features of the chemical synapse, and contain small synaptic vesicles, which are round when fixed with osmium tetroxide, but become elongated when fixed with aldehyde fixatives. Small myelinated club endings, SVBs, and large-vesicle boutoiis (LVBs) are observed on the proximal part of the lateral dendrite, on the ventral dendrite, and on the cell body (excluding the axon hillock region). The LVBs, mostly appearing as large boutons, show the structure of either the mixed or the chemical synapse. They contain large, round vesicles. On the axon hillock and initial axon segment, there exist unmyelinated club endings containing medium-size elongated vesicles and spiral fiber endings containing round medium-size vesicles. An attempt was made to correlate these different types of endings with physiological functions.

Interaction between connexin35 and zonula occludens-1 and its potential role in the regulation of electrical synapses

“…S4, and Movie S1) and very prominently in its ''axon cap'' (Fig. S4A) (19). Confirming the specificity of the monoclonal ZO-1 antibody in recognizing its goldfish ortholog, we observed positive labeling of contacts at known sites of tight junctions between cells of the ependema and liver (data not shown).…”

Colocalization of somatostatin with GABA or glutamate in distinct afferent terminals presynaptic to the Mauthner cell

“…4C,). All stained terminals had a mean diameter of 1.97 f: 0.43 pm (n = 22), in agreement with previous electron microscopic data for the size of SVBs (Nakajima, 1974). Electron microscopic studies with GABA and somatostatin antisera on serial ultrathin sections confirmed the existence of these three populations of SVBs (Fig.…”

“…The density of gold particles was the highest in LMCEs. These endings transmit both electrically and chemically (Furshpan, 1964;Korn and Faber, 1976;Lin and Faber, 1988) in agreement with electron microscopic (Roberston et al, 1963;Nakajima, 1974) and freezefracture (Tuttle et al, 1986) data. Previous iontophoretic (Diamond and Roper, 1973) and pharmacological (Wolszon and Faber, 1988) studies suggest that the chemical component of LMCEs is mediated by glutamate.…”

“…This phylogenetic consistency suggests that somatostatin intervenes in the regulation of the dendritic properties. At the ultrastructural level, the majority of somatostatin-positive boutons contacting the M-cell correspond to SVBs (Nakajima, 1974).…”

Voltage-Dependent Enhancement of Electrical Coupling by a Subthreshold Sodium Current

“…Auditory afferents terminating as mixed (electrical and chemical) synapses known as large myelinated club endings on the goldfish Mauthner (M-) cells ("club endings") (Bartelmez, 1915;Furshpan, 1964;Nakajima, 1974;Lin and Faber, 1988) provide a convenient in vivo model in the vertebrate CNS, amenable to experimental manipulation, to study how efficient bi-directional communication is achieved despite unfavorable electrical and geometrical conditions. This relatively homogeneous group of synaptic contacts is tightly segregated to the distal portion of the lateral dendrite of the M-cells (Bartelmez, 1915), a pair of large reticulospinal neurons responsible for the organization of escape responses evoked by sound and other senses (Eaton et al, 2001).…”