Ultrastructural study of ascending projections to the lateral mammillary nucleus of the rat

Hayakawa, Tetsu; Zyo, Katuya

doi:10.1007/bf00185614

Cited by 30 publications

(15 citation statements)

References 62 publications

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“…Membranes and structures of la- beled neurons were well preserved (Hayakawa and Zyo, 1992). Since the reaction products did not label all dendrite areas, we did not study dendrites and axodendritic terminals.…”

Section: Discussionmentioning

confidence: 99%

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Ultrastructural characterization of pharyngeal and esophageal motoneurons in the nucleus ambiguus of the rat

1996

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The viscerotopic organization of the upper alimentary tract has been established in the nucleus ambiguus, but there is little information about the morphology of the individual neurons innervating the pharynx and esophagus. We studied the ultrastructure of pharyngeal (PH), cervical esophageal (CE), and subdiaphragmatic esophageal (SDE) motoneurons labeled by retrogradely transported wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP) in the compact formation of the nucleus ambiguus. WGA-HRP was injected into the lower pharynx, or the cervical and subdiaphragmatic esophagus of male rats. The retrogradely labeled PH neurons in the rostral portion of the compact formation were large (26.1 x 50.1 microns, 906.7 microns2), polygonal, and contained well-developed cell organelles with a round nucleus. Subsurface cisterns connected with rough endoplastic reticulum were often present near the postsynaptic membrane. Both CE and SDE neurons in the compact formation were medium-sized, round or oval, and contained well-developed cell organelles, although the SDE neuron was significantly larger than the CE neuron (24.9 x 33.6 microns, 593.0 microns2 in the SDE neuron, and 19.5 x 30.2 microns, 440.3 microns2 in the CE neuron). The average number of axosomatic terminals in a sectional plane was largest in PH neurons (29.0), smaller in CE neurons (7.9), and smallest in SDE neurons (4.2). The number of axosomatic terminals containing round vesicles (Gray's type I) was almost equal to that of terminals containing pleomorphic vesicles (Gray's type II) in PH and CE neurons, but there were few Gray's type II axosomatic terminals in SDE neurons. Desmosome-like junctions at somato-somatic or somato-dendritic apposition were often present in the area surrounding SDE neurons. There were also small unlabeled neurons (9.5 x 18.1 microns, 131.8 microns2) in the compact formation of the nucleus ambiguus. The small neurons contained poorly developed cell organelles and an irregular shaped nucleus with invaginated nuclear membrane, and had no Nissl bodies. These results indicate that PH neurons have the characteristics of somatic motoneurons, and that CE and SDE neurons are similar to visceral motoneurons.

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Section: Discussionmentioning

confidence: 99%

“…In order to carry out electron microscopic studies, alternate sections were collected and processed with TMB at pH 5.8 by the method of Hayakawa and Zyo (1992). Briefly, the sections were presoaked with 40 ml of 0.025% ammonium heptamolybdate containing 2 mg TMB dissolved in 1 ml ethanol in 0.1 M phosphate buffer at pH 5.8.…”

Section: Methodsmentioning

confidence: 99%

Ultrastructural characterization of pharyngeal and esophageal motoneurons in the nucleus ambiguus of the rat

1996

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“…Since we used small amounts of WGA-HRP and CT-HRP, and short survival times in this and previous studies (Hayakawa and Zyo, 1991, 1992, no anterogradely transported reaction products were found in the postsynaptic dendrites or somata. Following a single injection of CT-HRP or WGA-HRP into the esophagus, no retrogradely transneuronal transport of WGA-HRP or CT-HRP was found in the axon terminals or the NTS neurons (Shapiro and Miselis, 1985;Hayakawa et al, 1996).…”

Section: Discussionmentioning

confidence: 89%

“…Alternate sections through the AmC were collected and processed for electron microscopic investigation (Hayakawa and Zyo, 1992). The sections were presoaked for 5 minutes with a solution containing 195 mg ammonium heptamolybdate, 4 mg TMB in 2 ml of ethanol, and 78 ml of 0.1 M phosphate buffer at pH 5.8.…”

Section: Methodsmentioning

confidence: 99%

Direct synaptic projections to esophageal motoneurons in the nucleus ambiguus from the nucleus of the solitary tract of the rat

1997

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Neurons of the nucleus of the solitary tract (NTS) serve as interneurons in swallowing. We investigated the synaptology of the terminals of these neurons and whether they project directly to the esophageal motoneurons in the compact formation of the nucleus ambiguus (AmC). Following wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP) injection into the NTS, many anterogradely labeled axodendritic terminals were found in the neuropil of the AmC. The majority of labeled axodendritic terminals (89%) contained round vesicles and made asymmetric synaptic contacts (Gray's type I), but a few (11%) contained pleomorphic vesicles and made symmetric synaptic contacts (Gray's type II). More than half of the labeled terminals contacted intermediate dendrites (1-2 microm diameter). There were no retrogradely labeled medium-sized motoneurons, but there were many retrogradely labeled small neurons having anterogradely labeled axosomatic terminals. A combined retrograde and anterograde transport technique was developed to verify the direct projection from the NTS to the esophageal motoneurons. After the esophageal motoneurons were retrogradely labeled by cholera toxin subunit B conjugated HRP, the injection of WGA-HRP into the NTS permitted ultrastructural recognition of anterogradely labeled axosomatic terminals contacting directly labeled esophageal motoneurons. Serial sections showed that less than 20% of the axosomatic terminals were labeled in the esophageal motoneurons. They were mostly Gray's type I, but a few were Gray's type II. In the small neurons, more than 30% of axosomatic terminals were labeled, which were exclusively Gray's type I. These results indicate that NTS neurons project directly not only to the esophageal motoneurons, but also to the small neurons which have bidirectional connections with the NTS.

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“…Cholinergic terminals from the laterodorsal tegmental nucleus contained round synaptic vesicles and formed asymmetric synaptic contacts (Gray's type I) in the SUM. On the other hand, terminals in the lateral mammillary nucleus coming from the laterodorsal tegmental nucleus contain exclusively pleomorphic vesicles and formed symmetric synaptic contacts (Hayakawa and Zyo 1992). This discrepancy may arise from the fact that the lateral mammillary nucleus receives fibers mainly from the rostral half of the laterodorsal tegmental nucleus, while the SUM and the mediodorsal thalamic nucleus receive fibers mainly from the caudal half of this nucleus (Kuroda and Price 1991;Hayakawa and Zyo 1992;Hayakawa et al 1993).…”

Section: Discussionmentioning

confidence: 97%

Synaptic organization of afferent projections to the supramammillary nucleus of the rat

Hayakawa

Zyo

1996

Anat Embryol

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We studied the fine structure of afferent terminals from the preoptic area, the nucleus of the diagonal band of Broca, the infralimbic cortex and the laterodorsal tegmental nucleus within the supramammillary nucleus (SUM) using the anterograde tracing method of horseradish peroxidase conjugated with wheat germ agglutinin (WGA-HRP). Injection of WGA-HRP into the preoptic area permitted ultrastructural recognition of many anterogradely labeled terminals in the SUM. Almost all labeled terminals (99%) contained clear round synaptic vesicles and formed asymmetric synaptic contacts (Gray's type I). About 86% of labeled terminals from the nucleus of the diagonal band were asymmetric (Gray's type I), whereas 14% contained pleomorphic synaptic vesicles and formed symmetric synaptic contacts (Gray's type II). Almost all labeled terminals from the infralimbic cortex were located in the ventral part of the SUM, and 95% of labeled terminals were Gray's type I. The majority of labeled terminals (90%) from the laterodorsal tegmental nucleus were Gray's type I, and the remaining (10%) were Gray's type II. The percentage of labeled terminals with dense-cored vesicles was very high in terminals from the preoptic area (70%), and low in terminals from the infralimbic cortex (19%). Labeled terminals in all cases contacted mainly intermediate-sized dendrites (0.5-1.0 micron diameter). All cases had only a few labeled axosomatic terminals. The cases of injections into the preoptic area and the diagonal band nucleus had some reciprocal connections at the ultrastructural level.

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Ultrastructural study of ascending projections to the lateral mammillary nucleus of the rat

Cited by 30 publications

References 62 publications

Ultrastructural characterization of pharyngeal and esophageal motoneurons in the nucleus ambiguus of the rat

Ultrastructural characterization of pharyngeal and esophageal motoneurons in the nucleus ambiguus of the rat

Direct synaptic projections to esophageal motoneurons in the nucleus ambiguus from the nucleus of the solitary tract of the rat

Synaptic organization of afferent projections to the supramammillary nucleus of the rat

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