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Monosynaptic input from Leu5-enkephalin-immunoreactive terminals to vagal motor neurons in the nucleus ambiguus: comparison with the dorsal motor nucleus of the vagus.
J Comp Neurol. 1995 Mar 13; 353(3):391-406.JC

Abstract

Vagal motor neurons in the rat dorsal motor nucleus of the vagus (DMN) are known to receive direct synaptic input from enkephalin-containing terminals. We examined 1) whether the vagal motor neurons within the nucleus ambiguus (NA) also received monosynaptic input from enkephalin-immunoreactive terminals and 2), if so, whether their ultrastructural relations differed from those in the DMN. In both regions, terminals containing Leu5-enkephalin-like immunoreactivity (LE-LI) were examined in relation to motor neurons identified by retrograde transport of wheat germ-agglutinated horseradish peroxidase (WGA-HRP) applied to the cut end of the cervical vagus nerve in single sections of the medulla oblongata of adult rats. By light microscopy, the most significant overlap between varicose processes with LE-LI and WGA-HRP-containing neurons was seen in the rostral compact portion of the NA and the DMN at the level of the obex. Thus, only these regions were examined by electron microscopy. The most distinguishing ultrastructural feature of WGA-HRP-labeled neurons in the NA compared to the DMN was their higher incidence of nonsynaptic appositions with other neurons. In both the NA and the DMN, terminals with LE-LI formed primarily symmetric synapses on smaller (presumably distal) dendrites; many of these dendrites, as well as most target perikarya, contained WGA-HRP. Additionally, in the compact portion of the NA compared to the DMN 1) multiple LE-labeled terminals more frequently contacted single perikarya or dendrites and 2) single terminals with LE-LI more commonly showed two contacts or active zones and contained more abundant LE-immunoreactive large (80-100 nm) dense-core vesicles (dcvs). In contrast to small (40-50 nm), clear vesicles, which were usually aggregated near active zones, the immunoreactive dcvs were usually located near glial processes distal to these zones. These results indicate that enkephalin immunoreactivity is intensely localized to dcvs within terminals that may have direct inhibitory (symmetric synapses) actions on vagal motor neurons in both the compact portion of the NA and the DMN. Moreover, because numbers of dcvs and active zones have been equated with synaptic strength, our findings suggest enhanced potencies of enkephalin-immunoreactive terminals in the compact portion of the NA. Our findings support a prominent role for enkephalin in the coordinated activity of esophageal motor neurons located in the compact portion of the NA.

Authors+Show Affiliations

Department of Neurology and Neuroscience, Cornell University Medical College, New York, New York 10021, USA.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

7751438

Citation

Milner, T A., et al. "Monosynaptic Input From Leu5-enkephalin-immunoreactive Terminals to Vagal Motor Neurons in the Nucleus Ambiguus: Comparison With the Dorsal Motor Nucleus of the Vagus." The Journal of Comparative Neurology, vol. 353, no. 3, 1995, pp. 391-406.
Milner TA, Okada J, Pickel VM. Monosynaptic input from Leu5-enkephalin-immunoreactive terminals to vagal motor neurons in the nucleus ambiguus: comparison with the dorsal motor nucleus of the vagus. J Comp Neurol. 1995;353(3):391-406.
Milner, T. A., Okada, J., & Pickel, V. M. (1995). Monosynaptic input from Leu5-enkephalin-immunoreactive terminals to vagal motor neurons in the nucleus ambiguus: comparison with the dorsal motor nucleus of the vagus. The Journal of Comparative Neurology, 353(3), 391-406.
Milner TA, Okada J, Pickel VM. Monosynaptic Input From Leu5-enkephalin-immunoreactive Terminals to Vagal Motor Neurons in the Nucleus Ambiguus: Comparison With the Dorsal Motor Nucleus of the Vagus. J Comp Neurol. 1995 Mar 13;353(3):391-406. PubMed PMID: 7751438.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Monosynaptic input from Leu5-enkephalin-immunoreactive terminals to vagal motor neurons in the nucleus ambiguus: comparison with the dorsal motor nucleus of the vagus. AU - Milner,T A, AU - Okada,J, AU - Pickel,V M, PY - 1995/3/13/pubmed PY - 1995/3/13/medline PY - 1995/3/13/entrez SP - 391 EP - 406 JF - The Journal of comparative neurology JO - J. Comp. Neurol. VL - 353 IS - 3 N2 - Vagal motor neurons in the rat dorsal motor nucleus of the vagus (DMN) are known to receive direct synaptic input from enkephalin-containing terminals. We examined 1) whether the vagal motor neurons within the nucleus ambiguus (NA) also received monosynaptic input from enkephalin-immunoreactive terminals and 2), if so, whether their ultrastructural relations differed from those in the DMN. In both regions, terminals containing Leu5-enkephalin-like immunoreactivity (LE-LI) were examined in relation to motor neurons identified by retrograde transport of wheat germ-agglutinated horseradish peroxidase (WGA-HRP) applied to the cut end of the cervical vagus nerve in single sections of the medulla oblongata of adult rats. By light microscopy, the most significant overlap between varicose processes with LE-LI and WGA-HRP-containing neurons was seen in the rostral compact portion of the NA and the DMN at the level of the obex. Thus, only these regions were examined by electron microscopy. The most distinguishing ultrastructural feature of WGA-HRP-labeled neurons in the NA compared to the DMN was their higher incidence of nonsynaptic appositions with other neurons. In both the NA and the DMN, terminals with LE-LI formed primarily symmetric synapses on smaller (presumably distal) dendrites; many of these dendrites, as well as most target perikarya, contained WGA-HRP. Additionally, in the compact portion of the NA compared to the DMN 1) multiple LE-labeled terminals more frequently contacted single perikarya or dendrites and 2) single terminals with LE-LI more commonly showed two contacts or active zones and contained more abundant LE-immunoreactive large (80-100 nm) dense-core vesicles (dcvs). In contrast to small (40-50 nm), clear vesicles, which were usually aggregated near active zones, the immunoreactive dcvs were usually located near glial processes distal to these zones. These results indicate that enkephalin immunoreactivity is intensely localized to dcvs within terminals that may have direct inhibitory (symmetric synapses) actions on vagal motor neurons in both the compact portion of the NA and the DMN. Moreover, because numbers of dcvs and active zones have been equated with synaptic strength, our findings suggest enhanced potencies of enkephalin-immunoreactive terminals in the compact portion of the NA. Our findings support a prominent role for enkephalin in the coordinated activity of esophageal motor neurons located in the compact portion of the NA. SN - 0021-9967 UR - https://www.unboundmedicine.com/medline/citation/7751438/Monosynaptic_input_from_Leu5_enkephalin_immunoreactive_terminals_to_vagal_motor_neurons_in_the_nucleus_ambiguus:_comparison_with_the_dorsal_motor_nucleus_of_the_vagus_ L2 - https://onlinelibrary.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=0021-9967&date=1995&volume=353&issue=3&spage=391 DB - PRIME DP - Unbound Medicine ER -