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Phenylethanolamine N-methyltransferase-containing neurons in the rostral ventrolateral medulla. II. Synaptic relationships with GABAergic terminals.
- Source :
-
Brain research [Brain Res] 1987 May 12; Vol. 411 (1), pp. 46-57. - Publication Year :
- 1987
-
Abstract
- The ultrastructural morphology of terminals synthesizing gamma-aminobutyric acid (GABA), as indicated by peroxidase immunoreactivity for its synthetic enzyme L-glutamate decarboxylase (GAD), was examined in the rostral ventrolateral medulla (RVL) of the adult rat brain. The objective of the study was to determine the types of synaptic associations between the GABAergic terminals and other neurons in the RVL, particularly the C1-adrenergic neurons containing phenylethanolamine N-methyltransferase (PNMT). The brains were fixed by perfusion with 3.75% acrolein and 2.0% paraformaldehyde in phosphate buffer. Coronal Vibratome sections through the RVL were singly labeled with a sheep antiserum to GAD using the peroxidase-antiperoxidase (PAP) method. Additional sections were dually labeled using the PAP technique for the GAD antiserum and immunogold labeling for a rabbit antiserum against PNMT. Ultrastructural analysis revealed that peroxidase labeling for GAD was localized primarily to axons and axon terminals in both single and dual labeled material. The axons were small and unmyelinated. The GAD-labeled terminals were 0.5-2.0 microns in diameter and contained a large population of small clear vesicles usually associated with a few mitochondria. These terminals formed synapses with many dendrites, a few nerve cell bodies and axon terminals. The junctions were all symmetric and the postsynaptic structures failed to exhibit immunoreactivity when processed only for GAD labeling. In sections incubated with both GAD and PNMT antisera, the peroxidase-labeled GABAergic terminals formed symmetric synapses with nerve cell bodies and dendrites showing immunogold labeling for PNMT. In addition, the GAD-labeled terminals were presynaptic to other dendrites which appeared to have equal access to the antisera and gold markers, but failed to exhibit detectable immunoreactivity for PNMT. Both the PNMT-labeled and unlabeled somata and dendrites also received symmetric and asymmetric contacts from terminals containing neither GAD nor PNMT-immunoreactivity. We conclude that GABA is at least one of the inhibitory transmitters regulating adrenergic as well as non-adrenergic outflow from the RVL.
- Subjects :
- Adrenergic Fibers enzymology
Animals
Glutamate Decarboxylase analysis
Gold
Histocytochemistry
Immunologic Techniques
Male
Medulla Oblongata enzymology
Microscopy, Electron
Neural Pathways enzymology
Neural Pathways ultrastructure
Rats
Rats, Inbred Strains
Synapses enzymology
Synapses ultrastructure
Adrenergic Fibers ultrastructure
Medulla Oblongata ultrastructure
Phenylethanolamine N-Methyltransferase analysis
Synapses classification
gamma-Aminobutyric Acid analysis
Subjects
Details
- Language :
- English
- ISSN :
- 0006-8993
- Volume :
- 411
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- Brain research
- Publication Type :
- Academic Journal
- Accession number :
- 3300846
- Full Text :
- https://doi.org/10.1016/0006-8993(87)90679-2