Ultrastructural Relationships Between GABAergic Terminals and Cardiac Vagal Preganglionic Motoneurons and Vagal Afferents in the Cat: A Combined HRP Tracing and Immunogold Labelling Study.

The ultrastructural relationships between gamma-aminobutyric acid-immunoreactive (GABA-ir) neurons and other neurons of the nucleus tractus solitarius (NTS) and motoneurons of the nucleus ambiguus (NA) and dorsal motor vagal nucleus (DMVN), were examined by electron microscopic (EM) immunogold labelling with an anti-GABA antiserum on brain stem sections in which vagal motoneurons and vagal afferent fibres were labelled with horseradish peroxidase (HRP). HRP was applied to the cervical vagus or the cardiac vagal branch of anaesthetized cats. After 24 - 48 h survival, brains were glutaraldehyde-fixed and a stable HRP-tetramethylbenzidine reaction product compatible with EM processing was revealed on 250 microm vibratome sections.

Distribution of calcitonin gene-related peptide-like immunoreactivity in the medulla oblongata of the cat, in relation to choline acetyltransferase-immunoreactive motoneurones and substance P-immunoreactive fibres.

The immunohistochemical distribution of calcitonin gene-related peptide (CGRP)-like immunoreactivity (ir) in the cat medulla oblongata was examined using an antiserum to rat alpha-CGRP. Comparative distributions of substance P (SP)-like and choline acetyltransferase (ChAT)-like ir were also studied on sections adjacent to those stained for CGRP, and on sections simultaneously stained for CGRP by double staining techniques. The vast majority of ChAT-ir motoneurones in somatomotor or branchiomotor cranial nuclei (of VI, VII and XII nerves) and their accessory nuclei also displayed a coarsely granular CGRP-ir, shown by electron microscopic examination to represent immunoreactive Golgi bodies.

Distribution of calcitonin gene-related peptide-like immunoreactivity in the nucleus ambiguus of the cat.

The distribution of calcitonin gene-related peptide (CGRP) in the cat nucleus ambiguus was examined by means of a combination of horseradish peroxidase (HRP) tracing and immunohistochemical techniques. Vagal motoneurones in the nucleus ambiguus were identified by applying HRP to either the thoracic vagus or the superior laryngeal nerve or the cervical vagus. Motoneurones in the nucleus ambiguus labelled with HRP from the thoracic vagus did not contain CGRP-like immunoreactivity although CGRP-like immunoreactive cells were present in this nucleus on the same sections.