A physiological role of GABA-B receptors in the cardiovascular system in the rat Nucleus Tractus Solitarius

• Published in: Japanese Journal of Pharmacology Vol. 76; no. suppl.1; p. 50
• Main Authors: Shihara, Miwako, Eshima, Kenichi, Hori, Nobuaki, Hirooka, Yoshitaka, Takeshita, Akira
• Format: Journal Article
• Language: English; Japanese
• Published: The Japanese Pharmacological Society 1998
• ISSN: 0021-5198; 1347-3506
• DOI: 10.1016/S0021-5198(19)40321-1

The nucleus tractus solitarius (NTS) plays an important role in the regulation and integration of cardiovascular responses. The GABAergic system is one of the mechanisms controlling cardiovascular responses. Since injecton of baclofen into the NTS alters cardiovascular regulation, GABA-B receptors must be involved, however, the physiological role of GABA-B and its active site have not yet been clearly defined. We have investigated the functional actions of GABA-B receptor activation at the single-neuron level. Methods. Semi-horizontal slices from rats were cut containing the solitary tract (ST), the NTS and the area postrema. Slices were mounted on a mesh in a submerged recording chamber. Concentric stimulating electrodes were placed in the ST and single unit discharges and single field potential (SFP) were recorded with a glass micropipette filled with Ringer solution. Drugs were either included in the perfusion media or were ionophoretically applied into the dendritic region. Results. The SFP was attenuated by baclofen. Paired pulse stimulation revealed paired pulse depression (PPD), where the second response was smaller than the first. The PPD-ratio was attenuated by phaclofen. Baclofen blocked spontaneous action potentials but spikes induced by iontophoretic application of quisqualic acid and acetylcholine persisted. Conclusion. GABA-B receptors on the ST terminal may regulate the cardiovascular system by controlling the amount of rleased transmitter and ones on the cell body integrate the information to the second level in the NTS.