Substance P depresses bioelectrical responses evoked in the nucleus tractus solitarii: interaction with gamma-aminobutyric acid-ergic neurons.
The effects of intracerebroventricular (i.c.v.) administration of substance P (SP) and gamma-aminobutyric acid (GABA) on responses evoked in the nucleus tractus solitarii (NTS) by electrical stimulation of the ipsilateral sinusal nerve were studied in alpha-chloralose-anesthetized rats. Both SP (0.01-10 micrograms) and GABA (100 micrograms) significantly depressed the presumably C-fiber mediated, late negative wave of the response. The effects were almost completely prevented by bicuculline (10 micrograms i.c.v.). It is concluded that i.c.v. administered SP induces dose-dependent depression of baro- and/or chemosensory transmission in the NTS, via a mechanism involving interactions with GABAergic neurons of the NTS.
Pérez
H
H
Unit of Neurophysiology and Biophysics, University of Chile, Santiago.
Ruiz
S
S
Inostroza
H
H
Perretta
M
M
D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D003864:Depression, Chemical; D004558:Electric Stimulation; D058787:GABA-A Receptor Antagonists; D007276:Injections, Intraventricular; D008526:Medulla Oblongata / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D008845:Microinjections; D009475:Neurons, Afferent / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D013373:Substance P / Q000494:pharmacology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology / Q000502:physiology*
D058787:GABA-A Receptor Antagonists; D013373:Substance P; D005680:gamma-Aminobutyric Acid; D001640:Bicuculline