Abstract
Whole-cell recordings were made in the nucleus tractus solitarii (NTS) in transverse brainstem slices from rats. Monosynaptic GABA A-receptor-mediated inhibitory postsynaptic currents (IPSCs) or potentials (IPSPs) were evoked (0.1–0.2 Hz) by electrical stimulation within and medial to the tractus solitarius in the presence of the ionotropic glutamate receptor antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 10 μM) or 6,7-dinitroquinoxaline-2,3-dione (DNQX; 10 μM) and d-amino-5-phosphonopentanoic acid (APV; 50 μM). A brief period of tetanic stimulation (20 Hz, 2 s) resulted in posttetanic (< 5 min, 69 of 73 recordings) and sustained potentiation (> 15 min, 31 of 73 recordings) of the IPSP/Cs. Sustained potentiation was not due to alterations in the reversal potential of IPSP/Cs. Both pre- and post-tetanus IPSP/Cs were completely blocked by the GABA A antagonist bicuculline (10 μM). Postsynaptic responses to pressure ejection of the GABA A-receptor agonist muscimol were unaltered in cells displaying sustained potentiation. Sustained potentiation of IPSP/Cs could be induced by tetanus in the presence of either metabotropic glutamate receptor antagonists or bicuculline. However, sustained potentiation could not be induced in the presence of the GABA B-receptor antagonists 2-OH-saclofen (400 μM) or CGP35348 (3-amino-propyl-(diethoxymethyl)phosphinic acid, 100 μM), although a subsequent tetanus following washout induced sustained potentiation. Posttetanic potentiation was unaffected by GABA B-receptor antagonists. These data suggest that neuronal or terminal excitability of GABAergic interneurons in the NTS is enhanced following brief periods of increased frequency of activation in vitro. This novel phenomenon within the rat medulla may be involved in the temporal modulation of autonomic reflex sensitivity observed during certain behavioral states, such as the defense reaction.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
