Electrophysiological characterization of excitatory amino acid responses in rat lateral parabrachial neurons in vitro.
The pontine parabrachial nucleus (PBN) is a major recipient of a diverse array of autonomic-related information from the caudal brainstem. Recent data indicate the presence of glutamate-like immunoreactivity within this nucleus. The effect of specific excitatory amino acid (EAA) receptor agonists and antagonists were studied in the lateral PBN (LPBN) by the use of whole-cell patch recordings in an in vitro brainstem slice preparation. Under current and voltage clamp conditions, independent bath applications of N-methyl-D-aspartate (NMDA; 10 microM), quisqualic acid (QUIS; 10 microM) and kainic acid (kainate; 10 microM) evoked membrane depolarization and an inward current in 28 of 31 LPBN neurons. In voltage clamp mode, the NMDA current (INMDA) was undetectable at potentials negative to -70 mV and a small inward current was observed at more depolarized potentials. However, in the absence of external Mg2+, the voltage dependence of INMDA was similar to that observed for QUIS and kainate. The allosteric modulation of the NMDA receptor by the strychnine-insensitive glycine binding site was examined by the application of the amino acid D-serine (0.5 mM). A marked and sustained potentiation of the steady-state INMDA (-60 mV holding potential) was observed. The selective NMDA-antagonist DL-2-amino-5-phosphonovaleric acid (APV; 10 microM) completely and reversibly blocked the NMDA-induced current, that was maximized in the absence of external Mg2+. Furthermore, this dose of APV was found to reversibly reduce the firing frequency of spontaneously active LPBN neurons.(ABSTRACT TRUNCATED AT 250 WORDS)
Zidichouski
J A
JA
Department of Medicine (Neurology), University of Alberta, Edmonton, Canada.
Jhamandas
J H
JH
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D004594:Electrophysiology / Q000379:methods; D005071:Evoked Potentials / Q000187:drug effects; D066298:In Vitro Techniques; D007608:Kainic Acid / Q000494:pharmacology*; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D016202:N-Methylaspartate / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D011149:Pons / Q000502:physiology*; D016318:Quisqualic Acid / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017459:Receptors, Amino Acid / Q000187:drug effects / Q000502:physiology*; D012694:Serine / Q000494:pharmacology; D013997:Time Factors
D017459:Receptors, Amino Acid; D012694:Serine; D016202:N-Methylaspartate; D015763:2-Amino-5-phosphonovalerate; D016318:Quisqualic Acid; D008274:Magnesium; D007608:Kainic Acid