NMDA receptors in the intermediolateral column of the spinal cord mediate sympathoexcitatory cardiac responses elicited from the ventrolateral medullary pressor area.
Microinjections of L-glutamate into the intermediolateral column of the spinal cord (IML) at T1-T3 produced increases in heart rate (predominantly from the right IML) and myocardial contractility (predominantly from the left IML). Maximum responses were elicited from T2 segment. At this site, microinjections of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA), quisqualic acid, kainic acid and N-methyl-D-aspartic acid (NMDA) produced dose-dependent increases in heart rate and contractility which were blocked by kynurenate (a non-selective excitatory amino acid receptor antagonist). D-2-Aminophosphonoheptanoate (DAP-7) blocked the effects of NMDA but not kainic acid, quisqualic acid and AMPA. Bilateral microinjections of kynurenate (2 nmol) and DAP-7 (5 nmol) into the IML at T1-T3 significantly decreased the baseline values for contractility index and blocked the usual increase in contractility induced by unilateral microinjections of L-glutamate (1.77 nmol) into the ventrolateral medullary pressor area (VLPA). These observations suggest that: (1) a tonic excitatory input, involving an NMDA-like amino acid as a transmitter, is present in the IML at T1-T3 and (2) the stimulation of VLPA neurons results in the release of an NMDA-like excitatory amino acid in the IML at this level.
Section of Neurosurgery, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark 07103.
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Sundaram
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Sapru
D015763:2-Amino-5-phosphonovalerate / Q000031:analogs & derivatives*; D000596:Amino Acids / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D003292:Convulsants / Q000494:pharmacology; D005971:Glutamates / Q000008:administration & dosage / Q000494:pharmacology*; D018698:Glutamic Acid; D006339:Heart Rate / Q000187:drug effects*; D007051:Ibotenic Acid / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D007608:Kainic Acid / Q000008:administration & dosage / Q000494:pharmacology; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects / Q000502:physiology*; D008845:Microinjections; D009200:Myocardial Contraction / Q000187:drug effects*; D016202:N-Methylaspartate / Q000008:administration & dosage / Q000494:pharmacology*; D016318:Quisqualic Acid / Q000008:administration & dosage / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000502:physiology*; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology*; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid
D000596:Amino Acids; D003292:Convulsants; D005971:Glutamates; D016194:Receptors, N-Methyl-D-Aspartate; D007051:Ibotenic Acid; D018698:Glutamic Acid; D016202:N-Methylaspartate; D015763:2-Amino-5-phosphonovalerate; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D016318:Quisqualic Acid; C031231:2-amino-7-phosphonoheptanoic acid; D007608:Kainic Acid