title: GABA and glycine receptors in the nucleus ambiguus mediate tachycardia elicited by chemical stimulation of the hypothalamic arcuate nucleus.
abstract: We have previously reported that stimulation of the hypothalamic arcuate nucleus (ARCN) by microinjections of N-methyl-d-aspartic acid (NMDA) elicits tachycardia, which is partially mediated via inhibition of vagal inputs to the heart. The neuronal pools and neurotransmitters in them mediating tachycardia elicited from the ARCN have not been identified. We tested the hypothesis that the tachycardia elicited from the ARCN may be mediated by inhibitory neurotransmitters in the nucleus ambiguus (nAmb). Experiments were done in urethane-anesthetized, artificially ventilated, male Wistar rats. In separate groups of rats, unilateral and bilateral microinjections of muscimol (1 mM), gabazine (0.01 mM), and strychnine (0.5 mM) into the nAmb significantly attenuated tachycardia elicited by unilateral microinjections of NMDA (10 mM) into the ARCN. Histological examination of the brains showed that the microinjections sites were within the targeted nuclei. Retrograde anatomic tracing from the nAmb revealed direct bilateral projections from the ARCN and hypothalamic paraventricular nucleus to the nAmb. The results of the present study suggest that tachycardia elicited by stimulation of the ARCN by microinjections of NMDA is mediated via GABAA and glycine receptors located in the nAmb.
authors.affiliation: Department of Neurological Surgery, Rutgers New Jersey Medical School, Newark, New Jersey.
authors.forename: Vineet C
authors.initials: VC
authors.lastname: Chitravanshi
authors.affiliation: Department of Neurological Surgery, Rutgers New Jersey Medical School, Newark, New Jersey.
authors.forename: Kazumi
authors.initials: K
authors.lastname: Kawabe
authors.affiliation: Department of Neurological Surgery, Rutgers New Jersey Medical School, Newark, New Jersey sapru@njms.rutgers.edu.
authors.forename: Hreday N
authors.initials: HN
authors.lastname: Sapru
mesh_terms: D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D018756:GABA Antagonists / Q000494:pharmacology; D058785:GABA-A Receptor Agonists / Q000494:pharmacology; D018684:Glycine Agents / Q000494:pharmacology; D006321:Heart / Q000187:drug effects*; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects / Q000378:metabolism*; D008845:Microinjections; D009118:Muscimol / Q000494:pharmacology; D016202:N-Methylaspartate / Q000494:pharmacology*; D011724:Pyridazines / Q000494:pharmacology; D017208:Rats, Wistar; D011963:Receptors, GABA-A / Q000378:metabolism*; D018009:Receptors, Glycine / Q000378:metabolism*; D013268:Stimulation, Chemical; D013331:Strychnine / Q000494:pharmacology; D013610:Tachycardia / Q000139:chemically induced* / Q000378:metabolism
chemical_list: D018756:GABA Antagonists; D058785:GABA-A Receptor Agonists; D018684:Glycine Agents; D011724:Pyridazines; D011963:Receptors, GABA-A; D018009:Receptors, Glycine; D009118:Muscimol; D016202:N-Methylaspartate; C049853:gabazine; D013331:Strychnine
keywords: N-methyl-d-aspartic acid; gabazine; muscimol; strychnine; tachycardia; γ-aminobutyric acid