Tachycardia after glutamate injection in rat spinal cord is not blocked by kynurenate or mimicked by metabotropic agonists

Leonard F. Arnolda, P. M. Pilowsky, J. B. Minson, I. J. Llewellyn-Smith, J. P. Chalmers

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

1. We have used microinjections of glutamate, an ionotropic excitatory amino acid receptor antagonist (kynurenate) and selective ionotropic (NMDA and kainate) and metabotropic (1S-3R-ACPD, trans-ACPD and L-AP4) receptor agonists in the thoracic IML of the rat to define the receptors mediating the tachycardia produced by excitatory amino acid agonists. 2. Injection of glutamate (Δ heart rate = 76 ± 8 beats/min n = 16), NMDA (Δ heart rate = 116.5 ± 5 beats/min n = 6) or kainate (Δ heart rate = 92 ± 22 beats/min n = 6) evokes a tachycardia when injected into the thoracic intermediolateral column. Kynurenate blocked the response to NMDA (-2% of initial response) and markedly attenuated the response to kainate (14% of initial response) but did not alter the response to glutamate (106% of initial response). 3. IS-3R-ACPD did not elicit a tachycardia when injected into the thoracic intermediolateral column and neither trans-ACPD nor L-AP4 induced a tachycardia after kynurenate injection into the thoracic intermediolateral column. 4. Thus stimulation of either NMDA or AMPA/kainate receptors elicits a tachycardia in rat thoracic spinal cord but glutamate also activates another receptor type to elicit a tachycardia. The lack of a tachycardia when trans-ACPD, 1S-3R-ACPD or L-AP4 were injected into the thoracic spinal cord suggests that the kynurenate resistant tachycardia elicited by glutamate is not mediated by metabotropic receptors. The kynurenate resistant tachycardia elicited by glutamate is not mediated by any of the known excitatory amino acid receptor types.

Original languageEnglish
Pages (from-to)813-818
Number of pages6
JournalClinical and Experimental Pharmacology and Physiology
Volume23
Issue number9
DOIs
Publication statusPublished - 1 Jan 1996
Externally publishedYes

Keywords

  • Glutamate
  • Intermediolateral column
  • Metabotropic receptors
  • Spinal cord

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