Spinal cord substance P mediates carbachol-induced cardiovascular responses from the rostral ventrolateral medulla

These studies investigated the role of spinal N-methyl-D-aspartic acid (NMDA) receptors in the mediation of cardiovascular responses evoked by L-glutamate (L-Glu) stimulation of the rostral ventrolateral medulla (RVM). Microinjections of L-Glu into the RVM of urethan-anesthetized rats increased mean arterial pressure (MAP) and heart rate. Intrathecal administration of the NMDA receptor antagonists D-(-)-2-amino-7-phosphonoheptanoic acid (D-AP-7) or 3-((+-)-2-carboxypiperazin-4-yl)-propyl-1-phosphonate (CPP) reduced MAP and heart rate. Blockade of NMDA receptors by D-AP-7 or CPP in the caudal thoracic spinal cord markedly reduced RVM pressor responses with little effect on evoked tachycardia. Administration of D-AP-7 to the rostral thoracic spinal cord had no effect on RVM pressor or tachycardic responses. Intrathecal D-AP-7 and CPP abolished the cardiovascular effects of intrathecal NMDA without reducing those produced by intrathecal kainic acid or the quisqualate agonist DL-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA). These results indicate that 1) tonic activation of spinal NMDA receptors participates in the maintenance of sympathetic outflow to the heart and blood vessels, 2) pressor responses evoked from the RVM require synaptic activation of spinal NMDA receptors, and 3) an excitatory amino acid may be the neurotransmitter of pressor pathways descending from the RVM to the spinal cord.

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Do pressor neurons in the ventrolateral medulla release amines and neuropeptides?

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y87-251 ◽

1987 ◽

Vol 65 (8) ◽

pp. 1598-1604 ◽

Cited By ~ 11

Author(s):

John Chalmers ◽

Vimal Kapoor ◽

Eric Mills ◽

Jane Minson ◽

Margaret Morris ◽

...

Keyword(s):

Spinal Cord ◽

Substance P ◽

Neuropeptide Y ◽

Pressor Response ◽

Rostral Ventrolateral Medulla ◽

Ventrolateral Medulla

Activation of neurons arising in the rostral ventrolateral medulla evokes a pressor response in the rat and the rabbit. This region of the medulla gives rise to bulbospinal neurons containing many different neurotransmitters, including amines such as adrenaline, noradrenaline and serotonin, and neuropeptides such as substance P and neuropeptide Y. Colocalization of amines and neuropeptides has been described in some neurons descending from the rostral ventrolateral medulla. In this paper we discuss the evidence that bulbospinal serotonin-containing neurons (B3) and adrenaline-containing neurons (C1) arising from this part of the medulla exert pressor effects by distinct central pathways and conclude that they do. We also consider the possibility that the pressor effects of activating these two groups of neurons are associated with release of neuropeptides and highlight evidence that substance P is released into the spinal cord by activation of descending serotonin-containing neurons, while neuropeptide Y may be released by activation of bulbospinal adrenaline-containing neurons.

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