Substance P released in the rostral brainstem of cats interacts with NK-1 receptors during muscle pressor response.
The release of immunoreactive substance P-like substances (irSP) was measured from sites in the rostral brainstem (at a level 1.3 mm anterior to the obex) of anesthetized cats in response to fatiguing isometric contractions using SP antibody-coated glass microprobes. The contractions caused a pressor and tachycardic response. irSP were released from sites in the medial subnucleus of the nucleus tractus solitarius (mNTS), the solitary tract and lateral tegmental field at this level of the brainstem. Injections of the specific NK-1 receptor antagonist, GR 82334, bilaterally into the mNTS significantly reduced the muscle pressor response, while bilateral injections of the SP NK-1 agonist, GR 73632, into the mNTS significantly increased the pressor and tachycardic responses during the contractions. Neither the antagonist nor the agonist, at the doses tested, affected the resting arterial pressure or heart rate. These data indicate that irSP are released from sites in the mNTS during the reflex pathways activated by isometric contractions and that they interact with NK-1 receptors in the area of the mNTS to affect the cardiovascular responses during the muscle pressor reflex.
Williams
C A
CA
Department of Physiology, College of Medicine, East Tennessee State University, Johnson City 37614, USA. williamc@washington.xtn.net
Fowler
W L
WL
D000818:Animals; D001933:Brain Stem / Q000737:chemistry / Q000378:metabolism*; D002319:Cardiovascular System / Q000378:metabolism; D002415:Cats; D007537:Isometric Contraction / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D064729:Neurokinin-1 Receptor Antagonists; D010446:Peptide Fragments / Q000494:pharmacology; D010803:Physalaemin / Q000031:analogs & derivatives / Q000494:pharmacology; D018040:Receptors, Neurokinin-1 / Q000819:agonists / Q000378:metabolism*; D012018:Reflex / Q000502:physiology; D013373:Substance P / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology
D064729:Neurokinin-1 Receptor Antagonists; D010446:Peptide Fragments; D018040:Receptors, Neurokinin-1; C079014:GR 82334; C068032:GR 73632; D010803:Physalaemin; D013373:Substance P