Cardiovascular responses to somatosensory stimulation and their modulation by baroreflex mechanisms.
Exposure of experimental animals to noxious somatic stimulations sometimes induces sustained hypertension. Information regarding the medullary projections of somatic afferents and the neurotransmitters involved in them is incomplete. The present investigation in urethane-anesthetized, artificially ventilated, adult male Wistar rats was undertaken to clarify some of these issues. It was observed that the inhibition of contralateral, ipsilateral, or bilateral rostral ventrolateral medullary pressor area (RVLM) with muscimol attenuated the pressor and tachycardic responses to sciatic nerve stimulation. Similar inhibition of the medial subnucleus of the solitary tract (mNTS) exaggerated the cardiovascular responses to sciatic nerve stimulation. Interruption of the baroreflex by microinjections of ionotropic glutamate receptor antagonists into the mNTS or barodenervation also exaggerated the responses to sciatic nerve stimulation. Unilateral stimulation of the aortic nerve blocked the cardiovascular responses to the sciatic nerve stimulation. These results indicated that in the rat, the ascending afferents in the sciatic nerve project bilaterally to the RVLM as well as mNTS; an excitatory amino acid, probably glutamate, is released in the mNTS in response to the sciatic nerve stimulation; and barodenervation or blockade of baroreflex in the mNTS exaggerates, while baroreceptor stimulation inhibits, cardiovascular responses to somatosensory stimulation.
Kawabe
Tetsuya
T
Department of Neurological Surgery, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, New Jersey 07103, USA.
Kawabe
Kazumi
K
Sapru
Hreday N
HN
D000344:Afferent Pathways / Q000033:anatomy & histology / Q000502:physiology; D000818:Animals; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology; D002320:Cardiovascular Physiological Phenomena; D002319:Cardiovascular System / Q000294:innervation / Q000378:metabolism; D018691:Excitatory Amino Acid Antagonists / Q000008:administration & dosage / Q000378:metabolism; D018698:Glutamic Acid / Q000008:administration & dosage / Q000378:metabolism; D006339:Heart Rate / Q000502:physiology; D008297:Male; D008526:Medulla Oblongata / Q000033:anatomy & histology / Q000502:physiology; D008845:Microinjections; D051381:Rats; D017208:Rats, Wistar; D012018:Reflex / Q000502:physiology; D012584:Sciatic Nerve / Q000502:physiology; D017552:Solitary Nucleus / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology; D013564:Sympathetic Nervous System / Q000033:anatomy & histology / Q000502:physiology
D018691:Excitatory Amino Acid Antagonists; D018698:Glutamic Acid