Abstract
Physiological and anatomic methods were used to determine whether neurons in the rostral ventrolateral medulla (RVLM), nucleus tractus solitarius (NTS), or hypothalamic paraventricular nucleus (PVN) mediate the cardiovascular response evoked from the dorsomedial hypothalamic nucleus (DMH), which is believed to play a key role in mediating responses to stress. In urethane-anesthetized rats, activation of neurons in the DMH by microinjection of bicuculline resulted in a large increase in arterial pressure, heart rate, and renal sympathetic nerve activity. The pressor and sympathoexcitatory responses, but not the tachycardic response, were greatly reduced after bilateral muscimol injections into the RVLM even when baseline arterial pressure was maintained at a constant level. These responses were not reduced by muscimol injections into the PVN or NTS. Retrograde tracing experiments identified many neurons in the DMH that projected directly to the RVLM. The results indicate that the vasomotor and cardiac components of the response evoked from the DMH are mediated by pathways that are dependent and independent, respectively, of neurons in the RVLM.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adrenergic beta-Antagonists / administration & dosage
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Animals
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Bicuculline / administration & dosage
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Blood Pressure / drug effects
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Blood Pressure / physiology
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Cardiovascular System / innervation*
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Dorsomedial Hypothalamic Nucleus / cytology
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Dorsomedial Hypothalamic Nucleus / drug effects
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Dorsomedial Hypothalamic Nucleus / physiology*
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GABA Agonists / administration & dosage
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GABA Antagonists / administration & dosage
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Heart Rate / drug effects
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Heart Rate / physiology
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Injections, Intravenous
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Kidney / innervation
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Male
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Medulla Oblongata / cytology
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Medulla Oblongata / drug effects
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Medulla Oblongata / physiology*
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Microinjections
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Microspheres
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Muscimol / administration & dosage
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Neural Inhibition / drug effects
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Neural Inhibition / physiology
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Neural Pathways / physiology*
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Neurons / drug effects
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Neurons / physiology
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Paraventricular Hypothalamic Nucleus / cytology
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Paraventricular Hypothalamic Nucleus / drug effects
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Paraventricular Hypothalamic Nucleus / physiology
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Rats
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Rats, Sprague-Dawley
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Solitary Nucleus / cytology
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Solitary Nucleus / drug effects
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Solitary Nucleus / physiology
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Sympathetic Nervous System / drug effects
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Sympathetic Nervous System / physiology
Substances
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Adrenergic beta-Antagonists
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GABA Agonists
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GABA Antagonists
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Muscimol
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Bicuculline