The role of the ventrolateral medulla in the pressor reflex to static muscular contraction
Bauer, Robert McHenry, II
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Permalink
https://hdl.handle.net/2142/22095
Description
Title
The role of the ventrolateral medulla in the pressor reflex to static muscular contraction
Author(s)
Bauer, Robert McHenry, II
Issue Date
1990
Doctoral Committee Chair(s)
Waldrop, Tony G.
Department of Study
Physiology
Discipline
Physiology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Neuroscience
Biology, Animal Physiology
Language
eng
Abstract
This research investigated the role of the ventrolateral medulla (VLM) in regulating the pressor reflex elicited by static muscular contraction. Muscular contraction was induced in these studies by electrical stimulation of L7 and S1 ventral spinal roots in anethetized cats. In one study, the pressor reflex elicited by muscular contraction was attenuated following bilateral VLM microinjections of an excitatory amino acid antagonist, kynurenic acid. The extracellular single unit discharge patterns in 107 of 167 VLM neurons increased by more than 70% during muscular contraction. Computer signal averaging techniques were used to determine if VLM unit discharge correlated temporally with a 2 to 6 Hz rhythm of sympathetic nerve activity. Sympathetic related rhythms of discharge were found in 45 of 117 VLM neurons examined in baroreceptor intact and barodenervated cats. Furthermore, 29 of the 45 sympathetic VLM neurons were excited by hindlimb muscular contraction. In another study, 21 of 54 VLM neurons were activated antidromically by stimulation in the spinal cord. Signal averaging analyses showed that 8 of the 21 spinally projecting VLM neurons exhibited sympathetic related discharge and six of those were excited by muscular contraction. In another study intrathecal injections of kynurenic acid in the upper thoracic spinal cord attenuated the pressor reflex to muscular contraction. In addition, glutamate immunoreactive neurons were identified in the same region of the VLM as reticulospinal sympathetic neurons that responded to muscular contraction. These findings suggest that sympathetic reticulospinal VLM neurons participate in the pressor reflex to muscular contraction. This reflex is modulated in part by an excitatory amino acid mechanism in the spinal cord that may involve input from a reticulospinal glutamatergic pathway.
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