Extracellular glutamate increases in rostral ventrolateral medulla during static muscle contraction.
The ventrolateral medulla is an important site involved in increases in arterial pressure and heart rate during static muscle contraction. Glutamate, an excitatory amino acid neurotransmitter, appears to play a role in mediating these responses. We measured glutamate concentration in the extracellular fluid of the rostral ventrolateral medulla during static muscle contraction in anesthetized rats. A 2-min tibial nerve stimulation-evoked muscle contraction increased blood pressure by 30 +/- 4 mmHg and heart rate by 32 +/- 4 bpm. Extracellular glutamate in the rostral ventrolateral medulla also increased from 9 +/- 1 pmol/4 microl to 14 +/- 1 pmol/4 microl. Results were repeatable over two subsequent contractions. Tibial nerve stimulation following neuromuscular blockade did not elicit changes in blood pressure, heart rate or extracellular fluid glutamate. Data demonstrate that muscle contraction increases extracellular fluid concentration of glutamate in the rostral ventrolateral medulla, suggesting that rostral ventrolateral medullary glutamate release is a neurochemical change associated with cardiovascular responses during static muscle contraction.
Caringi
D
D
Department of Pharmacology, University of New England College of Osteopathic Medicine, 11, Hills Beach Rd., Biddeford, ME 04005, USA.
Maher
T J
TJ
Chaiyakul
P
P
Asmundsson
G
G
Ishide
T
T
Ally
A
A
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004558:Electric Stimulation; D004563:Electrochemistry; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism*; D006439:Hemodynamics / Q000502:physiology; D008297:Male; D008526:Medulla Oblongata / Q000378:metabolism* / Q000502:physiology*; D017551:Microdialysis; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000502:physiology*; D019148:Neuromuscular Blockade; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D018698:Glutamic Acid