Attenuated pressor responses to amino acids in the rostral ventrolateral medulla after swimming training in conscious rats.
The cardiovascular effects of microinjection of the amino acids glutamate and glycine within the rostral ventrolateral medulla (RVLM) after swimming training (ST) in unrestrained awake rats were investigated. Unilateral microinjection of l-glutamate (5, 20 and 50 mM, in 100 nl) produced a dose dependent increase in mean arterial pressure (MAP) in control (C) (16+/-5 mm Hg; 29+/-6 mm Hg; 43+/-6 mm Hg) and swim (SW) (1+/-1 mm Hg; 16+/-2 mm Hg; 25+/-3 mm Hg) groups. However, the magnitude of this response was lower in the swim group. Prazosin injection produced hypotension and tachycardia in both groups (C=-43+/-3 mm Hg/98+/-16 bpm; SW=-61+/-5 mm Hg/115+/-32 bpm). In the SW group the hypotension caused by prazosin was greater compared to C group, but the tachycardia was not different between them. After prazosin, glutamate response in RVLM was blocked in both groups as well. When glycine (10 mM or 1 M, in 100 nl) were microinjected into the RVLM of C group we observed two different effects: decrease in MAP with the lower dose and an increase in MAP with the higher dose (10 mM=-13+/-2 mm Hg; 1 M=47+/-6 mm Hg). However, after ST the hypertensive response to glycine was blunted with no alterations in the hypotensive response (10 mM=-14+/-1 mm Hg; 1 M=18+/-4 mm Hg). These findings suggest that RVLM is involved in the modulation of the sympathetic outflow to the cardiovascular system during exercise training.
Martins-Pinge
Marli Cardoso
MC
Department of Physiological Sciences, Center of Biological Sciences, State University of Londrina, Londrina, Paraná, Brazil. pinge@sercomtel.com.br
Becker
Lenice Kappes
LK
Garcia
Martha Regina Luccizano
MR
Zoccal
Daniel Breseguello
DB
Neto
Renata Vasconcelos
RV
Basso
Leonardo Salomão
LS
de Souza
Hugo Celso Dutra
HC
Lopes
Oswaldo Ubríaco
OU
D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D002319:Cardiovascular System / Q000187:drug effects; D003243:Consciousness; D004305:Dose-Response Relationship, Drug; D018698:Glutamic Acid / Q000008:administration & dosage*; D005998:Glycine / Q000008:administration & dosage*; D006339:Heart Rate / Q000187:drug effects; D006973:Hypertension / Q000503:physiopathology; D007022:Hypotension / Q000503:physiopathology; D007276:Injections, Intraventricular; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects* / Q000502:physiology*; D008845:Microinjections; D010805:Physical Conditioning, Animal / Q000502:physiology*; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013550:Swimming / Q000502:physiology; D013610:Tachycardia / Q000503:physiopathology
D000959:Antihypertensive Agents; D018698:Glutamic Acid; D005998:Glycine; D011224:Prazosin