title: Altered baroreflex and autonomic modulation in monosodium glutamate-induced hyperadipose rats.
abstract: We aimed to examine the cardiovascular function by tonic and baroreflex alterations in obese rats induced by monosodium glutamate (MSG). Neonatal male Wistar rats were injected with MSG (4 mg/g body weight) or equimolar saline (control, C). At 90 days, all rats were anesthetized for catheterization of the femoral artery for mean arterial pressure (MAP) and heart rate (HR) recordings in the conscious state. After baseline, we performed IV treatment with hexamethonium (25 mg/kg), or atropine (1 mg/kg) or propranolol (3 mg/kg). We also performed the spectral analysis of heart rate variability (HRV) and baroreflex sensitivity. Baseline comparison showed that obese rats are hypertensive compared with control (C=110±2 mmHg; MSG=: 123±3 mmHg, P<0.05). After ganglionic blockade with hexamethonium the differences in MAP between control and obese rats disappeared. Beta adrenergic blockade with propranolol induced a greater decrease in heart rate compared with control. The analysis of HRV showed that obese rats have increased modulation by both components of the autonomic nervous system compared with control rats. The baroreflex gain showed increased sensitivity for the parasympathetic component in the obese rats (C=-2.41±0.25; MSG=-3.34±0.23 bpm/mmHg) compared with control. Our data suggest that both components of autonomic cardiac tonus and the parasympathetic component of the baroreflex sensitivity are increased in the MSG obese rat. It is possible that the parasympathetic alterations observed in these MSG obese rats may have originated from central areas of cardiovascular control.
authors.affiliation: Department of Physiological Sciences, State University of Londrina, Londrina, PR, Brazil.
authors.forename: Marlusa
authors.initials: M
authors.lastname: Karlen-Amarante
authors.forename: Natália Veronez
authors.initials: NV
authors.lastname: da Cunha
authors.forename: Ozahyr
authors.initials: O
authors.lastname: de Andrade
authors.forename: Hugo Celso Dutra
authors.initials: HC
authors.lastname: de Souza
authors.forename: Marli Cardoso
authors.initials: MC
authors.lastname: Martins-Pinge
mesh_terms: D000818:Animals; D001341:Autonomic Nervous System / Q000503:physiopathology*; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D009765:Obesity / Q000503:physiopathology*; D051381:Rats; D017208:Rats, Wistar; D012970:Sodium Glutamate / Q000633:toxicity*
chemical_list: D012970:Sodium Glutamate