Submitted on September 30, 2008
Revised on March 24, 2009
Accepted on March 24, 2009
Lateralization of Expression of Neural Sympathetic Activity to the Vessels and Effects of Carotid Baroreceptor Stimulation
Andre Diedrich1, Alberto Porta2, Franca Barbic3, Robert J. Brychta1, Pietro Bonizzi4, Laura Diedrich1, Sergio Cerutti5, David Robertson6, and Raffaello Furlan4*
1 Vanderbilt University
2 Universita' degli Studi di Milano
3 Bolognini Hospital
4 University of Milan
5 Politecnico di Milano
6 Vanderbilt University School of Medicine
* To whom correspondence should be addressed. E-mail: raffaello.furlan{at}unimi.it.
Background Human studies suggest that cardiovascular neural sympathetic control is predominantly modulated by the right cerebral hemisphere. It is unknown if postganglionic sympathetic activity (muscle sympathetic nerve activity, MSNA) shows any functional asymmetry. Methods Eight right handed volunteers (3 women , 5 men, age 32±2 years) underwent electrocardiogram (ECG), beat by beat blood pressure (BP), respiratory activity and simultaneous right and left MSNA recordings during spontaneous and controlled breathing (CB, 15 breaths/min, 0.25 Hz). Dynamic carotid baroreceptor stimulation was obtained by 0.1 Hz sinusoidal suction, from 0 to -50 mmHg, randomly applied to the right, left and combined right and left sides of the neck, during CB. Laterality was assessed by changes in the MSNA burst rate (bursts/min, burst/100 beats), strength (amplitude, A and area, AA) and oscillatory component at 0.1 Hz during baroreceptor stimulation. Amplitude parameters were normalized by CB burst mean amplitude and area of the same side. Results At rest, right and left MSNA burst rate and total MSNA activity were similar. Conversely, right MSNA normalized burst AN (1.36±0.18) and AAN (1.31±0.16) were larger than left MSNA AN (1.04±0.09) and AAN (1.02±0.08). Unilateral and bilateral carotid baroreflex stimulation abolished the right prevalence of AN and AAN. Conclusions Right lateralization of sympathetic activity to the vessels is indicated by normalized burst strength parameters of bilateral MSNA recordings at rest during spontaneous breathing. Carotid baroreceptor stimulation disrupted such expression of MSNA lateralization possibly by disturbing the synchronizing action of right cerebral hemisphere.
