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(Hypertension. 1995;25:1287-1293.)
© 1995 American Heart Association, Inc.

Articles

Sympathectomy and Cardiovascular Spectral Components in Conscious Normotensive Rats

Anna Daffonchio; Cristina Franzelli; Alberto Radaelli; Paolo Castiglioni; Marco Di Rienzo; Giuseppe Mancia; Alberto U. Ferrari

From Centro Fisiologia Clinica e Ipertensione, Ospedale Maggiore and CNR (A.D., C.F., A.R., G.M., A.U.F.), Milano; Cattedra di Fisiopatologia Applicata, Divisione di Cardioriabilitazione, Ospedale di Seregno, USSL 62 (A.U.F.); Cattedra di Medicina Interna, Ospedale S. Gerardo (G.M.), and Clinica Medica, Universitá di Milano (A.D., C.F., A.R., G.M., A.U.F.); and LaRC–Centro di Bioingegneria, Fondazione Don Gnocchi, Politecnico di Milano (P.C., M. Di R.) (Italy).

Correspondence to Prof Alberto Ferrari, Centro Fisiologia Clinica e Ipertensione, Ospedale Maggiore, Via F. Sforza, 35, 20122, Milano, Italy.

Abstract We examined the extent to which sympathetic influences are reflected by spectral powers of blood pressure and pulse interval in specific frequency bands in spontaneously behaving Wistar-Kyoto rats subjected to continuous intra-arterial blood pressure recording. The rats were pretreated with 6-hydroxydopamine (150 mg/kg twice in 1 week, n=19) to produce chemical sympathectomy or received vehicle (n=15). In the sympathectomized group, additional monitoring sessions were performed with rats under -adrenergic receptor blockade with phenoxybenzamine (n=8), ß-receptor blockade with propranolol (n=7), or cholinergic receptor blockade with atropine (n=8). Blood pressure signals were analyzed by a computer to calculate spectral powers (fast Fourier transform) in the low-frequency (0.025 to 0.1 Hz), mid-frequency (0.1 to 0.6 Hz), and high-frequency (0.8 to 3.0 Hz) bands. In sympathectomized rats, low-frequency power of blood pressure was 70% greater than in intact rats, whereas mid-frequency power was 60% smaller (P<.05 for both) and high-frequency power was unchanged. High-frequency power of pulse interval was also unchanged in sympathectomized rats, whereas low- and mid-frequency powers were reduced by approximately 50% (P<.05). No further alterations in spectral powers were observed by adding - or ß-adrenergic blockade to sympathectomy, whereas adding cholinergic blockade caused a striking reduction in all pulse interval powers. Thus, mid-frequency blood pressure power depends on sympathetic but also to a substantial extent on nonsympathetic influences. Sympathetic influences do not contribute to low-frequency blood pressure power, having instead a restraining effect. The low- and mid-frequency pulse interval powers depend on both sympathetic and vagal influences. Thus, no blood pressure or pulse interval power in the mid- and low-frequency ranges can be regarded as a specific marker of sympathetic activity.

Key Words: spectrum analysis • sympathetic nervous system • blood pressure • pulse interval • sympathectomy

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