title: Sympathectomy and cardiovascular spectral components in conscious normotensive rats.
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 intraarterial 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 alpha-adrenergic receptor blockade with phenoxybenzamine (n = 8), beta-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 alpha- or beta-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.
authors.affiliation: Centro Fisiologia Clinica e Ipertensione, Ospedale Maggiore, Milano, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Daffonchio
authors.forename: C
authors.initials: C
authors.lastname: Franzelli
authors.forename: A
authors.initials: A
authors.lastname: Radaelli
authors.forename: P
authors.initials: P
authors.lastname: Castiglioni
authors.forename: M
authors.initials: M
authors.lastname: Di Rienzo
authors.forename: G
authors.initials: G
authors.lastname: Mancia
authors.forename: A U
authors.initials: AU
authors.lastname: Ferrari
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure; D008297:Male; D010276:Parasympatholytics / Q000494:pharmacology; D011674:Pulse; D051381:Rats; D011921:Rats, Inbred WKY; D012815:Signal Processing, Computer-Assisted; D013563:Sympathectomy, Chemical; D013564:Sympathetic Nervous System / Q000502:physiology*
chemical_list: D000317:Adrenergic alpha-Antagonists; D000319:Adrenergic beta-Antagonists; D010276:Parasympatholytics