Effect of alpha-adrenoceptor blockade on the 0.4 Hz sympathetic rhythm in conscious XXXX .

@entity35 @entity1063 @entity5521 @entity855
1. The present study examined the origin of the 0.4 Hz rhythm in renal sympathetic nerve activity (RSNA) in @entity35 . It was anticipated that, after elimination of 0.4 Hz oscillations of arterial pressure (AP) by alpha-adrenoceptor blockade, the persistence or disappearance of a 0.4 Hz rhythm in RSNA would point to an endogenous (central oscillator) or baroreflex origin, respectively. 2. Arterial pressure and RSNA were recorded in seven conscious @entity35 , before and after acute alpha-adrenoceptor blockade with @entity5521 (5 mg/kg, i.v.). In each condition, power and coherence spectra were calculated over 15 min periods of rest. 3. In control conditions, highly coherent AP and RSNA oscillations were observed near 0.4 Hz. After @entity5521 administration, spectral power in the mid-frequency (0.27-0.74 Hz) band was significantly reduced for both AP and RSNA and maximum power was shifted towards 0.7 Hz. 4. The disappearance of the RSNA rhythm at 0.4 Hz after @entity5521 administration favours the hypothesis of a baroreflex origin. The new oscillation near 0.7 Hz can derive either from the activity of a previously unrecognized central oscillator or from a faster feedback mechanism involving cotransmitters of @entity1063 acting with shorter time constants (e.g. @entity855 ).
