[Characteristics of central acute resetting of low threshold baroreflex in rabbit's aortic nerve].

Experiments were performed on 40 urethane-anesthetized rabbits. The aortic nerves, carotid sinus nerves and vagus nerves were cut, mean arterial pressure (MAP) and renal sympathetic nerve activity (RSNA) were recorded. The conditional stimulation (0.02 ms, 50 Hz, 4-6 V, 5 min) of central cut end of aortic nerve was used to evoke the afferent A-fibers and to mimic the response of low threshold baroreflex to holding pressure, so as to induce the central process of acute resetting. It was observed that after conditional stimulation ceased 1 min, the MAP and RSNA for response to stimulation of myelinated aortic afferent was attenuated at 41.8 +/- 7.6% (P less than 0.01, n = 11) and 19.31 +/- 2.6% (P less than 0.05, n = 11), but both MAP and RSNA were not significantly changed for non-myelinated fibers. The result suggests that the characteristics of central resetting were dependent on the component of baroreflex afferent fibers. The central resetting of low threshold myelinated afferent activities was attenuated only on the baroreflex produced by myelinated afferent fibers.