Blood pressure displays an oscillation at 0.1 Hz in humans that is well established to be due to oscillations in sympathetic nerve activity (SNA). However, the mechanisms that control the strength or frequency of this...
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Blood pressure displays an oscillation at 0.1 Hz in humans that is well established to be due to oscillations in sympathetic nerve activity (SNA). However, the mechanisms that control the strength or frequency of this oscillation are poorly understood. The aim of the present study was to define the dynamic relationship between SNA and the vasculature. The sympathetic nerves to the kidney were electrically stimulated in six pentobarbital-sodium anesthetized rabbits, and the renal blood flow response was recorded. A pseudo-random binary sequence (PRBS) was applied to the renal nerves, which contains equal spectral power at frequencies in the range of interest (<1 Hz). Transfer function analysis revealed a complex system composed of low-pass filter characteristics but also with regions of constant gain. A model was developed that accounted for this relationship composed of a 2 zero/4 pole transfer function. Although the position of the poles and zeros varied among animals, the model structure was consistent. We also found the time delay between the stimulus and the RBF responses to be consistent among animals (mean 672 +/- 22 ms). We propose that the identification of the precise relationship between SNA and renal blood flow (RBF) is a fundamental and necessary step toward understanding the interaction between SNA and other physiological mediators of RBF.
A technique is described for the measurement of the frequency response of a sensory receptor. The input function (stimulus) consists of a wide-spectrum binary signal and correlation techniques are used to recover info...
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A technique is described for the measurement of the frequency response of a sensory receptor. The input function (stimulus) consists of a wide-spectrum binary signal and correlation techniques are used to recover information from the output pulse train (afferent neural discharge). The method has been tested using an electronic model. The possible advantages are discussed.
The ‘static’ stimulus-response curves of single baroreceptors were determined in four cats, anaesthetised with pentobarbitone, paralysed with gallamine and artificially ventilated. They consisted of a steep increase...
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The ‘static’ stimulus-response curves of single baroreceptors were determined in four cats, anaesthetised with pentobarbitone, paralysed with gallamine and artificially ventilated. They consisted of a steep increase of the frequency of discharge with pressure at pressures immediately above threshold and a flatter relation at higher pressures. From this relation, binary levels of pressure were selected within the linear range and a pseudo-randombinarys equence used as an input to the receptors, the frequency response being obtained by crosscorrelating the output (discharge) with the input. The response was similar to that obtained previously by sinusoidal stimulation at various frequencies, but was obtained in a fraction of the time. In discussion, it is suggested that the method may be applied to most biological sensory receptors for the determination of their frequency characteristics and the mechanisms which regulate receptor sensitivity.
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