Factors determining post-stimulation dilatation.
Post-stimulation dilatation (PSD) of the femoral artery and vein after cessation of postganglionic sympathetic stimulation were related to the frequency and pulse number of the preceding stimulation. It was found that: 1) A minimum number of pulses (MNP) is needed to evoke PSD. MNP is inversely related to the stimulation frequency. A marked PSD develops after stimulation at 1 Hz when only 100 pulses were applied, whereas, if stimulated at 4 Hz or at higher frequencies, even 2,000 pulses fail to induce PSD. 2) The maximum value, the maximum rate and the overall diameter change of PSD (expressed either in absolute values or in relation to the preceding contraction) are a) directly related to the number of pulses at a constant stimulation frequency, b) for a constant number of pulses the above values are inversely related to the stimulation frequency. 3) The relation of PSD values to the stimulation parameters contradict the assumption that PSD is elicited either by a neurogenic transmitter released by the stimulation, or by an extraneuronal transmitter whose release is associated with the release of noradrenaline. PSD is suggested to be due to a decreased noradrenaline level within the synaptic cleft due to persistence of the reuptake after the release of noradrenaline had ceased.
D000320:Adrenergic Fibers / Q000502:physiology*; D000818:Animals; D001338:Autonomic Fibers, Postganglionic / Q000502:physiology; D004285:Dogs; D004558:Electric Stimulation; D005260:Female; D005263:Femoral Artery / Q000294:innervation; D005268:Femoral Vein / Q000294:innervation; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000294:innervation*; D014655:Vascular Resistance; D014664:Vasodilation