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Sympathetic single axonal discharge after spinal cord injury in humans: activity at rest and after bladder
B G Wallin1, T Karlsson1, G Pegenius1
1Department of Clinical Neurophysiology, Institute of Neuroscience and Physiology, Sahlgren Academy at University of Gothenburg, Sahlgren University Hospital, Gothenburg, Sweden.
Study Design:
Clinical experimental mechanistic study.
Objectives:
(1) To determine in three spinal cord-injured patients whether individual muscle sympathetic nerve fibres below the level of the spinal lesion display spontaneous activity. (2) To determine in these patients if individual sympathetic vasoconstrictor fibres show a prolonged discharge following a bladder stimulus.
Setting:
University hospital in Gothenburg, Sweden.
Methods:
Microneurographic recordings of action potentials from individual muscle nerve sympathetic fibres in a peroneal nerve. Recordings of skin blood flow and electrodermal responses in a foot.
Results:
In all patients, there was sparse ongoing spontaneous impulse traffic in individual sympathetic fibres. Brisk mechanical pressure over the urinary bladder evoked a varying number of action potentials in individual fibres, but the activity was brief and did not continue after the end of the evoked multiunit burst.
Conclusion:
Prolonged discharges in individual sympathetic fibres are unlikely to contribute to a long duration of blood pressure increases induced by brief bladder stimuli.
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