Summary
Somato-vegetative reflexes elicited by electrical stimulation of various spinal afferents and the effect of conditioning were investigated in immobilized cats, conscious or anaesthetized with chloralose or urethane. Test stimuli (1–2–4 imp/s) were applied before and after higher frequency (30 imp/s) conditioning stimulation on the same (homotopic conditioning) or different (heterotopic conditioning) nerves. Changes in reflex blood pressure responses and in renal sympathetic efferent activity were evaluated.
In case of homotopic conditioning facilitation of reflexes was observed in anaesthetized cats. It manifested itself in reversal of depressor reactions into biphasic or pressor ones and in the appearance of marked reflex discharges in the sympathetic efferent activity, if the testing stimulations involved A-fibre afferents only. Pressor reflexes elicited by testing stimulations of A+C-afferents were enhanced; in the renal neurograms second bursts of discharges (C-reflexes) appeared or, if they had been present, were enlarged.
Facilitation failed 1. if conditioning stimulation was not strong enough to excite C-fibre afferents; 2. in case of heterotopic stimulations; 3. in conscious animals independently of the site of conditioning. Depression of reflexes could be observed if heterotopic conditioning was performed in urethane anaesthesia or in conscious animals.
It is concluded that post-tetanic facilitation of sympathetic reflexes may be due to enhanced excitability of the first spinal interneurons; controlling role of supraspinal influences is admitted.
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Lukoshkova, E.V., Pavlik, G. Post-tetanic facilitation of vasomotor reflexes elicited by electrical stimulation of spinal afferents. Pflugers Arch. 336, 134–146 (1972). https://doi.org/10.1007/BF00592928
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DOI: https://doi.org/10.1007/BF00592928