Abstract
In order to analyse the neuronal mechanisms of sympathetic nervous activities step by step from the periphery, response patterns of galvanic skin response (GSR) and photoelectric digital plethysmogram (PTG) were compared each other under various experimental conditions in 45 cats. For this purpose, direct responses of these two phenomena by stimulation of the ipsilateral preganglionic or postganglionic sympathetic nerves as well as reflex responses of these phenomena by stimulation of the contralateral sciatic nerve were recorded simultaneously in animals immobilized with Flaxedil. Acute as well as chronic spinal animals were used for the observation of the reflex responses.
1. In the case of GSR, distinct responses were observed even with single pulse stimulation of the preganglionic as well as of postganglionic nerves, whereas no response of PTG was obtained unless repetitive stimulation was employed. Furthermore, the response patterns of these two phenomena with repetitive stimulation were different with each other, the former showing the maximum height in the initial phase of the stimulation whereas the latter doing at about the end of the stimulation. These results may be attributable to the different characteristics of the effectors: the sweat gland and the skin blood vessel.
2. Reflex responses of GSR appeared even with single pulse stimulation in acute as well as in chronic spinal animals, whereas reflex responses of PTG did solely with repetitive one in either group of animals. Increase in amplitude of pulse waves of PTG was observed in association with rise of blood pressure in acute spinal animals in contrast to its decrease in chronic ones. Release from intensive tonic sympathetic impulses of the skin vessel following spinal transection may account for this result in acute spinal animals.
3. Frequency response curves of these phenomena differed according to the sites of stimulation of the preganglionic, postganglionic nerve and contralateral sciatic nerve, although no essential difference between the results of the two phenomena obtained by stimulation of each site of these nerves was observed. These differences may be respectively due to the specific characteristics of synaptic transmission in the sympathetic ganglia and also to the specific neuronal mechanisms of the spinal cord.
On the basis of these experimental results, it may be said that there is no essential difference between the neuronal mechanisms of GSR and PTG, so far as the spinal reflex mechanism and peripheral one are concerned.
