Dual Action of Nicotine on the Sympathetic Ganglion of the Cat.

Summary. When transmission in the sympathetic ganglion has been blocked by arterial injection of nicotine it can in some cases be restored post‐tetanically, in others not. Soon after the injection of nicotine a partial block may be restored only to a small extent, whereas some times after an injection a more pronounced block may be relieved post‐tetanically to a considerable extent. Simultaneous measurements of the demarcation potential and the transmitted action potential have demonstrated that there is not full correlation between the block and the ganglion cell depolarization. Even when the demarcation potential has returned to the normal level the block remains but can now be relieved post‐tetanically. It is concluded that the first phase of block which can not be relieved post‐tetanically is due to ganglion cell depolarization, whereas the block which can be relieved post‐tetanically has another cause.