Time Relations of Degeneration Mydriasis and Degeneration Vasoconstriction in the Rabbit Ear after Sympathetic Denervation. Effect of Bretylium.



Removal of the superior cervical ganglion in rabbits causes homolateral mydriasis starting about 14 hrs and ending about 32 hrs after the operation. In the external ear a vasoconstriction starts around 20 hrs and ends around 40 hrs after operation. A residual vasoconstriction sensitive to systemic ganglionblocking agents is often seen. Both phenomena are similarly delayed by bretylium. No time difference between the end of vasoconstriction at the base and at the tip of the ear (5–7 cm apart) was observed under conditions where a time difference of 2–3 hrs would have been detected. The conclusion is that the time between operation and transmitter release from the degenerating terminals is longer than is needed for the message of the interruption of the axon to reach the terminals. Time differences between degeneration release of transmitter in different organs may be partly due to intrinsic differences between the populations of terminals.