126 



Blood Flow and Secretion 



of vasoconstrictor fibres but attributed to loss of water into the 

 saliva and particularly to the action of vasodilator fibres ; with a 

 restricted arterial flow the first effect of the lowered arteriolar 

 tone would be to diminish the venous outflow. 



Experiments by Graham and Stavraky (1953) show, however, 

 that under certain conditions a vasoconstriction can be obtained on 

 chorda stimulation. Whether a dilatation or a constriction will be 

 obtained when the chorda is excited depends, according to these 

 investigators, on the concentration of acetylcholine acting on the 

 vessels. A small dose of acetylcholine, injected intra-arterially to- 

 wards the gland, causes a dilatation, a big dose constriction. When 

 eserine has been given, even a small dose of acetylcholine could 

 cause a constriction. Similarly, after eserine or a big dose of acetyl- 



Bl.pr. 



Sal. seer. 



Bl. flow 



\m\wmm\\\\\\\\ 



Ch. T. coil 18cm. 



1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 1 

 Time S sec. 



B 



After 

 20/f eserine 



Mm. Hq. 

 80n 



40- 



V 



Ch. T. coil 18cm 



I I I ! I I I I I I I I 



Fig. 7.2. Reversal of the response of the submaxillary gland of a cat to stimu- 

 lation of the chorda tympani (Ch.T.) by the intra-arterial injection of eserine. 



In A stimulation resulted in vasodilatation and secretion, in B, 2 minutes after eserinization, 

 stimulation led to vasoconstriction and a reduced secretorv response (Graham and Stavraky, 

 1953)- 



