CONTROL 
W. p. GEIS AND M. P. KAYE 
RT. ANT. ANSA 
SVC TRANSECTION 
IVC-ILA JUNCTION 
303 
RVF 
HRyMn. 146 
250 
Figure 5. — Regional Denervation of the Canine Heart. 
Rt. anterioi- Ansa Stimulation 
RAF=rt. atrial contractile force 
BE(RA) = bipolar electrogram, rt. atrium 
RVF=:rt. ventricular contractile force 
BE (RV) =bipolar electrogram, rt. ventricle 
Column, stimulation results in slight cardio- 
acceleration, but electrical and mechanical acti- 
vation of the RA continues to occur 70 msec 
prior to that of the RV. 
Parasympathetic Innervation 
Parasympathetic innervation of the AV node 
was demonstrated in all animals in vv^hich 
transection of the SVC was the first pro- 
cedure performed. Following effective para- 
sympathetic denervation of the sinus node, 
stimulation of parasympathetic nerves results 
in slowing or cessation of ventricular rate 
accompanied by no change in atrial rate. In 
all eleven animals, AV nodal innervation was 
demonstrated during stimulation of the right 
thoracic vagus nerve, right vagosympathetic 
trunk, left thoracic vagus nerve and left 
vagosympathetic trunk. AV nodal parasympa- 
thetic innervation was demonstrated during 
stimulation of the caudovagal nerve in four 
experiments, during stimulation of the cranio- 
vagal nerve in two experiments and during 
stimulation of the recurrent cardiac nerve in 
one experiment. The remaining cardiac nerves 
did not provide evidence for parasympathetic 
innervation of the AV node in any experiment. 
In all experiments the AV nodal parasym- 
pathetic response to stimulation of each nerve 
was interrupted following either transection of 
the superior margin of LA or transection of the 
inferior margin of the LA. Total interruption of 
depression of the AV node to nerve stimulation 
was accomplished by transection of the superior 
LA to right thoracic vagus nerve stimulation in 
3 experiments, to right cervical vagosympathetic 
trunk stimulation in 2 experiments, to left cer- 
vical vagosympathetic nerve stimulation in 5 
experiments, in one experiment each to left tho- 
racic vagus nerve, craniovagal nerve and 
caudovagal nerve stimulation. In many experi- 
ments, transection of the superior LA did not 
totally interrupt slowing of the AV node during 
nerve stimulation. In these experiments, tran- 
section of the inferior LA invariably inter- 
rupted the AV nodal response to stimulation of 
each of the nerves. The left thoracic vagus 
nerve response was interrupted in 10 experi- 
ments, the right thoracic vagus response was 
interrupted in 8 experiments, the right cervical 
vagosympathetic trunk response in 9 experi- 
ments, the left cervical vagosympathetic trunk 
