Absence of ganglionated plexus in bullfrog gallbladder

We first carried out microscopic observation of the intramural nerves of a bullfrog gallbladder which were fixed and stained with a solution of OsO4 and ZnI2. We then investigated if the responses of isolated frog gallbladder evoked by electrical stimulation are mediated through the intramural nerves. The following results were obtained: 1. The nerve plexus and the perivascular nerves were observed in the subserosal layer of the wall of the gallbladder. These nerves do not have a ganglia. That is to say, no ganglionated plexus or ganglia were observed in the subserosal layer of the wall of the gallbladder. 2. Electrical stimulation caused the gallbladders to contraction with rectangular pulses (50 volt, 40 Hz) of durations of 0.5, 1, 2, 3, 4 and 5 msec for a period of 10 sec. Three blockers of nerve mediated responses, atropine (1 x 10(-6) M), guanethidine (1 x 10(-6) M) and tetrodotoxin (3 x 10(-7) M), had no effect on the gallbladder contractions induced by stimulation with pulses as short as 0.5 msec or as long as 5 msec. These results suggest that the bullfrog gallbladder may not contain nerves related to movement. Thus, the contraction of the bullfrog gallbladder induced by electrical stimulation does not seem to be modulated by extrinsic nerve terminals distributed in the gallbladder wall.