Studies on the intramural nerves of the hamster and mouse gallbladders

We first carried out microscopic observation of the intramural nerves of hamster and mouse gallbladders which were fixed and stained with a solution of OsO4 and ZnI2. For this microscopic observation, the guinea-pig gallbladder was used as a control. We then investigated the relationship between the motility and intramural nerves of the isolated gallbladder in both the hamster and mouse. The following results were obtained: 1. The ganglionated plexus and the perivascular nerves as the intramural nerves of the guinea-pig gallbladder were observed in the subserosal layer. These perivascular nerves were not possessed of ganglia. On the other hand, the nerve plexus and the perivascular nerves as the intramural nerves of the gallbladders of hamster and mouse were observed in the subserosal layer. These nerves, that is, the nerve plexus and the perivascular nerves, were not possessed of ganglia. That is to say, no ganglionated plexus or ganglia were observed in the subserosal layer of the walls of hamster and mouse gallbladders. 2. The isolated hamster and mouse gallbladders evoked spontaneous motility. This spontaneous motility was little affected by either atropine (1 x 10(-6) M) or tetrodotoxin (1 x 10(-7) M). 3. The hamster and mouse gallbladders showed a contractile response to electrical stimulation with rectangular pulses (50 volt, 40 Hz) of durations of 0.5, 1, 2, 3, 4, 5 or 6 msec for a period of 10 sec. These contractile responses were little affected by either atropine (1 x 10(-6) M) or tetrodotoxin (1 x 10(-7) M). 4. The long duration of the contractile response was mediated by electrical stimulation with rectangular pulses (50 volt, 40 Hz) of durations of 4, 5 or 6 msec for a period of 10 sec. That is to say, its duration time was approximately from 8 to 15 minutes for both hamster and mouse. These results suggest that the hamster and mouse gallbladders may not contain the nerves that take part in the movement of the gallbladder. That is to say, the contractile response of the hamster and mouse gallbladders seems to be myogenic rather than neurogenic in its control. It is, however, possible that some substance other than the neurotransmitter in the walls of these gallbladders may also play a part in the control of the contractile response, although further study will be necessary to verify this suggestion.