ORIGIN AND EXTENT OF GASTRO-INTESTINAL MOTILITY IN THE CAT AND GUINEA PIG

Abstract

The earliest indication of motility in the G-I tract of both the fetal cat and guinea pig was a simple localized contraction in response to mechanical stimulation in 17 mm. specimens. Spontaneous gastric and intestinal peristalsis was present in 27 to 28 mm. cat fetuses and in 35 mm. guinea pig fetuses. Peristalsis was observed earlier than rhythmic segmentation in the fetal cat although the reverse was true in the guinea pig. Apparently G-I motility begins later and at a lower level of activity in the fetal guinea pig than in the cat. From the 50th day to term, G-I activity, especially in the stomach, cecum and colon, functioned at a more mature level in the fetal guinea pig than in the cat of comparable gestation age. Clamping the umbilical cord led to a replacement of peristalsis by rhythmic segmentation and finally to diminished intestinal tonus with slow, pendulous, writhing movements. Anoxemia likewise excited inactive intestines to an initial hyperactive state of generalized segmentation, but activity usually ceased abruptly with the intestines severely contracted in such instances. Light ether anesthesia produced the same effects as clamping the cord. Deep ether anesthesia inhibited activity completely. Nembutal first depressed fetal G-I activity, but gradually tonus and rhythmic motility returned and the gut became hyperactive. In young fetuses of both spp., anastalsis and general non-directional activity characterized the hyperactive state during anesthesia. Circular and longitudinal muscle surrounded the G-I tract, and the myenteric and submucous ganglia and plexuses were established as early as 17 mm. in both spp. A rich vagal supply to the stomach and an equally prominent sympathetico-vagal supply from the coeliac ganglion innervated the intestinal tract in the 13 mm. cat.