Auerbach's plexus of the rat cecum in relation to the germfree state

Abstract

Abstract The cecum of germfree rats, after the second week of life, enlarges sixfold over that of conventional tank‐raised controls. Poor muscle tone as well as dietary factors have been incriminated. We have studied the myenteric plexus of the cecum in conventional and germfree rats, in an effort to find a neuronal explanation of the phenomenon and to test whether the neurovegetative periphery is capable of adapting to the changing size. With routine and histochemical technics three salient features stood out: (1) The myenteric neurones in the cecum of the germfree rat on an average were three times larger than those of the controls (42 μ vs 16 μ). Some neurones of the germfree cecum attained giant size (over 150 μ). (2) They showed a lower DPNH diaphorase activity, unrelated to the increased cell size, (3) In the germfree rat cecum the meshes of the primary fiber plexus of Auerbach had increased in size along the antimesenteric border, while the network under the mesenteric attachment was smaller. The ratio between the network of the two sides was 1:12 in the germfree, 1:5 in the controls. We have concluded that the neurones of Auerbach's plexus in the germfree cecum are indeed less active metabolically — a factor which may perpetuate the cycle of cecal distention in these animals. The neurovegetative periphery in the cecum has shown itself capable to responding to the increased cecal volume by neuronal hypertrophy.