Abdominal reflex

Abstract: The cerebellum modulates different nociceptive phenomena and influences visceral functions. This study shows cerebellar modulation of an abdominal reflex elicited by a visceral noxious stimulus (colorectal distension, CRD). The intensity of the reflex was measured by electromyographic (EMG) recording from the rectus abdominus muscle, and the cerebellar cortex (vermis, lobule VIII), the fastigial nucleus, or the dentate nucleus was stimulated using d,l-homocysteic acid (0.1 M, 1 μl). To release the fastigial nucleus from inhibition by the Purkinje cells, bicuculline (GABA A receptor antagonist, 100 μM, 1 μl) was used. Stimulation of the cerebellar cortex enhanced, whereas stimulation or disinhibition of the fastigial nucleus decreased, the responses to CRD measured by EMG. Stimulation of the dentate nucleus did not have an obvious effect on the intensity of the reflex. These results are in agreement with the hypothesis that the cerebellum modulates visceral nociceptive functions, whereby the cerebellar cortex and the fastigial nucleus, respectively, play a pro-nociceptive and an anti-nociceptive role.

Abstract: The possible contribution of spinal reflexes to abdominal muscle activation during vomiting was assessed in decerebrate cats. The activity of these muscles is partly controlled by bulbospinal expiratory neurons in the caudal ventral respiratory group (VRG). In a previous study it was found that the abdominal muscles are still active during vomiting after midsagittal lesion of the axons of these neurons between C1 and the obex (A.D. Miller, L.K. Tan, and I. Suzuki. J. Neurophysiol. 57: 1854-1866, 1987). The present experiments indicate that this postlesion activity was due to spinal stretch reflexes because 1) such midsagittal lesions eliminate abdominal muscle nerve activity during fictive vomiting in paralyzed cats in which there are no abdominal stretch reflexes, 2) the abdominal muscles are activated during vomiting by spinal reflexes after upper thoracic cord transections, and 3) the normal 100-ms delay between diaphragmatic and abdominal activation during vomiting is reduced to approximately 20-25 ms after both types of lesions, which is consistent with postlesion abdominal reflex activation. Our results also suggest that, during normal vomiting, abdominal stretch and tension reflexes have only a minor role if any and abdominal muscle activation is probably mediated primarily or exclusively by expiratory neurons in the caudal ventral respiratory group. However, our finding that phrenic activity is reduced both during vomiting after thoracic transections and during fictive vomiting after paralysis is consistent with a contribution of reflex activity from abdominal and/or intercostal muscles to phrenic discharge during normal vomiting.

Abstract: Rosenbach, 20 in 1876, first described visible contractions of abdominal musculature evoked by gentle scratching of skin. Since the zone of effective stimulation was not necessarily limited to areas immediately adjacent to the site of muscular response, and since the contractions were abolished by appropriate motoneuron lesions, the responses were justifiably considered reflex in origin. They have, in fact, been commonly termed superficial abdominal reflexes, although considerable doubt exists concerning their basic mechanisms. Since these reflexes may be depressed or absent in patients with rostrally situated lesions of the central nervous system, some observers, including Astwazaturow 1 and Monrad-Krohn, 17 have postulated that the intrinsic reflex arc in normal persons must traverse the highest levels of the nervous system. The superficial abdominal reflex may be retained, however, on the corresponding side after ablation of the premotor cortex (Bucy 3 ), after removal of the cortex of the hemisphere (Dandy 6 ), and

Abstract: In a monograph on the abdominal reflexes,1I have pointed out that one cannot regard every reflex contraction of the abdominal wall elicitable from the abdominal region as identical with the normal cutaneous abdominal reflex. First, there is a periosteal reflex of the costal margin, elicitable by percussion of the costal border a little mesiad to the mammillary line. This reflex consists in a contraction of the abdominal muscles—particularly the external oblique—with deviation of the umbilicus toward the point of percussion. This reflex is easily distinguished from the cutaneous abdominal reflex; in the great majority of cases, when the latter is abolished on account of pyramidal lesion, the former is found to be brisk—sometimes even distinctly exaggerated.2 More difficult to distinguish from the normal abdominal reflex is a reflex which is sometimes encountered in cases in which there can be no doubt that the pyramidal fibers are seriously