Tyrosine hydroxylase-containing fibres extend from the rat corpus striatum into grafts of muscularis externa and myenteric plexus

Early postnatal low-protein nutrition, metabolic programming and the autonomic nervous system in adult life

Protein restriction during lactation has been used as a rat model of metabolic programming to study the impact of perinatal malnutrition on adult metabolism. In contrast to protein restriction during fetal life, protein restriction during lactation did not appear to cause either obesity or the hallmarks of metabolic syndrome, such as hyperinsulinemia, when individuals reached adulthood. However, protein restriction provokes body underweight and hypoinsulinemia. This review is focused on the regulation of insulin secretion and the influence of the autonomic nervous system (ANS) in adult rats that were protein-malnourished during lactation. The data available on the topic suggest that the perinatal phase of lactation, when insulted by protein deficit, imprints the adult metabolism and thereby alters the glycemic control. Although hypoinsulinemia programs adult rats to maintain normoglycemia, pancreatic β-cells are less sensitive to secretion stimuli, such as glucose and cholinergic agents. These pancreatic dysfunctions may be attributed to an imbalance of ANS activity recorded in adult rats that experienced maternal protein restriction.

Intrastriatal grafts of rat colonic smooth muscle lacking myenteric ganglia stimulate axonal sprouting and regeneration

Grafts of living or freeze-killed freshly dissected colonic smooth muscle from young inbred Fischer rats were implanted into the corpus striatum of adult Fischer rats. Sections of brain were examined electron microscopically 3 and 6 wk after implantation. At both times, living grafts were vascularised and contained healthy differentiated smooth muscle cells, fibroblasts, interstitial cells of Cajal and some macrophages. Large bundles of small nonmyelinated axons, identified as CNS axonal sprouts, could be observed in the brain at and near the interface between the living smooth muscle and the CNS tissue. Bundles of regenerating CNS axons, often associated with astrocyte processes, had grown into the grafts. Some axons within the grafts had matured, enlarged and become myelinated by oligodendrocyte processes or Schwann cells. In some cases, smooth muscle cells were observed in close and intricate association with axons. In contrast to the living grafts, grafts of freeze-killed smooth muscle, examined 3 and 6 wk after implantation, contained macrophages, fibroblasts, collagen and large amounts of cellular debris, but no living muscle cells, astrocytes or Schwann cells. The striatal neuropil around freeze-killed grafts did not contain large bundles of CNS axonal sprouts and bundles of axons were not observed within the freeze-killed graft. This study demonstrates that cells from the smooth muscle layers of the colon, in the absence of myenteric ganglia, can stimulate a vigorous regenerative response from CNS axons when implanted into the corpus striatum of adult rats.