Regeneration of neurosecretory axons into intrahypothalamic grafts of neural lobe, sciatic nerve, and optic nerve: a neurophysin-immunohistochemical, HRP-histochemical, and fine structural study

Abstract

their ability to support regeneration of transected neurosecretory axons; (4) to monitor recovery from diabetes insipidus (restoration of arginin-vasopressin, AVP, function) by measuring pre-and post-operative water intake.

An immunohistological and electron microscopic investigation of neurosecretory neuronal regeneration following hypophysial stalk transection in animals subjected to chronic intermittent salt loading

“…It is suggested that the chances for the axotomized axons to survive and subsequently to form a new neural lobe depend on their reaching the fenestrated vessels to imbibe the necessary blood-derived growth factor from the capillary [258]. This hypothesis was first proposed by Dellmann [47] and tested by Ouassat [184]. They reported that the degree of vascular permeability to horseradish peroxidase in various grafts (such as neural lobe, sciatic nerve or optic nerve) transplanted into contact with the intrahypothalamically lesioned HNT area, correlates with the number of regenerating neurosecretory axons.…”

“…This is not so for other grafts, such as sciatic and optic nerve grafts. In optic nerve grafts, where the BBB was restored after 10 days, only relatively few neurosecretory axons regenerate [184].…”

“…Spontaneous regeneration of axotomized neurosecretory neurons is observed only in areas in which the BBB is likewise absent -i.e., in the median eminence and hypophysial stalk; but spontaneous regeneration does not occur in the hypothalamus, where a BBB is present [121,122]. The contention, that regeneration of neurosecretory axons requires absence of the BBB was tested by Ouassat [184]. He reported that the degree of vascular permeability to horseradish peroxidase in various intrahypothalamic grafts is correlated with the magnitude of neurosecretory axon regeneration.…”

“…Spontaneous regeneration of axotomized neurosecretory neurons does not occur in the hypothalamus, where a BBB is present. The contention, that regeneration of neurosecretory axons requires absence of the BBB was tested in a series of experiments that led to this conclusion: Only tissues that lack a BBB, support neurosecretory axon regeneration [53,54,184]. And, of course, axons regenerate only in association with glial cells.…”