The acute effect of selective surgical interruption of the anterior pituitary’s blood supply on the release of ACTH has been investigated in surgically stressed rats. The corticosterone secretory rate was used to evaluate the release of ACTH. In intact, sham-operated animals, corticosterone secretion was near maximal throughout a 50-min observation period. Removal of the pituitary greatly suppressed the secretion of corticosterone. Posterior lobectomy or transection of the portal vessels in the upper stalk had no apparent effect on ACTH release. This finding was interpreted to mean that the posterior pituitary and post-chiasmatic eminence are not obligatory sources of CRF. Transection of the pituitary stalk greatly suppressed ACTH release. This finding supports the view that the caudal hypophysial arteries do not provide the anterior pituitary with a significant amount of blood via the short portal vessels. Transection of the peduncular arteries or the stalk portal vessels in the lower stalk suppressed ACTH release. This finding is consistent with the notion that CRF enters portal blood via the post-peduncular and/or pituitary stalk capillaries. These findings indicate that CRF comes from the stalk, postpedunuclar eminence and/or the cerebrospinal fluid.
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