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Time-dependent changes of vasoactive substances in the rat amygdaloid complex after transient cerebral ischemia
Abstracts from the l l th International Symposium on Regulatory Peptides
127
THE AUGMENTATION O F PITUITARY ADENYLATE CYCLASE ACTIVATING POLYPEPTIDE
(PACAP) IN THE STREPTOZOTOCIN-INDUCED DIABETIC RATS A. Miyata, H. Tamakawa, M. Honzawa, *A. Arimura, H. Matsuo, K. Kangawa, National Cardiovascular Center Research Institute, Suita Osaka 565, Japan, *US-Japan Biomedical Research Laboratories, Tulane University Hebert Center, Belle Chasse, LA70037, USA Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuropeptide which was first identified from ovine hypothalamic tissues based upon the ability to stimulate adenylate cyclase activity in rat pituitary cell cultures. Besides the rat hypothalamus, PACAP-Iike immunoreactivity and its transcripts were also found in the pancreas. Interestingly it was demonstrated that PACAP as low as 10-13M potentiates glucose-induced insulin secretion from rat islets, indicating the involvement of PACAP in the regulation of insulin secretion. Therefore we have attempted to clarify the pathophysiological implication of PACAP in diabetes mellitus using streptozotocin-treated rats. Male Sprague-Dawley rats (6 weeks) were injected intravenously with streptozotocin (50mg/kg). Four weeks later, the animals were sacrificed and the collected blood samples were subjected to glucose analysis The tissues (pancreas, hypothalamus, lung and adrenal gland) were collected and extracted with 1M AcOH and subjected to the PACAP38 specific radioimmunoassay. The plasma glucose levels of the treated rats were increased 4-fold compared to those of the controls. In the pancreas and hypothalamus, the PACAP immunoreactivity was increased significantly 30%, 10%, respectively. In contrast, the PACAP immunoreactivity in the lung and adrenal gland did not changed. These observation suggest that PACAP might be implicated in the regulation of insulin or islets function as autocrine or paracrine and that the blood glucose level might be involved in the regulation of PACAP synthesis in the hypothalamus
Time-dependent Changes of Vasoactive Substances in the Rat Amygdaloid Complex after Transient Cerebral Ischemia Mizushima, H., Sasaki, K., Arai, Y., Honma, H., DohI, K., Matsumoto, K., Shioda, S.* and Nakai, Y.* Depts. Neurosurgeryand *Anatomy, ShowaUniv. Sch. Med.,Tokyo, Japan. Time-dependent changes of vasoconstrictive substances [adrenaline (A), noradrenalin (NA), neuropeptide Y (NPY)I and vasodilative substances [caleitonin gene-related peptide (CGRP), substance P (SP), vasoactive intestinal peptide (VIP)] were studied in the rat amygdaloid complex after transient cerebral ischemia by immunohistochemical staining. Under general anesthesia, middle cerebral artery of the animals was clipped and after 1 h the clip ,vas released for resumption of blood flow. Each of the immunostaining density was analyzed semiquantitatively by image analyzer and verified as the ratio (100% X ischemic side/control side). Immunoreactivity (IR) of tyrosine hydroxylase (TH), a marker enzyme of A and NA, was decreased at 6 h, showed a nadir at 24 h, and gradually returned to normal value after ischemia. NPY-IR was decreased at 6 h, showed a nadir at 24 h, but it was not recovered during 1-7 days after ischemia. Blood concentration of A and NA was increased after ischemica, reached the peak at 12 h, decreased gradually, and returned to normal at 3 days after ischemia. CORP-IR and SP-IR were not changed at 6 h, but decreased and showed the lowest value at 12 h and 12-24 h on the lesioned side after ischemia, respectively. Blood concentration of CORP was increased gradually, reached the peak at 12 h, decreased at 24 h, returned the normal value at 3 days after ischemia. On the other hand, blood concentration of SP was decreased at 12 h but not returned to the normal value at 3 days after ischemia. There was no change of VIP-IR in the amygdala during the experiment. Our results revealed that immunoreactivities of both vasoconstrictive and vasodilative substances were decreased in the amygdala after transient brain ischemia. However, it appears there exists a different sensitivity to cerebral ischemia among vasoactive substances.
127
THE AUGMENTATION O F PITUITARY ADENYLATE CYCLASE ACTIVATING POLYPEPTIDE
(PACAP) IN THE STREPTOZOTOCIN-INDUCED DIABETIC RATS A. Miyata, H. Tamakawa, M. Honzawa, *A. Arimura, H. Matsuo, K. Kangawa, National Cardiovascular Center Research Institute, Suita Osaka 565, Japan, *US-Japan Biomedical Research Laboratories, Tulane University Hebert Center, Belle Chasse, LA70037, USA Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuropeptide which was first identified from ovine hypothalamic tissues based upon the ability to stimulate adenylate cyclase activity in rat pituitary cell cultures. Besides the rat hypothalamus, PACAP-Iike immunoreactivity and its transcripts were also found in the pancreas. Interestingly it was demonstrated that PACAP as low as 10-13M potentiates glucose-induced insulin secretion from rat islets, indicating the involvement of PACAP in the regulation of insulin secretion. Therefore we have attempted to clarify the pathophysiological implication of PACAP in diabetes mellitus using streptozotocin-treated rats. Male Sprague-Dawley rats (6 weeks) were injected intravenously with streptozotocin (50mg/kg). Four weeks later, the animals were sacrificed and the collected blood samples were subjected to glucose analysis The tissues (pancreas, hypothalamus, lung and adrenal gland) were collected and extracted with 1M AcOH and subjected to the PACAP38 specific radioimmunoassay. The plasma glucose levels of the treated rats were increased 4-fold compared to those of the controls. In the pancreas and hypothalamus, the PACAP immunoreactivity was increased significantly 30%, 10%, respectively. In contrast, the PACAP immunoreactivity in the lung and adrenal gland did not changed. These observation suggest that PACAP might be implicated in the regulation of insulin or islets function as autocrine or paracrine and that the blood glucose level might be involved in the regulation of PACAP synthesis in the hypothalamus
Time-dependent Changes of Vasoactive Substances in the Rat Amygdaloid Complex after Transient Cerebral Ischemia Mizushima, H., Sasaki, K., Arai, Y., Honma, H., DohI, K., Matsumoto, K., Shioda, S.* and Nakai, Y.* Depts. Neurosurgeryand *Anatomy, ShowaUniv. Sch. Med.,Tokyo, Japan. Time-dependent changes of vasoconstrictive substances [adrenaline (A), noradrenalin (NA), neuropeptide Y (NPY)I and vasodilative substances [caleitonin gene-related peptide (CGRP), substance P (SP), vasoactive intestinal peptide (VIP)] were studied in the rat amygdaloid complex after transient cerebral ischemia by immunohistochemical staining. Under general anesthesia, middle cerebral artery of the animals was clipped and after 1 h the clip ,vas released for resumption of blood flow. Each of the immunostaining density was analyzed semiquantitatively by image analyzer and verified as the ratio (100% X ischemic side/control side). Immunoreactivity (IR) of tyrosine hydroxylase (TH), a marker enzyme of A and NA, was decreased at 6 h, showed a nadir at 24 h, and gradually returned to normal value after ischemia. NPY-IR was decreased at 6 h, showed a nadir at 24 h, but it was not recovered during 1-7 days after ischemia. Blood concentration of A and NA was increased after ischemica, reached the peak at 12 h, decreased gradually, and returned to normal at 3 days after ischemia. CORP-IR and SP-IR were not changed at 6 h, but decreased and showed the lowest value at 12 h and 12-24 h on the lesioned side after ischemia, respectively. Blood concentration of CORP was increased gradually, reached the peak at 12 h, decreased at 24 h, returned the normal value at 3 days after ischemia. On the other hand, blood concentration of SP was decreased at 12 h but not returned to the normal value at 3 days after ischemia. There was no change of VIP-IR in the amygdala during the experiment. Our results revealed that immunoreactivities of both vasoconstrictive and vasodilative substances were decreased in the amygdala after transient brain ischemia. However, it appears there exists a different sensitivity to cerebral ischemia among vasoactive substances.