Endothelins promote the activation of astrocytes in rat neostriatum through ET(B) receptors.
The effects of endothelin (ET)-3 and an ET(B) receptor agonist on astrocytic activation in rat caudate putamen were examined by an immunohistochemical staining of glial fibrillary acidic protein (GFAP), a marker of reactive astrocytes. A single injection of 40 pmol ET-3 into rat caudate putamen increased the number of GFAP positive cells compared to that in the contralateral saline-injected side. Ala(1,3,11,15)-ET-1 (40 pmol), an ET(B) receptor agonist, also increased the number of striatal GFAP positive cells. The increases in GFAP positive cells were maximum (about 150% of the control side) in 1-2 weeks after injections of the ETs, and then reduced in 4 weeks. A continuous infusion of BQ788, an ET(B) receptor antagonist (23 nmol/day), into the lateral ventricle of the cerebrum antagonized the effect of Ala(1,3,11,15)-ET-1, while BQ788 also reduced the number of GFAP positive cells in saline-injected caudate putamen. Intrastriatal injection of 40 pmol Ala(1,3,11,15)-ET-1 did not affect the number of cells stained by B4 isolectin from Griffonia simplicifolia, which labels activated microglia/macrophages. Intraperitoneal administration of 5 mg/kg per day chloroquine and 0.2 mg/kg per day colchicine did not affect the action of Ala(1,3,11,15)-ET-1. These results suggest that activation of ET(B) receptors is involved in the induction of reactive astrocytes.
Ishikawa
N
N
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Osaka University, Yamada-Oka, Suita, Japan.
Takemura
M
M
Koyama
Y
Y
Shigenaga
Y
Y
Okada
T
T
Baba
A
A
D000818:Animals; D001253:Astrocytes / Q000187:drug effects*; D019334:Endothelin-3 / Q000494:pharmacology*; D007150:Immunohistochemistry; D008297:Male; D017072:Neostriatum / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017466:Receptors, Endothelin / Q000187:drug effects*
D019334:Endothelin-3; D017466:Receptors, Endothelin