Intracisternal administration of Angiotensin II AT 1 receptor antisense oligodeoxynucleotides protects against cerebral ischemia in spontaneously hypertensive rats Haruki Yamakawa, M. Ian Phillips 1 , Juan M. Saavedra * Section on Pharmacology, IRP, NIMH, NIH, DHHS, 10 Center Drive, Bldg. 10, Room 2D-57, Bethesda, MD 20892, USA Received 6 October 2002; received in revised form 31 October 2002; accepted 5 November 2002 Abstract Pharmacological blockade of peripheral and brain Angiotensin II (Ang II) AT 1 receptors protects against brain ischemia. To clarify the protective role of brain AT 1 receptors, we examined the effects of specific antisense oligodeoxynucleotides (AS-ODN) targeted to AT 1 receptor mRNA administered intracisternally to spontaneously hypertensive rats (SHRs), 4 and 7 days before middle cerebral artery (MCA) occlusion, and we determined the infarct size and tissue swelling 24 h after surgery. A single intracisternal injection of AT 1 mRNA receptor antisense oligodeoxynucleotides reduced systemic blood pressure for 5 days and AT 1 receptor binding for at least 4 days in the area postrema and the nucleus of the solitary tract. A similar injection of scrambled oligodeoxynucleotides (SC-ODN) was without effect. Both blood pressure and AT 1 receptor binding returned to normal 7 days after antisense receptor mRNA administration. Both the infarction size and the tissue swelling after middle cerebral artery occlusion were reduced when the antisense oligodeoxynucleotide was administered 7 days, but not 4 days, before the operation. We conclude that 4 to 5 days of decrease in brain AT 1 receptor binding by a single administration of an AT 1 receptor mRNA oligodeoxynucleotide are sufficient to significantly protect the brain against ischemia resulting from total occlusion of a major cerebral vessel. D 2002 Elsevier Science B.V. All rights reserved. Keywords: Renin – angiotensin system; Stroke; Brain ischemia; Genetic hypertension; Cerebral blood flow 1. Introduction Angiotensin II (Ang II) controls not only the peripheral but also the brain circulation by stimulation of Ang II AT 1 receptors in peripheral and brain arteries; this produces vasoconstriction and stimulates the sympathetic system [1,2]. The activity of both the brain Ang II and sympathetic systems is stimulated in spontaneously hypertensive rats (SHRs) [3], and these animals exhibit increased vasocon- strictor tone and arterial remodeling, with decreased lumen diameter and increased thickness of the vessel wall [4]. The result is decreased cerebrovascular compliance and decreased capacity of brain arteries to dilate, leading to alterations in the cerebrovascular autoregulation, higher sensitivity to hypo- perfusion, and increased vulnerability to stroke [5]. We have found that peripheral pretreatment with the AT 1 receptor antagonist candesartan, which blocks both periph- eral and central AT 1 receptors [6], protects the brain of SHR from ischemia after occlusion of a major cerebral artery [7,8]. The mechanism we proposed was related to the progressive reversal of the hypertension-induced cerebro- vascular remodeling, leading to increased vascular compli- ance and to the progressive correction of the hypertension- induced alterations in cerebrovascular autoregulation [7]. In turn, correction of cerebrovascular alterations improved cerebrovascular flow during hypoxia and substantially pro- tected the brain during occlusion of a major cerebral vessel such as the middle cerebral artery (MCA) [8]. Such a protection was not dependent on the blood pressure reduc- tion. Instead, protection depended on the Ang II system blockade because it did not occur after adrenergic receptor or calcium channel antagonism [7]. Treatment with AT 1 receptor antagonists did not offer immediate protection against ischemia, and the effect required at minimum about 7 days to develop [8]. We hypothesized that time was 0167-0115/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved. PII:S0167-0115(02)00264-1 * Corresponding author. Tel.: +1-301-496-0160; fax: +1-301-402- 0337. E-mail address: Saavedrj@irp.nimh.nih.gov (J.M. Saavedra). 1 Department of Physiology, Medical School, Gainesville, FL. www.elsevier.com/locate/regpep Regulatory Peptides 111 (2003) 117–122