Magnetic resonance imaging quantification of regional cerebral blood flow and cerebrovascular reactivity to carbon dioxide in normotensive and hypertensive rats

• Autor(a) principal: Leoni, Renata F.
• Data de Publicação: 2011
• Outros Autores: Paiva, Fernando F., Henning, Erica C., Nascimento, George Carlos do, Tannús, Alberto, Araújo, Dráulio Barros de, Silva, Afonso C.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da UFRN
• Texto Completo: https://repositorio.ufrn.br/jspui/handle/123456789/23116
• topic: Arterial spin labeling; Hypercapnia; Magnetic resonance imaging; Perfusion; Spontaneously hypertensive rat

Hypertension afflicts 25% of the general population and over 50% of the elderly. In the presentwork, arterial spin labeling MRI was used to non-invasively quantify regional cerebral blood flow (CBF), cerebrovascular resistance and CO2 reactivity in spontaneously hypertensive rats (SHR) and in normotensive Wistar Kyoto rats (WKY), at two different ages (3 months and 10months) and under the effects of two anesthetics, α-chloralose and 2% isoflurane (1.5 MAC). Repeated CBF measurements were highly consistent, differing by less than 10% and 18% within and across animals, respectively. Under α-chloralose, whole brain CBF at normocapnia did not differ between groups (young WKY: 61±3 ml/100 g/min; adult WKY: 62±4 ml/100 g/min; young SHR: 70± 9 ml/100 g/min; adult SHR: 69±8 ml/100 g/min), indicating normal cerebral autoregulation in SHR. At hypercapnia, CBF values increased significantly, and a linear relationship between CBF and PaCO2 levels was observed. In contrast, 2% isoflurane impaired cerebral autoregulation. Whole brain CBF in SHR was significantly higher than inWKYrats at normocapnia (young SHR: 139±25 ml/100 g/min; adult SHR: 104±23 ml/100 g/min; young WKY: 55±9ml/100 g/min; adult WKY: 71±19 ml/100 g/min). CBF values increased significantly with increasing CO2; however, there was a clear saturation of CBF at PaCO2 levels greater than 70 mm Hg in both young and adult rats, regardless of absolute CBF values, suggesting that isoflurane interferes with the vasodilatory mechanisms of CO2. This behavior was observed for both cortical and subcortical structures. Under either anesthetic, CO2 reactivity values in adult SHRwere decreased, confirming that hypertension, when combined with age, increases cerebrovascular resistance and reduces cerebrovascular compliance.