Hypoxic modulation of striatal lesions induced by administration of endothelin-1

Effect of irbesartan on expression of ET-1 and AT1R in gastric tissues of diabetic rats with gastroparesis

AIM: To investigate the therapeutical effect of irbesartan on diabetic gastroparesis (DG) in rats and to explore potential mechanisms involved.

METHODS: Thirty male Sprague-Dawley rats were randomly divided into either a normal control group (NC group, n = 10) or a diabetes mellitus group (DM group, n = 20). Diabetes mellitus was induced with streptozotocin (50 mg/kg i.p.). The DM group was further divided into a diabetic control group (DC group, n = 10) and an irbesartan group (DI group, n = 10). The DI group was given irbesartan 0.012 g/(kg•d) through stomach feeding, while the NC and DC groups were given equal volume of saline by gavage. Six weeks later, all the rats were administered with phenol red solution to measure the rate of gastric emptying. Endothelin (ET-1) content in stomach tissue was measured by radioimmunoassay. Chemical colorimetry was used to measure the activity of nitric oxide synthase (NOS) in the stomach tissue. The expression level of angiotensin receptor (AT1R) mRNA was determined by RT-PCR.

RESULTS: Compared to the NC group, the rate of gastric emptying significantly decline in the other two groups (62.64% ± 4.51% vs 18.65% ± 4.30%, 22.64% ± 2.88%); however, the rate of gastric emptying was significantly higher in the DI group than in the DC group (22.64% ± 2.88% vs 18.65% ± 4.30%). There was a significant difference in ET-1 content among the three groups (NC 18.520 pg/mgpro ± 2.795 pg/mgpro vs DC 26.850 pg/mgpro ± 2.897 pg/mgpro vs DI 21.660 pg/mgpro ± 4.686 pg/mgpro). Compared to the NC group, cNOS activity significantly declined in the DC and DI groups (0.521 pg/mgpro ± 0.057 pg/mgpro vs 0.323 pg/mgpro ± 0.079 pg/mgpro, 0.384 pg/mgpro ± 0.067 pg/mgpro); however, there was no significant change in cNOS activity between the DC and DI groups (0.323 pg/mgpro ± 0.079 pg/mgpro vs 0.384 pg/mgpro ± 0.067 pg/mgpro). iNOS activity in the DI group was significantly lower than that in the DC group (0.246 pg/mgpro ± 0.033 pg/mgpro vs 0.276 pg/mgpro ± 0.021 pg/mgpro), but higher than that in the NC group (0.246 pg/mgpro ± 0.033 pg/mgpro vs 0.209 pg/mgpro ± 0.015 pg/mgpro). The expression of AT1R mRNA in DC group and DI group was up-regulated significantly (0.741 ± 0.010, 0.546 ± 0.005 vs 0.207 ± 0.004) compared with the NC group. After intervention with irbesartan, the level of AT1R mRNA in the DI group was lower than that in the DC group (0.546 ± 0.005 vs 0.741 ± 0.010).

CONCLUSION: Irbesartan can improve, to some extent, gastric emptying in rats with diabetic gastroparesis possibly by altering the levels of ET, NOS, and AT1R mRNAs in the stomach tissue.

A New Model for Determining the Influence of Age and Sex on Functional Recovery following Hypoxic-Ischemic Brain Damage

Stroke is a disorder affecting the lives of all age groups, and particularly those at the opposite ends of the age spectrum. It is generally believed that the immature brain is more resistant to damage resulting from a hypoxic/ischemic injury, and that it is also more 'plastic' in terms of its ability to recover. Evidence from our laboratory, and a host of others, has indicated, however, that the developing brain may in fact be more sensitive to injury resulting from hypoxia-ischemia. The question remains, however, whether the immature brain has a greater capacity for recovery. In order to determine the relative capability for functional recovery between age groups, a stroke model of comparable injury is required. This paper describes a new rodent model of ischemic injury allowing for comparisons of behavioral recovery spanning the spectrum of ages between newborn and the elderly. Endothelin-1, a potent vasoconstrictor, was stereotactically injected into the brains of 10-, 63-, and 180-day-old Wistar rats, immediately adjacent to the middle cerebral artery. Regionally, the cortex, caudate, and thalamus were most significantly affected, with sparing of the hippocampus. Pathologic assessment indicated a similar degree of injury across age groups affecting the territorial distribution of the middle cerebral artery, with a predominance of damage in the anterior sections of the cortex and caudate (p < 0.05), compared to the posterior sections including the cortex and thalamus. There were no regional differences in the extent of damage between age groups. Interestingly, however, there were significant differences between males and females regarding the overall extent of brain damage (p < 0.05), with males showing greater damage than females. In addition, there were significant regional differences in the extent of damage between males and females, particularly regarding cortical damage (p < 0.05), both anteriorly and posteriorly, and the caudate anteriorly (p < 0.05). Our findings provide an important new model for comparison of brain damage among the entire spectrum of ages affected by stroke. Importantly, this will allow for further investigations regarding both functional recovery and gender difference comparisons. This may have important ramifications for the development of therapeutic interventions that are age and gender specific.