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Cardiac sympathetic nerve activity is an important short-term controller of cardiac function and arterial pressure. Studies also suggest that long-term increases in cardiac sympathetic nerve activity may contribute to hypertension, coronary artery disease, and cardiac remodeling in heart failure. However, our understanding of the role of cardiac sympathetic nerves in chronic models of cardiovascular disease has been limited by inadequate experimental approaches. The present study was conducted to develop a surgical method to surgically denervate the sympathetic nerves of the rat heart for long-term cardiovascular studies. We characterized the effect of cardiac sympathetic denervation on basal levels of mean arterial pressure (MAP) and heart rate (HR) and the responses to a chronic administration of atenolol, a 31-adrenoceptor antagonist. Rats were instrumented with telemetry transmitters for continuous recording of MAP and HR. After a 4-day baseline period, the rats were subjected to bilateral stellate ganglionectomy (SGX; n = 9) or sham surgery (Sham; n = 8). Seven days following SGX or Sham, the rats were administered atenolol for 5 days, followed by a 7-day recovery period. Following a transient decrease, SGX had no effect on basal MAP but decreased HR compared with baseline and Sham rats. Five days of atenolol treatment decreased MAP similarly in SGX and Sham rats. Atenolol resulted in a marked bradycardia in Sham rats but had a neglible effects on HR in SGX rats. The measurement of the content of cardiac catecholamines in all cardiac chambers at the end of the study verified a successful sympathetic denervation. This study confirms that bilateral SGX is a useful method to study the contribution of cardiac sympathetic nerves on the regulation of cardiac function. Moreover, these results suggest that cardiac sympathetic nerves are relatively unimportant in maintaining the basal level of MAP or the depressor response to atenolol in conscious, unrestrained rats. [ABSTRACT FROM AUTHOR]

Statins have recently been shown to exert neuronal protection in ischemic stroke. Reactive oxygen species, specifically superoxide formed during the early phase of reperfusion, augment neuronal injury. NADPH oxidase is a key enzyme for superoxide production. The present study tested the hypothesis that atorvastatin protects against cerebral infarction via inhibition of NADPH oxidase-derived superoxide in transient focal ischemia. Transient focal ischemia was created in halothane-anesthetized adult male Sprague-Dawley rats (250-300 g) by middle cerebral artery occlusion (MCAO). Atorvastatin (Lipitor, 10 mg/kg Sc) was administered three times before MCAO. Infarct volume was measured by triphenyltetrazohum chloride staining. NADPH oxidase enzymatic activity arid superoxide levels were quantified in the ischemic core and penumbral regions by lucigenin (5 µM)-enhanced chemiluminescence. Expression of NADPH oxidase membrane subunit gp91phox and membrane-translocated subunit p47phox and small GTPase Rac-1 was analyzed by Western blot. NADPH oxidase activity and superoxide levels increased after reperfusion and peaked within 2 h of reperfusion in the penumbra, but not in the ischemic core, in MCAO rats. Atorvastatin pretreatment prevented these increases, blunted expression of membrane subunit gp91phox, and prevented translocation of cytoplasmic subunit p47phox to the membrane in the penumbra 2 h after reperfusion. Consequently, cerebral infarct volume was significantly reduced in atorvastatin-treated compared with nontreated MCAO rats 24 h after reperfusion. These results indicate that atorvastatin protects against cerebral infarction via inhibition of NADPH oxidase-derived superoxide in transient focal ischemia. [ABSTRACT FROM AUTHOR]

Superoxide anion (O-2·) production is elevated in sympathetic ganglion neurons and in the vasculature of hypertensive animals; however, it is not known what enzymatic pathway(s) are responsible for O-2· production. To determine the pathway(s) of O-2· production in sympathetic neurons, we examined the presence of mRNA of NADPH oxidase subunits in sympathetic ganglionic neurons and differentiated PC-12 cells. The mRNAs for NADPH oxidase subunits p47phox, p22phox, gp91phox, and NOX1 were present in sympathetic neurons and PC-12 cells, whereas the NOX4 homologue was present in sympathetic neurons but not PC-12 cells. Freshly dissociated celiac ganglion neurons from normal rats and PC-12 cells produced O-2· when treated with the PKC activator PMA; O-2· production increased by 317% and 254%, respectively. The PMA-evoked increases were reduced by pretreatment with the NADPH oxidase inhibitor apocynin. These findings indicate that NADPH oxidase is the primary source of O-2· in sympathetic ganglion neurons. When celiac ganglia from hypertensive rats were incubated with apocynin, O-2· levels were reduced to the same levels as normotensive animals, indicating that NADPH oxidase activity accounted for the elevated O-2· levels in hypertensive animals. To test this latter finding, we compared NADPH oxidase activity in extracts of prevertebral sympathetic ganglia of DOCA-salt hypertensive rats and shamoperated rats. NADPH oxidase activities were 49.9% and 78.6% higher in sympathetic ganglia of DOCA rats compared with normotensive controls when using β-NADH and β-NADPH as substrates, respectively. Thus elevated O-2· levels in hypertension may be a result of the increased activity of NADPH oxidase in postganglionic sympathetic neurons. [ABSTRACT FROM AUTHOR]