Different susceptibility of stress-induced gastric ulcer and the autonomic nervous function in the hereditary hypertensive rats

Altered physiology of acid secretion in depression-prone Flinders rats results in exacerbated NSAID and stress-induced gastric damage

BACKGROUND

Flinders Sensitive Line (FSL) rats are characterized by hypersensitivity to cholinergic stimuli and have been extensively used for studying depressive disorders. A link between depression and peptic ulcers has long been established; however, there is a lack of data from animal models.

METHODS

We studied the physiology of acid secretion in FSL and Flinders Resistant Line (FRL) rats in vivo and in vitro. We also examined the susceptibility of Flinders rats to water immersion restraint stress (WIRS) or NSAID-induced gastric damage and explored the effect of an anticholinergic agent, atropine, in reversing this effect.

KEY RESULTS

Basal acid output was more than twofold greater in FSL compared with FRL rats in vivo, 213.5 and 92.8 μEq/3 h/100 g (P = 0.02), respectively. Carbachol was a more potent secretagog in vitro, and somatostatin was a less potent inhibitory agent, while paradoxically stimulating acid secretion over and above the carbachol response in gastric glands from FSL rats. The FSL rats were more susceptible to indomethacin and WIRS-induced gastric mucosal damage compared with FRL rats. Atropine reduced acid output, which resulted in a reduction in indomethacin and stress-induced gastric damage in FSL rats.

CONCLUSIONS & INFERENCES

Our study, for the first time, demonstrates that the altered vagally mediated physiology of acid secretion in depression-prone FSL rats contributes to gastric hypersecretion and, consequently, results in exacerbated stress and NSAID-induced gastric damage. Flinders rats may be a useful animal model for studying acid-related and also gastrointestinal functional disorders in depression.

Rho-kinase inhibition suppresses bladder hyperactivity in spontaneously hypertensive rats

AIMS

Spontaneously hypertensive rats (SHR) exhibit overactive bladder (OAB) symptoms and have an up-regulated calcium sensitizing RhoA/Rho-kinase pathway in their vascular smooth muscle tissues. This study examined the role of RhoA/Rho-kinase pathway in bladder hyperactivity by evaluating the effect of a specific Rho-kinase inhibitor (Y-27632) on SHR bladder function.

METHODS

Adult male SHR (n = 9) and their normotensive controls (Wistar-Kyoto; WKY) (n = 8) were anesthetized and the carotid artery cannulated for blood pressure monitoring. A catheter was fixed into the bladder dome and connected to a pressure transducer and an infusion pump. After equilibration, systemic and bladder pressure were recorded. Continuous filling cystometrograms (CMGs) were performed and threshold pressure (TP), peak pressure (PP), and number of voids and non-voiding contractions (NVCs) per unit time recorded. Each SHR then received Y-27632, 10 mumol intra-arterially. After 10 min, CMG was repeated and the same measurements recorded. Bladder tissues were evaluated immunohistochemically (IHC) for RhoA protein expression.

RESULTS

SHR exhibited significantly higher number of voids and NVCs than normotensive WKY rats (P < 0.05). In SHR, Y-27362 administration significantly decreased the number of voids (29%, from 0.83 +/- 0.3 to 0.63 +/- 0.17 voids/min) and NVCs (61%, from 1.8 +/- 0.54 to 0.64 +/- 0.167 NVC/min). IHC showed significantly higher RhoA protein expression in SHR bladder tissues.

CONCLUSIONS

Overexpression of RhoA may play a role in hypertension-related OAB. Inhibition of Rho-kinase activity with Y-27632 produced a significant suppression of bladder overactivity. Identification of Rho-kinase isoforms that are bladder-tissue specific and their selective inhibitors may help to disassociate the unwanted hypotensive effects of this approach.

Exaggerated response to restraint stress in rats congenic for the chromosome 1 blood pressure quantitative trait locus

1. To understand the roles of a putative hypertension gene in the chromosome 1 quantitative trait locus (QTL) region, the response to restraint stress was studied in strains congenic for this QTL. 2. To establish congenic strains, the QTL region was introgressed from stroke-prone spontaneously hypertensive rats (SHRSP)/Izm to Wistar-Kyoto/Izm (WKY/Izm) rats by repeated backcrossing. Two congenic strains (WKYpch1.0 and WKYpch1.1) were established to cover the whole QTL region between D1Wox29 and D1Arb21 (approximately 40 cM) and a smaller region between D1Smu11 and D1Arb21 (approximately 10 cM), respectively. After telemetry probes were implanted, rats were exposed to restraint stress to investigate the blood pressure response. 3. Basal blood pressure measured by radiotelemetry differed significantly between WKY rats and WKYpch1.0 (103 +/- 10 and 116 +/- 4 mmHg, respectively; P = 0.002 by anova). When exposed to restraint stress, WKYpch1.0 showed a greater increase in blood pressre than did WKY rats. The exaggerated response in the WKYpch1.0 strain was abolished by chemical sympathectomy using guanethidine. The WKYpch1.1 rats did not differ significantly from WKY rats either in basal blood pressure or in the response to restraint stress. 4. In conclusion, a QTL for high blood pressure was successfully introgressed in the established congenic strain, WKYpch1.0. A gene (or genes) in the chromosome 1 QTL region modulates the cardiovascular responses to restraint stress in these congenic rats, probably through the sympathetic nervous system.

Autonomic nervous system disorders in stroke

Disturbances of the autonomic nervous system are common in patients with various cerebrovascular diseases. They are attributed to damage of the central autonomic network, particularly in the frontoparietal cortical areas and in the brain stem, or to a disruption of the autonomic pathways descending from the hypothalamus via the mesencephalon, pons, and medulla to the spinal cord. The most common clinical problems include abnormalities in heart rate and blood pressure regulation, reflecting cardiovascular autonomic dysfunction, and asymmetric sweating with cold hemiplegic limbs, reflecting changes in the sudomotor and vasomotor regulatory systems. Bladder and bowel dysfunction and impotence are also frequent complaints after stroke, but the present knowledge concerning their prevalence and clinical significance is still limited. Cardiovascular autonomic dysfunction, which is mainly related to increased sympathetic activity, is most evident in the acute phase of stroke, whereas other autonomic disorders, such as abnormal sweating, are long-standing or even irreversible. In addition to the well-established sympathetic hyperfunction, abnormalities of the parasympathetic nervous system may also contribute to the autonomic imbalance after stroke. Reliable recognition of autonomic dysfunction using quantitative analysis methods is important, because these disturbances are not only subjectively disabling and uncomfortable, but they may also be prognostically unfavorable. Moreover, quantitative measurements also form the ground for successive treatment of various stroke-related autonomic disorders.

Spinal and peripheral mechanisms contributing to hyperactive voiding in spontaneously hypertensive rats

The influence of noradrenergic mechanisms involved in micturition in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats was investigated using continuous cystometry in in vivo and in vitro studies on isolated bladder and urethral tissues. Compared with WKY rats, SHR had a significantly lower bladder capacity (SHR: 0.7 +/- 0. 05 ml; WKY rats: 1.3 +/- 0.06 ml; P < 0.001), micturition volume (SHR: 0.4 +/- 0.04 ml, WKY rats: 1.2 +/- 0.05 ml; P < 0.001), and an increased amplitude of nonvoiding (unstable) bladder contractions. The effects of intrathecal and intra-arterial doxazosin on cystometric parameters were more pronounced in SHR than in WKY rats. There was a marked reduction in nonvoiding contractions after intrathecal (but not intra-arterial) doxazosin in SHR. Norepinephrine (0.1 microM-1 mM) failed to evoke contractions in bladder strips from WKY rats, in contrast to a weak contractile response in SHR. The response to electrical field stimulation was significantly less in bladder strips from SHR than from WKY rats. In WKY rats, norepinephrine produced concentration-dependent inhibition (87 +/- 5%, n = 6) of nerve-evoked bladder contractions. Almost no inhibition (11 +/- 8%, n = 6) was found in SHR. Alterations in bladder function of SHR appear to be associated with changes in the noradrenergic control of the micturition reflex, in addition to an increased smooth muscle and decreased neuronal responsiveness to norepinephrine. The marked reduction in nonvoiding contractions after intrathecal doxazosin suggests that the bladder hyperactivity in SHR has at least part of its origin in supraspinal and/or spinal structures.