Effect of rosuvastatin on spatial learning, memory, and anxiety-like behaviour in ovariectomized rats

The effect of rosuvastatin (Ros) on cognitive function and anxiety-like behaviour in ovariectomized rats were evaluated. Eighteen female Wistar rats (218-310 g, 6-8 months old) were allocated into sham (n = 6), ovariectomy (Ovx, n = 6) or Ovx + Ros (up to eighth week n = 6, then n = 4) groups. Ros was administered at 20 mg/kg/day by oral gavage for 12 weeks. Behavioural tests were performed at 4, 8 and 12 weeks following Ovx. At 12 weeks, Ovx group had significantly longer escape latency than the sham group at the first day of the four-day training period of the Morris Water Maze test (p < .01). In the Elevated Plus Maze test, Ovx group spent significantly more time in the closed arms than the sham group (p < .01), and this anxiety-like behavioural effect of Ovx was prevented by 12-weeks Ros treatment (p < .05). In conclusion, Ros prevents memory deficit and anxiety-like behaviour in the ovariectomized rats, a model for human surgical menopause. Impact StatementWhat is already known on this subject? Reduced levels of oestrogen in surgical postmenopausal period has been linked to an increased risk of cognitive dysfunction. Although statins have been shown to improve cognitive function in experimental and clinical studies, there are limited studies evaluating the effect of statins on the cognitive decline and anxiety-like behaviour associated with surgical menopause.What do the results of this study add? Rosuvastatin, a long-acting statin, prevents learning and memory deficit and anxiety-like behaviour in the ovariectomized rat model.What are the implications of these findings for future clinical practice and/or future clinical research? These findings will form the basis for further experimental and clinical research on the effects of statins on cognitive functions and anxiety-like behaviour in the surgical menopause.

The role of nitric oxide in the electrical field stimulation-induced contractions of sphincter of oddi and gallbladder strips in Guinea pigs

The aim of this study was to investigate the modulatory role of nitric oxide (NO) in the electrical field stimulation (EFS)-induced contractions of isolated sphincter of Oddi (SO) and gallbladder strips from guinea pigs. EFS was used to activate the intrinsic nerves in SO and gallbladder strips. EFS produced frequency-dependent biphasic contractile responses in the SO strips. A smaller contraction, "on response", occurred during EFS, which was followed by a bigger contraction, "off response". Both responses were completely and irreversibly abolished by tetrodotoxin (TTX) (10(-6) M). Atropine (10(-6) M) inhibited the "on response", but not the "off response". EFS produced frequency-dependent monophasic contractile responses in gallbladder strips, which were completely and irreversibly abolished by TTX (10(-6) M) and atropine (10(-6) M). A nitric oxide synthase (NOS) inhibitor, NG-nitro-L-arginine (10(-4) M and 3 x 10(-4) M, in SO and gallbladder strips, respectively), significantly increased all EFS-induced contractions of SO and gallbladder strips. L-Arginine, but not D-arginine reversed the effect induced by the NOS inhibitor, at all frequencies, in both strips. These results suggested that NO released from nitrergic nerve endings might play a regulatory role in the cholinergic neurotransmission of guinea pig SO and gallbladder strips. The "off response" in he SO preparations might be a rebound increase that was modulated by the nonadrenergic, noncholinergic inhibitory mediator NO.

Mechanism of action of the cisapride-induced vasodilatation in renal vasculature of rat

BACKGROUND & OBJECTIVES

Cisapride is a prokinetic agent with cholinomimetic and 5-HT4 receptor agonistic properties. It has been proposed that cisapride-induced hypotension is partly mediated by cholinergic system. The aim of this study was to investigate the mechanism of cisapride-induced dilatation in the rat isolated perfused kidney.

METHODS

Left kidneys of Wistar rats were isolated and perfused via renal artery and the perfusion pressure was recorded. Cisapride given as bolus injections (10(-10)-3x10(-5) mol/l) produced dose-dependent dilatations. Perfusion of antagonists or inhibitors was started 30min before the onset of phenylephrine perfusion.

RESULTS

4-Diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP; blocker of M1, and M3 muscarinic receptors; 10(-7) mol/l) inhibited the responses to the lower doses of cisapride while, dextran (10(-7) mol/l), glibenclamide (inhibitor of ATP-sensitive potassium channels; 10(-5) mol/l) and capsaicin (for neuromediator depletion; 10(-6) mol/l) inhibited those to the higher doses. Dilatations induced by most of the doses of cisapride were inhibited by atropine (non-selective muscarinic receptor antagonist; 10(-7) mol/l), methylene blue (inhibitor of soluble guanylate cyclase; 10(-5) mol/l), 1H-[1,2,4] oxadiazolo-[4,3-a] Quinoxalin-1-One (ODQ; inhibitor of soluble guanylate cyclase; 10(-5) mol/l), and NG-nitro-L-arginine (L-NOARG; NO synthase inhibitor; 10(-4) mol/l). Inhibition induced by L-NOARG was reversed by L-arginine (10(-3) mol/l). The dilatation induced by cisapride was not affected by GR113808 (5-HT4 receptor antagonist; 10(-7) mol/l) and indomethacin (cyclooxygenase inhibitor; 10(-5) mol/l).

INTERPRETATION & CONCLUSION

The findings indicated that cisapride caused vasodilatation through the release of nitric oxide (NO) as a result of the release of a substance acting on muscarinic receptors, in the renal vascular bed of the rat. The role of 5-HT4 receptors and prostanoids seemed unlikely.