Kansu Büyükafşar

Objectives: We aimed to investigate effects of the proton pump inhibitors (PPIs) omeprazole, lansoprazole and pantoprazole, which are currently used for the treatment of hyperacidity and gastro-oesophageal reflux, on the reactivity of the isolated rat lower oesophageal sphincter.Methods: Omeprazole, lansoprazole and pantoprazole (all 10–9–10–3m, cumulatively) were tested on carbachol-induced (10–6m) contraction. In addition, the effects of PPI preincubation (all 10–3m) on the contractions induced by cumulative carbachol (10−9–10−5m), angiotensin-2 (10−9–10–5m) or electrical field stimulation (EFS; 40 V, 32 Hz, 1 ms, 10 s) were assessed. Finally, the effects of PPI on the spontaneous contractile activity of the tissue were also evaluated.Key findings: PPI relaxed precontracted lower oesophageal sphincter in a concentration-dependent manner and suppressed carbachol-, angiotensin- and EFS-induced contractions. Furthermore, PPI attenuated spontaneous contractile activity of the tissue.Conclusions: Omeprazole, lansoprazole and pantoprazole had a suppressor effect on lower oesophageal sphincter contractions.

Background and purpose: Rho/Rho‐kinase signalling is involved in many cellular events, including some in the CNS. However, the role of this pathway in epilepsy has not yet been assessed. Therefore, we determined the effects of two Rho‐kinase inhibitors, Y‐27632 and fasudil, on seizures induced by pentylenetetrazole (PTZ) or maximal electroconvulsive shock (MES).Experimental approach: Effects of Y‐27632 (5–10 mg kg⁻¹) and fasudil (5–25 mg kg⁻¹) on duration of myoclonic jerks, clonic and tonic convulsions, tonic hindlimb extensions and percentage of tonic convulsion index, as well as recovery latency for righting reflex were investigated in mice stimulated with PTZ (65 mg kg⁻¹) or MES (50 Hz, 50 mA and 0.4 s). These inhibitors were also tested on a model of kindling induced by PTZ (35 mg kg⁻¹, for 11 days). Membrane and cytosolic levels of RhoA protein were measured in brain homogenates from kindled mice.Key results: Y‐27632 and fasudil diminished onset of myoclonic jerks, clonic convulsions and tonic hindlimb extensions in mice given PTZ. These inhibitors suppressed the percentage of tonic convulsion index and recovery latency for righting reflex in the mice excited with MES. Western blotting demonstrated that Rho translocation to plasma membrane increased in the brain homogenates obtained from PTZ‐kindled mice. However, the Rho‐kinase inhibitors at the given doses did not change motor coordination of the mice.Conclusions and implications: Rho/Rho‐kinase signalling may play a role in epilepsy induced by PTZ and MES. Furthermore, Rho‐kinase inhibitors could be novel important antiepileptic agents.British Journal of Pharmacology (2008) 155, 44–51; doi:10.1038/bjp.2008.225; published online 9 June 2008

Expression of two isoforms of Rho‐kinase (ROCK) and its functional role in the physiological control of smooth muscle contraction in the sheep ureter were investigated. Helical strips of the ureteric smooth muscle were stimulated by electrical field stimulation (EFS, 60 V, 1 mS, 2, 4, 8, 16 and 32 Hz, for 20 S), KCl (80 mM), carbachol (CCh, 10⁻⁸–10⁻⁴ M) or phenylephrine (Phe, 10⁻⁸–10⁻⁴ M). EFS produced a reproducible contractile activity, which was abolished by tetrodotoxin (3 × 10⁻⁶ M), a Na⁺ channel blocker. A muscarinic receptor antagonist, atropine (2 × 10⁻⁶ M), and an adrenergic neuron blocker, guanethidine (10⁻⁵ M), significantly suppressed the contraction induced by EFS. However, this contraction was augmented in the presence of N^G‐nitro‐L‐arginine (L‐NA, 10⁻⁴ M), a nitric oxide synthase inhibitor. Two Rho‐kinase inhibitors, Y‐27632 (5 × 10⁻⁵ M) and fasudil (5 × 10⁻⁵ M), markedly attenuated the EFS‐elicited contraction. CCh and Phe produced concentration‐dependent contraction in the sheep ureter. pD₂ values for Phe and CCh were 5.04±0.11 and 5.00±0.22, respectively. Y‐27632 (5 × 10⁻⁵ M) and fasudil (5 × 10⁻⁵ M) also significantly inhibited CCh‐ and Phe‐induced contractions. Moreover, these ROCK inhibitors produced relaxations in the KCl‐elicited contraction in a concentration‐dependent manner. pD₂ values for Y‐27632 and fasudil were, respectively, 5.17±0.07 and 4.58±0.08 (P−6–10⁻⁵ M) were able to suppress the spontaneous contractile activity. Western blot analysis has revealed that both isoforms of Rho‐kinase (ROCK‐1 and ROCK‐2) are expressed in the sheep ureter. Densitometric analysis has indicated that these enzymes are less expressed in the sheep ureter than are in the sheep aorta in a significant manner. These results show that a contractile enzyme, Rho‐kinase, is expressed, and it mediates agonist‐ and EFS‐induced contractions as well as spontaneous contractile activity of the isolated sheep ureter. Since Y‐27632 and fasudil depressed the contractions, it seems plausible to postulate that Rho‐kinase inhibitors may be beneficial in the treatment of renal colic. British Journal of Pharmacology (2004) 143, 431–437. doi:10.1038/sj.bjp.0705961

The effects of two Rho-kinase inhibitors, Y-27632 and fasudil, were investigated on the contractions produced by electrical field stimulation (EFS, 40 V, 1 mS, 2, 4, 8 and 16 Hz, for 20 s), KCl (30 - 60 mm), phenylephrine (Phe) (10-5 - 10-4 m), adenosine-3', 5'-triphosphate (ATP) (10-4 - 10-3 m) and alpha,beta-methylene ATP (10-5 m). EFS produced frequency-dependent reproducible contractile activity, which was almost abolished by guanethidine (10-5 m, for 1 h). This contraction consisted of two components (a phasic initial contraction followed by a tonic one), and it was inhibited by Y-27632 and fasudil (both at 10-5 m). However, these inhibitors had no effect on resting tension of the tissue. Contractions elicited by KCl (30 - 60 mm) were insensitive to guanethidine (10-5 m, for 1 h), but suppressed by Y-27632 (10-5 m) and fasudil (10-5 m). In addition, the contractions induced by Phe (an alpha1-adrenoceptor agonist) and ATP (a purinergic agent) were inhibited significantly by Y-27632 (10-5 m). Phasic contractions evoked by the selective P2X purinoceptor agonist alpha,beta-methylene ATP were also suppressed by Y-27632 (10-5 m). Western blot analysis revealed that the mouse vas deferens expresses Rho-kinase (ROKalpha, ROCK-2 isoform) protein with a molecular weight of approximately 160 kDa. As a positive control, the presence of this protein was also shown in homogenates of smooth muscle from the rat mesenteric artery. In conclusion, Rho-kinase protein is expressed in the mouse vas deferens, and it mediates neurogenic contractile activity as well as the contractions induced by KCl, Phe, ATP and alpha,beta-methylene ATP. Owing to the suppressive effects of Rho-kinase inhibitors on the contractile activity of the vas deferens, the possibility that these compounds might impair ejaculation must be taken into account when considering them as potential agents in the treatment of erectile dysfunction.