Dihydropyridine calcium channel antagonists disrupt migrating myoelectric complexes and counteract intestinal disorders associated with morphine withdrawal diarrhea

Effects of prototypic calcium channel blockers in methadone-maintained humans responding under a naloxone discrimination procedure

Accumulating evidence suggests that L-type calcium channel blockers (CCBs) attenuate the expression of opioid withdrawal and the dihydropyridine L-type CCB isradipine has been shown to block the behavioral effects of naloxone in opioid-maintained humans. This study determined whether two prototypic L-type CCBs with differing chemical structures, the benzothiazepine diltiazem and the phenylalkamine verapamil, attenuate the behavioral effects of naloxone in methadone-maintained humans trained to distinguish between low-dose naloxone (0.15 mg/70 kg, i.m.) and placebo under an instructed novel-response drug discrimination procedure. Once discrimination was acquired, diltiazem (0, 30, 60, 120 mg) and verapamil (0, 30, 60, 120 mg), alone and combined with the training dose of naloxone, were tested. Diltiazem alone produced 33-50% naloxone- and novel-appropriate responding at 30 and 60 mg and essentially placebo-appropriate responding at 120 mg. Verapamil alone produced 20-40% naloxone- and 0% novel-appropriate responding. Diltiazem at 60 mg decreased several ratings associated with positive mood and increased VAS ratings of "Bad Drug Effects" relative to placebo, whereas verapamil increased ratings associated with euphoria. When administered with naloxone, diltiazem produced 94-100% naloxone-appropriate-responding with 6% novel-appropriate responding at 60 mg (n=3). When administered with naloxone, verapamil produced 60-80% naloxone- and 0% novel-appropriate responding (n=5). Diltiazem decreased diastolic blood pressure and heart rate whereas verapamil decreased ratings of arousal relative to placebo. These results suggest that CCBs with different chemical structures can be differentiated behaviorally, and that diltiazem and verapamil do not attenuate the discriminative stimulus effects of naloxone in humans at the doses tested.

Effects of motilin on intracellular free calcium in cultured smooth muscle cells from the antrum of neonatal rats

AIM

The aim of this study was to determine the effects of motilin on [Ca(2+)](i) regulation and its underlying molecular mechanism in cultured antral smooth muscle cells (ASMCs).

METHODS

Antral cells were isolated and cultured from neonatal rats, and then the [Ca(2+)](i) in these cells was evaluated by calcium fluorescent probe Fluo-3/AM on a laser scanning confocal microscope.

RESULTS

We show that motilin dose-dependently increased [Ca(2+)](i) concentration in cultured ASMCs. Pre-incubation of cells with either the calcium antagonist verapamil (10(-5) mol L(-1)) or the calcium chelator Egtazic (EGTA, 0.1 mmol L(-1)) significantly suppressed motilin (10(-6) mol L(-1)) induced [Ca(2+)](i) increase as indicated by fluorescent intensity. Interestingly, after mixing with the non-selective intracellular calcium release blocker TMB-8 (10(-5) mol L(-1)), guanosine triphosphate regulatory protein antagonist NEM (10(-5) mol L(-1)), phospholipase C (PLC) inhibitor compound 48/80 (1.2 microg mL(-1)) and ryanodine at high concentration (10(-5) mol L(-1)), the motilin-induced [Ca(2+)](i) increase was only partially blocked. The protein kinase C inhibitor d-sphingosine (10(-6) mol L(-1)), however, did not show any inhibitory effect on motilin-induced [Ca(2+)](i) elevation.

CONCLUSIONS

Our study suggests that motilin-stimulated [Ca(2+)](i) elevation in ASMCs is probably due to sustained extracellular Ca(2+) influx and Ca(2+) release from Ca(2+) stores via inositol tris-phosphate receptors and ryanodine receptors. Specifically, motilin-induced [Ca(2+)](i) release is accompanied with guanosine triphosphate-binding protein-coupled receptor-PLC-inositol tris-phosphate signalling cascades.

Topical Nifedipine(®) for conservative treatment of acute haemorrhoidal thrombosis

OBJECTIVE

The aim of this prospective, randomized trial was to test the efficacy of the local application of Nifedipine gel(®) in healing acute thrombosed haemorrhoids by relaxing the internal anal sphincter.

PATIENTS AND METHODS

Ninety patients who gave written informed consent were recruited; they received a clinical examination, anoscopy and a questionnaire to evaluate symptoms, pain and concurrent use of analgesics. Patients treated with Nifedipine (n=46) received topical 0.3% Nifedipine and 1.5% lidocaine gel every 12 h for 2 weeks. The control group, consisting of 44 patients, received topical 1.5% lidocaine and 1% hydrocortisone acetate gel during therapy.

RESULTS

The results were as follows: relief of pain in 84.7% in Nifedipine group as opposed to 50% of controls after 7 days of therapy (P < 0.01); oral analgesics were used by 8.6% of patients in the Nifedipine group as opposed to 54.5% of the control group (P < 0.01); resolution of thrombosed haemorrhoids occurred after 14 days of therapy in 91.3% of the Nifedipine-treated patients, as opposed to 45.4% of the controls (P < 0.01). No systemic side effects or significant anorectal bleeding were observed in patients treated with Nifedipine.

CONCLUSION

Our study clearly demonstrates that the use of Nifedipine, which at present is for treatment of cardiovascular disorders, should be extended to the conservative treatment of acute thrombosed haemorrhoids, using a topical application.

Nifedipine for local use in conservative treatment of anal fissures: preliminary results of a multicenter study

PURPOSE

This study was performed according to a prospective, randomized, double-blind, multicenter design. The aim was to test the efficacy of local application of nifedipine gel" in healing acute anal fissure by relaxing the internal anal sphincter.

METHODS

Two hundred eighty-three patients who gave informed consent were recruited; they received a clinical examination. A questionnaire to evaluate the symptoms and the pain was administered, and a proctoscopy and anorectal manometry were performed. Patients treated with nifedipine (n = 141) used topical 0.2 percent nifedipine gel every 12 hours for three weeks. The control group, consisting of 142 patients, received topical 1 percent lidocaine and 1 percent hydrocortisone acetate gel during therapy. Manometry was performed before and on Days 14 and 21. Anal pressures were measured by recording resting and squeeze pressures.

RESULTS

Results obtained were as follows: total remission from acute anal fissure was achieved after 21 days of therapy in 95 percent of the nifedipine-treated patients (P < 0.01), as opposed to 50 percent of the controls (P < 0.01), and previously elevated maximum resting anal pressures decreased from a mean value +/- standard deviation of 72.5 +/- 10.07 mmHg to 50.5 +/- 10.03 mmHg in the nifedipine group. This represents a mean reduction of 30 percent (P < 0.01). We also observed a significant decrease in squeeze pressures in nifedipine-treated patients (from a mean +/- standard deviation of 130.5 +/- 19.25 mmHg to 108.5 +/- 18.55 mmHg, a mean reduction of 16.8 percent; P < 0.01). No changes in anal pressures were observed in the control group. We did not observe any systemic side effect or significant anorectal bleeding in patients treated with nifedipine.

CONCLUSIONS

Our study clearly demonstrates that the therapeutic use of nifedipine, which at present is used only in cardiovascular pathologies, should be extended with local use to the conservative treatment of anal fissures.

Ca2+ channel blockade by verapamil inhibits GMCs and diarrhea during small intestinal inflammation

The aim of this study was to investigate whether the blockade of L-type Ca2+ channels with verapamil suppresses giant migrating contractions (GMCs) and therefore diarrhea during small intestinal inflammation. Small intestinal inflammation was induced by infection with the nematode Trichinella spiralis. T. spiralis infection alone significantly increased the frequency of GMCs and decreased the frequency of phase III activity in the small intestine for 9 days. The increased frequency of GMCs was associated with diarrhea. Immunohistochemical staining with specific antibodies indicated that the number of neutrophils and mast cells increased significantly in the jejunal lamina propria during T. spiralis infection. Only the neutrophils increased significantly in the muscularis externa of the jejunum. Myeloperoxidase (MPO) activity increased significantly in the jejunal and ileal lamina propria. Daily verapamil administration during T. spiralis infection significantly reduced the frequency of GMCs and diarrhea but had no further significant effect on the already reduced frequency of phase III activity. Verapamil administration, however, did not reduce MPO activity or immunocyte infiltration in the jejunum or ileum. We conclude that blockade of L-type Ca2+ channels selectively reduces the frequency of GMCs and therefore diarrhea during small intestinal inflammation. The decreased frequency of GMCs is not secondary to a reduction in the inflammatory response.

Calcium-channel blockers and gastrointestinal motility: basic and clinical aspects

Several calcium-channel blockers currently in use for the treatment of cardiovascular disorders have recently been tested for their effects on gastrointestinal motility. The rationale for this approach centers on the concept that calcium-channel blockers are at least as potent in inhibiting intestinal smooth muscle as in relaxing vascular smooth muscle. This review will give an outline of the most recent findings on the role of calcium and calcium channels in smooth muscle and neuronal function in the digestive system. It will also consider the mechanisms by which calcium-channel blockers may affect gastrointestinal motility and assess potential clinical applications in gastroenterology. The main goal for researchers in this field will be the development of gut-selective agents, with no cardiovascular side effects.