Inhibitory effect of cilnidipine on pressor response to acute cold stress in spontaneously hypertensive rats

Antihypertensive and cardioprotective effects of different monotherapies and combination therapies in young spontaneously hypertensive rats - A pilot study

Spontaneously hypertensive rats (SHR) are an established animal model for antihypertensive treatment. The aim of this pilot study was a systematic search for two lines of antihypertensive treatment - a monotherapy and a combination of two drugs - to be applied in a future study on old SHR. Originally, representatives of three drug classes recommended for antihypertensive therapy in humans should be applied, namely captopril (CAP) as an antagonist of the renin-angiotensin-aldosterone system, nifedipine (NIF) as calcium channel blocker and propranolol (PROP) as β-adrenergic blocker. As we observed that PROP had been poorly ingested, all groups with PROP therapy were excluded from the study. CAP (60 mg kg^-1 d^-1), NIF (10 mg kg^-1 d^-1) or both were administered orally to seven-week-old SHR over 3 weeks. A further group of SHR received no treatment (SHR/CTRL). Age-matched normotensive Wistar-Kyoto rats served as normotensive controls. We examined the effect of the antihypertensive therapies on systolic blood pressure, heart weight and on histological and biochemical markers of cardiac hypertrophy and fibrosis. CAP proved to be the most effective treatment reducing blood pressure and relative heart weight significantly compared to SHR/CTRL without reaching normotensive values. Beginning cardiac fibrosis observed in SHR/CTRL was completely abrogated with CAP treatment. Similar effects were achieved with a combination of CAP and NIF. CAP as monotherapy and CAP + NIF as combination therapy were chosen for the forthcoming study on old SHR.

Efficacy of Cilnidipine (L/N-type Calcium Channel Blocker) in Treatment of Hypertension: A Meta-Analysis of Randomized and Non-randomized Controlled Trials

INTRODUCTION

 Hypertension is one of the most common cardiovascular diseases, and the prevalence of hypertension continues to rise across the globe. National and international guidelines recommend angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs), calcium channel blockers (CCBs), diuretics, and beta-blockers for the management of hypertension. CCBs are among the most used antihypertensive medications and Cilnidipine is a newer dihydropyridine CCB shown to have a prolonged antihypertensive property.

OBJECTIVE

 This meta-analysis of comparative randomized and non-randomized clinical trials evaluated the effect of Cilnidipine monotherapy or combination therapy on systolic blood pressure (SBP), diastolic blood pressure (DBP), and pulse rate (PR) over 48 weeks of therapy.

STUDY DESIGN

 PubMed (MEDLINE) and Google scholar databases were searched to identify studies designed to evaluate the effects of Cilnidipine in the treatment of hypertensive patients. The study criteria for inclusion into the meta-analysis were all prospective, randomized, and non-randomized clinical studies published till March 2021, studies published in a peer-reviewed journal, the inclusion of patients with hypertension, assessment of blood pressure and heart rate, and a follow-up of four weeks or longer. The initial search identified 82 potential articles; of these, 24 met the inclusion criteria. Studies with <4 weeks treatment period and those not having a CCB were excluded.

OUTCOMES

 Change in SBP, DBP, and PR from baseline at the end of therapy compared between the Cilnidipine and other CCB's.

RESULTS

Cilnidipine caused a significant reduction (p<0.05) in SBP, DBP, and PR at end of therapy, whereas the reduction in SBP, DBP, and PR with Cilnidipine was similar to other CCB's (p>0.05). The results of this meta-analysis revealed that there were no significant differences in the efficacy in the treatment of hypertensive patients with Cilnidipine and the other therapies.

CONCLUSION

 Cilnidipine has similar anti-hypertensive effects compared with other first-line antihypertensive drugs commonly used in practice. We recommend Cilnidipine as a novel first-line CCB for the management of hypertension either as a monotherapy or as a combination therapy.

Switching to an L/N-type calcium channel blocker shows renoprotective effects in patients with chronic kidney disease: the Kyoto Cilnidipine Study

OBJECTIVE

This open-label, randomized controlled trial investigated the effects of cilnidipine, an L/N-type calcium channel blocker (CCB), in patients with chronic kidney disease (CKD).

METHODS

Sixty patients with CKD and well-controlled hypertension being treated with a renin- angiotensin system (RAS) inhibitor and an L-type CCB (L-CCB) were randomly assigned either to switch from the L-CCB to cilnidipine after a 4-week observation period or to continue with L-CCB treatment. Blood pressure, heart rate and renal function were monitored for 12 months. Data were available for analysis from 50 patients: 24 from the cilnidipine group and 26 from the L-CCB group.

RESULTS

Blood pressure was well controlled in both groups. After 12 months, proteinuria and heart rate were significantly decreased in the cilnidipine group, but proteinuria increased and heart rate remained unchanged in the L-CCB group. There was a significant positive correlation between the percentage changes in proteinuria and heart rate.

CONCLUSIONS

Cilnidipine has antihypertensive effects equivalent to those of L-CCBs. In patients with CKD, proteinuria can be decreased by switching from an L-CCB to cilnidipine, thereby improving renal function.

The N-type and L-type calcium channel blocker cilnidipine suppresses renal injury in Dahl rats fed a high-salt diet

The aims of the present study were to compare the effects of cilnidipine [L-type/N-type calcium channel blocker (CCB)] and amlodipine (L-type CCB) alone or in combination with the angiotensin II receptor blocker (ARB), valsartan, on blood pressure (BP), kidney function in Dahl salt-sensitive (DS) rats. DS rats fed a high-salt diet were divided into six groups; control (n = 13), two CCB (cilnidipine or amlodipine) groups at 1 mg/kg/day (n = 10), ARB (valsartan) at 10 mg/kg/day (n = 12), cilnidipine + valsartan (CV, n = 12), and amlodipine + valsartan (AV, n = 12). BPs were lower in the combination therapy groups than in those given either drug alone, but only CV inhibited the increase in urinary albumin excretion (UAE) and lowered the glomerular sclerosis score. In addition, AV elevated plasma renin activity and the angiotensin II concentration, and thus failed to inhibit increases in UAE and to lower glomerular sclerosis score. In conclusion, combination therapy with CCB and ARB decreases BP more effectively than either drug alone. When used in combination with valsartan, cilnidipine is more effective than amlodipine for preventing kidney injury.

Azelnidipine Attenuates Cardiovascular and Sympathetic Responses to Air-Jet Stress in Genetically Hypertensive Rats

Azelnidipine is a new dihydropyridine calcium channel blocker that causes minimal stimulation of the sympathetic nervous system despite its significant depressor effect. In the present study, we examined the effects of oral or intravenous administration of azelnidipine on cardiovascular and renal sympathetic nerve activity (RSNA) responses to air-jet stress in conscious, unrestrained stroke-prone spontaneously hypertensive rats. Oral administration of high-dose azelnidipine (10 mg/kg per day) or nicardipine (150 mg/kg per day) for 10 days caused a significant and comparable decrease in blood pressure, but low-dose azelnidipine (3 mg/kg per day) did not. Air-jet stress increased mean arterial pressure (MAP), heart rate (HR) and RSNA. High-dose azelnidipine significantly attenuated the increases in MAP, HR and RSNA in response to air-jet stress while nicardipine did not. Low-dose azelnidipine significantly attenuated the pressor response with a trend of decrease in RSNA. Intravenous injection of azelnidipine induced a slowly developing depressor effect. To obtain a similar time course of decrease in MAP by azelnidipine, nicardipine was continuously infused at adjusted doses. Both drugs increased HR and RSNA significantly, while the change in RSNA was smaller in the azelnidipine group. In addition, intravenous administration of azelnidipine attenuated the responses of MAP, HR, and RSNA to air-jet stress; by comparison, the inhibitory actions of nicardipine were weak. In conclusion, oral or intravenous administration of azelnidipine inhibited cardiovascular and sympathetic responses to air-jet stress. This action of azelnidipine may be mediated at least in part by the inhibition of the sympathetic nervous system.

The dorsomedial hypothalamus: a new player in thermoregulation

Neurons in the dorsomedial hypothalamus (DMH) play key roles in physiological responses to exteroceptive (“emotional”) stress in rats, including tachycardia. Tachycardia evoked from the DMH or seen in experimental stress in rats is blocked by microinjection of the GABAA receptor agonist muscimol into the rostral raphe pallidus (rRP), an important thermoregulatory site in the brain stem, where disinhibition elicits sympathetically mediated activation of brown adipose tissue (BAT) and cutaneous vasoconstriction in the tail. Disinhibition of neurons in the DMH also elevates core temperature in conscious rats and sympathetic activity to least significant difference interscapular BAT (IBAT) and IBAT temperature in anesthetized preparations. The latter effects are blocked by microinjection of muscimol into the rRP, while microinjection of muscimol into either the rRP or DMH suppresses increases in sympathetic nerve activity to IBAT, IBAT temperature, and core body temperature elicited either by microinjection of PGE2 into the preoptic area (an experimental model for fever), or central administration of fentanyl. Neurons concentrated in the dorsal region of the DMH project directly to the rRP, a location corresponding to that of neurons transsynaptically labeled from IBAT. Thus these neurons control nonshivering thermogenesis in rats, and their activation signals its recruitment in diverse experimental paradigms. Evidence also points to a role for neurons in the DMH in thermoregulatory cutaneous vasoconstriction, shivering, and endocrine adjustments. These directions provide intriguing avenues for future exploration that may expand our understanding of the DMH as an important hypothalamic site for the integration of autonomic, endocrine, and behavioral responses to diverse challenges.

Exposure to stress

Stress-induced vascular adaptive response in SHR was investigated, focusing on the endothelium. Noradrenaline responses were studied in intact and denuded aortas from 6-week-old (prehypertensive) and 14-week-old (hypertensive) SHR and age-matched Wistar rats submitted or not to acute stress (20-min swimming and 1-h immobilization 25 min apart), preceded or not by chronic stress (2 sessions 2 days apart of 1-h day immobilization for 5-consecutive days). Stress did not alter the reactivity of denuded aorta. Moreover, no alteration in the EC50 values was observed after stress exposure. In intact aortas, acute stress-induced hyporeactivity to noradrenaline similar between strains at both age. Chronic stress potentiated this adaptive response in 6- and 14-week-old Wistar but not in 6-week-old SHR, and did not alter the reactivity of 14-week-old SHR. Maximum response (g) in intact aortas [6-week-old: Wistar 3.25+/-0.12, Wistar/acute 1.95+/-0.12*, Wistar/chronic 1.36+/-0.21*(+), SHR 1.75+/-0.11, SHR/acute 0.88+/-0.08*, SHR/chronic 0.85+/-0.05*; 14-week-old: Wistar 3.83+/-0.13, Wistar/acute 2.72+/-0.13*, Wistar/chronic 1.91+/-0.19*(+), SHR 4.03+/-0.17, SHR/acute 2.26+/-0.12*, SHR/chronic 4.10+/-0.23; inside the same strain: *P < 0.05 relate to non-stressed rat, +P < 0.05 related to acute stressed rat; n = 6-18]. Independent of age and strain, L-NAME and endothelium removal abolished the stress-induced aorta hyporeactivity.

CONCLUSION

The vascular adaptive response to stress is impaired in SHR, independently of the hypertensive state. Moreover, this vascular adaptive response is characterized by endothelial nitric oxide-system hyperactivity in both strains.

Effects of L/N-Type Calcium Channel Antagonist, Cilnidipine on Progressive Renal Injuries in Dahl Salt-Sensitive Rats

The sympathetic nerve activity plays an important role on the renal function through the vasoactive system and the renin-angiotensin system. Although interest in the renal protective effects of anti-sympathetic agents has been increased, there are not enough data to clarify this efficiency. Therefore, we investigated the effects of L/N-type calcium channel antagonist, cilnidipine on progressive renal injury in Dahl salt-sensitive (Dahl S) rats. Male Dahl S rats (6 weeks of age) were fed a high salt (4% NaCl) diet. They were divided into groups with similar blood pressure at 12 weeks of age and they received vehicle (n=7) or cilnidipine (30 mg/kg/d as food admix, n=9) for 8 weeks. Cilnidipine treatment suppressed the increase in systolic blood pressure. Although urinary protein excretion was not influenced, cilnidipine inhibited the increase in blood urea nitrogen and decrease in creatinine clearance. Histological investigation revealed that progression of glomerular sclerosis was inhibited in cilnidipine treatment group. Of notes, cilnidipine reduced plasma norepinephrine level and plasma rennin activity compared with vehicle-treated Dahl S rats. These data indicated that cilnidipine has suppressive effects against progressive renal injury in Dahl S rats. This effect is not only explained by the L-type calcium channel blocking action that lowered blood pressure, but also partially explained by the N-type calcium channel blocking action that lead to suppression of the sympathetic nerve activity and renin-angiotensin system.

The evaluation of the N-type channel blocking properties of cilnidipine and other voltage-dependent calcium antagonists

Sympathetic neurotransmission in tissues with intact sympathetic nerve arborization is extensively dependent on calcium influx via N-type calcium-channels. It was the objective of the present study to assess and compare the claimed sympatholytic effect of the 1,4-dihydropyridine compound cilnidipine with other voltage-dependent calcium-channel (VDCC) antagonists. We studied these compounds by means of three different models. In the rabbit isolated thoracic aorta, the alleged sympatholytic properties displayed by these compounds were evaluated in the noradrenaline spillover model. Additionally, the influence of cilnidipine on stimulation-induced constrictor responses was studied in the rat isolated tail artery (male Wistar rats, 250-300 g) in addition to its effect on noradrenaline-induced contractions. Finally, we studied the influence of cilnidipine and other calcium-channel blockers on stimulation-induced chronotropic responses, in order to address N- or L-type selectivity, in the pithed rat model (male Wistar rats, 260-320 g). Furthermore, we evaluated their effect on noradrenaline-induced tachycardia. In the isolated rabbit thoracic aorta preparation omega-conotoxin GVIA (0.1 microM) nearly abolished the sympathetic outflow caused by stimulation, whereas nifedipine (0.1 microM) and amlodipine (1 microM) did not influence the evoked noradrenaline release. Cilnidipine (1 microM) significantly attenuated the response by nearly 18% and mibefradil (1 microM) by c. 42%. The stimulation-induced constrictor response (prejunctional effect) in the rat isolated tail artery could be blocked by omega-conotoxin GVIA (0.5 and 1 microM). Cilnidipine (10 nm and 0.1 microM) significantly attenuated responses to stimulation by maximally 20%, whereas it did not influence the constrictor response to noradrenaline (postjunctional effect). The mean heart rate in the pithed rat model amounted to 309.3 +/- 3.6 beats/min (bpm). Electrical stimulation of the cardio-accelerator nerves (C7-Th1) resulted in an increase by 106.7 +/- 2.2 bpm. All antagonists studied, except for nifedipine, attenuated the chronotropic response to stimulation (P < 0.05). The rank order of sympatholytic efficacy was: omega-conotoxin GVIA (84.8%), mibefradil (75.1%), cilnidipine (43.0%) and amlodipine (34.8%). Noradrenaline (10 nmol/kg) increased the heart rate by 117.8 +/- 2.7 bpm. This chronotropic response was influenced equally well by the calcium-channels blockers as observed in the stimulation (prejunctional) experiment. In conclusion, the N-type channel blocking properties and thus sympatholytic effect of cilnidipine could be demonstrated in some (vascular) but not all (cardiac) models studied. At the level of the vasculature cilnidipine reduced the neurotransmitter release to electrical stimulation in both the noradrenaline spillover model and in the model of the rat isolated tail artery, respectively. For amlodipine and nifedipine no sympatholytic activity could be demonstrated. In the pithed rat model, we were unable to demonstrate a selective N-type blocking effect for the VDCC-antagonists.

Effect of Morning and Bedtime Dosing with Cilnidipine on Blood Pressure, Heart Rate, and Sympathetic Nervous Activity in Essential Hypertensive Patients

Cilnidipine has a blocking action against N-type calcium channels as well as L-type calcium channels. We studied the effect of morning and bedtime dosing on circadian variation of blood pressure (BP), heart rate (HR), and activity of the autonomic nervous system, using an open randomized crossover study in 13 essential hypertensive patients. An automated device allowed 24-hour monitoring of ambulatory BP and HR and the power spectrum of the R-R interval, at the observation period, the morning dosing regimen, and the bedtime dosing regimen. Morning dosing and bedtime dosing with cilnidipine reduced the average systolic BP over 24 hours, during daytime, and during nighttime. The average HR and the average LF/HF ratio over 24 hours, during daytime, and during nighttime, were similar for the three periods. Both morning and bedtime dosing reduced the maximum systolic BP in the early morning and suppressed the morning rise of BP, which were accompanied by partial inhibition of the increase in LF/HF ratio. Our results show that cilnidipine administered once daily is an efficient antihypertensive drug regardless of the time of dosing, without reflex tachycardia and increase in sympathetic nervous activity, and with partial inhibition of the morning activation of the sympathetic nervous system.

Cilnidipine improves spontaneously hypertensive rat coronary hemodynamics without altering cardiovascular mass and collagen

OBJECTIVE

The present study was designed to determine the effects of prolonged treatment with cilnidipine, a novel dihydropyridine calcium antagonist which blocks both L-type and N-type calcium channels, on systemic, regional and coronary hemodynamics, cardiovascular mass and collagen content in normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats.

METHODS

Male 23-week-old WKY and SHR rats were divided into two groups for each strain. One group received cilnidipine (10 mg/kg per day), whereas their respective controls were given no therapy. Systemic and regional hemodynamics (radionuclide-labeled microspheres), left and right ventricular and aortic mass, and hydroxyproline concentration were determined after 12 weeks treatment.

RESULTS

The data demonstrated that cilnidipine neither affected systemic hemodynamics nor cardiovascular mass and collagen content in WKY rats. The same treatment in the SHR reduced arterial pressure and total peripheral resistance without changes in heart rate and cardiac index. Ventricular and aortic mass indices as well as ventricular collagen content remained unchanged. There were no differences in organ blood flows between two SHR groups, whereas renal, liver and left ventricular coronary vascular resistances were reduced by cilnidipine. After dipyridamole infusion left ventricular minimal coronary vascular resistance decreased further in cilnidipine-treated SHR as compared with control SHR rats.

CONCLUSION

These data suggest that cilnidipine, an L- and N- type calcium channel antagonist, exerted beneficial effects on coronary hemodynamics without altering cardiovascular mass or collagen content in SHR.

In vivo measurement of 1,4-dihydropyridine receptors in mesenteric arteries of spontaneously hypertensive rats and effect of nifedipine and cilnidipine

The present study was undertaken to measure 1,4-dihydropyridine (DHP) receptor binding sites in vivo in the mesenteric artery and other tissues of spontaneously hypertensive rats (SHR) and to examine the effect of nifedipine and cilnidipine. Specific in vivo binding of (+)-[3H]PN 200-110 in the SHR mesenteric artery was dose dependently reduced by oral administration of nifedipine at relatively low doses. Oral administration of cilnidipine (6.09 micromol/kg) significantly reduced the specific in vivo binding of (+)-[3H]PN 200-110 in the mesenteric artery, aorta, and myocardium. A significant reduction in (+)-[3H]PN 200-110 binding was seen at 1-12 h in the mesenteric artery and at 1-7 h in the aorta and myocardium. In contrast, oral administration of nifedipine (28.9 micromol/kg) markedly reduced in vivo (+)-[3H]PN 200-110 binding in all tissues of SHR at 1-6 h, and the degree and time course of the reduction did not differ much among the tissues. The area under the curve (AUC) for receptor occupancy vs. time was calculated from the reduction rate (%) of specific in vivo (+)-[3H]PN 200-110 binding. The ratio (1.4 or 1.7) of the AUC(mesenteric artery) to AUCaorta or AUCmyocardium after oral administration of cilnidipine was greater than the corresponding value (1.1) for nifedipine. In conclusion, the present study demonstrates that cilnidipine, but not nifedipine, may occupy 1,4-DHP receptors in the small artery in a more selective and sustained manner than in other tissues of SHR, and thus such receptor binding specificity may be responsible for the long-lasting hypotensive effect of this drug.

Conserved smooth muscle contractility and blood pressure increase in response to high-salt diet in mice lacking the beta3 subunit of the voltage-dependent calcium channel

Voltage-dependent calcium channels are crucially important for calcium influx and the following smooth muscle contraction. Beta subunits of these channels are known to modify calcium currents through pore-forming alpha subunits. Among the four reported independent beta subunits, the beta3 subunit is expressed in smooth muscle cells and thought to compose L-type calcium channels in the tissue. To determine the role of the beta3 subunit in the cardiovascular system, we have analyzed beta3-null mice. Electrophysiological examinations proved the existence of dihydropyridine (DHP)-sensitive. L-type calcium channels in the smooth muscle cells. Beta3-null mice show no apparent changes in smooth muscle contraction and sensitivity to DHP, and normal blood pressure when they are raised on a normal diet, but the 13 subunit deficient mice show elevated blood pressure in response to a high-salt diet, with significant reductions in plasma catecholamine concentrations. Our finding strongly suggests a close relationship between voltage-dependent channels and high blood pressure.

Effects of cilnidipine, a novel dihydropyridine calcium antagonist, on autonomic function, ambulatory blood pressure and heart rate in patients with essential hypertension

AIMS

The aim of the present study was to evaluate the effects of cilnidipine, a novel dihydropyridine calcium antagonist, on autonomic function, ambulatory blood pressure and heart rate in patients with essential hypertension.

METHODS

Ten inpatients with mild to moderate essential hypertension (four men and six women; age: 44-64 years) underwent a drug-free period for 7 days and a treatment period with cilnidipine 10 mg orally for another 7 days, in a randomized crossover study. On the sixth day of each period, they underwent autonomic function tests including a mental arithmetic test, a cold pressor test and a Valsalva manoeuvre. After these tests, 24 h ambulatory blood pressure, heart rate, and the electrocardiogram R-R intervals were monitored every 30 min. A power spectral analysis of R-R intervals was performed to obtain the low-and high-frequency components.

RESULTS

Cilnidipine significantly decreased the 24 h blood pressure by 6.5 +/- 1.7 mm Hg systolic (mean +/- s.e.mean; P < 0.01) and 5.0 +/- 1.1 mmHg diastolic (P < 0.01), whereas cilnidipine did not change heart rate or any indices of power spectral components. During the cold pressor test, the maximum change in systolic blood pressure and percentage changes in both systolic and diastolic blood pressures were significantly lower during the treatment period with cilnidipine than during the drug-free period. The baroreflex sensitivity measured from the overshoot phase of the Valsalva manoeuvre did not differ significantly between the two periods.

CONCLUSIONS

Cilnidipine is effective as a once-daily antihypertensive agent and causes little influence on heart rate and the autonomic nervous system in patients with mild to moderate essential hypertension. Moreover, it is suggested that cilnidipine has an additional clinical benefit in the inhibition of the pressor response induced by acute cold stress.

Selectivity of dihydropyridines for cardiac L-type and sympathetic N-type Ca2+ channels

The blocking effects of cilnidipine and other dihydropyridines on L-type cardiac Ca2+ channels (I(Ca,L)) and N-type sympathetic Ca2+ channel currents (I(Ca,N)) were studied using a whole-cell patch-clamp technique. At -80 mV, cilnidipine had little inhibitory effect below concentrations of 1 microM on I(Ca,L) (IC50 value; 17 microM). However, 1 microM cilnidipine strongly shifted the steady-state inactivation curve of I(Ca,L) toward negative potentials without changing the current-voltage relationship. Each action of cilnidipine was characterized by a high affinity for the inactivated channel in preference to the resting channel. The IC50 values of dihydropyridines for I(Ca,L) were in the range between 0.01 and 10 microM, and those for I(Ca,N) were between 3 and 30 microM. Cilnidipine had the strongest affinity for I(Ca,N) among the dihydropyridines tested. These results suggest that cilnidipine did not cause hypotension-evoked tachycardia deficiency by depression of cardiac L-type channels but by sympathetic N-type channels blockade.

Current status of calcium antagonists in Japan

Calcium antagonists comprise the most popular drug class for treatment of hypertension in Japan. More than half of Japanese clinicians use calcium antagonists as initial drug treatment for mild-to-moderate hypertension and, despite recent controversies, their use continues to increase. Nearly a fourth of clinicians use angiotensin-converting enzyme (ACE) inhibitors, and 9% use beta-receptor blockers. There are 12 dihydropyridine calcium antagonists and 1 benzothiazepine agent in clinical use. Amlodipine is the most widely used agent in the class. Efonidipine and cilnidipine, recently developed in Japan, both have a slow onset of action and long-lasting hypertensive effect and possess characteristics unique to the class. Efonidipine dilates the efferent as well as the afferent arterioles of the glomerulus; therefore, it appears to have a more pronounced renoprotective effect than other calcium antagonists. Cilnidipine is a dual-channel antagonist, acting on both the peripheral neuronal N-type and vascular L-type calcium channels. It depresses the pressor response to acute cold stress but does not induce tachycardia by hypotensive baroreflex.

Effect of cilnidipine, a novel dihydropyridine Ca2+ channel blocker, on adrenal catecholamine secretion in anesthetized dogs

We investigated the effect of cilnidipine, a novel dihydropyridine Ca2+ channel blocker possessing blocking actions on N-type and L-type voltage-dependent Ca2+ channels (VDCCs), in comparison with the L-type VDCC blocker nifedipine, on adrenal catecholamine secretion in response to splanchnic nerve stimulation (SNS), acetylcholine (ACh), the nicotinic receptor stimulant 1,1-dimethyl-4-phenyl-piperazinium (DMPP), and muscarine in anesthetized dogs. Ca2+ channel blockers and cholinergic agonists were infused and injected, respectively, into the adrenal gland through the phrenicoabdominal artery. Cilnidipine (0.3-3 microg/min) inhibited increases in both epinephrine (EPI) and norepinephrine (NE) output induced by SNS (2 Hz), ACh (1.5 microg), and DMPP (0.2 microg). However, cilnidipine inhibited increase in NE output induced by muscarine (1 microg) without affecting increase in EPI output. Nifedipine (0.3-3 microg/min) inhibited the ACh- and DMPP-induced increases in EPI and NE output without affecting the SNS- and muscarine-induced increases in EPI and NE output. From these results, it seems likely that the inhibition by cilnidipine of the SNS-induced EPI and NE secretion and of the muscarine-induced NE secretion is related to its blocking action on N-type VDCCs.

Comparison of 24-hour blood pressure, heart rate, and autonomic nerve activity in hypertensive patients treated with cilnidipine or nifedipine retard

We compared the effects of cilnidipine and nifedipine retard on 24-h blood pressure (BP), heart rate (HR), and autonomic nerve activity in patients with essential hypertension. Cilnidipine is a novel and unique 1,4-dihydropyridine calcium antagonist that has the L-type and N-type voltage-dependent calcium channel-blocking action. Fourteen hypertensive outpatients (four men and 10 women; aged 64 +/- 2 years, mean +/- SEM) were enrolled in this study. Their ambulatory BP and electrocardiogram were monitored for 24 h at intervals of 30 min with a portable recorder after a 4-week drug-free period, after a 4-week treatment period with cilnidipine (5 or 10 mg once daily), and after a 4-week treatment period with nifedipine retard (10 or 20 mg twice daily). The order of the three periods was randomized. Autonomic nerve activity was evaluated by a power spectral analysis of HR variability, by using the high-frequency (HF) component as an index of parasympathetic nerve activity and the ratio of the low-frequency (LF) component to the HF component (LF/HF) as an index of sympathovagal balance. Cilnidipine and nifedipine retard significantly reduced the 24-h BP of these patients to similar extents (cilnidipine, -11 +/- 3/-6 +/- 1 mm Hg; nifedipine retard, -15 +/- 3/-6 +/- 2 mm Hg). Cilnidipine did not change the 24-h average HR, whereas nifedipine retard significantly increased it (+3.3 +/- 1.4 beats/min; p < 0.05). Nifedipine retard significantly increased the LF/HF ratio in the daytime and the nighttime. Such changes were limited to the daytime in the treatment period with cilnidipine. These results suggest that cilnidipine is effective as a once-daily antihypertensive agent and had less influence on autonomic nervous system and HR than did nifedipine retard.

Comparison of haemodynamic responses to cilnidipine and nicardipine in an experimental model of acute congestive heart failure

1. The haemodynamic effects of cilnidipine, a new calcium channel blocker, were examined in a canine model of acute congestive heart failure and were compared with those of nicardipine at equihypotensive doses. 2. The model was prepared by injections of saponin into coronary arteries of anaesthetized open-chest dogs followed by volume loading and continuous i.v. infusion of methoxamine. After the treatment, aortic blood flow (AoF) and left ventricular dP/dt markedly decreased, while left ventricular end-diastolic pressure (LVEDP), right atrial pressure and systemic vascular resistance (SVR) increased. Cilnidipine (0.3, 1.0 and 3.0 micrograms/kg per min), nicardipine (0.3, 1.0 and 3.0 micrograms/kg per min) or the respective vehicle was given i.v. after accomplishment of heart failure. 3. These drugs both produced a comparable reduction in aortic pressure and an increase in AoF associated with profound decreases in LVEDP, SVR and coronary vascular resistance. In contrast, administration of nicardipine was associated with significant increases in heart rate and cardiac contractility but that of cilnidipine was not. 4. These results indicate that cilnidipine as well as nicardipine can exert beneficial haemodynamic effects in a model of acute heart failure probably through lessening afterload and cilnidipine may moderate reflex-induced sympathetic stimulation.

Effects of a novel antihypertensive drug, cilnidipine, on catecholamine secretion from differentiated PC12 cells

Effects of a novel dihydropyridine type of antihypertensive drug, cilnidipine, on the regulation of the catecholamine secretion closely linked to the intracellular Ca2+ were examined using nerve growth factor (NGF)-differentiated rat pheochromocytoma PC12 cells. By measuring catecholamine secretion with high-performance liquid chromatography coupled with an electrochemical detector, we showed that high K+ stimulation evoked dopamine release from PC12 cells both before and after NGF treatments. Cilnidipine depressed dopamine release both from NGF-treated and untreated PC12 cells in a concentration-dependent manner. In contrast, inhibition by nifedipine was markedly decreased in the differentiated PC12 cells. With intracellular Ca2+ concentration ([Ca2+]i) measurements using fura 2, the elevation of high K+-evoked [Ca2+]i was separated into nifedipine-sensitive and -resistant components. The nifedipine-resistant [Ca2+]i increase was also blocked by cilnidipine, as well as omega-conotoxin-GVIA. By the use of the conventional whole-cell patch-clamp technique, the compositions of the high-voltage-activated Ca2+ channel currents in the NGF-treated PC12 cells were divided into types: L-type, N-type, and residual current components. It was also estimated that cilnidipine at 1 and 3 micromol/L strongly blocked the N-type current without affecting the residual current. These results suggest that cilnidipine inhibits catecholamine secretion from differentiated PC12 cells by blocking Ca2+ influx through the N-type Ca2+ channel, in addition to its well-known action on the L-type Ca2+ channel.

Blockade of N-type Ca2+ current by cilnidipine (FRC-8653) in acutely dissociated rat sympathetic neurones

1 The inhibitory effects of cilnidipine (FRC-8653) and various organic Ca2+ channel blockers on high voltage-activated Ba2+ currents (HVA IBa) in rat sympathetic neurones were examined by means of the conventional whole-cell patch-clamp recording mode under voltage-clamped conditions. 2 HVA IBa was classified into three different current components with subtype selective peptide Ca2+ channel blockers. No omega-Agatoxin IVA-sensitive (P-type) or omega-conotoxin MVIIC-sensitive (Q-type) current components were observed. Most (> 85%) IBa was found to consist of omega-conotoxin GVIA-sensitive N-type components. 3 The application of cilnidipine inhibited HVA 1Ba in a concentration-dependent manner. The Kd value for cilnidipine was 0.8 microM. Cilnidipine did not shift the current-voltage (I-V) relationship for HVA IBa, as regards the threshold potential and peak potential where the amplitude reached a maximum. 4 High concentration of three hypotensive Ca2+ channel blockers, nifedipine, diltiazem and verapamil, all inhibited HVA IBa in a concentration-dependent manner. The Kd values for nifedipine, diltiazem and verapamil were 131, 151 and 47 microM, respectively. A piperazine-type Ca2+ channel blocker, flunarizine, showed a relatively potent blocking action on IBa. The Kd value was about 3 microM. 5 These results thus show that cilnidipine potently inhibits the sympathetic Ca2+ channels which predominantly consist of an omega-Cg-GVIA-sensitive component. This blockade of the N-type Ca2+ channel, as well as the L-type Ca2+ channel by cilnidipine suggests that it could be used therapeutically for treatment of hypersensitive sympathetic disorders associated with hypertension.

Inhibitory effect of cilnidipine on vascular sympathetic neurotransmission and subsequent vasoconstriction in spontaneously hypertensive rats

We reported previously that cilnidipine inhibited increases in blood pressure and plasma norepinephrine (NE) level in response to cold stress in spontaneously hypertensive rats (SHRs). In the present study, we investigated the effect of cilnidipine on sympathetic neurotransmission and subsequent vasoconstriction in SHRs. In pithed SHRs, electrical sympathetic nerve stimulation (ESNS) elevated blood pressure, and this pressor response was abolished by guanethidine. Cilnidipine at 10 micrograms/kg, i.v. and phentolamine at 1 mg/kg, i.v. suppressed the pressor response to ESNS by 28 +/- 6% and 67 +/- 3%, respectively. Neither nifedipine nor nicardipine inhibited it. The pressor response to exogenous NE was not influenced by cilnidipine. alpha, beta-Methylene ATP inhibited the pressor response to ESNS in the presence or absence of phentolamine. Cilnidipine also attenuated the phentolamine-resistant pressor response to ESNS. In SHR mesenteric vasculatures preloaded with [3H]-NE, cilnidipine (10(-7) M) as well as omega-conotoxin significantly inhibited the 3H overflow evoked by periarterial nerve stimulation. In radioligand binding experiments, cilnidipine inhibited [125I]-omega-conotoxin binding to rat synaptosomes, but it did not inhibit [3H]-prazosin binding to rat cortex membranes. These results suggest that cilnidipine may reduce electrically stimulated NE release from the sympathetic nerve endings of SHR vasculatures probably through its N-type Ca channel blocking action and that cilnidipine may also inhibit the vasoconstriction induced by ATP released concomitantly during nerve stimulation.