Basal and stimulated sympathetic responses after epinephrine: no evidence of augmented responses

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.

Sympathetic control of the circulation in hypertension: lessons from autonomic disorders

PURPOSE OF THE REVIEW

Inappropriate sympathetic overactivity is consistently observed in patients with essential hypertension. The present review summarizes the recent advances that have been made in our understanding of the role of the sympathetic nervous system in hypertension.

RECENT FINDINGS

Studies in patients with autonomic disorders underscore the role of the sympathetic nervous system in the long-term maintenance of hypertension. Abnormalities in the afferent limb of the sympathetic nervous system, in the regulation of central neurons where sympathetic outflow originates, and in the modulation of efferent sympathetic function, can all produce autonomic disorders that are associated with hypertension. More subtle dysfunctions in any of these components have been described in essential hypertension and can contribute to its pathogenesis. These include impaired buffering capacity of arterial baroreflexes, increased central sympathetic outflow, and enhanced norepinephrine release (or decrease reuptake) from sympathetic nerve terminals. Whether genetic polymorphisms of adrenoreceptors are associated with essential hypertension is an area of active research.

SUMMARY

Increased sympathetic activity can contribute to sustained hypertension not only because of its hemodynamic effects (increased cardiac output and vascular resistance), but also by altering renal and water handling by the kidney, and by inducing cardiac and vascular remodeling. Antihypertensive agents that directly or indirectly target this sympathetic overactivity may be particularly useful in long-term treatment of essential hypertension.

Cilnidipine more highly attenuates cold pressor stress-induced platelet activation in hypertension than does amlodipine

The clinical significance of N-type calcium channel blockade has not been fully examined. We here compared the effects of the N-type calcium channel blockers cilnidipine and amlodipine on the sympathetic nervous system and platelet function in hypertension under resting and stressed conditions. Thirty-two patients with hypertension (58+/-9 years) received cilnidipine or amlodipine for 4 weeks in this crossover study. On day 28 of each treatment, plasma levels of epinephrine (EP), norepinephrine (NEP), and beta-thromboglobulin (BTG), and EC50 of ADP-induced platelet aggregation (ADPE50) were determined at rest and after a cold pressor test. On day 29, the group receiving cilnidipine was switched to amlodipine treatment, and vice versa. At rest, the blood pressure, heart rates, EP, NEP, ADPEC50, and BTG, were similar in both treatments. After the cold pressor test, increases in EP (35+/-17 to 44+/-25 pg/ml; p<0.05) and BTG (40+/-13 to 49+/-22 ng/ml; p<0.01) and a decrease in ADPEC50 (32+/-26 to 27+/-24 micromol; p<0.05) were observed in the amlodipine treatment, but not in the cilnidipine treatment. In addition, the increase in NEP was significantly greater (p<0.05) in the amlodipine (276+/-78 to 318+/-87 pg/ml; p<0.01) than in the cilnidipine treatment (273+/-88 to 291+/-100 pg/ml; p<0.05). Cilnidipine more highly attenuates the activation of platelet function in response to cold pressor stress than does amlodipine. Attenuated activation of the sympathetic nervous system via N-type calcium channel blockade may contribute to this phenomenon.

beta2-adrenoceptor gene polymorphisms and blood pressure variations in East Anglian Caucasians

OBJECTIVE

The amino-terminal polymorphisms, Arg16Gly and Gln27Glu, of the beta2-adrenergic receptor (beta2AR) have been shown to affect regulation of the receptor expression by an agonist in cell culture studies. The Arg16Gly polymorphism has also been recently shown to be associated with essential hypertension. We therefore evaluated whether the amino-terminal polymorphisms of beta2AR are associated with hypertension in a Caucasian population.

SUBJECTS AND METHODS

We performed an association study in 298 hypertensive patients and an equal number of age-matched normotensive controls from the East Anglian region, with blood pressure assessed categorically and quantitatively. We also examined the influence of the amino-terminal polymorphisms on blood pressure response to beta-blockade in 144 of the patients randomly assigned to this class of drug. Genotyping of the Arg16Gly polymorphism was undertaken by a newly designed mismatched polymerase chain reaction (PCR) and digestion with Nde I, whereas the Gln27Glu polymorphism was genotyped by PCR followed by Fnu4H I cleavage.

RESULTS

We found no differences in the genotype or allele frequencies of the beta2AR polymorphisms between hypertensive and normotensive participants. There was also no association between the beta2AR genotypes and variations in either basal blood pressure or the blood pressure response to a beta-blocker.

CONCLUSION

These findings suggest that the amino-terminal polymorphisms of the beta2AR gene are unlikely to constitute major susceptibility for essential hypertension in the East Anglian population.