小倉 俊郎

To gain further insight into the central nervous system (CNS)-action of beta-adrenergic blocking agents (beta-blockers), we examined the effects of various kinds of beta-blockers on opioid receptors (Op-Rs) using radiolabeled receptor assay (RRA). We demonstrated that beta-blockers are competitively bound to Op-Rs in the CNS. Sodium index of beta-blockers in [3H]naloxone binding study indicated that beta-blockers had the mixed agonist-antagonist activity of opiates. The relative potency of beta-blockers in opioid RRA was negatively correlated with their membrane stabilizing activity. Neither beta-blocking activity nor intrinsic sympathomimetic activity was correlated with IC50 values of beta-blockers in opioid RRA. While it is widely accepted that beta-blockers have a tranquilizing activity, a part of the tranquilizing action of beta-blockers may be mediated through Op-Rs in the CNS. Although beta-blockers may have effects on their own receptors (beta-receptors) in the CNS, the more precise mechanisms of central action of these drugs must be further investigated.

To establish the actual serial changes in body weight in Japanese people and to elucidate the influence of changes in BMI on morbidity, we conducted a historical cohort study of university graduates from 1955 to 1990 using questionnaires and BMI data. The subjects of this study were 3,675 university graduates aged 26-62 years in whom BMI was determined at the time of enrollment in the university (Pre-BMI), 5 to 40 years earlier. Morbidity (one or more system diseases or obesity-related system diseases) was analyzed according to current age, sex, current BMI, deltaBMI (difference between current BMI and pre-BMI), and various lifestyle variables. The proportion of overweight subjects at enrollment to university was higher in recent male students compared to old students, but not in female graduates, and the BMI in both genders increased progressively after graduation, especially in recent male graduates. Pre-BMI correlated negatively and significantly with deltaBMI. The percentages of obese (BMI > or = 30 kg/m2) males and females were 1.6% and 0.5%, respectively, and high morbidity was observed in 56.1% and 42.2% of males and females, respectively. Stepwise regression analysis showed that in subjects with normal BMI at enrollment, prospective morbidity was dependent on ABMI in addition to age. Our results indicate that in subjects with normal body weight, prospective morbidity is determined by increment of ABMI, and suggest that maintenance of BMI at the late adolescence level is an important factor in preventing future disease.

To elucidate the effect of the arginine vasopressin (AVP) system in vivo, especially V1 and V2 activity, on blood pressure, we measured the acute changes in blood pressure and heart rate after AVP, OPC-21,268 (a V1 receptor antagonist), and OPC-31,260 (a V2 receptor antagonist) were injected intravenously in anesthetized spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats at the age of 15 weeks. Compared with the control period, single injection of AVP 5 ng/kg significantly increased systolic blood pressure in WKY rats without a concomitant increase in heart rate, but there was no significant increase in blood pressure in SHR. In contrast, single injection of either OPC-21,268 3 mg/kg or OPC-31,260 3 mg/kg did not affect blood pressure or heart rate in either SHR or WKY rats. Injection of AVP after the administration of OPC-31,260 induced a greater increase in blood pressure in SHR than in WKY rats, whereas injection of AVP after the administration of OPC-21,268 did not induce any clear increase in blood pressure in SHR or WKY rats. These results suggest that SHR have enhanced pressor activity mediated by V1 receptors and that this increase may be due to an increase in their number. In conclusion, enhancement of V1 activity may contribute to the development of high blood pressure in SHR.

<p>To assess the role of the kidney dopamine system on the diuretic state induced by angiotensin-converting enzyme (ACE) inhibitors, we examined the changes in urinary excretion and plasma level of dopamine, and kidney dopamine receptors in spontaneously hypertensive rats (SHR) treated with cilazapril, an ACE inhibitor. We administered cilazapril 10 mg/kg orally to 13-week-old SHR daily for 21 days (CILAZA group). Systolic blood pressure was significantly decreased in the CILAZA group on Day 6 compared with that in vehicle-treated SHR (control group). The urine volume was three- to fivefold higher in the CILAZA group, and total urinary dopamine secretion was also increased compared with the control group. There was no significant difference in affinity and number of kidney dopamine receptors between the CILAZA and the control groups. In conclusion, the diuretic effect caused by cilazapril is partly mediated by inhibition of the water reabsorption via the increase of dopamine production in the kidney.</p>

We recently reported that stimulation of the arginine vasopressin (AVP) V1-receptor enhanced the pressor response in spontaneously hypertensive rats (SHR). In the present study, we investigated acute changes in systolic blood pressure (SBP) and heart rate (HR) after intravenous injections of AVP, OPC-21268 (a V1-receptor antagonist), and OPC-31260 (a V2-receptor antagonist), in anesthetized DOCA-salt hypertensive rats (DOCA) and age-matched sham-operated Wistar rats (control) to determine whether the pressor effect is specific to SHR or is present in other hypertensive animal models. SBP increased significantly in DOCA rats 9 min after injection of AVP 5 ng/kg without a concomitant increase in HR. Neither OPC-21268 3mg/kg nor OPC-31260 3mg/kg caused significant changes in SBP or HR. SBP tended to increase when AVP was administered after injection of OPC-31260. HR increased significantly 15 min after the combined treatment with OPC-31260 and AVP in DOCA rats compared with control rats. SBP did not change significantly when AVP was administered after injection of OPC-21268 in DOCA or control rats, but HR decreased significantly from 1 to 4 min after injection of AVP in DOCA rats. Our results suggest that V1-receptor stimulation does not enhance the pressor response in the DOCA rat, which is a model of volume-dependent hypertension, suggesting that the AVP system, especially V1-receptor, is not as important in the development or maintenance of hypertension in DOCA rats as in SHR.