Effects of ayahuasca on the development of ethanol-induced behavioral sensitization and on a post-sensitization treatment in mice.

BACKGROUND: Hallucinogenic drugs were used to treat alcoholic patients in the past, and recent developments in the study of hallucinogens led to a renewal of interest regarding the application of these drugs in the treatment of addiction. In this scenario, accumulating evidence suggests that the hallucinogenic brew ayahuasca (Aya) may have therapeutic effects on substance abuse problems. METHODS: We investigated the effects of Aya on spontaneous locomotor activity and ethanol(Eth)-induced hyperlocomotion and subsequent locomotor sensitization by a two-injection protocol. Additionally, we tested the effect of Aya on an 8-day counter-sensitization protocol to modify sensitized responses induced by a repeated treatment with Eth (1.8g/kg) for 8 alternate days. RESULTS: Aya showed high sensitivity in preventing the development of Eth-induced behavioral sensitization, attenuating it at all doses (30, 100, 200, 300 or 500 mg/kg) without modifying spontaneous locomotor activity. At the highest doses (300 and 500 mg/kg), Aya also showed selectivity to both acute and sensitized Eth responses. Finally, a counter-sensitization strategy with 100 or 300 mg/kg of Aya for 8 consecutive days after the establishment of Eth-induced behavioral sensitization was effective in blocking its subsequent expression on an Eth challenge. CONCLUSIONS: We demonstrated that Aya not only inhibits early behaviors associated with the initiation and development of Eth addiction, but also showed effectiveness in reversing long-term drug effects expression, inhibiting the reinstatement of Eth-induced behavioral sensitization when administered in the Eth-associated environment.

Response of arginine vasopressin-enhanced green fluorescent protein fusion gene in the hypothalamus of adjuvant-induced arthritic rats.

Arginine vasopressin (AVP) and corticotrophin-releasing hormone (CRH) in the parvocellular neurosecretory cells of the paraventricular nucleus (PVN) play a major role in activating the hypothalamic-pituitary-adrenal axis, which is the main neuroendocrine response against the many kinds of stress. We examined the effects of chronic inflammatory/nociceptive stress on the expression of the AVP-enhanced green fluorescent protein (eGFP) fusion gene in the hypothalamus, using the adjuvant arthritis (AA) model. To induce AA, the AVP-eGFP rats were intracutaneously injected heat-killed Mycobacterium butyricum (1 mg/rat) in paraffin liquid at the base of their tails. We measured AVP, oxytocin and corticosterone levels in plasma and changes in eGFP and CRH mRNA in the hypothalamus during the time course of AA development. Then, we examined eGFP fluorescence in the PVN, the supraoptic nucleus (SON), median eminence (ME) and posterior pituitary gland (PP) when AA was established. The plasma concentrations of AVP, oxytocin and corticosterone were significantly increased on days 15 and 22 in AA rats, without affecting the plasma osmolality and sodium. Although CRH mRNA levels in the PVN were significantly decreased, eGFP mRNA levels in the PVN and the SON were significantly increased on days 15 and 22 in AA rats. The eGFP fluorescence in the SON, the PVN, internal and external layers of the ME and PP was apparently increased in AA compared to control rats. These results suggest that the increases in the concentrations of ACTH and corticosterone in AA rats are induced by hypothalamic AVP, based on data from AVP-eGFP transgenic rats.

Dietary fat and meat intake and idiopathic pulmonary fibrosis: a case-control study in Japan.

SETTING: There is sparse epidemiologic information regarding the role of dietary factors in the development of idiopathic pulmonary fibrosis (IPF). OBJECTIVE: To examine the relationship between specific types of fatty acids and selected foods high in fat and IPF in Japan. DESIGN: Included were 104 cases aged > or = 40 years who had been diagnosed in the last 2 years in accordance with the most recent criteria. Controls aged > or = 40 years consisted of 56 hospitalised patients diagnosed as having acute bacterial pneumonia and four out-patients with common cold. RESULTS: Intake of saturated fatty acids, mono-unsaturated fatty acids, n-6 polyunsaturated fatty acids and meat was independently associated with an increased risk of IPF. Specifically, the multivariate OR for comparison of the highest with the lowest quartile of intake of saturated fatty acids was 6.26 (95%CI 1.79-24.96, P for trend = 0.01) and for meat it was 7.19 (95%CI 2.15-27.07, P for trend = 0.02). Intake of cholesterol, n-3 polyunsaturated fatty acids, fish, eggs and dairy products was not related to the risk. CONCLUSION: These findings suggest that consumption of saturated fatty acids and meat may increase the risk of IPF.

Kinetic analyses of alcohol-induced potentiation of the response of GABA(A) receptors composed of alpha(1) and beta(1) subunits.

To investigate the kinetics of both the potentiation and desensitization of the response of ionotropic GABA receptors (GABA(A) receptors) in the presence of various compounds, we expressed receptors composed of alpha(1) and beta(1) subunits by injecting cells with the cRNAs synthesized from cloned bovine GABA(A) receptor cDNAs and measured the electrical responses of the cells electrophysiologically with or without the compounds. The potentiation of the GABA(A) receptor-mediated response was quantitatively analyzed using a simple model with the assumption that the receptors have two identical binding sites for GABA molecules with a dissociation constant of K(1), and one potentiation site for the compound with a dissociation constant of K(p), and that the binding of the compound to the potentiation site only increases the affinity of the GABA binding sites, changing K(1) to K(1p). The estimated K(p) and K(1p) were dependent on the functional groups and the chain length of the compounds. These results could be satisfactorily analyzed using this simple model. The potentiation of the GABA(A) receptor-mediated response by the components of essential oils used for aromatherapy was also examined. These compounds accelerated the decay of the response, possibly due to desensitization of the receptors, which was also analyzed on the basis of the model.

Studies on interactions between traditional herbal and Western medicines. IV: lack of pharmacokinetic interactions between Saiko-ka-ryukotsu-borei-to and carbamazepine in rats.

The possibility of pharmacokinetic interactions between Saiko-ka-ryukotsu-borei-to extract powder (TJ-12), a widely used traditional Chinese herbal (Kampo) medicine, and carbamazepine (CBZ), an important anti-epileptic drug, was examined in rats. There were no significant differences in the serum protein binding of CBZ and carbamazepine- 10,11-epoxide (CBZ-E), its active metabolite, at two concentrations (1 and 10 Bg/ml) between twogroups pretreated orally with the vehicle andTJ-12 suspension (1 g/kg/d, p.o.) for 1 week. One-week repeated pretreatment with TJ- 12 (1 g/kg/d) did not influence liver weight, contents of cytochromes P450 and b5 in hepatic microsomes or the formation rate of CBZ-E from CBZ by its microsomes, while pretreatment with phenobarbital (80 mg/kg/d, i.p.) significantly increased these parameters. Neither a single nor 1-week repeated oral pretreatment with TJ-12 (1 g/kg/d) affected the plasma concentration-time profile and any pharmacokinetic parameter of CBZ or CBZ-E after oral administration of CBZ (50 mg/kg). These results indicated that oral co-administration of TJ-12 with CBZ has no effect ofthe pharmacokinetics of CBZ or CBZ-E in rats. Concomitant treatment with TJ- 12 and CBZ appears to be pharmacokinetically safe in humans.

The optimal stimulation site for chronic stimulation of the subthalamic nucleus in Parkinson's disease.

To determine the optimal stimulation site within the subthalamic nucleus (STN), monopolar stimulation of four electrode contacts and the resulting effects on parkinsonian symptoms were evaluated in 10 consecutive patients. The UPDRS score for rigidity and akinesia improved significantly after stimulation at each of the contacts, compared to the pre-evaluation state (Fisher's test, p < 0.05). The most significant improvement was obtained after stimulation at contact-2 (rigidity: 74.4 +/- 20.4%, akinesia: 53.7 +/- 14.3%) (Fisher's test, p < 0.001). Contact-2 was located at the dorsal border of the STN at a mean distance of 0.3 +/- 0.7 mm. DBS at the dorsal border of the STN, where the stimulation affects the neurons as well as their axonal fibers, produces the greatest clinical improvement in parkinsonian symptoms.

[Neurosurgical treatment for dopamine-induced dyskinesias in Parkinson's disease patients].

The effects of current neurosurgical interventions for levodopa-induced dyskiensias (DID) in Parkinson's disease are reviewed. Thalamotomy has been reported to be effective for DID when the lesions include Vo or CM-Pf nucleus, while thalamic deep brain stimulation(DBS) is less effective than thalamotomy. Both pallidotomy and pallidal DBS are probably the most effective neurosurgical treatment for DID, because they significantly improve all of the DID, including off-period dystonia, without reduction of levodopa dosage. Subthalamic DBS has no direct therapeutic effects on DID, but substantially can improve DID as a result of decreased levodopa dosage. The effects of cerebral transplantation on DID remain undefined. More researches are expected to clarify the pathophysiology of DID.

Adsorption and removal of oxo-anions of arsenic and selenium on the zirconium(IV) loaded polymer resin functionalized with diethylenetriamine-N,N,N',N'-polyacetic acid.

A polymer adsorbent in which a Zr(IV)-edta complex analogue is immobilized has been prepared and applied to the removal of oxo-anions of As(III), As(V) and Se(IV). Effective retention of these anions has been demonstrated with the proposed polymer complex system. The adsorption mechanism of oxo-anions onto the Zr(IV)-chelated polymer complex has been investigated using Zr(IV)-edta as the model compound. The formation of mixed complexes with oxo-anions has been exemplified by the isolation of the carbonato complex K2[Zr(CO3)edta].3H2O, the structure of which has been confirmed by X-ray crystallography. NMR study suggests that oxo-anions that form weak or moderate conjugate acids, including those of As(III), As(V) and Se(IV), can form mixed complexes with Zr(IV)-edta using the unsaturated coordination site. However, oxo-anions of strong conjugate acids did not show any appreciable interaction with this complex. According to these observations, retention of oxo-anions on the Zr(IV)-chelated polymer complex has been interpreted by a ligand substitution reaction. The adsorption characteristics of As(III), As(V) and Se(IV) on the Zr(IV)-loaded resin have been examined with respect to the equilibrium adsorption, percentage extraction and the effect of co-existing ions. The adsorption and desorption cycles of the oxo-anions have been demonstrated using a column packed with the proposed resin without any loss of column performance, which indicates the possibility for repeated use.

Induction of T lymphocyte apoptosis by treatment with glycyrrhizin.

The effect of glycyrrhizin (GL), a Chinese herbal drug extracted from licolice roots, on murine lymphocytes for inducing apoptotic cell death was studied. Addition of GL (25-400 micrograms/ml) to cultured splenocytes and thymocytes from BALB/c mice definitely promoted DNA fragmentation. A single injection of GL (100 micrograms/mouse) into BALB/c mice did not cause any detectable DNA fragmentation or cell death of splenocytes and thymocytes. Cytofluorometric analysis of these cells, however, demonstrated a reduction in mitochondrial transmembrane potentials (delta psi m). Repeated injections of GL (100 micrograms/mouse/day) into mice for 7 days actually resulted in induction of low grade DNA fragmentation selectively in splenocytes. Cell population analysis of viable lymphocytes suggested that both CD4+ Th lymphocytes and CD8+ Tc lymphocytes may have been relatively more sensitive than B220+ B lymphocytes for the apoptotic cell death. We concluded from these results that GL acts as a rather selective inducer of mature T lymphocyte apoptosis with a reduction in delta psi m potentially preceding lymphocyte death.

Membrane transport and antitumor activity of pirarubicin, and comparison with those of doxorubicin.

We have compared the membrane transport and antitumor activity of pirarubicin with those of doxorubicin in M5076 ovarian sarcoma, which exhibits low sensitivity to doxorubicin. Pirarubicin was rapidly taken up by M5076 cells and the intracellular concentration of pirarubicin reached more than 2.5-fold that of doxorubicin. In terms of the 50% cell growth-inhibitory concentration in vitro, pirarubicin was more effective than doxorubicin. Thus, the intracellular concentration influenced the cytotoxicity of these anthracycline agents. On comparison of the nuclear uptake of pirarubicin and doxorubicin, the nucleus/cell ratio of pirarubicin was found to be about 40%, whereas that of doxorubicin reached more than 80%. As the intranuclear concentration of pirarubicin is dependent on nuclear transport, the increases in not only cell membrane transport, but also nuclear membrane transport contributed to the enhancement of the efficacy of pirarubicin. In M5076 solid tumor-bearing mice, pirarubicin reduced the tumor weight to 60% of the control level, although doxorubicin had no effect. These results were supported by the intracellular uptake of pirarubicin. Moreover, theanine, which inhibited the pirarubicin efflux from M5076 cells, increased by 1.3-fold the pirarubicin concentration in the tumor and enhanced the therapeutic efficacy of pirarubicin 1.7-fold. In conclusion, our results suggest that an increase in the concentration of an anthracycline derivative in tumor cells due to alteration of cell membrane transport results in enhancement of the antitumor activity.

A newly developed assay for melatonin using cells expressing human mel-1a receptor.

We have developed a radioreceptor binding assay (RRA) method for melatonin using membranes from Chinese hamster ovary cells that can stably express human mel-1a receptors. We measured melatonin levels in plasma samples collected every 4h for 24h using the RRA and radioimmunoassay (RIA) methods, simultaneously. There was a statistically significant correlation between the melatonin levels measured by the two methods, this newly developed method providing a sensitive bioassay. As it is possible to circumvent the cross-reactivity usually occurring in the RIA method, this method may be an important tool for detecting bioactive substances relative to the mel-1a receptor.

[Prevalence rate of allergy to Japanese cedar pollen in Tokyo--from field investigation in 1996 by Tokyo Japanese Cedar Pollen Allergy Measurements and Review Committee].

Prevalence rate of allergy to Japanese cedar pollen was investigated by means of questionnaires and immunological examinations in residents of 3 regions in Tokyo (Akiruno city, Chofu city, and Ota ward). The results were as follows: 1) the prevalence rate of allergy to Japanese cedar pollen in Tokyo was 25.7% in Akiruno city, 21.1% in Chofu city, and 17.7% in Ota ward in 1996; 2) stratification by the age reveal that the prevalence rate was the highest in the age group of 30 to 44, and the group showed prevalence rate of above 40% in Akiruno city; 3) overall prevalence rate of Tokyo was 19.4% in 1996, which was approximately twice as much as that in 1985; 4) increase in prevalence rate in the recent decade was most significant in Akiruno city where the largest number of Japanese cedar pollen was detected in the air, and prevalence rate tended to rise in the young group of 14 or less.

Subthalamic nucleus stimulation for gait disturbance in Parkinson's disease.

OBJECTIVE: A preliminary study of subthalamic nucleus (STN) stimulation was performed to determine its applicability for the treatment of gait and postural disturbances in Parkinson's disease. METHODS: Five Parkinson's disease patients with freezing gait and postural instability were selected for this study. Their ages ranged from 60 to 73 years (mean+/-standard deviation, 65.6+/-4.8 years). Semi-microelectrode recording was used to identify the STN and to place a chronic electrical stimulation electrode within the right STN in all patients. The Unified Parkinson's Disease Rating Scale and the modified Hoehn and Yahr Staging Scale were used to assess patients in on- and off-drug conditions before surgery and 3 months after surgery. RESULTS: The scores on the Hoehn and Yahr Staging Scale and the total Unified Parkinson's Disease Rating Scale for akinesia (P < 0.05), gait (P < 0.05), and gait and posture (P < 0.01) in off-drug on-stimulation conditions significantly improved over the preoperative and postoperative off-drug off-stimulation conditions (analysis of variance [ANOVA], P < 0.01). Improvement over the preoperative scores was 24% on the Hoehn and Yahr Staging Scale, 43.6% on the total Unified Parkinson's Disease Rating Scale, 33.4% for akinesia, 36.6% for gait, and 38.7% for gait and posture. However, stimulation in the on-drug phase did not show a significant difference compared with pre- and postoperative conditions (ANOVA, P > 0.05). Comparisons between preoperative on-drug and postoperative off-drug on-stimulation conditions revealed that there were no significant differences in the scores, except for gait (ANOVA, P < 0.05). The scores on subscales for falling, freezing, walking, and gait in off-drug on-stimulation conditions were significantly improved over the scores for preoperative and postoperative off-stimulation (ANOVA, P < 0.05), but the score for postural stability remained unchanged. CONCLUSION: Our findings showed that STN stimulation effectively alleviates freezing gait and improves walking to its status during the preoperative on-drug phase and can be applied for treatment of Parkinson's disease patients with these symptoms.

Studies on interactions between traditional herbal and Western medicines. I. Effects of Sho-seiryu-to on the pharmacokinetics of carbamazepine in rats.

The effects of oral co- and pre-administration of Sho-seiryu-to extract powder (TJ-19, 1 g/kg), a widely used Kampo (traditional Chinese herbal) medicine, on the pharmacokinetics of an anti-epileptic drug, carbamazepine (CBZ), and its active metabolite (carbamazepine-10,11-epoxide, CBZ-E) after oral administration of CBZ (50 mg/kg) were examined in male rats. The simultaneous administration of TJ-19 significantly lengthened the time to reach the peak plasma concentration (Tmax), but did not influence the peak plasma concentration, area under the plasma concentration-time curve or terminal elimination half-life (t1/2). Each parameter for CBZ or CBZ-E with a single pretreatment with TJ-19 was not significantly different from that with the vehicle. Tmax and the elimination rate constant for CBZ were significantly increased by 1-week repeated pretreatment with TJ-19, by 83% (p<0.01) and 88% (p<0.001), respectively. t1/2 and the mean residence time from zero to infinity (MRT0-infinity) in the TJ-19 pretreatment group were significantly shortened, by 52 and 34% (p<0.005), respectively. No significant difference in the bound fraction of each drug at two concentrations (1 and 10 microg/ml) was observed between the control and TJ-19 pretreatment groups. These results indicate that simultaneous oral administration of TJ-19 delays the oral absorption of CBZ, while 1-week repeated pretreatment with TJ-19 accelerates the metabolism of CBZ in rats, without affecting the protein binding of CBZ.

A schwannoma of the cecum: case report and review of Japanese schwannomas in the large intestine.

A 66-year-old Japanese man had a positive fecal occult blood test at a regular check-up, and a large polypoid mass was detected in the cecum by barium enema study. Colonoscopy showed a submucosal tumor with ulcer protruding into the cecal lumen. A large-forceps biopsy specimen was taken from the bottom of the ulcer. With the tentative diagnosis of neurogenic tumor, ileocecal resection was performed. The tumor showed spindle-cell proliferation in a concentric or fascicular pattern. Immunohistochemically, the tumor cells were diffusely positive for S-100 protein, and they had intracytoplasmic periodic acid Schiff (PAS)-positive crystalloids. The mitosis count was low (about 1 per 20 high-power fields). The pathological diagnosis of this tumor was benign gastrointestinal schwannoma. A large number of schwannoma cases have been reported since 1910 when Verocay reported it as a true tumor that stemmed from Schwann cells and did not contain neuroganglion cells. However, gastrointestinal schwannomas are rare, and schwannomas of the large intestine are extremely rare. We reviewed 40 cases already reported in Japan and this present case in order to clarify the clinicopathological features of this tumor.

Neural activity of the subthalamic nucleus in Parkinson's disease patients.

The neural activity pattern of the subthalmic nucleus (STN) was investigated in five patients with Parkinson's disease who were scheduled for electrode implantation for chronic stimulation of the STN. The initial target was placed 8 mm or 10 mm lateral to the midline, 3 mm to 4 mm posterior to the midcommissural point, and 5 mm to 6 mm below the intercommissural (AC-PC) line. The STN was identified by semi-microelectrode recordings with a trajectory moving laterally in 2-mm steps. The amplitudes of multi-unit activities were relatively low at depths from 8 mm to 5 mm above and from 1 mm to 4 mm below the target, while those 4 mm to 0 mm above the target were significantly higher than at the other sites (ANOVA, Fisher's test, p < 0.05), with the highest amplitude at 2 mm above the target (91.0 +/- 23.3 mu v, n = 15). In the mediolateral direction, amplitudes were relatively higher in the lateral portion, and amplitudes at 14 mm lateral to the midline were significantly higher than at the other sites (ANOVA, Fisher's test, p < 0.05). The target for chronic electrical stimulation was determined to be at the midpoint of the hyperactive STN, i.e., 12 mm lateral to the midline in three patients and 13 mm lateral in two patients. Movement-related neural activity was observed at 5 sites, i.e., 3 sites responded to passive movement of the contralateral wrist and 2 sites to passive knee and/or ankle movement. In conclusion, our data show that the lateral part of the STN is hyperactive in PD, and recordings of neural activities contributed greatly to identifying the STN and determining the target for chronic stimulation within it.

Genetic variability of the common nod gene in soybean bradyrhizobia isolated in Thailand and Japan.

To determine the taxonomic relationship between Thai soybean bradyrhizobia and soybean bradyrhizobia from other regions, a total of 62 Bradyrhizobium strains were isolated in Thailand. The genetic diversity of the strains was examined with reference to 46 Japanese and 15 USDA strains. The degree of sequence divergence in and around common nod gene regions of the 123 strains was estimated by restriction fragment length polymorphism analysis using the Bradyrhizobium japonicum USDA 110 common nodDYABC gene probe. The phylogenetic grouping of the strains resulted in four major clusters. Cluster 1 comprised the Japanese and USDA strains, which originated in temperate regions, whereas clusters 3 and 4 comprised the tropical Thai strains. Cluster 1 strains comprised the DNA homology groups I and Ia, and hence, were classified as B. japonicum. Cluster 2 strains were in the DNA homology group II, and hence, were classified as Bradyrhizobium elkanii. Clusters 3 and 4 strains, however, did not correspond to any known DNA homology groups. These results indicate that Thai soybean bradyrhizobia are distantly related to B. japonicum and B. elkanii.

Recovery of gastrointestinal motility from post-operative ileus in dogs: effects of Leu13-motilin (KW-5139) and prostaglandin F2 alpha.

Cyclical motor activity of the gastrointestinal tract, normally occurring during the interdigestive period in several mammals, is disrupted in the post-operative ileus. We determined the recovery from the disappearance of cyclical motor activity, from the stomach to the colon, in dogs after laparotomy with the force transducers. Moreover, we examined the effects of Leu13-motilin (KW-5139) and prostaglandin F2 alpha (PGF2 alpha), administered in the early post-operative period, on the gastrointestinal motility. Following laparotomy, the cyclical motor activity reappeared firstly in the ileum and the colon, then in the jejunum and the duodenum, and finally in the stomach. The reappearance time of the phase III contractions in the stomach was 105.8 +/- 10.6 h (n = 4). In the early post-operative period, KW-5139 (0.5 microgram kg-1, i.v.) induced phase-III-like contractions, whereas PGF2 alpha (50 micrograms kg-1, i.v.) induced simultaneously occurring contractions over the whole gastrointestine. The treatment with KW-5139 (0.5 microgram kg-1, i.v.) four times (twice daily on the first and the second post-operative day) significantly (P < 0.05) shortened the time required to recover the phase III contractions in the stomach (64.2 +/- 2.2 h, n = 4), whereas that with PGF2 alpha (50 micrograms kg-1, i.v.) four times did not (111.3 +/- 17.2 h, n = 4). The present results indicate that, after laparotomy, the cyclical motor activity recovers faster in the distal intestine than in the proximal intestine and the stomach, and that KW-5139, but not PGF2 alpha, shortens the reappearance time of the phase III activity in the stomach.

[Mechanism of inhibition of aldosterone secretion by a Ca2+ channel blocker in patients with essential hypertension and patients with primary aldosteronism].

Three studies were conducted in order to investigate the suppressive effects of a calcium antagonist on aldosterone secretion and a possible mechanism. Study 1: A long-term (4 weeks) treatment with slow-release nifedipine (Nif), 40-60 mg/day, was performed in 9 in-patients with essential hypertension (EHT). Mean arterial pressure (MAP), plasma renin activity (PRA), plasma angiotensin II levels (pAII) and plasma aldosterone concentration (PAC) were determined before and after Nif treatment. Study 2: In another 7 in-patients with EHT, Nif treatment (40-60 mg, 7-10 days) was carried out to study its effect on aldosterone secretion in response to 2-hour ambulation, angiotensin II (AII) infusion (2.5 ng/kg/min, for 1-hour) and ACTH injection (2.5 mg i.v.). Study 3: The effects of Nif (40-60 mg/day, for 7-10 days) on MAP, PAC, serum potassium, potassium clearance (Ck) and changes in PAC or plasma cortisol levels in response to ACTH injection (2.5 mg i.v.) were studied in 6 in-patients with primary aldosteronism (PA). In patients with EHT, MAP was reduced significantly at 1 week and 4 weeks after the administration of Nif. PRA and pAII increased significantly, though the increase of PAC was not significant. In the low-renin EHT group, PAC was reduced significantly (Study 1). The increase of PAC in response to 2-hour ambulation or AII infusion was inhibited by Nif, but no inhibition of aldosterone response to ACTH was observed (Study 2). In patients with PA, Nif lowered MAP, PAC, and Ck, and elevated serum potassium concentration significantly. On the other hand, Nif had no effect on the aldosterone or cortisol response to ACTH (Study 3). These results indicated that the hypotensive effect of Nif is due in part to the inhibition of aldosterone secretion from the adrenal gland both in patients with EHT and in those with PA. Regarding the mechanism of the inhibition of aldosterone secretion by Nif, these data suggest that in patients with EHT, inhibition of the aldosterone response to AII is the most important factor, although it was not clear from this study whether Nif inhibits the potassium-induced aldosterone release or not. In patients with PA, ACTH-induced aldosterone secretion was not inhibited by Nif and the reduction of PAC is not likely via inhibition of AII action since the renin-angiotensin system is markedly suppressed. Reduced cytosolic calcium concentration in the adenomatous tissue by Nif may have something to do with the lowered aldosterone synthesis in PA.