Review: drug therapy in Chinese traditional medicine

This article addresses the differences between the basic concepts of drug therapy in Chinese traditional medicine (CTM) and modern Western medicine. In ancient times, throughout the world, humans used plants as food and medicine. In Europe, chemistry developed rapidly after the influence of Paracelsus. Active principles were isolated from plants, and drugs were prepared in the salt form to use as medication. In China, several drugs isolated from plants have been prepared in the salt form in recent years, but herbal medication, developed in the ancient tradition, continued to be widely used in Chinese populations. Some theories such as the yin-yang theory and the five-element theory were commonly employed to explain the rationale for the use of CTM. In this review, hypertension and diabetes mellitus are used as examples to illustrate the applications of CTM. The notions of the "whole" and the use of "relative" rather than absolute are important concepts, which distinguish CTM from modern medicine.

The change of beta-adrenergic system in lead-induced hypertension

Lead exposure is considered to be a risk factor of cardiovascular disease. To investigate the relationship between lead and cardiovascular disease/hypertension in lead exposure, beta-adrenergic system is explored in this study. We address three topics in this study: (a) the relationship between beta-adrenergic receptor and lead level in heart, aorta, and kidney of lead-exposed rats; (b) the relationship between beta-adrenergic receptor in heart, aorta, kidney, and blood pressure in lead-exposed rats; and (c) the change of cyclic AMP level in heart, aorta, and kidney of rats with different lead levels. Wistar rats were chronically fed with 2, 1, 0. 5, 0.1, 0.05, and 0.01% lead acetate and water for 2 months. Plasma catecholamine level was measured by high-performance liquid chromatography. Radioligand binding assay was measured by a method that fulfilled strict criteria of beta-adrenoceptor using the ligand [(125)I]iodocyanopindolol. Cyclic AMP (cAMP) level was determined by radioimmunoassay. The levels of lead were determined by electrothermal atomic absorption spectrometry. The results showed that increased plasma norepinephrine level, decreased aorta beta-adrenergic receptor and cAMP, and increased kidney beta-adrenergic receptor and cAMP contributed to the elevation of blood pressure in lead-induced hypertension. The decrement of beta-adrenoceptor and cAMP in heart resulted in decreased contractility in heart.

Decrease of adenosine A-1 receptor gene expression in cerebral cortex of aged rats

Changes of adenosine A-1 receptor (A1-AR) gene expression in aging were investigated in cerebral cortex using the rat aged from 2 months (adult) to 24 months (aged). Quantification of A1-AR protein level by immunoblotting analysis showed an age-related decrease of A1-AR in cerebral cortex of Wistar rats. Compared to the preparations from 2-month-old animals, the levels of A1-AR in the 6-, 12-, and 24-month-old rats were reduced by 14.3+/-5.2, 32.5+/-4.5 and 28.2+/-5.7%, respectively. Similar decrease of mRNA level in A1-AR was also obtained using Northern blotting analysis. Two representative spots of mRNA, a 3.4-kb transcript and a 5.6-kb transcript, were observed in X-ray film from cerebral cortex of rat hybridized with rat A1-AR cDNA probe. Compared to the 2 month-old rats, levels of the 5.6-kb transcript were decreased by 17.9+/-2.5, 27.4+/-3.2 and 23.1+/-2.1% in the 6-, 12- and 24-month-old rats, respectively. These results indicated an age-related decrease of A1-AR in cerebral cortex of the rat that seems responsible for the change of response to adenosine.

Less of insulin desensitization in sympathetic nerve terminals from wistar rats with insulin resistance

In an attempt to determine the effect of hyperinsulinemia on sympathetic function, release of norepinephrine (NE) from isolated aorta by insulin was measured in Wistar rats with insulin resistance. Insulin resistance was produced when the hypoglycemic action of glibenclamide at a dose of 10 mg/kg was almost abolished in rats that received daily injections of long-acting insulin for 15 days. Moreover, the stimulatory effect of insulin on glucose uptake was markedly reduced in both skeletal muscle strips and white adipocytes obtained from these rats with insulin resistance. However, the stimulatory effects of insulin at concentrations from 5 to 15 U/l on the release of NE from the aortic strip of insulin-resistant rats were not modified in the same manner but only slightly reduced compared with that of normal rats. These results suggest that insulin desensitization was produced later in sympathetic nerve terminals than in other organs in insulin-resistant rats and this may be helpful to explain the sympathetic hyperactivity associated with diabetes in clinics.

Differentiation status modulates transcription factor NF-kappaB activity in unstimulated human hepatocellular carcinoma cell lines

We report herein a novel finding that under an unstimulated condition, a group of four human hepatocellular carcinoma (HCC) cell lines with varying degrees of differentiation, can spontaneously activate NF-KB. The propensity of activation coincided inversely with the differentiation status, with order being SK-Hep-1 > J5 > Hep3B > HepG2. Further studies indicate that this pattern of activation correlates excellently with the descending order of intracellular GSH/GSSG ratios as well as with the ascending order in the ability of these cells to generate hydrogen peroxide. Taken together, our data suggest that differentiation status may play a pivotal role in modulating intracellular thiol redox status and the extent of catalase expression, which may be crucial in the control of NF-kappaB activity in these HCC cells.

Caffeic acid as active principle from the fruit of Xanthium strumarium to lower plasma glucose in diabetic rats

The antihyperglycemic effect of caffeic acid, one of the phenolic compounds contained in the fruit of Xanthium strumarium, was investigated. After an intravenous injection of caffeic acid into diabetic rats of both streptozotocin-induced and insulin-resistant models, a dose-dependent decrease of plasma glucose was observed. However, a similar effect was not produced in normal rats. An insulin-independent action of caffeic acid can thus be considered. Otherwise, this compound reduced the elevation of plasma glucose level in insulin-resistant rats receiving a glucose challenge test. Also, glucose uptake into the isolated adipocytes was raised by caffeic acid in a concentration-dependent manner. Increase of glucose utilization by caffeic acid seems to be responsible for the lowering of plasma glucose.

Stimulatory effect of trans-cinnamaldehyde on noradrenaline secretion in guinea-pig ileum myenteric nerve terminals

The effect of trans-cinnamaldehyde (CNMA) on the release of noradrenaline (NA) from nerve terminal was investigated using isolated ileal synaptosomes of guinea-pig. Release was determined as the amount of NA, quantified by h.p.l.c.-electrochemical detection, from samples incubated with CNMA minus that in parallel blanks treated with same volume of vehicle. CNMA stimulated the secretion of NA in a concentration-dependent manner from 5 microM to 50 microM, while the value of lactate dehydrogenase in the incubated medium was not influenced by CNMA. However, trans-cinnamic acid, cinnamoyl chloride and cinnamamide failed to produce similar effect. Specific action of CNMA can thus be considered. Guanethidine inhibited the release of NA by CNMA in a concentration- dependent manner. Saxitoxin attenuated the action of CNMA at concentrations sufficient to block sodium channels. The depolarizing effect of CNMA on the membrane potential was also illustrated by a concentration-dependent increase in the fluorescence of bisoxonol, a potential sensitive dye. The NA releasing action of CNMA was deleted by removal of calcium chloride from the bathing medium. This action of CNMA was also attenuated by Rp-cAMP at concentrations sufficient to inhibit the action of cyclic AMP. These findings suggest that CNMA can depolarize the membrane to result in a calcium-dependent and cyclic AMP-related release of NA from noradrenergic terminals.

Role of adenosine in insulin-stimulated release of leptin from isolated white adipocytes of Wistar rats

Leptin, the ob gene product that can decrease caloric intake and increase energy expenditure, is functionally released by insulin from adipose tissue. Adenosine is thought to be an important regulator of the action of insulin in adipose tissue. The present study investigated the role of adenosine in the release of leptin by insulin in isolated rat white adipocytes. Release of leptin, measured by radioimmunoassay, from insulin-stimulated samples was seen after 30 min. Adenosine deaminase, at concentrations sufficient to metabolize endogenous adenosine, decreased insulin-stimulated leptin release. Also, the insulin-stimulated leptin release was completely blocked by the adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX). Mediation of endogenous adenosine in this action of insulin was further supported by the assay of adenosine released into the medium from adipocytes stimulated with insulin. In addition, activation of adenosine A1 receptors by N6-cyclopentyladenosine (CPA) induced an increase in leptin release in a concentration-dependent manner that could be blocked by antagonists, either DPCPX or 8-(p-sulfophenyl)theophylline (8-SPT). In the presence of U73312, a specific inhibitor of phospholipase C (PLC), CPA-stimulated leptin secretion from adipocytes was reduced in a concentration-dependent manner, but it was not affected by U73343, the negative control for U73312. Moreover, chelerythrine and GF 109203X diminished the CPA-stimulated leptin secretion at concentrations sufficient to inhibit protein kinase C (PKC). These results suggest that, in isolated white adipocytes, the released adenosine acts as a helper and/or a positive regulator for insulin in the release of leptin via an activation of adenosine A1 receptors that involves the PLC-PKC pathway.

Alterations in urinary bladder M2-muscarinic receptor protein and mRNA in 2-week streptozotocin-induced diabetic rats

The M2 receptor (M2-mAChR) is quantitatively the dominant muscarinic subtype in animal bladders. The alterations in its protein quantity and biosynthesis during diabetic cystopathy were investigated. Three-month-old male Wistar rats were divided into two groups: (1) 2-week-old diabetics; and (2) normoglycemic control rats. Diabetes was induced by single intravenous injection of 60 mg/kg streptozotocin. The amount of M2 receptor protein in the rat bladder body tissue was measured by Western immunoblotting using monoclonal antibodies. For determination of M2 muscarinic receptor mRNA in the bladder tissue, the method of Northern blotting was employed. The results of the Western immunoblotting showed that the amount of M2-mAChR protein in the diabetic bladder was significantly increased by 40.0 +/- 6.2% when compared with the control bladder (P < 0.05, n = 8). The Northern blotting demonstrated a 69.3 +/- 8.5% increase of the M2-mAChR mRNA in the diabetic bladder (P < 0.05, n = 8). The findings of the present study demonstrated an up-regulation of M2-mAChR biosynthesis in the diabetic urinary bladder. This phenomenon could lead to increased reactivity to acetylcholine and thus results in detrusor instability.

Superoxide dismutase gene expression and activity in the brain of spontaneously hypertensive rats and normotensive rats

OBJECTIVE

To determine if changes in superoxide dismutase (SOD) in the brain occur in the hypertensive state.

METHODS

We compared the levels of the two main subtypes of this enzyme in spontaneously hypertensive rats (SHR) with age-matched normotensive Wistar Kyoto (WKY) rats using enzyme activity estimation, Western blotting for enzyme contents, and Northern blotting of mRNA level. Five discrete brain regions, cerebrocortex, hypothalamus, hippocampus, the remaining non-cortex cerebrum (NCC area), and cerebellum, were employed for comparison in 30-31 weeks old rats.

RESULTS

A lower level of both Mn-SOD activity and Mn-SOD mRNA expression was found in all areas of the brain of SHR as compared with WKY rats. Also, the mRNA levels of Cu, Zn-SOD in the brain of SHR differed from WKY rats in parallel to the enzyme activities. The activity and mRNA expression of Cu, Zn-SOD were lower in the hypothalamus and cerebellum of SHR but the mRNA level and the activity in hippocampus were significantly higher in the SHR compared to WKY rats. No differences for Cu, Zn-SOD were observed in cerebrocortex or NCC area in the two species. However, the amount of SOD enzyme subtypes, determined by Western blotting analysis, was not different between SHR and WKY rats.

CONCLUSIONS

The results indicate a lower gene expression and less activity of Mn-SOD in SHR brain. This alternation of SOD may be one of the important factors for the vulnerability of the brain from oxygen free radicals or may be related to the pathogenesis of hypertension in this species.

Effects of a nitric oxide scavenger, carboxy-PTIO, on isoflurane MAC and cerebellar nitric oxide synthase activity in rats

Recent studies have indicated that nitric oxide may play a role in inhalation anaesthesia. Inhibition of nitric oxide synthase reduces the minimum alveolar concentration (MAC) for inhalation anaesthetics and decreases cerebellar nitric oxide synthase (NOS) activity in rats. In this study, we have explored further the role of nitric oxide in isoflurane anaesthesia by examining the effects of a nitric oxide scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy-PTIO 0.075-0.6 mg kg-1) on MAC values and cerebellar NOS activity in rats. Bolus injection of carboxy-PTIO at doses greater than 0.15 mg kg-1 reduced the MAC value of isoflurane (mean 1.36 (SEM 0.07)% at 0.15 mg kg-1, 1.39 (0.14)% at 0.3 mg kg-1 and 1.31 (0.06)% at 0.6 mg kg-1 vs control value of 1.61 (0.19)%. Administration of carboxy-PTIO 0.125 and 0.15 mg kg-1 resulted in increased cerebellar NOS activity during isoflurane anaesthesia (P < 0.05). These findings suggest that the level of nitric oxide may set a baseline from which isoflurane then acts.

The antihypertensive effect of the berberine derivative 6-protoberberine in spontaneously hypertensive rats

Berberine is a natural isoquinoline alkaloid found in plants of the Ranunculaceae and Berberidaceae families. Extracts from berberine-containing plants have been used as traditional Chinese folk remedies for centuries. The antihypertensive effects of the berberine derivative 6-protoberberine (PTB-6) were studied in spontaneously hypertensive rats (SHRs). In conscious SHRs, PTB-6 lowered the systolic blood pressure in a dose-dependent manner (6-PTB: 5 mg/kg, -31.1 +/- 1.6 mm Hg; 10 mg/kg, -42.4 +/- 3.1 mm Hg). Cardiac output using the thermodilution method was reduced in PTB-6-treated anesthetized SHRs with a tendency to decrease in heart rate. Injection of PTB-6 into the intracerebral ventricles of SHRs lowered the systolic arterial blood pressure and heart rate. The berberine derivative PTB-6 is an effective antihypertensive agent. The mechanism of the antihypertensive effect of PTB-6 is probably through a central sympatholytic effect.

Isoferulic acid as active principle from the rhizoma of Cimicifuga dahurica to lower plasma glucose in diabetic rats

Isoferulic acid extracted from the rhizome of Cimicifuga dahurica Maxim. (Ranunculaceae) has been determined to have in vivo antihyperglycemic activity. An antihyperglycemic action of isoferulic acid in spontaneously diabetic rats, similar to type I diabetes, is presented.

Changes of superoxide dismutase gene expression and activity in the brain of streptozotocin-induced diabetic rats

In an attempt to discover the changes of superoxide dismutase (SOD) in the brain of diabetic state, we investigated the level of SOD in streptozotocin-induced diabetic rats (STZ-diabetic rats) using enzyme activity assay, Northern blotting analysis of mRNA levels and Western blotting of enzyme amount. Five discrete brain regions, cerebrocortex, hypothalamus, hippocampus, the remaining non-cortex cerebrum (NCC area) and cerebellum, were examined in STZ-diabetic rats to compare with age-matched normal rats. Higher levels of Mn-SOD including the activity, mRNA expression and immunoblot of enzyme were found in all areas of the brain from STZ-diabetic rats as compared with that in Wistar rats. Except in the cerebellum, similar changes of Cu,Zn-SOD were found in the brain of STZ-diabetic rats. These results indicate an increase of SOD both gene expression and activity in the brain of STZ-diabetic rats. This alteration of SOD may be one of the important factors for the vulnerability of the brain to oxygen free radicals or may be related to the pathophysiology of diabetes.

Paeoniflorin reverses guanethidine-induced hypotension via activation of central adenosine A1 receptors in Wistar rats

1. Intravenous injection of paeoniflorin, a glycoside purified from the root of Paeonia lactiflora, reversed guanethidine-induced hypotension in Wistar rats. 2. Pretreatment with the adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine inhibited this effect of paeoniflorin in a dose-dependent manner. 3. The action of paeoniflorin was not modified by 8-(p-sulfophenyl)theophylline, the polar antagonist of the adenosine A1 receptor, which is not able to enter the central nervous system. 4. We conclude that paeoniflorin can reverse guanethidine-induced hypotension via activation of adenosine A1 receptors in the brain of Wistar rats.

Decrease of nitric oxide synthase in the cerebrocortex of streptozotocin-induced diabetic rats

In an attempt to know the role of nitric oxide in the disease of insulin-dependent diabetic mellitus (IDDM), the present study examined the change of nitric oxide synthase (NOS) both the activity and gene expression in cerebrocortex of streptozotocin-induced diabetic rats (STZ-diabetic rats). The activity of NOS determined by conversion of [3H] L-arginine to [3H] L-citrulline was markedly decreased in STZ-diabetic rats. Northern blot showed that STZ-diabetic rats expressed a lower mRNA level of neuronal NOS (nNOS). Western blot showed a similar decrease of nNOS in STZ-diabetic rats. However, the NOS activity was increased in rats receiving repeated supply of glucose named glucose-challenged rats. Although the mRNA level of nNOS was not changed in the glucose-challenged rats, the immunoblot of nNOS was also decreased in glucose-challenged rats. These findings suggested that NOS was lowered in the brain of STZ-diabetic rats in a way unrelated to the increase of glucose.

An in vivo evaluation of the therapeutic potential of sympatholytic agents on premature ejaculation

OBJECTIVE

To evaluate the therapeutic potential of sympatholytic agents on premature ejaculation in an animal model, using monitoring of rat seminal vesicle pressure change in response to electrical stimulation of the lesser splanchnic nerve.

MATERIALS AND METHODS

Male Wistar rats (aged 12-14 weeks) were injected intra-arterially with sympatholytic agents (phenoxybenzamine, prazosin, WB-4101, chloroethylclomidine, yohimbine and RX 821002) at various concentrations 10 min before electrical stimulation of the lesser splanchnic nerve. The change in phasic tension (triangle upmmHg) of the seminal vesicle induced by electrical nerve stimulation before and after the addition of sympatholytic agents was used for statistical analysis. The maximum inhibition and the concentration required to induce 50% inhibition of the maximal contractile response (IC50) were obtained from the concentration-response curves, and used to determine the potency of test agents.

RESULTS

The seminal vesicle contractile response to electrical nerve stimulation was suppressed in a dose-dependent manner by all test drugs except RX 821002. The mean (sd) maximal inhibition was 78.4 (9. 3)% by 0.03 mg/kg of phenoxybenzamine, 77.1 (10.1)% by 0.03 mg/kg of WB-4101, 73.4 (6.0)% by 0.1 mg/kg of yohimbine, 67.9 (9.7)% by 0.1 mg/kg of prazosin, 75.5 (7.5)% by 3 mg/kg of chloroethylclomidine and 25.3 (4.8)% by 0.01 mg/kg of RX 821002. The potencies of WB-4101 (IC50 3 microgram/kg) and yohimbine (IC50 0.8 microgram/kg) were similar to that of phenoxybenzamine (IC50 0.5 microgram/kg) and much higher than that of prazosin (IC50 0.03 mg/kg) or chloroethylclomidine (IC50 0.3 mg/kg).

CONCLUSIONS

Phenoxybenzamine, prazosin, WB-4101, chloroethylclomidine and yohimbine all inhibit the contractile response of the rat seminal vesicle to electrical nerve stimulation. As phenoxybenzamine is effective in treating premature ejaculation, the comparable in vivo potencies of WB-4101 and yohimbine strongly suggest that they have clinical therapeutic potential.

Investigations of the mechanism of the reduction of plasma glucose by cold-stress in streptozotocin-induced diabetic rats

Exposure to a cold environment may increase the activity of the sympathetic nervous system inducing an elevation of plasma norepinephrine and may result in hyperglycemia. In the present study, we found that a hypoglycemic effect was produced in streptozotocin-induced diabetic rats after cold-exposure at 4 degrees C for 1 h. In addition to the blockade of this hypoglycemic effect by guanethidine (a ganglion-blocking agent) and prazosin (an alpha1-adrenoceptor antagonist), an increase of plasma norepinephrine was also observed in streptozotocin-induced diabetic rats receiving this cold-stress. Participation of sympathetic hyperactivity can thus be considered. Furthermore, naloxone, in a dose (0.5 mg/kg, i.p.) sufficient to block opioid receptors, reversed this hypoglycemia. Also, an increase of plasma beta-endorphin-like immunoreactivity was observed in streptozotocin-induced diabetic rats receiving this cold-stress. Intravenous injection of beta-endorphin into streptozotocin-induced diabetic rats produced a lowering of plasma glucose. Administration of methoxamine at a dose sufficient to activate the alpha1-adrenoceptors produced hypoglycemia and a similar increase of plasma beta-endorphin-like immunoreactivity in streptozotocin-induced diabetic rats. However, plasma beta-endorphin-like immunoreactivity level was not modified by similar treatment with methoxamine or cold-stress in normoglycemic rats. Therefore, beta-endorphin appears to be responsible for the induction of hypoglycemic effects in streptozotocin-induced diabetic rats after cold exposure which is different to the response in normal rats.

Effect of trilinolein on the activity and gene expression of superoxide dismutase in cultured rat brain astrocytes

Cerebrovascular disease is one of the major causes of morbidity and mortality in recent. Oxygen free radicals produced during cerebral infarction increases the damage to neurons. Superoxide dismutase (SOD) is the endogenous antioxidant enzyme that can effectively scavenge superoxide radicals. Trilinolein is a lipophilic antioxidant purified from the herb of Panax pseudoginseng. In the cultured rat brain astrocytes (RBA), the activity of SOD (both Cu,Zn-SOD and Mn-SOD subtypes) was markedly increased by incubation with trilinolein at low concentration (0.1 microM) for 2 days. This stimulatory effect of trilinolein was not related to the incubating concentration. However, long-term (7 days) incubation with trilinolein at same concentration decreased the activity. Similar changes were also observed in the gene expression of SOD in RBA; short-term (2 days) incubation of RBA by 0.1 microM trilinolein increased the mRNA level that was lowered in RBA received a long-term incubation with 0.1 microM trilinolein. This result shows that trilinolein is an effective antioxidant to increase the activity of SOD in RBA which would be beneficial to neurons subjected to oxygen free radical damage. However, long-term medication of antioxidant shall be concerned.

Hepatitis C virus-associated glomerular disease in patients with human immunodeficiency virus coinfection

Chronic infection with hepatitis C virus (HCV) has been linked to the development of glomerular disease. HCV infection is highly prevalent among intravenous drug users, a population that is also at risk for HIV coinfection. This study reports the clinical-pathologic features and outcome of HCV-associated glomerular disease (HCV-GD) in 14 patients with HIV coinfection. All were intravenous drug users and all but one were African-Americans. Renal presentations included renal insufficiency, microscopic hematuria with active urine sediment, hypertension, and nephrotic syndrome or nephrotic-range proteinuria without hypercholesterolemia. Hypocomplementemia and cryoglobulinemia were present in 46 and 33% of patients, respectively. The predominant renal biopsy findings were membranoproliferative glomerulonephritis type 1 or type 3 (Burkholder subtype) in 79% of patients and membranous glomerulopathy with atypical features in 21% (including overlap with collapsing glomerulopathy in one patient). The clinical course was characterized by rapid progression to renal failure requiring dialysis. The overall morbidity and mortality were high with median time of 5.8 mo to dialysis or death. Although most patients died in renal failure, cause of death was primarily attributable to long-term immunosuppression and advanced AIDS. Patients with AIDS had shorter survival than those without (median survival time of 6.1 mo versus 45.9 mo, log-rank test P = 0.02). Only two patients were alive with stable renal function at follow-up of 28.5 mo. In patients with HCV-GD, coinfection with HIV leads to an aggressive form of renal disease that can be easily confused with HIV-associated nephropathy. Although hypocomplementemia, cryoglobulinemia, and more prominent hypertension and microscopic hematuria may provide clues to the presence of HCV-GD, renal biopsy is essential to differentiate HCV-GD from HIV-associated nephropathy.

Nicotine-induced hyperlocomotion is not modified by the estrous cycle, ovariectomy and estradiol replacement at physiological level

The present study was designed to investigate whether nicotine's effect on locomotion might be modulated by the ovarian hormone at physiological level. Rats at normal cycling of estrus and diestrus were selected for the comparison of nicotine-induced hyperlocomotion based on the document that the release of striatal dopamine was greatest at the estrous phase. Ovariectomized rats primed with or without estrogen at physiological level were also selected for comparison. Increase in spontaneous locomotion by nicotine was statistically significant at the doses of 0.15 and 0.3 mg/kg (p < 0.001). The stimulating effect of nicotine led the locomotor response to almost the same magnitude in all hormonal groups studied. Nicotine-induced hyperlocomotion appeared to be mediated by central nicotinic receptor because it was blocked by mecamylamine (0.5 and 1.0 mg/kg, i.p.). Also it was blocked by haloperidol (0.04 and 0.08 mg/kg, i.p.) indicating the involvement of dopaminergic neurotransmission. These effects were similar in all groups regardless of the estrous cycle or ovariectomy. The observed data provided behavioral evidence to suggest that the effect of nicotine on locomotion-related dopaminergic neurons might not be modified by the physiological action of estrogen.

Calcium influx inhibition: possible mechanism of the negative effect of tetrahydropalmatine on left ventricular pressure in isolated rat heart

The active ingredient dl-tetrahydropalmatine (THP) isolated from the traditional Chinese herb Corydalis racemosa has been found to have antihypertensive effects. However, severe cardiac and neurological toxic effects were reported from using this herb for the treatment of pain. In an isolated perfused rat heart model, THP at the concentration of 100 microM was found to have a negative effect (-45%) on left ventricular pressure and this effect was produced concentration-dependently from concentrations lower than 50 microM. In isolated cardiomyocytes, radioactive calcium influx was also inhibited significantly by THP at the concentration of 100 microM and this effect was also in a concentration-dependent manner (-39%). In a patient with latent heart disease, the use of Corydalis should probably be detrimental, the toxic effect was probably due to calcium influx inhibition.

Activation of opioid mu-receptor by loperamide to lower plasma glucose in streptozotocin-induced diabetic rats

We investigated the effect of loperamide, a selective agonist of opioid mu-receptor, on the plasma glucose in diabetic rats induced by an intravenous injection of streptozotocin (STZ; 60 mg/kg). Intravenous injection of loperamide induced a dose-dependent decrease of plasma glucose in fasting STZ-diabetic rats at 30 min later, but did not modify the plasma glucose level in Wistar rats. Plasma glucose lowering effect of loperamide was abolished by the pretreatment with naloxone or naloxonazine at the dose sufficient to block opioid mu-receptor. In isolated skeletal muscle, loperamide enhanced the glucose uptake into soleus muscles in a concentration-dependent manner. Blockade of this action by naloxonazine indicated the mediation of opioid mu-receptor. These results suggest that an activation of opioid mu-receptor by loperamide can increase the utilization of glucose in peripheral tissue to lower the plasma glucose in STZ-diabetic rats.

Effects of losartan on the sexual behavior of male rats

Many commonly used antihypertensive drugs such as diuretics and beta-blockers can interfere with sexual function in both sexes, causing loss of libido, impairment of erectile function and ejaculation in men, and delay or prevent orgasm in women. Newly developed antihypertensive drugs should ideally not interfere with the patients' quality of life including sexual function. This study examined the effects of losartan, a nonpeptide, specific antagonist for type I angiotensin II receptors, on the male sexual behavior of rats. Spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto (WKY) rats were treated with losartan 30 mg/ kg/day or saline control for 7, 30 and 90 days. Dark-cycle video recording was used to analyze the male sexual activities of the rats. No significant alteration in male sexual performance was observed after 7 and 30 days of treatment with losartan. In contrast, SHRs treated with propranolol 5 mg/kg/day showed increases in intromission latency, ejaculation latency and postejaculatory period indicating decreased libido and erectile and ejaculatory function. Upon completion of 90 days of losartan administration, the mount latency of the SHR was significantly increased, suggesting a decrease in libido although other parameters were unchanged and there was no effect in WKY rats. It is therefore concluded that losartan may have an advantage in preservation of sexual function when used clinically for the treatment of hypertensive disorders.

Effect of serum in medium on the expression of inducible nitric oxide synthase and superoxide dismutases in cultured C6 glioma cells

It has been documented that C6 glioma cells can be changed into normal glial cells when they were cultured in serum free medium. In the present study, the expressions of inducible nitric oxide synthase (iNOS) and superoxide dismutase (SOD) were investigated. The mRNA level of iNOS was markedly increased by lipopolysaccharide (LPS) in cultured rat brain astrocytes (RBA-1) but not in C6 glioma cells. However, increase of mRNA for iNOS by LPS can be obtained in C6 glioma cells when they were cultured in serum free medium. The mRNA level of magnesium-SOD (Mn-SOD) was increased by LPS in both cells while the expression of constituted SOD (Cu,Zn-SOD) was not stimulated by LPS. Western blotting analysis indicating the amount of protein showed a similar change. After serum deprivation, the protein of iNOS or Mn-SOD was increased by LPS in C6 glioma cells in a way similar as that in RBA-1 cells. These results suggest that serum free conditioned C6 glioma cells were adapted to astroglial cell-like properties which may express more iNOS and Mn-SOD mRNA in the presence of LPS.