The role of free radicals in the release of noradrenaline from myenteric nerve terminals of guinea-pig ileum

In an attempt to understand the role of free radicals in the regulation of sympathetic neurotransmission, the in vitro secretion of noradrenaline (NA) from synaptosomal preparations of guinea-pig ileum was investigated. Release of endogenous NA was quantified by an electrochemical detection (HPLC-ECD). In the presence of superoxide dismutase (SOD) and catalase at concentrations sufficient to scavenge the free radicals, secretion of NA was attenuated in samples with stimulation of 4-aminopyrine (4-AP) or not (spontaneous release). However, inducing superoxide radicals via the reaction of hypoxanthine with xanthine oxidase failed to modify the secretion of NA, both the 4-AP-stimulated release and the spontaneous secretion. Then, free radicals were induced in synaptosomes using hypoxia-normoxia exposure. Secretion of NA was markedly increased in samples receiving this treatment in a calcium-dependent way because it was attenuated by the removal of calcium chloride from bathing medium. An increase of SOD activity, both Mn-SOD and Cu, Zn-SOD, was also obtained by this exposure. Changes of SOD activities in response to free radicals produced by hypoxia-normoxia exposure in ileal synaptosomes can thus be considered. In conclusion, these results suggest that free radicals are formed to involve in the regulation of sympathetic neurotransmission via an increase of calcium influx to enhance the NA release in guinea-pig ileum.

The role of nitric oxide in the control of plasma glucose concentration in spontaneously hypertensive rats

Glucose homeostasis was studied in the spontaneously hypertensive rat (SHR). The fasting plasma glucose levels were similar in the SHR and normotensive Wistar-Kyoto (WKY) rat (102.7+/-2.4 vs. 107.4+/-4.2 mg/dl, P > 0.01). One hour after glucose challenge, the plasma glucose level was slightly but insignificantly increased in both SHR and WKY rat (117+/-2.5 vs. 114.3+/-3.2 mg/dl, P > 0.01). After N(G)nitro-L-arginine methyl ester (L-NAME) 20 mg/kg per day was administered intraperitoneally (i.p.) for 4 days, the plasma glucose level was significantly increased in the rats (SHR 167.3+/-4.9; WKY rat 136.0+/-4.8 mg/dl); the increase was significantly more pronounced in the SHR. The fasting insulin levels were similar in the SHR and WKY rats (2.3+/-0.4 vs. 2.0+/-0.3 ng/ml, P > 0.01). One hour after glucose challenge, the insulin level was significantly increased in the WKY rat (4.8+/-0.7 ng/ml) but not in the SHR (2.2+/-0.4 ng/ml). With L-NAME treatment, plasma insulin increase was noted in the WKY rat but not SHR (4.6+/-0.6 vs. 2.6+/-0.4 ng/ml, n = 8, P < 0.01). One hour after insulin 1 IU/kg was injected intramuscularly (i.m.), the plasma glucose level was significantly decreased in both the SHR (from 115.0+/-6.5 to 48.6+/-3.6 mg/dl, n = 8) and WKY rat (from 108.3+/-3.8 to 52.6+/-4.2 mg/dl, n = 8). No significant difference was noted between the decrease of the two groups (P > 0.01). The present findings suggested that NO plays a role in the glucose homeostasis of rats. NO-synthase blockade resulted in an increase of plasma glucose level. The SHR maintains normal glucose level and tolerance in spite of a defective insulin release response. This is probably due the compensatory effect of a more prominent NO-dependent glucose homeostatic function.

NitroG-L-arginine methyl ester reduces the minimal alveolar concentration of isoflurane in rabbits

BACKGROUND

Recently, some studies suggested that nitric oxide (NO) plays a role as a mediator in the central nociceptive pathways and is possibly involved the mechanisms of anesthesia and wakefulness. Inhibition of the L-arginine-NO pathway in the central nervous system may result in an anesthetic, analgesic, or sedative effect. The aim of the present study was to evaluate the effects of the nitric oxide synthase inhibitor (NOSI), nitroG-L-arginine methyl ester (L-NAME), on the threshold for isoflurane anesthesia in rabbits.

METHODS

Sixteen New Zealand rabbits were randomly divided into two groups, with eight rabbits in each group. In the study group, a dose of L-NAME 30 mg/kg was injected i.v. daily as pretreatment on three consecutive days, and the fourth dose of L-NAME was given 30 min before the study began. Normal saline was given to the control group. Data of minimal alveolar concentration (MAC), blood pressure (BP), and heart rate (HR) were collected from both groups. Vital signs, such as EtCO2, O2 saturation, and temperature, were maintained within the normal range. All data were described as mean +/- SEM. Statistical analysis was performed using Student's t-test, where p < 0.05 was considered significant.

RESULTS

MAC of isoflurane in the control group was 1.90 +/- 0.12%. MAC of the L-NAME group was 1.70 +/- 0.22%, significantly lower than the control group (p < 0.05).

CONCLUSIONS

Our preliminary result shows that the MAC of isoflurane in animals treated with L-NAME was lower than that in the control group. It is suggested that inhibition of the nitric oxide pathway may enhance the effect of isoflurane.

Changes of superoxide dismutase (SOD) mRNA and activity in response to hypoxic stress in cultured Wistar rat glioma cells

In an attempt to understand the change of superoxide dismutase (SOD) in tumor cells by hypoxia and hypoxia-normoxia exposure, the present study performed an in vitro investigation using rat glioma cell line in culture. Hypoxia was induced by an incubation with nitrogen gas for 15 h followed the normoxia exposure with air for 30 min. Activity of SOD in cytosolic and particulate of cells was determined by the reduction of nitroblue tetrazolium. Changes of mRNA for Cu,Zn-SOD or Mn-SOD were also characterized using Northern blotting analysis. Hypoxic stress decreased the activity of SOD, both Cu,Zn-SOD and Mn-SOD, in glioma cells. Expression of mRNA for SOD was elevated by hypoxic stress and the increase of mRNA level for Cu,Zn-SOD was more marked than that for Mn-SOD. In response to hypoxia-normoxia exposure, an increase of activity with a lower mRNA level for Mn-SOD was observed in glioma cells. However, changes of Cu,Zn-SOD both the activity and the level of mRNA were not found in glioma cells by hypoxia-normoxia. The obtained results suggest that the SOD in glioma cells can be activated to compensate the damage from free radicals during hypoxic stress.

Antihyperglycemic effects of paeoniflorin and 8-debenzoylpaeoniflorin, glucosides from the root of Paeonia lactiflora

Paeoniflorin and 8-debenzoylpaeoniflorin were isolated from the dried root of Paeonia lactiflora Pall. (Ranunculaceae). They produced a significant blood sugar lowering effect in streptozotocin-treated rats and had a maximum effect at 25 min after treatment. This hypoglycemic action was also observed in normoglycemic rats only at 1 mg/kg. The antihyperglycemic activity of 8-debenzoylpaeoniflorin seems lower than that of paeoniflorin. Plasma insulin was not changed in paeoniflorin-treated normoglycemic rats indicating an insulin-independent action. Also, this glucoside reduced the elevation of blood sugar in glucose challenged rats. Increase of glucose utilization by paeoniflorin can thus be considered. There are no previous data showing the hypoglycemic activity of paeoniflorin and/or 8-debenzoylpaeoniflorin in rats.

Attenuation of the catecholamine responses by electroacupuncture on Jen-Chung point during postoperative recovery period in humans

In this study, Jen-Chung (J-C) point was stimulated by electroacupuncture (EA) in 10 patients, and by placebo treatment in 10 controls, immediately after termination of inhalation for 15 min. During the postoperative recovery period, plasma catecholamine (CA) levels were assessed before (0) and 15 and 30 min after treatment. The time from cessation of inhalation to the first eye opening and to extubation did not differ between groups. The plasma catecholamine levels increased by 30% from 0 to 15 min in the control group but decreased by 6% in the EA group. The levels at 30 min were approximately the same as at time 0. The change in catecholamine levels from 0 to 15 min was significantly lower (P < 0.02) in the EA groups than the control group.

Subtyping of alpha1-adrenoceptors responsible for the contractile response in the rat corpus cavernosum

The subtyping of alpha1-adrenoceptors responsible for mediating contraction in isolated corpus cavernosum of mature male Wistar rats was studied pharmacologically. Concentration-response studies of the cavernosal smooth muscle to three agonists: methoxamine, norepinephrine and octopamine showed that methoxamine exhibited the highest potency in inducing contractile response; the respective pD2 values were: 6.22, 5.83 and 5.38. In the presence of 2-(2,6-dimethoxyphenoxyethyl)aminomethyl-1,4-benzodioxane (WB4101), a specific antagonist for alpha1A-adrenoceptors, a parallel rightward shift of the concentration-response curve to methoxamine was observed. On the other hand, chloroethylclonidine (CEC) caused a rightward shift of the concentration-response curve to methoxamine with significant suppression of the maximum response. The pA2 value for WB4101 obtained from Schild plot was 9.03 +/- 0.06 with slope (95% CL) equal to 0.955 (1.088-0.832). In the absence of extracellular calcium ions, the methoxamine-induced contraction was reduced by 92%. Ca2(+)-Channel blockers, nifedipine 10(-6) M and diltazem 10(-6) M decreased the contractile response by 18 and 23%, respectively. The present findings suggest that alpha1A-adrenoceptors are responsible for the methoxamine-induced contraction of the rat cavernosal smooth muscle.

Simulatory effect of porcine insulin on noradrenaline secretion in guinea-pig ileum myenteric nerve terminals

1. The effect of insulin on the release of noradrenaline (NA) from nerve terminals was investigated in 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 insulin minus that in parallel blanks treated with some volume of vehicle. 2. Porcine insulin stimulated the secretion of NA in a concentration-dependent manner from 0.01 i.u. ml-1, while the value of lactate dehydrogenase in the incubated medium was not influenced by insulin. 3. The presence of insulin receptors in this preparation was illustrated by immunoblotting with insulin receptor monoclonal antibodies. 4. The release of NA by insulin was reduced by guanethidine and bretylium and it was markedly lowered in the samples obtained from guinea-pigs that had received an intraperitoneal injection of DSP-4, the noradrenergic neurotoxin. 5. Tetrodotoxin attenuated the action of insulin at concentrations sufficient to block sodium channels. The depolarizing effect of insulin on the membrane potential was also illustrated by a concentration-dependent increase in the fluorescence of bisoxonol, a potential-sensitive dye. 6. The action of insulin was attenuated by removal of calcium chloride from the bathing medium. The induction of calcium ion influx by insulin into the synaptosomes is supported by the inhibitory effects of the calcium channel blockers omega-conotoxin GVIA (for the N-type channels) and nifedipine (for the L-type channels). 7. These findings suggest that insulin can stimulate NA release from noradrenergic terminals via activation of calcium influx.

Evidence of P2Y-purinoceptor mediated bladder neck smooth muscle post-contractile relaxation in the male mini-pig

The functional role of non-adrenergic non-cholinergic (NANC) nerves in the autonomic control of the male mini-pig bladder neck was investigated in the present study. Electrical stimulation of muscle strips from male mini-pig bladder neck showed biphasic response with initial phasic contraction followed by post-contractile relaxation. Electrical stimulation in the presence of four autonomic blockers (atropine 10(-6) M, propanolol 10(-6) M, phentolamine 10(-6) M) showed suppression of 68 +/- 15% of the contractile response (P < 0.05, n = 8) but no significant change in the relaxation response. Alpha-chymotrypsin 2 U/ml, L-NG-monomethyl-L-arginine acetate (a nitric oxide synthetase inhibitor) 10(-4) M, 8-phenylthlophylline (a P1-purinoceptor antagonist) 10(-6) M, and pyridoxal-phosphate-6-azophenyl-2', 4'-disulphoric acid tetrasodium salt (a P2Y-purinoceptor antagonist) 3 x 10(-5) M did not alter the NANC response significantly. On the other hand, reactive blue-2 (a P2Y-purinoceptor antagonist) 3 x 10(-5) significantly reduced the relaxation by 79 +/- 9%. The result suggested that the P2Y-purinoceptor is involved in the electrically induced NANC post-contractile relaxation of the mini-pig bladder neck smooth muscle.

Pharmacological characterization of the muscarinic receptor subtypes responsible for the contractile response in the rat urinary bladder

1. Contractile responses of smooth muscle from the Wistar rat urinary bladder were studied with the use of muscarinic agonists and antagonists. 2. McN-A-343 induced only weak contractile responses of the bladder muscle. In contrast, oxotremorine showed higher potency than either acetylcholine or bethanechol in inducing a contractile response (the respective pD2 values were 6.38 +/- 0.25, 4.82 +/- 0.24 and 4.42 +/- 0.14). 3. The M2 antagonists, methoctramine (10(-9) M to 10(-5) M) and gallamine (10(-9) M to 10(-5) M), did not reduce acetylcholine-induced (10(-5) M) contractions of the bladder muscle strip. On the other hand, 4-diphenyl-acetoxy-N-methyl piperidine methiodide (4-DAMP, 10(-10) M to 10(-7) M), an M3 receptor blocker, effectively antagonized the acetylcholine-induced contractions in a concentration-dependent manner. 4-DAMP had a similar pA2 value to those of the non-selective antagonists, atropine and scopolamine (pA2 values were 8.26 +/- 0.05, 8.36 +/- 0.05 and 8.41 +/- 0.11, respectively). Pirenzepine, and M1 blocker, antagonized the contractions at higher concentrations (10(-8) M to 10(-5) M, pA2 = 6.23 +/- 0.04). 4. It is concluded that (1) the dominant muscarinic receptor subtype responsible for smooth muscle contraction in the rat urinary bladder is M3; and (2) the muscarinic agonist oxotremorine was more potent than acetylcholine and bethanechol in inducing a contractile response.

Elevated basic fibroblast growth factor levels in stroke-prone spontaneously hypertensive rats

Basic fibroblast growth factor is a biologically active polypeptide with mitogenic, angiogenic and neurotrophic properties. In the present study, the temporal and spatial expressions of basic fibroblast growth factor in stroke-prone spontaneously hypertensive rats were compared to two related strains of rat: spontaneously hypertensive rats and normotensive Wistar Kyoto rats. Higher levels of total RNA concentration were found in cerebral cortex of four-week-old stroke-prone rats compared to spontaneously hypertensive rats and Wistar Kyoto rats. Northern blot analysis showed no changes in levels of basic fibroblast growth factor messenger RNA with increasing age in cerebral cortex of Wistar Kyoto and spontaneously hypertensive rats. However, significant increases were found in 26- and 38-week-old stroke-prone rats compared to four-week-old stroke-prone rats. Although messenger RNA increases were also found in subcortical and cerebellar regions, a significant difference in levels of basic fibroblast growth factor messenger RNA was observed only in cerebral cortices among these three strains. This age-related increase in basic fibroblast growth factor messenger RNA correlated with the increase incidence of stroke in stroke-prone rats. Immunohistochemical study further revealed a dramatic increase in levels of basic fibroblast growth factor immunoreactivity in cerebral cortex of 30-week-old stroke-prone rats as compared to young stroke-prone rats, as well as age-matched Wistar Kyoto and spontaneously hypertensive rats. This increase in basic fibroblast growth factor immunoreactivity therefore appears very specific to aged stroke-prone rats. However, immunoreactivity decreased once severe tissue damages were observed in the cerebral cortex. Basic fibroblast growth factor-positive cells were diffusely expressed in cerebral cortex; double staining with glial fibrillary acidic protein showed the majority of these basic fibroblast growth factor-positive cells to be astrocytes. In summary, although young stroke-prone spontaneously hypertensive rats showed significantly higher RNA concentration, significant increases in levels of basic fibroblast growth factor, including both messenger RNA and protein expression, were observed in aged stroke-prone rats with a high incidence of stroke. These findings suggest the possibility that basic fibroblast growth factor may play a role in the developmental sequelae of cerebral lesions in stroke-prone spontaneously hypertensive rats.

Expression of NGFI-B mRNA in a rat focal cerebral ischemia-reperfusion model

Cerebral ischemia is known to induce the expression of several immediate early genes (IEGs), including c-fos and c-jun, which subsequently regulate a number of late effector genes. In this study, we examined the expression of NGFI-B (or nur 77) mRNA in a rat focal cerebral ischemia-reperfusion model. NGFI-B is a member of the IEGs which encodes for a nuclear receptor and is rapidly induced by nerve growth factor (NGF). Northern blot analysis showed a rapid but transient enhancement of NGFI-B mRNA, a peak level for which was observed at 30 min of reperfusion following 60 min ischemic insult. At the peak level, quantitative analysis of the blot indicated a 12-fold and 4-fold increase of NGFI-B mRNA in the ischemic cortex and ipsilateral hippocampus, respectively, as compared to the sham-operated control. No apparent changes in mRNA levels were observed within contralateral sites of the cortex. Results from in situ hybridization showed that severe ischemia (60 min) resulted in a marked increase of NGFI-B mRNA throughout the entire ischemic cerebral cortex. The increase was particularly notable in the frontal, occipital, perirhinal and piriform cortical regions and in the dentate gyrus and CAI-3 regions of the ipsilateral hippocampus. A marked induction was also noted in the ipsilateral caudate putamen. Unlike the induction profile of NGFI-B mRNA, severe ischemia resulted in bilateral increases of its family gene, NGFI-A mRNA. The spatial induction profile is similar to that of NGFI-B mRNA in both hemispheres, except within the region of the contralateral dentate gyrus which showed low levels of NGFI-A mRNA. The expression pattern of NGF and BDNF mRNA, upstream genes of NGFI-B, were also examined. Interestingly the temporal and spatial expression patterns of BDNF mRNA were very similar to that of NGFI-A mRNA under the same conditions, whereas increased NGF and NGFI-B mRNA were observed only in the ipsilateral hemisphere. It is likely that multiple and/or overlapping pathways are activated subsequent to ischemic challenge which in turn are crucial for cel survival and/or functional recovery following focal cerebral ischemia.

Activation of alpha 1-adrenoceptors to lower cerebrocortical neuropeptide Y (NPY)-like immunoreactivity in rats receiving pargyline treatment

Role of neuropeptide Y (NPY) in noradrenergic neurotransmission has been mentioned as co-transmitter in both central and peripheral nervous system. Cerebral NPY content was changed by drugs influencing endogenous norepinephrine (NE) in rats. In an attempt to understand this mechanism, the present study was carried out using the radioimmunoassay of NPY. Values of NPY-like immunoreactivity (NPY-ir) were reduced in rats receiving the treatment of pargyline, the inhibitor of monoamine oxidase, with an elevation of catecholamine in parallel. This action was abolished by pretreatment with a mixture of phentolamine, propranolol and haloperidol at concentration sufficient to block the receptors. However, it was not influenced by treatment with haloperidol alone. Cerebrocortical NPY-ir was lowered in rats receiving an intracerebroventricular (i.c.v.) injection of methoxamine, the agonist of alpha 1-adrenoceptors. This action was prevented by prazosin via an i.c.v. injection at the dose sufficient to block alpha 1-adrenoceptors. Moreover, decrease of cerebrocortical NPY-ir by pargyline was also reversed by similar treatment of prazosin. The data obtained suggests that activation of alpha 1-adrenoceptors by endogenous NE which was increased by pargyline may lower the contents of NPY in cerebrocortex of the rat.

Comparison of isoproterenol with BRL37344 in activation of beta 3-adrenoceptors to inhibit the uptake of [14C]deoxy-D-glucose and translocation of glucose transporter (GLUT4) to membrane fraction in rat adipocytes

In an attempt to understand the role of beta 3-adrenoceptors in the regulation of glucose uptake, the effect of isoproterenol was compared with BRL37344 in isolated white adipocytes of the rat using [14C]deoxy-D-glucose as an indicator. In the presence of BRL37344, the specific agonist of beta 3-adrenoceptors, spontaneous uptake of [14C]deoxy-D-glucose (glucose uptake) into adipocytes was markedly attenuated. Similar concentration-dependent inhibition of glucose uptake was also observed in the samples treated with isoproterenol, an agonist for all kinds of beta-adrenoceptors. Action of BRL37344 was blocked by propranolol at concentrations sufficient to abolish the activity of isoproterenol. Pindolol reversed BRL37344-induced inhibition more effectively than propranolol. Moreover, unlike the action of isoproterenol, BRL37344 did not modify the insulin-stimulated glucose uptake. Translocation of glucose transporter (GLUT4) from cytosol to membrane stimulated with insulin was reduced by isoproterenol but not by BRL37344. Combination with the findings that isoproterenol prolonged the time for insulin to reach maximum stimulation of glucose uptake, leads to the conclusion that delay of insulin action by isoproterenol can be considered as one of the mechanisms for this inhibition. The results obtained suggest that BRL37344 decreased the spontaneous uptake of glucose via an activation of beta 3-adrenoceptors while the insulin stimulated glucose uptake was inhibited by isoproterenol but not by BRL37344.

The in vitro antioxidant activity of trilinolein and other lipid-related natural substances as measured by enhanced chemiluminescence

There is abundant evidence for the premise that oxygen-derived free radicals (OFR) mediate ischemia/reperfusion injury to the myocardium. OFR scavengers such as superoxide dismutase can effectively reduce damage through lipid peroxidation during ischemia/reperfusion. Enhanced chemiluminescence, which has been used to measure OFR, was used to measure the antioxidant activity of fatty acids (palmitic and linoleic acid) and triglycerides (triolein, tristearin) and natural plant antioxidants (magnolol, catechin, trilinolein). Trilinolein, which has recently been isolated from natural products, as well as the well-known water soluble analogue of vitamin E-Trolox, were used as control. During pretreatment with chemicals, at concentrations of 10(-9) to 10(-7) M, enhanced chemiluminescence of linoleic acid (C 18:2) showed a dose-responsive reduction of OFR with a maximal mean reduction of -31.9% when compared to baseline. A saturated fatty acid such as palmitic acid (C 16:0) showed only relatively weak antioxidant activity at concentrations of 10(-7) to 10(-6) M with a maximum reduction of OFR of- 15.2% only. control chemicals such as trilinolein and Trolox showed significant antioxidant activity. At concentrations between 10(-10) and 10(-6) M and trilinolein has the most potent antioxidant activity with a maximal mean reduction of OFR of -48.0%, whereas Trolox showed only -39.2%. As for the natural plant antioxidants, only catechin showed potent antioxidant activity (-40%). Polyunsaturated triglycerides such as triolein (oleic acid, C 18:1) also possess significant OFR scavenging effect (-31.9%) whilst saturated triglycerides such as tristearin (stearic acid, C 18:0) had only relatively weak antioxidant activity (-15.2%). Generally, the antioxidant activity of unsaturated compounds is stronger than saturated compounds; double-bond existence may partially explain this phenomenon.

The β-adrenoceptors and catecholamine levels in lead poisoned rats

To investigate β-adrenoceptor dysfunction upon exposure to lead, we measured (a) β-adrenoceptor density in brain, heart, blood vessels and lymphocytes and (b) plasma catecholamine levels in rats with lead poisoning. Wistar rats were given drinking water containing lead acetate (2% w/v) for a period of 60 days. The radioligand [(125)I]iodocyanopindolol was used for determining the density of β-adrenoceptors in membrane fragments in vitro and a high performance liquid chromatography (HPLC) for measuring plasma catecholamine levels. Plasma norepinephrine levels were found to be significantly higher in lead-exposed rats than in control animals (4.69 ± 0.58 μg/l vs. 3.67 ± 0.53 μg/l, p < 0.01). In lead-exposed animals the density of β-adrenoceptors in brain (36%), heart (68%), blood vessels (57%) and lymphocytes (48%) was significantly less than in controls (p < 0.001), whereas the K(d) did not vary between the two groups. We have found that β-adrenoceptor dysfunction in lead-poisoned rats was brought about by a decline in β-adrenoceptor density.

In vitro inhibitory effects of chebulinic acid on the contractile responses of cardiovascular muscles

1. The effects of chebulinic acid, which has been shown to elicit blood pressure lowering effect in rats, on aortic vascular contraction as well as cardiac contraction were studied in rats. 2. Chebulinic acid had no effect on KCl-induced aortic contraction, but irreversibly inhibited the contractile responses to phenylephrine in an apparently non-competitive manner. Chebulinic acid also inhibited contractile responses of rat aorta to 5-hydroxytryptamine and angiotensin II. 3. Chebulinic acid inhibited the binding of [3H]-prazosin to dog aortic microsomal membranes in a concentration-dependent manner with an IC50 value of 0.34 mmol/L. Results of saturation binding experiments suggest a mixed mode of inhibition by chebulinic acid (i.e. a decrease in both the maximal number of binding sites and the affinity for prazosin). 4. Chebulinic acid concentration-dependently and reversibly inhibited the maximal left ventricular pressure of rat heart in a Langendorff preparation with 50% inhibition occurring at a concentration of 0.3 nmol/L. 5. We conclude that chebulinic acid exerts non-specific inhibitory actions in vascular preparations. Its inhibitory effect on cardiac contraction was reversible and three orders of magnitude more potent than that on vascular contraction. We suggest that the hypotensive effect of chebulinic acid is probably mediated via the decrease in cardiac output resulting from reduced left ventricular contraction.

Clinical evidence of genetic anticipation in adult-onset idiopathic dystonia

Idiopathic dystonia occurs in both hereditary and sporadic forms. In this report, we studied the age of onset and family history of 260 patients (probands) with idiopathic adult-onset dystonia (IAD), cranial or cervical. The mean age at onset of these patients was (45.71 +/- 15.85) years. Forty-nine probands had a positive family history of dystonia or tremor in first- and second-degree relatives, and 7 had affected siblings only. The significance of tremor as a part of clinical manifestation of dystonia was evidenced by a high frequency of postural or action tremor in patients and relatives. Retrospectively, we examined the age of onset of dystonia (cervical or cranial) on successive generations in 49 families. Age of onset of clinical symptoms was earlier, by an average of 21.25 years, in the second generation than in the first generation. The mean age at onset of affected family members differed significantly between successive generations in these 49 families (p = 1.11 x 10(-8)). Our results suggest a tendency for earlier onset of dystonia and worsening of disease phenotype in succeeding generations in the same family. These findings are most compatible with genetic anticipation and suggest that an unstable trinucleotide repeat is most likely involved in adult-onset primary cranial or cervical dystonia. In addition, tremor as an integral part of dystonia needs further evaluation by molecular genetic studies.

Increase of locomotor activity by acupuncture on Bai-Hui point in rats

The effect of acupuncture on locomotor activity was investigated in rats. Stimulation with acupuncture inserted in Bai-Hui point, which is located at the vertex of the head, increased the spontaneous locomotor activity of rats measured in ANIMEX meter. This effect was obtained in rats which received acupuncture significantly at 60 min later as compared with sham-treated control. The sleeping time induced by hexobarbital was also reduced markedly in rats receiving acupuncture. An activation of the central nervous system by acupuncture at Bai-Hui point can thus be considered. This action was unrelated to opioids because naloxone failed to modify it. Increase in locomotor activity was abolished by an intraperitoneal (i.p.) injection of alpha-methyl-p-tyrosine (200 mg/kg) at 2 h before insertion of acupuncture. Deprenyl at the dose sufficient to elevate monoamine enhanced this action of acupuncture. Mediation of cerebral monoamines can also be considered. This view was supported by the dose-dependent inhibition of chlorpromazine. Action of acupuncture was not observed in apomorphine (0.5 mg/kg, i.p.)-treated rats, probably due to an activated receptor of dopamine. Otherwise, action of acupuncture was enhanced by para-chlorophenylalanine, the depleter of endogenous 5-hydroxytryptamine (5-HT), and eliminated by 5-hydroxytryptophan, the precursor of 5-HT, in the initial stage of insertion. Participation of 5-HT can be considered as an initial way in rats that received acupuncture at Bai-Hui point. These results suggested that stimulation of Bai-Hui point with acupuncture can activate central neurotransmission of monoamines to increase the spontaneous locomotor activity in rats.

Changes of neuropeptide Y messenger RNA and peptide by drugs influencing endogenous norepinephrine content in cerebrocortex of the rat

Cotransmission of classic transmitters at the synapse has been mentioned for both the CNS and the PNS. Neuropeptide Y (NPY) is a cotransmitter in noradrenergic neurotransmission. In an attempt to understand the heteroregulation of norepinephrine (NE) and NPY biosynthesis, the present study was performed using radioimmunoassay of NPY and northern blotting of cDNA probes for characterization of NPY mRNA. Values of NPY-like immunoreactivity (NPY-ir) were elevated in the cerebrocortex from rats that received treatment with fusaric acid, an inhibitor of dopamine-beta-hydroxylase, with a parallel decrease in NE. Similar results were also observed in rats treated with DSP-4, an alkylator of vesicles in noradrenergic nerve terminals. Moreover, cerebrocortical NPY-ir was reduced in rats receiving treatment with pargyline, an inhibitor of monoamine oxidase, with an elevation of catecholamine in parallel. Activity of NPY mRNA was modified by these drugs in a similar way. However, values of NPY-ir and NE in the cerebrocortex were not influenced by treatment with sodium nitroprusside or guanethidine at a dose producing hypotensive effect. Mediation of hypotensive reflex can thus be ruled out. The data obtained suggest that in vivo decrease of NE by drugs increases biosynthesis of NPY in the cerebrocortex of rats.

Isolation of synaptosomes from the rat urinary bladder

Synaptosomes are nerve-end particles (NEP) isolated by using the technique of differential centrifugation. The synaptosome offers a good model for biochemical and pharmacological studies of the nerve endings. No report has been made on synaptosome isolation from the urinary bladder. The purpose of our work was to develop the use of synaptosome in the research of neurophysiology and neuropharmacology of the urinary bladder. Synaptosome-rich fraction was prepared from tissue homogenate of male Wistar rat urinary bladder by differential centrifugation (1000, 17,000 and 100,000 g) with discontinuous sucrose gradient. Electron microscopy showed synaptosomes as thin-walled bags containing a large number of synaptic vesicles. Two types of synaptosomes were easily discerned: those containing small agranular vesicles, and those containing dense-cored vesicles. The acetylcholine, norepinephrine, epinephrine and dopamine contents in the preparation were measured by the method of high-performance liquid chromatography. The respective concentrations were 300.4 +/- 30.1, 962.8 +/- 58.5, 617.3 +/- 59.8 and 1354.8 +/- 144.2 pmol/mg synaptosomal protein. In conclusion, it has been demonstrated that synaptosome-rich fractions can be prepared from the rat urinary bladder. Thus it is possible to apply this methodology for the investigation of the neurobiology of urinary bladders.

6-Hydroxydopamine induces thymocyte apoptosis in mice

6-Hydroxydopamine (6-OHDA) induces degeneration of noradrenergic nerves and has been shown to alter the immune responses. In this study, intraperitoneal administration of 6-OHDA induces mouse thymus atrophy. The lowest levels of thymus weight and cell number were reached at days 3 and 5 in mice receiving 6-OHDA treatment; they gradually recovered thereafter. On flow cytometry analysis, the most substantial reductions were recorded for CD4+CD8+ thymocytes, although the numbers of other subpopulations, i.e. CD4+CD8-, CD4-CD8+ and CD4-CD8- cells were also reduced. DNA fragmentation, a characteristic of apoptosis, was detected in the thymocytes following 6-OHDA injection. Pretreatment with desipramine greatly blocked the reduction in thymus size and thymocyte number, the changes in thymocyte subpopulations, the percentage of subdiploid (apoptotic) cells and the appearance of DNA fragmented bands. Furthermore, 6-OHDA-induced thymocyte apoptosis could also be detected in vitro, and was blocked by desipramine treatment. These results indicate that 6-OHDA induces mouse thymocytes to undergo apoptosis both in vivo and in vitro, and this effect is inhibited by catecholamine uptake blocker.

Trilinolein preserves mitochondria ultrastructure in isolated rat heart subjected to global ischemia through antioxidant activity as measured by chemiluminescence

Oxygen-derived free radicals (OFR) have been proposed as the cause of myocardial damage through lipid peroxidation during ischemia and reperfusion. Antioxidants can effectively ameliorate the damage induced by lipid peroxidation. Trilinolein is a triacylglycerol recently purified from the well known traditional Chinese herb Panax pseudoginseng, which has been used in treating circulatory disorders among Chinese for hundreds of years; it has linoleate as the only fatty acid residue in all three esterified positions of glycerol. This chemical has recently been demonstrated to have antioxidant activity by enhanced chemiluminescence. The addition of phorbol myristic acetate (PMA) to medium containing leukocytes produces OFR; this phenomenon was measured by chemiluminescence. Addition of trilinolein to medium containing leukocytes preceding the addition of PMA suppressed the production of OFR. The control value of chemiluminescence of a medium containing leukocytes with addition of PMA was 9.23 +/- 1.19 x 10(3) mV. The most effective concentration of trilinolein was 10(-7) mol/l which decreased the signals to 4.59 +/- 0.02 x 10(3) mV (p < 0.001). The antioxidant effect had a concentration-response curve similar to alpha-tocopherol. After pretreatment for 15 min with trilinolein at a concentration of 10(-7) mol/l in isolated perfused rat heart which had been subjected to 60 min of global ischemia, the integrity of the rat heart mitochondria was preserved as examined under the electron microscope. No swelling of mitochondria occurred and there was good alignment of cristae and absence of amorphous density. Previous experiments have shown that trilinolein can also improve erythrocyte deformability in vitro. Infarct size reduction of about 50% was also demonstrated in in vivo rat heart subjected to 4 h coronary occlusion. The mechanism of myocardial protection, in addition to the antioxidant effect, is suggested as maintaining the membrane fluidity of cardiomyocytes.

Alterations in urinary bladder synaptosomal neurotransmitter concentrations in two-week streptozotocin-induced diabetic rats

Three-month-old male Wistar rats were rendered diabetic with a single intravenous injection of streptozotocin (60 mg/kg body weight). Two weeks after induction of diabetes, synaptosome-rich fractions were prepared from urinary bladder tissue homogenate of the diabetic rats and control rats by differential centrifugation (1000 x g, 17,000 x g and 100,000 x g) with discontinuous sucrose gradient. Synaptosomal acetylcholine, norepinephrine, epinephrine and dopamine were measured by the method of high-performance liquid chromatography. The respective neurotransmitter concentrations for the diabetic rats were 1537.8 +/- 65.3, 4757.7 +/- 361.9, 3720.7 +/- 276.1, and 2447.8 +/- 196.8 pmol/mg synaptosomal protein, respectively; those for the control rats were 338.1 +/- 25.0, 1009.0 +/- 54.6, 645.3 +/- 52.2, and 1426.1 +/- 123.9 pmol/mg protein, respectively. Thus, the synaptosomal concentrations for all the measured neurotransmitters were significantly higher in the diabetic rats (P < 0.05 for each comparison). In conclusion, it has been demonstrated that the vesicle-bound acetylcholine and catecholamines in the synaptosome-rich fraction of the urinary bladder were significantly increased in 2-week diabetic rats. This finding would suggest impaired neurotransmitter release from both the bladder sympathetic and parasympathetic efferent nerve endings in early streptozotocin-induced diabetes.

Comparisons of neurotransmitter concentrations in the synaptosomal preparation of the normotensive and hypertensive rat urinary bladder

Synaptosome-rich fractions were prepared from tissue homogenate of the urinary bladder of the spontaneously hypertensive rat and normotensive Wistar-Kyoto rat by differential centrifugation (1000 x g, 17 000 x g and 100 000 x g) with discontinuous sucrose gradient. Synaptosomal acetylcholine, norepinephrine, epinephrine and dopamine were measured by the method of high-performance liquid chromatography. The respective neurotransmitter concentrations for the normotensive rats were 300.4 +/- 30.1, 962.8 +/- 58.5, 617.3 +/- 59.8, and 1354.8 +/- 144.2 pmol/mg synaptosomal protein. For the hypertensive rats, the acetylcholine concentration (203.8 +/- 23.0 pmol/mg protein) was significantly lower (P < 0.05), while the norepinephrine, epinephrine and dopamine concentrations (1459.0 +/- 180.3, 971.3 +/- 62.2, and 2161.0 +/- 243.4 pmol/mg protein, respectively) were significantly higher (P < 0.05 for all) than those of the normotensive rats. In conclusion, it has been demonstrated that the vesicle-bound catecholamines in the synaptosome-rich fraction of the urinary bladder were significantly increased in hypertensive rats. On the contrary, the synaptosomal acetylcholine concentration was significantly decreased. These findings are suggestive of increased sympathetic innervation and decreased parasympathetic innervation in the urinary bladder of the spontaneously hypertensive rat.