Hydroxysafflor yellow A attenuates lymphostatic encephalopathy-induced brain injury in rats.

Hydroxysafflor yellow A (HSYA) is a main chemical component of the flower of Carthamus tinctorius. The present study investigated whether HSYA could attenuate brain injury induced by lymphostatic encephalopathy (LE). This was induced in adult male Wistar rats by cervical lymphatic blockade (CLB). Heart rate variability (HRV) was used as an indirect measurement of the regulatory function of the autonomic nervous system by recording the ECG signals from rats. It was shown that treatment with HSYA (5 mg/kg, i.p.) significantly alleviated the neurological deficits observed in rats with LE. Histological staining revealed that HSYA treatment attenuated LE-induced cell apoptosis in the rostral ventrolateral medullus (RVLM). Animals in the LE groups exhibited impaired regulatory roles of the autonomic nervous system in cardiovascular function, which was suppressed by pretreatment with HSYA. Additionally, HSYA administration significantly prevented the decrease of endothelial nitric oxide synthase (eNOS) mRNA and protein expression in the RVLM of rats with LE. These findings suggest that HSYA might provide neuroprotection against LE-induced brain injury and the associated functional alterations, which is likely regulated by the nitric oxide pathway.

HIF-1-α and survivin involved in the anti-apoptotic effect of 2ME2 after global ischemia in rats.

Survivin is an anti-apoptotic gene that decreases the apoptosis by depressing the expression of caspase-3. Hypoxia-inducible factor-1-alpha (HIF-1-alpha) is a transcription factor specifically activated by hypoxia. 2-methoxyestradiol (2ME2) is an estradiol derivative and a known HIF-1-alpha inhibitor. 2ME2 decreased apoptosis by inhibiting HIF-1-alpha. The aim of the present study was to investigate if survivin is involved in the anti-apoptotic effect of 2ME2. Male adult rats were used to make the global ischemia (GI) model. Ten minutes after GI, 2ME2 was injected intraperitoneally (16 mg/kg weight). Rats were killed at 6 hours, 12 hours, 24 hours, 48 hours, 96 hours, and 7 days. GI produced a marked increase in HIF-1-alpha expressions in the hippocampus at 6 hours and peaked at 48-96 hours. The expressions of survivin and caspase-3 were increased lightly in a similar time course. These molecular changes were accompanied by massive cell loss and apoptosis in the hippocampal regions. 2ME2 treatment reduced the expression of HIF-1-alpha, increased survivin expression, and decreased the expression of caspase-3. These results indicate that survivin and HIF-1-alpha were involved in the anti-apoptotic effect of 2ME2 treated following GI. 2ME2 may decrease the HIF-1-alpha expression, up-regulate the survivin expression, inhibit the expression of caspase-3, and finally reduce apoptosis after GI.

Protection by 3'-methoxypuerarin of rat hippocampal neurons against ischemia/reperfusion injury.

3'-Methoxypuerarin (3'-MOP) is an isoflavone extracted from radix puerariae. The aim of this study was to investigate the role and the mechanism of 3'-MOP in the protection of hippocampal neurons against cerebral ischemia/reperfusion (I/R) injury in rats. I/R injury was induced by a modified four-vessel occlusion model. Rats were randomly divided into an I/R group, an I/R + 3'-MOP group and a control group. Histological changes in the neurons of the hippocampal CA1 region were observed with hematoxylin and eosine (H&E) staining. The apoptotic neurons in the hippocampal CA1 area were counted with the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining. The results showed that compared with the I/R group, 3'-MOP increased the number of surviving neurons in the hippocampal CA1 region (P < 0.001) and markedly reduced the number of apoptotic pyramidal neurons (P < 0.001) after I/R injury. In conclusion, 3'-MOP can protect hippocampal neurons against I/R injury by inhibiting apoptosis.

Both ischemic preconditioning and ghrelin administration protect hippocampus from ischemia/reperfusion and upregulate uncoupling protein-2.

BACKGROUND: A major endogenous protective mechanism in many organs against ischemia/reperfusion (I/R) injury is ischemic preconditioning (IPC). By moderately uncoupling the mitochondrial respiratory chain and decreasing production of reactive oxygen species (ROS), IPC reduces apoptosis induced by I/R by reducing cytochrome c release from the mitochondria. One element believed to contribute to reduce ROS production is the uncoupling protein UCP2 (and UCP3 in the heart). Although its implication in IPC in the brain has been shown in vitro, no in vivo study of protein has shown its upregulation. Our first goal was to determine in rat hippocampus whether UCP2 protein upregulation was associated with IPC-induced protection and increased ROS production. The second goal was to determine whether the peptide ghrelin, which possesses anti-oxidant and protective properties, alters UCP2 mRNA levels in the same way as IPC during protection. RESULTS: After global forebrain ischemia (15 min) with 72 h reperfusion (I/R group), we found important neuronal lesion in the rat hippocampal CA1 region, which was reduced by a preceding 3-min preconditioning ischemia (IPC+I/R group), whereas the preconditioning stimulus alone (IPC group) had no effect. Compared to control, UCP2 protein labelling increased moderately in the I/R (+39%, NS) and IPC+I/R (+28%, NS) groups, and substantially in the IPC group (+339%, P < 0.05). Treatment with superoxide dismutase (10000 U/kg ip) at the time of a preconditioning ischemia greatly attenuated (-73%, P < 0.001) the increase in UCP2 staining at 72 h, implying a role of oxygen radicals in UCP2 induction.Hippocampal UCP2 mRNA showed a moderate increase in I/R (+33%, P < 0.05) and IPC+I/R (+40%, P < 0.05) groups versus control, and a large increase in the IPC group (+333%, P < 0.001). In ghrelin experiments, the I/R+ghrelin group (3 daily administrations) showed considerable protection of CA1 neurons versus I/R animals, and increased hippocampal UCP2 mRNA (+151%, P < 0.001). CONCLUSION: We confirm that IPC causes increased expression of UCP2 protein in vivo, at a moment appropriate for protection against I/R in the hippocampus. The two dissimilar protective strategies, IPC and ghrelin administration, were both associated with upregulated UCP2, suggesting that UCP2 may often represent a final common pathway in protection from I/R.

Variations in blood pressure and heart rate in conscious rats with cervical lymphatic blockade.

The possible effects of cervical lymphatic blockade (CLB) on a series of parameters in conscious freely moving rats were analysed. Blood pressure (BP) and heart rate (HR) for conscious male Sprague-Dawley rats at 1, 3, 7, 11, 15 and 21 days after a CLB or a sham operation were monitored continuously for 24 hours with a computerized recording system. Since BP and HR were subjected to spontaneous variations, blood pressure variability (BPV) and heart rate variability (HRV) were expressed as the standard deviation of beat-to-beat BP and HR values. The baroreflex sensitivities (BRS) were determined by measuring the heart period (HP = 60,000/HR) prolongation in response to the elevation in BP induced by an intravenous administration of phenylephrine at 1, 7, 15 and 21 days after the CLB or sham operation. Compared with those in sham-operated rats, the values of systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MAP), HR and BRS in CLB rats were significantly lower, whereas the values of BPV and HRV were markedly raised in CLB rats at different time points. Furthermore, the impaired ultrastructure in the dorsomedial nucleus of the solitary tract (dmNTS) including degeneration, apoptosis and necrosis in neurons and gliacytes, were apparent from the 1st to 15th day but the changes were most significant at 7th day after CLB operation. Structural changes appeared to be closely related to functional changes of the dmNTS at each time point. Thus, in CLB conscious rats, a significant decline in blood pressure accompanied by dysfunction in its regulation might be due to the impaired structure in the dmNTS.

Inhibition of beta-amyloid precursor protein gene in SK-N-SH cells by piperlonguminine/dihydropiperlonguminine components separated from Chinese herbal medicine Futokadsura stem.

Alzheimer disease (AD) is a progressive neurodegenerative disease characterized by progressive cognitive and memory decline. Amyloid precursor protein (APP) is a transmembrane protein, it has been known to play an important role in AD pathogenesis. Previous studies have shown that a Chinese herb Futokadsura stem can selectively inhibit the expression of amyloid precursor protein (APP) gene. We want to find the effective components in Futokadsura stem which have the inhibitory effect. Futokadsura stem was separated and purified with chemical methods, and then different separation components were added on SK-N-SH cells in different concentrations. Using MTT methods, we detected proliferation activity of SK-N-SH cells which were treated with different separation components of Futokadsura stem. Using RT-PCR, Western blot methods, we detected APP gene expression in SK-N-SH cells after they are treated with different Futokadsura stem separation components. We found that piperlonguminine/dihydropiperlonguminine components (1:0.8) separated from Futokadsura stem acetic ether extracts could selectively inhibit the expression of APP gene in SK-N-SH cells in mRNA and protein levels. This inhibition effect is concentration-dependent. Under experimental concentrations, the components did not affect the proliferation activity of SK-N-SH cells. These data suggest that piperlonguminine/dihydropiperlonguminine components are the effective components in Futokadsura stem which can inhibit the expression of APP gene.

Molecular basis of dysfunctional Kv channels in small coronary artery smooth muscle cells of streptozotocin-induced diabetic rats.

We have previously shown that diabetes impaired cAMP-mediated endothelium independent vasodilation of rat small coronary arteries. Inhibition of Kv channel activity plays an important role in the decrease of cAMP mediated vasodilation. The present study investigated the effect of streptozotocin (STZ)-induced diabetes on mRNA and protein expressions of Kv1.2 and Kv1.5 channels in vascular smooth muscle cells of rat small coronary artery using RT-PCR, Western blot and immunohistochemistry methods. STZ-induced diabetes obviously impaired mRNA expression of Kv1.2 and Kv1.5 channel. The mRNA levels of Kv1.2 channel were 0.65 +/- 0.08 and 1.02 +/- 0.17 in STZ rats and control rats, respectively (n = 7, P < 0.05). Whereas the levels of Kv1.5 channel were 0.58 +/- 0.05 and 0.94 +/- 0.13 in STZ rats and control rats, respectively (n = 7, P < 0.05). Western blotting analysis showed that protein expression of Kv1.2 channel was decreased significantly but not Kv1.5 channel. Protein expressions of Kv1.2 channel were 0.49 +/- 0.04 and 0.70 +/- 0.06 in STZ rats and control rats, respectively (n = 5, P < 0.05), but those of Kv1.5 channel were 0.61 +/- 0.12 and 0.59 +/- 0.14 in STZ rats and control rats, respectively (n = 5, P > 0.05). Immunohistochemistry identification indicated that immunological reaction of Kv1.2 channel protein was attenuated, but Kv1.5 channel protein was not altered. Positive staining intensity normalized by gray values of Kv1.2 channel were 173 +/- 13 and 131 +/- 11 in STZ rats and control rats, respectively (n = 5, P < 0.05), but those of Kv1.5 channel were 139 +/- 16 and 141 +/- 12 in STZ rats and control rats, respectively (n = 5, P > 0.05). These results suggested that impairment of cAMP-mediated endothelium independent vasodilation of rat small coronary artery by STZ-induced diabetes was resulted from decrease of mRNA and protein expressions of Kv channels, and which eventually leads to a reduced current from Kv channels.

Ischemic preconditioning relieves ischemia/reperfusion injury of hippocampus neurons in rat by inhibiting p53 and bax expressions.

OBJECTIVE: To examine whether ischemic preconditioning (IPC) can protect neuron against delayed death in CA1 subfield of hippocampus following reperfusion of a lethal ischemia in rats, and explore the role of p53 and bax in this process. METHODS: We examined the effect of IPC on delayed neuron death, neuron apoptosis, expressions of p53 and bax gene in the CA1 area of hippocampus in the rats using HE staining, flow cytometry, RT-PCR, and immunohistochemistry technique. RESULTS: IPC enhanced the quantity of survival cells in the CA1 region of hippocampus (216 +/- 9 cells/0.72 mm2 vs. 30 +/- 5 cells/0.72 mm2, P < 0.01) , decreased the percentages of apoptotic neurons of hippocampus caused by ischemia/reperfusion (2.06% +/- 0.21% vs. 4.27% +/- 0.08%, P < 0.01 ), and weakened the expressions of p53 and bax gene of hippocampus compared with ischemia/reperfusion without IPC. CONCLUSION: IPC can protect the neurons in the CA1 region of hippocampus against apoptosis caused by ischemia/reperfusion, and this process may be related to the reduced expressions of p53 and bax.

Inhibition of caspase-9 activation and apoptosis is involved in ischemic preconditioning-induced neuroprotection in rat brain.

OBJECTIVES: Cerebral ischemic pre-conditioning (IPC) is capable of protecting hippocampal neurons from ischemia/reperfusion (I/R) injury. In the current study, we investigated the role of activated caspase-9 in the protective process induced by IPC and related it to cytochrome c release and apoptosis. METHODS: I/R injury was induced by a four-vessel occlusion model in Wistar rats which were randomly divided into ischemia/reperfusion group (I/R), ischemic pre-conditioning + I/R group (IPC + I/R) and control group. Histologic changes in the pyramidal layer of the hippocampal CA1 region were determined by hematoxylin and eosin (H&E) staining. The relative proportion of apoptotic neurons in this area was assessed with TUNEL staining. The redistribution of cytochrome c and activation of caspase-9 were detected in the same area with immunohistochemistry and Western blotting respectively. RESULTS: Compared to the I/R group, IPC increased the number of surviving neurons in the hippocampal CA1 region (p<0.001), markedly reduced the number of apoptotic pyramidal neurons (p<0.001), inhibited the release of cytochrome c from mitochondria to cytoplasm (p<0.001 for positively stained neurons) and decreased the amount of activated caspase-9 (p<0.001). DISCUSSION: These findings confirm that IPC is capable of protecting neurons from injury by apoptosis. The release of cytochrome c to the cytosol demonstrates that the mitochondrial pathway was involved, and the reduction in this release caused by IPC was clearly associated with reduced caspase-9 activation. Together, these results suggest that IPC protects neurons via action on the mitochondrial/caspase-9 pathway of apoptosis.

Ghrelin reduces injury of hippocampal neurons in a rat model of cerebral ischemia/reperfusion.

Ghrelin, an acyl-peptide gastric hormone and an endogenous ligand for growth hormone secretagogue (GHS) receptor 1a (GHS-R 1a) exerts multiple functions. It has been reported that synthetic GHS-hexarelin reduces injury of cerebral cortex and hippocampus after brain hypoxia-ischemia in neonatal rats. However, the effect of ghrelin in tolerance of the brain tissues to cerebral ischemia/reperfusion (I/R) injury has not been studied. The aim of the present study was to examine whether ghrelin have potential protective effect on hippocampal neurons of rats against I/R injury. I/R injury was induced by a modified four-vessel occlusion model. Ghrelin was administered intraperitoneally after the insult. Histological damage of the neurons was determined with hematoxylin-eosin (H&E) staining and assay of the neuronal apoptosis was performed by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL). The results showed that I/R decreased the number of surviving neurons and induced apoptosis of the neurons in CA1 area of the hippocampus in rats. In contrast, administration of ghrelin significantly increased the number of surviving neurons and reduced the number of TUNEL-positive apoptotic neurons in the equivalent areas after I/R. In conclusion, the present data provide evidence for the first time that ghrelin can exert a neuroprotective role in vivo in the tolerance of hippocampal neurons to I/R injury, and that the mechanism underlying this effect involves an anti-apoptotic property of ghrelin.

Effects of cervical-lymphatic blockade on brain edema and infarction volume in cerebral ischemic rats.

To observe the effects of cervical-lymphatic blockade (CLB) on brain edema and infarction volume of ischemic (MCAO) rat, we examined changes in cerebral water content, Ca2+ and glutamate concentrations, cerebral infarction volume and mRNA expression levels of N-methyl-D-aspartame receptor 1 (NMDA receptor 1) in the ischemic (left) hemisphere. The present results demonstrated that all the above indices in rats with middle cerebral artery occlusion plus cervical lymphatic blockade (MCAO+CLB) were markedly higher than those with only middle cerebral artery occlusion (MCAO) at different time points. These results indicated [corrected] that CLB can aggravate cerebral ischemia by increasing brain edema and infarction volume.

Antihypertensive effect of total flavonoid fraction of Astragalus complanatus in hypertensive rats.

The purpose of the present study was to quantify the antihypertensive effect of the total flavonoid (TF), extracted from the seed of Astragalus complanatus R. Brown, and to observe its effect on the renin-angiotensin system (RAS) in both renal hypertensive rats (RHR) and spontaneously hypertensive rats (SHR). RHR were created by the two-kidney one clip (2K1C) method. Systolic blood pressure was measured in conscious rats by the tail-cuff method. Plasma angiotensin II (AngII) and plasma renin activity (PRA) were measured with radioimmunoassay at 60 min after drug administration. The effects of TF on cardiac hemodynamics were also recorded in anesthetized RHR and SHR. TF was given by oral administration in low dose (100 mg/kg) and high dose (200 mg/kg) respectively. Compared to pre-administration control, TF induced an obvious decrease in systolic blood pressure in conscious normotensive Wistar rat, RHR and SHR. In the three groups the systolic blood pressure reached the lowest value at 60 min after TF. TF also induced a significant decrease in blood pressure in anesthetized RHR and SHR. At 60 min after treatment of TF, mean arterial pressure in high dose group (200 mg/kg) was decreased by 17% in RHR and by 17% in SHR respectively (P < 0.01). The depressor effect of TF lasted for at least 60 min. Cardiac output, heart rate and +/- dp/dtmax did not change. Conversely, total peripheral resistance was significantly decreased. The decrease in plasma AngII was found in both RHR and SHR. On the contrary, PRA increased at the same time. These findings suggested that TF is effective in reducing blood pressure in both RHR and SHR. The antihypertensive action of TF was attributed to a decrease in TPR secondary to a decrease in plasma concentration of AngII caused by TF.

Drainage of macromolecules from the Caudato-Putamen of rat brain.

To study the drainage of interstitial fluid and macromolecules from the brain parenchyma, an improved method was developed to inject tracers including Chinese ink in group I and phycoerythrin (PE) in group II into the right caudato-putamen of rat brain. Rats were sacrificed on the 1st, 3rd, 7th, 14th, 21st day after injection in group I and at the 0.5, 1, 2, 5, 24 hour in group II. Distribution of tracers was observed by electron microscopy and fluorescence confocal microscopy. The results showed that tracers distributed diffusely in the white matter at all time points whereas they spread selectively along perivascular spaces in the gray matter by 7 days (d) in group I and 5 hours (h) in group II. Chinese ink was ingested by perivascular phagocytes by 7 d after ink injection. The endothelial cells of capillaries in the gray matter had fluorescence staining in cytoplasm and no staining in nuclei by 24 h after PE injection. Animals in group II were stained with tracers in lateral ventricles, bilateral cervical lymph nodes, and the wall of carotid arteries. These results demonstrated that [1] the macromolecules could be cleared from the caudato-putamen through extracellular space of the neuropil in the white matter and perivascular space in the gray matter, [2] perivascular phagocytes and endothelial cells of capillaries played important roles in clearing macromolecules from the perivascular space, and [3] cervical lymph nodes were involved in draining macromolecules from the brain parenchyma.

Effects of streptozotocin-induced diabetes on Kv channels in rat small coronary smooth muscle cells.

Diabetes impairs endothelium dependent vasodilation, but the mechanism of endothelium independent dilation is not well understood. In the present study, we examined the effect of streptozotocin (STZ)-induced diabetes on the vasomotor of small coronary artery and the activity of voltage-dependent K+ channel of vascular smooth muscle cells in STZ rats [corrected] using the videomicroscopy and patch clamp method. STZ-induced diabetes appeared to [corrected] reduce the vasodilation induced by beta-adrenoceptor agonist, isoproterenol (10(-9)-10(-5) mol/l), and adenylyl cyclase activator forskolin (10(-9)-10(-5) mol/l) respectively (isoproterenol: 44.2 +/- 6.7% vs. 82.5 +/- 4.8%, and forskolin: 54.4 +/- 4.5% vs. 94.3 +/- 2.4%). 4-AP, a Kv channel blocker of VSMC, further decreased dilation to isoproterenol (44.2 +/- 6.7% vs. 10.2 +/- 3.5%) and forskolin (54.4 +/- 4.5% vs. 13.8 +/- 11.0%) significantly. Whole cell K+ current recording demonstrated that STZ-induced diabetes decreased isoproterenol and forskolin-induced K+ current (ISO: 55.6 +/- 7.8 pA/pF vs. 28.4 +/- 3.4 pA/pF, forskolin: 61.3 +/- 9.8 pA/pF vs. 32.4 +/- 3.4 pA/pF). 4-AP further reduced the decreased K+ current (ISO: 28.4 +/- 3.4 pA/pF vs. 14.3 +/- 2.1 pA/pF, forskolin: 32.4 +/- 3.4 pA/pF vs. 14.8 +/- 2.9 pA/pF). These results indicated that STZ-induced diabetes impaired cAMP mediated dilation of small coronary artery and suppressed the Kv channel activity of vascular smooth muscle cells. Kv channel of VSMC was shown to play a determinate role reducing dilation of small coronary artery in STZ rats.

[The changes of bcl-2, bax expression and neuron apoptosis in the hippocampus after the blockade of cervical lymphatics of rats].

To investigate the changes in bcl-2, bax expression and neuron apoptosis in the hippocampus after the blockade of cervical lymphatics, the model of lymphostatic encephalopathy was established by occluding and removing both the superficial and deep cervical lymph nodes in rats. The animals were sacrificed at 1, 2, 3, 5, 7 and 14 d after operation. H and E staining was used to observe the structure of brain tissues and TUNEL staining was used to detect in situ cell apoptosis in the hippocampus. The expression of bcl-2 and bax in the hippocampus were examined by RT-PCR. The results showed that cerebroedema appeared at day 2 and was most serious at day 5 after the blockade of cervical lymphatics. The number of TUNEL positive cells began to increase at day 2 and reached the maximum at day 5. The expression of bax began to increase at day 1 and reached the maximum at day 2. The expression of bcl-2 began to decrease at day 1 and dropped to the minimum at day 5. The items mentioned above recovered to control level at day 14. These results suggest that lymphostatic encephalopathy following the blockade of cervical lymphatics result in changes in bcl-2 and bax expression in the hippocampus and that apoptosis is the main form of neuron death.

Chloride channel activity of vascular smooth muscle in the spontaneous hypertensive rats.

To characterize the activity of the Ca2+-activated Cl- channels in vascular smooth muscle (VSM) of the spontaneous hypertensive rats (SHR), the isolated mesenteric vascular beds and tail artery strips were preparated from SHR and Wistar rats aged 7-8 weeks. The changes in contractile response to norepinphrine (NE) were taken as an index of vascular mortion. Results showed that the contractile responses of mesenteric arteries and tail arteries to NE in SHR were significantly greater than that in Wistar rats. The inhibition magnitude of the contractile response by Ca2+-activated Cl- channel blocker, niflumic acid in SHR was significantly less than that in Wistar rats. Decreasing the extracellular Cl- concentration increased the contractile response to NE significantly, but the amplitude of enhanced contractile response in SHR was greater than that in Wistar rats. It can be concluded that NE-induced contraction was enhanced in SHR, which is partly due to an increase in Cl- efflux through the Ca2+-activated Cl- channels. The chloride channel activity may be increased in association with the elevation of blood pressure.

Arecoline excites the colonic smooth muscle motility via M3 receptor in rabbits.

Arecoline is an effective component of areca (betel nuts, a Chinese medicine named pinang or binglang). The purpose of this study was to investigate the effect of arecoline on the motility of distal colon in rabbits and its mechanisms involved. Strips of colonic smooth muscle were suspended in organ baths containing Krebs solution, and their isometric contractions were examined. The response of smooth muscle to arecoline in colonic strips was recorded. The effects of atropine, gallamine and 1,1-dimethyl-4-diphenylacetoxypiperidiniumiodide (4-DAMP) on arecoline-induced contraction were also observed. Arecoline (1 nM - 1 microM) produced a concentration-dependent contraction in both the longitudinal and the circular smooth muscle of rabbit colon. Atropine (10 microM) abolished the arecoline (80 nM)--induced contraction. M3 receptor antagonist, 4 - DAMP (0.4 microM), abolished the arecoline (80 nM)--related response, whereas M2 receptor antagonist, gallamine (0.4 microM), did not affect the effect of arecoline. These results suggest that arecoline excites the colonic motility via M3 receptor in rabbits.

Effect of oxytocin on contraction of rabbit proximal colon in vitro.

AIM: To investigate the effects of oxytocin (OT) on isolated rabbit proximal colon and its mechanism. METHODS: Both longitudinal muscle (LM) and circular muscle (CM) were suspended in a tissue chamber containing 5 mL Krebs solution (37 degrees ), bubbled continuously with 950 mL x L(-1) O(2) and 50 mL x L(-1) CO(2). Isometric spontaneous contractile responses to oxytocin or other drugs were recorded in circular and longitudinal muscle strips. RESULTS: OT (0.1 U x L(-1)) failed to elicit significant effects on the contractile activity of proximal colonic smooth muscle strips (P>0.05). OT (1 to 10 U x L(-1)) decreased the mean contractile amplitude and the contractile frequency of CM and LM. Hexamethonium (10 micromol x L(-1)) partly blocked the inhibition of oxytocin (1 U x L(-1)) on the contractile frenquency of CM. N(omega))-nitro-L-arginine-methylester (L-NAME, 1 micromol x L (-1)), progesterone (32 micromol x L(-1)) and estrogen (2.6 micromol x L(-1)) had no effects on OT-induced responses. CONCLUSION: OT inhibits the motility of proximal colon in rabbits. The action is partly relevant with N receptor, but irrelevant with that of NO, progesterone or estrogen.

Effects of progesterone on gastric emptying and intestinal transit in male rats.

AIM: To study the dose-dependent of progesterone (P) effect and the interaction between the oxytocin (OT) and P on gastrointestinal motility. METHODS: In order to monitor the gastric emptying and intestinal transit, the SD male rats were intubated via a catheter with normal saline (3 ml/kg) containing Na(2)(51)CrO(4) (0.5 microCi/ml) and 10% charcoal. OT was dissolved into normal saline and P was dissolved into 75% alcohol. RESULTS: Low does of P (1 mg/kg, i.p.) enhanced the gastric emptying (75+/-3%, P<0.05) and high dose of P (5 mg/kg, i.p.) inhibit it (42+/-11.2%, P<0.01). P (1 mg/kg) increased the intestinal transit (4.2+/-0.3, P<0.05) while the higher dose (10-20 mg/kg) had no effect. OT (0.8 mg/kg, i.p.) inhibited the gastric emptying (23.5+/-9.8%, P<0.01). The inhibitory effects of P(20 mg/kg) (32+/-9.7%, P<0.05) and OT (0.8 mg/kg) on gastric emptying enhanced each other when the two chemicals were administrated simultaneously (17+/-9.4%, P<0.01). CONCLUSION: Low dose of P increased GI motility while high dose of P decreased it. During the later period of pregnancy, elevated plasma level of OT may also participate in the gastrointestinal inhibition.

Effect of areca on contraction of colonic muscle strips in rats.

AIM: To investigate the effects of areca on the contractile activity of isolated colonic muscle strips in rats and mechanism involved. METHODS: Each strip (LMPC, longitudinal muscle of proximal colon; CMPC, circular muscle of proximal colon; LMDC, longitudinal muscle of distal colon; CMDC, circular muscle of distal colon.) was suspended in a tissue chamber containing 5 mL Krebs solution (37 degrees C), bubbled continuously with 950 mL.L(-1) O(2) and 50 mL.L(-1) CO(2). The mean contractile amplitude (A), the resting tension (T), and the contractile frequency (F) were simultaneously recorded on recorders. RESULTS: Areca dose dependently increased the mean contractile amplitude, the resting tension of proximal and distal colonic smooth muscle strips in rats (P<0.05). It also partly increased the contractile frequency of colonic smooth muscle strips in rats (P<0.05). The effects were partly inhibited by atropine (the resting tension of LMPC decreased from 0.44 +/- 0.12 to 0.17 +/- 0.03; the resting tension of LMDC decreased from 0.71 +/- 0.14 to 0.03 +/- 0.01; the mean contractile amplitude of LMPC increased from -45.8 +/- 7.2 to -30.5 +/- 2.9; the motility index of CMDC decreased from 86.6 +/- 17.3 to 32.8 +/- 9.3; P<0.05 vs areca), but the effects were not inhibited by hexamethonium (P>0.05). CONCLUSION: Areca stimulated the motility of isolated colonic smooth muscle strips in rats. The stimulation of areca might be relevant with M receptor partly.