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1.
During the deformation of single crystals of alpha-lactose monohydrate and anhydrous alpha-lactose in a crushing strength rig, their acoustic activity was monitored using a portable activity meter. The acoustic parameters measured were the average signal level (ASL), count rates and total acoustic counts. Both types of lactose, even though deformed by fragmentation, differed fundamentally in the degree and nature of this fragmentation. Close correlation was observed between the ASL, count rate profiles and the force-displacement profiles. The monohydrate form is acoustically more active than the anhydrous form during deformation. Small internal fractures which were neither visually observed nor detected in the force-displacement profiles (in particular the anhydrous alpha-lactose) were detected by monitoring the acoustic signals during the deformation of these crystals. This work illustrates the potential of using the acoustic emission technique as an aid in the assessment of the deformation characteristics of pharmaceutical materials during single crystal compression studies.  相似文献   

2.
The P2 receptor-mediated responses of isolated guinea pig urinary bladder and vas deferens (P2X receptors) and taenia caeci (P2Y receptors) were registered at the three temperature conditions of 30, 37 and 42 degrees C. The contractile responses of both urinary bladder and vas deferens to a P2X receptor agonist alpha,beta-methylene ATP (alpha,beta-meATP; 0.01-30 microM) and to electrical field stimulation (1-64 Hz, 0.1 ms, supramaximal voltage) in the presence of atropine (0.1 microM) and phentolamine (1 microM) were markedly more prominent at a temperature of 30 degrees C than at 37 or 42 degrees C. Similarly, relaxation of carbachol-precontracted taenia caeci caused by electrical field stimulation (0.5-8 Hz, 0.1 ms, supramaximal voltage) temperature-dependently increased with decrease of temperature, while relaxation of this tissue by exogenous ATP (1-100 microM) was not affected by the temperature. A P2 receptor antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS, 1-30 microM) at all three temperature conditions concentration-dependently antagonised contractile responses to alpha,beta-methylene ATP and electrical field stimulation in both urinary bladder and vas deferens. PPADS, even at the highest concentration tested (30 microM), had no effect on the relaxant responses of the taenia caeci either to electrical field stimulation or ATP and its action was not affected by the change of temperature. It is concluded from this study that the effectiveness of P2 receptor-mediated responses in guinea pig urinary bladder, vas deferens and taenia caeci increases by decrease of temperature.  相似文献   

3.
Reverse tolerance to stereotyped behavior was induced after repeated administration of beta-phenylethylamine (PEA) (50 mg/kg, i.p., daily for 10 days) in rats. The reverse tolerance was maintained for at least 4 weeks after the last administration. We studied the effects of acoustic stimulation on locomotor activity 2 days and 4 weeks after withdrawal from PEA and measured the changes in brain monoamine levels 4 weeks after the withdrawal. Locomotor activity during acoustic stimulation was increased in the saline treated group, and this response was unaffected after repeated PEA treatment. Four weeks after withdrawal, significant increases in noradrenaline levels in the cerebral cortex and decreases in 5-hydroxytryptamine levels in the hypothalamus were found. The effects of acoustic stimulation on locomotor activity and the changes in brain monoamine levels were different from those of methamphetamine treatment obtained in our previous study. In conclusion, it may be suggested that the response to acoustic stimulation after repeated PEA administration in rats cannot be a model for abnormal responsiveness to environmental stimulation that is observed in chronic paranoid schizophrenics.  相似文献   

4.
In the driven isolated left atrium of the rabbit theophylline shortened relaxation time in a similar manner to isoprenaline and histamine. 2 Phenylephrine lengthened relaxation time in a similar manner to calcium. 3 Theophylline caused phenylephrine to shorten relaxation time, which was inhibited by a beta-adrenoceptor blocking drug, but theophylline did not potentiate the effect of phenylephrine on peak tension. 4 Theophylline separated drug effects on cardiac relaxation and contraction: in the presence of theophylline at a low calcium concentration, phenylephrine shortened relaxation time by beta-adrenoceptor stimulation and increased peak tension by alpha-adrenoceptor stimulation. At a high calcium concentration, theophylline potentiated the effect of isoprenaline, histamine and phenylephrine on relaxation time but inhibited the effect on peak tension.  相似文献   

5.
Demonstration of release of ATP from smooth muscle preparations during stimulation of purinergic nerves is complicated by the difficulty in showing whether it comes from nerve or muscle. ATP released during relaxation of the guinea-pig taenia coli and contraction of bladder strips in response to purinergic nerve stimulation was measured in the superfusate using the luciferin-luciferase ATP assay method. The amount of ATP increased 2-6 fold during isometric responses to purinergic nerve stimulation. This release was blocked by tetrodotoxin but not by adrenergic nerve destruction with 6-hydroxydopamine. No significant release of ATP was detected during comparable responses elicited by direct muscle stimulation. These results provide further support for the purinergic nerve hypothesis.  相似文献   

6.
Previous work has shown that stimulation of alpha 2-adrenergic receptors depresses the startle responses in rats. The present study suggests that this depressant effect involves supraspinal rather than spinal alpha 2-adrenergic receptors because intraventricular but not intrathecal infusion of the hydrophilic alpha 2-adrenergic agonist ST-91 depressed the acoustic startle reflex. To determine the point in the acoustic startle pathway where alpha 2-adrenergic receptor activation might ultimately alter neural transmission, startle responses were elicited electrically from different points along the acoustic startle pathway after systemic administration of clonidine. Clonidine depressed acoustically-elicited startle and startle elicited by electrical stimulation of the ventral cochlear nucleus to a comparable magnitude and over a similar time course. It also partially depressed startle elicited by electrical stimulation of the nucleus reticularis pontis caudalis (RPC). Taken together, these data suggest that alpha 2-adrenergic stimulation depresses startle by acting on supraspinal receptors, but that this effect is ultimately expressed, at least in part, by actions at both spinal and brainstem levels of the acoustic startle response pathway. The results are compared to other drugs known to affect the startle reflex.  相似文献   

7.
1 Vasoactive intestinal polypeptide (VIP, 0.01- MicroM) produced dose-related relaxations of the mouse anococcygeus muscle. 2 Following incubation with indomethacin (2.8 microM 1 h) adenosine 5'-triphosphate (ATP, 0.5-10 mM) produced dose-related relaxations of the mouse anococcygeus. 3 Haemolysed blood reduced inhibitory responses of the mouse anococcygeus to field stimulation but had no effect on relaxations to VIP or ATP. 4 Apamin (0.5 microM) had no effect on the relaxation of mouse anococcygeus to field stimulation, VIP, or ATP. 5 2-2'-Pyridylisatogen tosylate (PIT, 50 microM) itself reduced muscle tone but it did not abolish inhibitory responses to field stimulation, VIP, or ATP. 6 During prolonged inhibitory nerve stimulation the relaxation of the mouse anococcygeus in response to VIP was reduced greatly while that to ATP was unaffected. 7 Bundles of VIP-immunoreactive sites were detected in sections of the mouse anococcygeus treated by the peroxidase-antiperoxidase (PAP) immunocytochemical technique. 8 The results suggest that the mechanisms underlying non-adrenergic, non-cholinergic inhibitory transmission in the mouse anococcygeus are similar to those in the bovine retractor penis and unlike those in the guinea-pig taenia caeci. 9 The possibility that VIP or ATP might be involved in inhibitory neurotransmission in the mouse anococcygeus is discussed.  相似文献   

8.
In the trigone (three portions) and proximal urethra isolated from castrated male pigs, transmural electrical stimulation (0.5-10 Hz) induced no or slight contractions followed by frequency-related relaxations. Atropine suppressed the contraction and potentiated the relaxation. N(G)-nitro-L-arginine methylester (L-NAME), a nitric oxide (NO) synthase inhibitor, depressed or abolished the relaxation induced by low frequency stimulation, but only slightly attenuated the response to high frequency stimulation. L-Arginine reversed the inhibitory effect. L-NAME-sensitive relaxation by 1 Hz stimulation was abolished by 1H-(1,2,4)oxadiazolo-(4,3-a)quinoxalin-1-one (ODQ), a guanylate cyclase inhibitor. Release of NO by nerve stimulation to trigonal strips was determined by increased formation of cyclic GMP in the incubation media containing guanylate cyclase and GTP. L-NAME-resistant relaxation by 10 Hz stimulation was not impaired by ODQ, capsaicin, chymotrypsin, K(+) channel inhibitors and beta-adrenoceptor antagonists. Similar results were obtained in the trigone and urethra from normal male and female pigs. Detrusor muscle responded to nerve stimulation with contraction followed by slight relaxation. Relaxations at 1 and 10 Hz stimulation under treatment with atropine and alpha,beta-methylene ATP were partially attenuated by L-NAME. It is concluded that there is no significant difference in the inhibitory responses, sensitive and resistant to L-NAME, to nerve stimulation in the trigone and proximal urethra from castrated and non-castrated male and female pigs. Relaxations to stimulation at 1 Hz seem to be mediated exclusively by neurogenic NO and cyclic GMP generation, whereas those to 10 Hz stimulation is mainly associated with non-NO relaxing factor(s), peptides, K(+) channel openers and beta-adrenoceptor agonist being unlikely involved.  相似文献   

9.
The possible involvement of vasoactive intestinal polypeptide (VIP) in the non-adrenergic non-cholinergic (NANC) relaxation of the cat gastric fundus was studied in circular and longitudinal muscle strips. Cumulative transmural stimulation induced a frequency-dependent relaxation, while cumulative administration of VIP induced a concentration-dependent relaxation. Tetrodotoxin almost completely antagonized the relaxation induced by transmural stimulation (1 Hz), but did not influence the relaxation induced by VIP (10(-7) M); the latter was not influenced by hexamethonium or propranolol plus phentolamine. Trypsin (30 min incubation) and VIP antiserum (1 h incubation) prevented the relaxation induced by VIP and reduced that induced by transmural stimulation, but did not influence the relaxation induced by isopropylnoradrenaline. Two putative VIP receptor antagonists, [AcTyr1]hGRF-(1-40)OH and [4Cl-D-Phe6,Leu17]VIP, did not influence the relaxation induced by VIP or transmural stimulation. These results are compatible with the hypothesis that VIP is involved in the NANC relaxation of the cat gastric fundus, although participation of a non-VIP component cannot be excluded.  相似文献   

10.
In dog duodenal longitudinal muscle strips, transmural electrical stimulation (10 Hz, 15 sec) elicited a transient contraction, which was abolished by tetrodotoxin and atropine but potentiated by treatment with NG-nitro-L-arginine (L-NA), a nitric oxide (NO) synthesis inhibitor. The potentiation was reversed by L-arginine but not by its D-enantiomer. Acetylcholine-induced contractions were not influenced by L-NA. After treatment with atropine, the electrical neural stimulation relaxed the muscle strips partially contracted with bradykinin, the relaxation being abolished by tetrodotoxin and suppressed by L-, but not D-, NA. L-arginine reversed the L-NA-induced inhibition. Oxyhemoglobin abolished the relaxation caused by nerve stimulation and NO. The neurally-induced relaxation was not attenuated by adrenoceptor antagonists and indomethacin. It is concluded that electrical stimulation of non-adrenergic, non-cholinergic nerves relaxes dog duodenal smooth muscle, due possibly to NO produced upon neural excitation, and potentiation by L-NA of the contractile response to cholinergic nerve stimulation, would be derived from elimination of the neurally-induced relaxation.  相似文献   

11.
Summary Arterial pressure, heart rate, preganglionic discharges of the cervical sympathetic nerve and action potentials of the phrenic nerve were recorded in 10 cats under four different conditions: fully conscious (artificial respiration with air, relaxation with suxamethonium), in analgesia (artificial respiration with 66.6% nitrous oxide in oxygen) and in chloralose-urethan anaesthesia (40 mg/kg and 200 mg/kg i.v., respectively) alone or in combination with nitrous oxide. In 10 control experiments cats received nitrous oxide in oxygen during a period of 160 min. In addition, 11 experiments were performed to compare the effects of 66.6% with those of 75% nitrous oxide. The above parameters were recorded both during rest and during acoustic stimulation or asphyxia.In the first series of experiments the effects of analgesia and anaesthesia were expressed as per cent change from the values recorded during the waking state. Inhalation of 66.6% nitrous oxide only slightly depressed the sympathetic activity and the heart rate at rest. The arterial blood pressure remained constant. During acoustic stimulation and asphyxia the sympathetic activity was depressed by 22.9 and 37.5%, respectively. In contrast to nitrous oxide, chloralose-urethan caused a pronounced inhibition of the sympathetic activity by 65.7% at rest; heart rate was decreased by 17.1% while blood pressure was unaltered. During acoustic stimulation and asphyxia the sympathetic activity was depressed by 70.2 and 73.4% respectively.In the second series the effects of 66.6% nitrous oxide observed during the initial inhalation period of 20 min remained unchanged throughout the following 140 min of the experiment. In the third group the administration of 75% nitrous oxide for a period of 20 min did not produce effects differing from those after 66.6% nitrous oxide.Nitrous oxide analgesia combined with suxamethonium appears to be more suitable for neuropharmacological research than chloralose-urethan anaesthesia because of the lesser depression of the sympathetic centers observed.
  相似文献   

12.
1 Contractions of the cat nictitating membrane were elicited on stimulation of the internal carotid nerve, and the effects were studied of desipramine and two inhibitors of catechol-O-methyltransferase, U-0521 and pyrogallol, on the subsequent relaxation of the muscle. 2 The relaxation of the nictitating membrane occurred in at least two phases. The late phase of relaxation was prolonged after increase in the period of nerve stimulation and the duration of this phase was further prolonged after treatment with pyrogallol. 3 After inhibition of neuronal uptake of noradrenaline with desipramine both the early and late phases of relaxation were increased in duration, and subsequent administration of pyrogallol or U-0521 caused a further increase in the duration of the late phase of relaxation. 4 The results suggest that the late phase of relaxation of the nictitating membrane is influenced by efflux of noradrenaline from an extraneuronal pool.  相似文献   

13.
A pithed rat preparation, stimulated electrically via the pithing rod left in position, was employed to examine the effects of drugs, administered intravenously, on relaxation of a loop of ileum. Relaxation due to injected isoprenaline could be largely blocked by propranolol but that due to nervous stimulation or injected noradrenaline was blocked to only a lesser extent by either propranolol or phenoxybenzamine alone. The combination of phenoxy-benzamine and propranolol was more effective against relaxation from nervous stimulation than either drug alone but was still not as effective against this as against noradrenaline, or as propranolol alone against isoprenaline. It is concluded that intestinal relaxation after nervous stimulation involves both α- and β-adrenergic activity, in variable proportions. Adrenoceptive antagonists are not as effective in blocking these receptors as they are for those concerned in relaxation after injected catecholamines.  相似文献   

14.
Field stimulation of the non-adrenergic, non-cholinergic inhibitory nerves to the bovine isolated retractor penis muscle evoked a relaxation that was preceded by a rise in the tissue content of cyclic GMP. There was no change in the content of cyclic AMP. The selective cyclic GMP phosphodiesterase inhibitor, 2-o- propoxyphenyl -8- azapurin -6-one (M&B 22948), elevated the tissue's cyclic GMP content, and potentiated both the relaxation and the rise in cyclic GMP produced by inhibitory nerve stimulation. Sodium nitroprusside and an inhibitory factor extracted from the bovine retractor penis muscle mimicked the effects of inhibitory nerve stimulation in that they each produced relaxation associated with a selective rise in cyclic GMP concentration. Haemoglobin (in the form of erythrocyte haemolysate) and N- methylhydroxylamine , which are known to block guanylate cyclase, blocked the relaxation and the rise in cyclic GMP content produced by inhibitory nerve stimulation, inhibitory factor and sodium nitroprusside. Haemoglobin itself caused a rise in muscle tone and at the same time reduced the cyclic GMP content of the tissue. 8-Bromocyclic GMP, a permeant derivative of cyclic GMP, produced a relaxation of the muscle that, as expected, was not blocked by haemoglobin. Vasoactive intestinal polypeptide, prostaglandin E1 and forskolin each produced relaxation associated with a selective rise in cyclic AMP content. Their effects were not blocked by haemoglobin or N- methylhydroxylamine . It is concluded that inhibitory nerve stimulation in the bovine retractor penis muscle produces a relaxation that is mediated by cyclic GMP, although some substances relax the muscle without affecting cyclic GMP levels. The results are also compatible with the view that the extracts of muscle contain the inhibitory neurotransmitter.  相似文献   

15.
The acoustic emission of lactose, sodium chloride, microcrystalline cellulose and paracetamol was monitored during compression, using an acoustic transducer coupled to a portable activity meter. Three stages were identified in the compression cycle. During the application of low forces (particle rearrangement) all the materials emitted extensively. With higher forces, during particle consolidation, the samples tended to be acoustically quiet. A significant exception was that of paracetamol, which did not exhibit a quiet stage through the whole compression cycle. This high level of energy dissipation indicated that little of the available compression energy was actually used for particle bonding, resulting in the poor compression properties well known for paracetamol. Acoustic emissions were again high during the third, post-compression stage. The extent of emission was dependent on tablet lubrication and the material being compressed. For sodium chloride and a free flowing lactose, a decrease in particle size produced a corresponding reduction in emmisive counts, indicating that as particle size is reduced the number of fractures reduces proportionally. The results suggest that acoustic emission measurements may enable the brittleness of tabletting materials to be quantified and aid the assessment of compression characteristics.  相似文献   

16.
1 Possible involvement of sympathetic purinergic transmission in the neurogenic response of dog cerebral and basilar arteries was examined with the use of alpha, beta-methylene ATP and adrenoceptor, cholinoceptor blocking agents. 2 In the isolated basilar arteries, electrical transmural stimulation produced a transient contraction which was frequently followed by a relaxation. This transient contraction was abolished after desensitization of P2-purinoceptors with alpha, beta-methylene ATP or by treatment with guanethidine. The relaxant response induced by electrical stimulation was also attenuated but was not abolished by such treatments. Prazosin, propranolol and atropine had no significant effect on the responses to electrical stimulation. Yohimbine augmented both the contractile and relaxant responses. 3 In most preparations of the dog middle cerebral arteries, electrical transmural stimulation produced only a relaxation. This relaxation was little affected after treatment with alpha, beta-methylene ATP or guanethidine, and was not inhibited by the other adrenoceptor and cholinoceptor blocking agents. 4 Tetrodotoxin abolished the responses induced by electrical transmural stimulation in both the basilar and middle cerebral arteries. 5 Exogenous ATP (10(-6) and 10(-5)M) produced a transient contraction followed by a relaxation of the basilar arteries and a relaxation of the middle cerebral arteries. Desensitization of P2-purinoceptors abolished the contractile response to ATP without affecting the amplitude of relaxation. 6 In the basilar and middle cerebral arteries preincubated with [3H]-noradrenaline, electrical transmural stimulation evoked an increase in 3H-efflux and this response was markedly inhibited by guanethidine or tetrodotoxin but was not affected by alpha, beta-methylene ATP. Yohimbine increased the evoked 3H-efflux.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

17.
Behavioral characteristics associated with acoustic stimulation and the neurochemical alterations of monoaminergic systems in rat brain at the steady state of repeated methamphetamine administration were investigated. We confirmed that reverse tolerance in stereotyped behavior was constructed up to the 28th day after repeated intermittent pretreatment with increasing doses of MAP (2.5, 5, and 7.5 mg/kg x 3 and 10 mg/kg x 2, every other day). During acoustic stimulation, locomotor activity in the saline group was significantly increased, but the activity after the stimulation was completely suppressed. In contrast to the saline group, locomotor activity was not influenced by the acoustic stimulation in the MAP group, suggesting that behavioral hyporesponsiveness to acoustic stimulation was induced by MAP treatment. Two days after the last injection, the contents of 5-hydroxytryptamine (5-HT) and 5-hydroxyphenylacetic acid (5-HIAA) in the cerebral cortex, midbrain + thalamus, hypothalamus and striatum were significantly decreased. These changes were maintained up to the 28th day after the drug withdrawal in the cerebral cortex and the midbrain + thalamus. From these results, the persistence of behavioral hyporesponsiveness to acoustic stimulation might be associated with long-lasting reduction of 5-HT synthesis.  相似文献   

18.
Isolated dog coronary arteries relax in response to electrical stimulation (0.1-8.0 Hz, 9 V, 1.0 ms) following contraction induced by serotonin. Cimetidine, metiamide and ranitidine inhibited this relaxation. The relaxation was not blocked by pyrilamine. Reducing the concentration of Ca+ (0.1 mM) decreased the rate of relaxation whereas relaxation was more rapid when the Ca2+ concentration was increased (3.2 mM). These results suggest that relaxation to electrical stimulation is modulated by Ca2+ and by the H2-subclass of histamine receptors.  相似文献   

19.
We investigated whether the glutamergic system plays a role in isolated trachea from control and ovalbumin-sensitized guinea-pigs. Electrical field stimulation induced contractile responses in control group, but electrical field stimulation produced relaxation responses in ovalbumin-challenged guinea-pigs. The responses induced by electrical field stimulation in both groups were completely abolished by tetrodotoxin, but unaffected by hexamethonium. DL-2-amino-5-phosphono-valeric acid (D-AP5) caused a concentration-dependent statistically significant inhibition in the contractile responses to electrical field stimulation50 (EFS50) in control guinea-pigs. But in the ovalbumin-challenged groups, D-AP5 did not cause any significant effect on the relaxation response to frequency of field stimulation (EFS50). N(G)-monmethyl-L-argine caused a significant inhibition in the relaxation effect of EFS50. L- and D-glutamate and N-methyl-D-aspartic acid (NMDA) alone had no effect on the resting tension on the trachea in both groups. Carbachol produced concentration-dependent contractile responses in ovalbumin-challenged groups. These results suggested that responses to electrical field stimulation in control groups might be due to NMDA receptor-mediated release of any substance on prejunctional neurones and, alternatively, NMDA might exert a modulatory effect on any substance at prejunctional level. Also, responses to electrical field stimulation in ovalbumin-challenged guinea-pigs might not be mediated by NMDA but rather by increasing the production of nitric oxide by inducible nitric oxide synthase.  相似文献   

20.
Erection involves cholinergic, adrenergic as well as non-cholinergic non-adrenergic nerves. Endothelial-derived relaxation factor plays an important role in mediating smooth muscle relaxation, which is crucial in initiating and maintaining erection. We previously showed that adenosine 5'-triphosphate (ATP) can induce significant relaxation in rabbit corporal cavernosal tissue. The present study presents effects of different neurotransmitters and the role of endothelium in controlling the contractile/relaxant status of rabbit cavernosal tissue. These studies utilized isolated tissue strips prepared from the corpus cavernosum of sexually mature male New Zealand white rabbits. The results can be summarized as follows: (1) field stimulation caused relaxations with rebound contractions in most strips; (2) bethanechol (250 microM), isoproterenol (20 microM) and ATP (1 mM) all induced relaxations, though the relaxation induced by bethanechol was poorly sustained; (3) removal of the endothelium by rubbing decreased the relaxation to field stimulation and virtually eliminated the relaxation induced by bethanechol, but had no effect on the relaxation responses to isoproterenol and ATP; (4) methoxamine (200 microM) stimulated a sustained contraction of corporal cavernosal tissue, an effect unaltered by rubbing the strips; (5) low dose epinephrine induced relaxation, whereas higher concentrations contracted the tissue, and (6) beta-adrenergic inhibition with propranolol (20 microM) was significantly more effective than mascarinic blockade with atropine (20 microM) in eliminating relaxation caused by field stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

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