Decrease in erythrocyte:plasma lithium ratio by concurrent administration of psychotropic drugs and lithium in mice

1. Previous studies paying attention to concurrent use of lithium (Li+) with a neuroleptic were not done under constant and controlled conditions. We were therefore encouraged to do a prospectively controlled study, presuming constant relevant factors, on concomitant use of Li+ with neuroleptic as well as other psychotropic agents. 2. The effects of concurrent administration of chlorpromazine, haloperidol, imipramine and carbamazepine with Li+ on the erythrocyte:plasma Li+ ratio and the intraerythrocyte Li+ concentration were studied in mice by using a new, direct method of measuring erythrocyte Li+ concentration. 3. All of the foregoing agents with the exception of carbamazepine were observed to significantly decrease the Li+ ratio. 4. Lack of any significant effect by carbamazepine on Li+ transport may be an indication of this drug's efficacy as a supplement in Li+ therapy of bipolar affective disorders. 5. The decrease in Li+ ratio observed with chlorpromazine, haloperidol and imipramine may be explained through the mechanism by which these drugs stabilize the cell membrane and consequently affect Li+ transport in erythrocytes. 6. Moreover, our study proves that, although the Li(+)-sodium countertransport mechanism does not exist in mice, the same interaction between Li+ and other psychotropic drugs is seen. It can be concluded that such interaction is not mediated through Li(+)-sodium countertransport. 7. It is suggested that, with concurrent use of a psychotropic drug and Li+, the amount of intraerythrocyte Li+ concentration be measured, instead of relying on the plasma Li+ concentration alone.

Syntheses and calcium channel antagonist activity of nifedipine analogues with methylsulfonylimidazolyl substituent

Various diester analogues of nifedipine in which the ortho nitrophenyl group at position 4 is replaced by 1-methyl-2-methylsulfonyl-5-imidazolyl substituent, were synthesized and evaluated as calcium channel antagonists on guinea-pig ileal smooth muscle. Nifedipine was used as a standard. Compound 6n was found to be the most active.

The effect of acute lithium and rubidium pretreatment on apomorphine-induced pecking in pigeons

The effects of different doses of lithium (5-320 mg/kg intramuscularly) and rubidium (0.25 32 mg/kg intramuscularly) on apomorphine-induced pecking were investigated in pigeons. These two cations did not induce pecking by itself. Intramuscular administration of apomorphine (a mixed D1/D2 dopamine receptors agonist, 0.1-1.6 mg/kg) induced pecking in a dose-dependent manner. SCH 23390 (D1 dopamine receptor antagonist, 0.02-0.08 mg/kg) and sulpiride (D2 dopamine receptor antagonist, 25-100 mg/kg) decreased apomorphine-induced pecking dose-dependently. Combination of SCH 23390 (0.04 mg/kg) with sulpiride (50 mg/kg) caused a stronger inhibitory effect on apomorphine response. This indicates that both D1 and D2 dopamine receptors are involved in apomorphine-induced pecking. The response induced by apomorphine (0.2-0.8 mg/kg) was decreased in animals pretreated with lithium and rubidium. In these conditions, SCH 23390 and sulpiride produced a larger inhibitory effect on the apomorphine response, suggesting that acute lithium and rubidium pretreatment inhibit pecking by interfering with dopaminergic mechanisms.

Endogenous nitric oxide modulates naloxone-precipitated withdrawal signs in a mouse model with acute cholestasis

Cholestasis liver disease is associated with clinical and experimental findings consistent with increased opioidergic neuromodulation, increased plasma total activity, and elevated plasma enkephalin concentrations. The effect of the nitric oxide (NO) synthase inhibitor, L-nitro-arginine (L-NA, 0.03, 0.1, 0.3, 1 mg/kg), and the nitric oxide precursor, L-Arg (30 mg/kg), on antinociception induced by bile duct resection or sham operation, as well as on opioid dependence, was examined in male albino Swiss mice. Repeated (5 days) administration of L-NA attenuated signs of dependence, as assessed by naloxone (5 mg/kg)-precipitated withdrawal, and decreased the antinociception; however, L-Arg potentiated withdrawal signs and increased the antinociception. The results of this study support the involvement of the L-arginine/nitric oxide pathway in the opioidergic-dependent manifestation of cholestasis in an animal model.

Alteration of rat submandibulary gland secretion of protein, calcium and N-acetyl-beta-D-glucosaminidase activity by lead

1. Effects of various doses of long-term lead treatment (0.01%, 0.04% and 0.05%) on rat submandibular saliva were investigated in this study. 2. Both submandibular ducts were cannulated intraorally with polyethylene tubes and saliva was collected from anesthetized lead treated and control rats using pilocarpine as secretagogue. 3. Saliva protein concentration was found to be reduced in lead (0.04%)- and (0.05%)-treated groups. 4. Saliva calcium concentration had a significant reduction only in the lead (0.05%)-treated group. 5. The secretion of the lysosomal enzyme, N-acetyl-beta-D-glucosaminidase (NAG) in saliva decreased significantly in the lead (0.04%)- and (0.05)-treated groups. Specific activity of the enzyme showed an increase in these treated groups. 6. Good correlations were found between saliva protein concentration and NAG activity, saliva protein and calcium concentrations and calcium concentration and NAG activity. 7. There was a correlation between blood and submandibular saliva lead levels, and the saliva/blood ratio was approximately constant for all treated groups. 8. With respect to the ability of lead to substitute for calcium in several intracellular regulatory events, explanation for these alterations in submandibular saliva composition can be made.

Alterations of physostigmine-induced yawning by chronic lithium administration in rats

The effect of chronic lithium pretreatment on physostigmine-induced yawning was investigated in male rats. Intraperitoneal administration of physostigmine to rats induced yawning in a biphasic manner. However the maximum response was obtained by 0.2 mg/kg of the drug. Intracerebroventricular administrations of a putative M1 and M2 muscarinic receptor antagonists, pirenzepine and methoctramine decreased physostigmine-induced yawning. Intraperitoneal administration of a non-selective muscarinic receptor antagonist, atropine, also decreased the physostigmine-induced yawning significantly. Chronic lithium pretreatment (30 days) reduced yawning induced by physostigmine. The inhibitory effect of pirenzepine, methoctramine and atropine on physostigmine-induced yawning increased in rats pretreated with chronic lithium. These findings indicate that yawning is induced by a central cholinergic mechanism and that chronic pretreatment of lithium may interact with the cholinergic-induced behaviour.

Inhibition by lithium of gentamicin-induced release of N-acetyl-beta-D-glucosaminidase in rat submandibular saliva

1. The effects of gentamicin, lithium and concurrent treatment of these drugs on concentration of total protein and activity of the enzyme N-acetyl-beta-D-glucosaminidase (NAG) in rat submandibular saliva were studied. 2. Pure submandibular saliva was collected intraorally by micropolyethylene canula from anesthetized rats with the use of pilocarpine as secretagogue. 3. Daily intraperitoneal injection of gentamicin (50 mg kg/day) for 5 consecutive days caused a marked increase in total protein concentration and the NAG activity. 4. Chronic treatment of rats for 10 days with lithium chloride solution (1,200 mg/l) caused a significant decrease in total protein concentration but did not affect the NAG activity. 5. Concurrent treatment of lithium with gentamicin caused the total protein concentration and the NAG activity of submandibular saliva to reach to those of controls. 6. In this regard, the protective effects of lithium may be due to interference of this ion with the phosphoinositide cycle.

The effects of dopaminergic and adrenergic drugs on twitch response of guinea-pig common bile duct

1. Effects of various doses of bromocriptine and apomorphine, dopamine receptor agonists, on electrically evoked contractile responses of guinea pig common bile duct (CBD) were investigated in this study. 2. Bromocriptine and apomorphine produced a concentration-dependent reduction of the twitch heights. IC50 values for bromocriptine and apomorphine were 2.75 +/- 0.715 x 10(-6) M, and 1.69 +/- 0.11 x 10(-5) M, respectively. 3. Pretreatment with sulpiride, 0.1 and 1.0 microM, prevented bromocriptine- and apomorphine-induced inhibition. pA2 values of sulpiride against bromocriptine and apomorphine were 8.26 and 6.29, respectively. 4. Clonidine, 0.1-100 microM, produced 49.3 +/- 2.5% inhibition of twitch responses. Its effect was partially antagonized by 1 microM of yohimbine. 5. It would appear that both dopamine D2- and alpha 2-adrenergic presynaptic receptors are present on the guinea-pig CBD cholinergic nerve.

Rapid method for the determination of piroxicam in rat plasma using high-performance liquid chromatography

A previously published method was used for the determination of piroxicam in plasma samples obtained from rat. The sample preparation involved liquid extraction, centrifugation and evaporation. Separation of piroxicam from internal standard occurred on a reversed-phase C18 column with a mobile phase consisting of methanol-phosphate buffer pH 2 (45:55). The detection limit of the assay was 0.02-20 micrograms/ml. The assay linearity was good (typically r = 0.9992). The method was applied for determination of piroxicam in rats after administration of an oral dose of 2 mg/kg piroxicam.

The effects of lithium, indomethacin, and neomycin on vasopressin-induced contractions in rat urinary bladder

1. [Arg8]Vasopressin (AVP) induced a contraction response in rat urinary bladder smooth muscle in a dose-dependent manner. 2. Indomethacin in a 10-microM concentration cannot change the effects of AVP on urinary bladder smooth muscle, which seem to be mediated by a direct action on the muscle rather than indirectly through prostanoid release. 3. Lithium (0.5, 1, and 10 mM) made the muscle more sensitive to AVP action. 4. Neomycin (1.25, 2.5, and 5 mM) had an inhibitory effect on AVP-induced contraction. 5. It seems that in rat urinary bladder vasopressin-induced contraction is mediated through phosphoinositide metabolism.

Inhibition by L-NA, a nitric oxide synthase inhibitor, of naloxone-precipitated withdrawal signs in a mouse model of cholestasis

Following the naloxone administration in bile duct resected animals, striking opioid withdrawal signs are observed due to increased opioidergic tone. Pretreatment of animals with L-nitro arginine, a nitric oxide synthase inhibitor, reduces the naloxone-precipitated withdrawal signs as well as increase the antinociception. The results of this study support evidence for the involvement of the L-arg-nitric oxide pathway in opioidergic-dependent manifestation of cholestasis in an animal model.

Anti-inflammatory and anti-nociceptive activity of disodium glycyrrhetinic acid hemiphthalate

The anti-inflammatory and anti-nociceptive effects of disodium glycyrrhetinic acid hemiphthalate (glycyrrhetinic acid 3 beta-O-hemiphthalate sodium) after parenteral administration were determined in several animal models. Disodium glycyrrhetinic acid hemiphthalate (GAP) significantly inhibited the rat paw edema induced by carrageenin (ID50 = 21.37 mg/kg), and mice writhing responses caused by acetic acid (ID50 = 9.12 mg/kg). The potency of disodium glycyrrhetinic acid hemiphthalate was about 13.05 times higher than acetylsalicylic acid in inhibiting rat paw edema and 12.84 times higher in inhibiting abdominal constrictions in mice.

Effects of cyclosporine A on the functions of submandibular and parotid glands of rats

1. The present study was designed to investigate the possible effects of long-term (45 days) administration of therapeutic doses of cyclosporine A (25 mg/kg/day), on the functions of submandibular and parotid glands of rats. Pure submandibular and parotid saliva were collected intraorally by microcannulation of the ducts. 2. The weight gains of the treated animals during the study and the weights of the salivary glands at the end of 45 days were reduced significantly as compared with those of controls. 3. Sialochemistry studies revealed a marked decrease in total protein concentration in saliva obtained from submandibular glands (P < 0.05). 4. Determination of electrolyte concentrations in saliva of submandibular gland and serum showed considerable differences between treated and control groups. 5. Significant elevation of amylase activity in serum and parotid saliva was observed in the treated rats in comparison with controls (P < 0.001). 6. Data presented here indicates that long-term administration of therapeutic doses of cyclosporine A causes significant alterations in salivary output and composition.

Inhibition by lithium and rubidium of gentamicin-induced release of N-acetyl-beta-D-glucosaminidase from perfused rat kidney

N-acetyl-beta-D-glucosaminidase (NAG) is one of the sensitive hydrolytic lysosomal enzymes which is released after renal tubular damages. We studied gentamicin-induced nephrotoxicity by determining the NAG release in perfused rat kidney. 100 micrograms/ml of gentamicin caused a time-dependent increase in enzymuria, peaking at 90 min. At this time the released NAG is about sixfold more than the control. The effect of concurrent perfusion with 100 micrograms/ml gentamicin and with 0.5 mmol/l lithium chloride or 0.5 mmol/l rubidium chloride in the perfusion fluid was also studied by measuring NAG activity in the perfusate. Both cations decrease the gentamicin-induced NAG release. However, the inhibitory effect of lithium chloride may be due to interference of this ion with the polyphosphoinositide cycle in renal tubular lysosomal membranes. There is no obvious evidence for an inhibitory effect of rubidium chloride.

Cyclosporin A-induced functional and morphological changes in pilocarpine treated rat submandibular glands

The effects of long-term administration of Cyclosporin A (CSA), an immunosuppressive agent, on submandibular glands of male albino rats were investigated. Sialochemistry studies revealed a reduction of pilocarpine-stimulated flow rates to 54% compared to the controls. Salivary Mg(2+) and K+ were elevated and a marked decrease in total protein concentration was observed. Light and electron microscopic features of treated glands show marked changes at tissue level. An irregular pattern of the nucleus, mitochondrial alterations, reduction in the number of secretory granules and their aggregation, disturbances of cytoplasmic organelles, and isometric vacuolation were among the most striking findings. Our results show that CSA causes marked functional and morphological alterations in rat submandibular glands, which may be due to the drug's direct effects on the tissue.

Clonidine-induced rhythmic activity in rabbit anococcygeus muscle

1. Clonidine 0.5 mM induced an extremely regular rhythmic activity in isolated rabbit anococcygeus muscle. The movements were resistant to tetrodotoxin effect. 2. Prazosin (5 x 10(-8)M-5 x 10(-6)M) and yohimbine (1.5 x 10(-7)M-5 x 10(-4)M) showed no remarkable effect on clonidine-induced rhythmic activity. 3. The clonidine-induced contractions were dependent on extracellular calcium and could be inhibited by the omission of calcium from medium or the introduction of verapamil (IC50 = 1.3 x 10(-7)M) or nifedipine (IC50 = 7.5 x 10(-8)M). 4. Pretreatment of animals with reserpine made the preparations 2800-fold more sensitive to this action of clonidine. 5. It can be concluded from this study that clonidine is able to induce rhythmic activity in rabbit anococcygeus muscle through a mechanism that increases intracellular concentration of Ca++ via membrane calcium channels.

The effect of concomitant use of neuroleptic drugs and lithium on the erythrocyte/plasma lithium ratio in Iranian patients with bipolar disorder

Patients treated with lithium (Li+) and neuroleptic drugs concomitantly are reported to show more pronounced adverse effects than patients on Li+ alone. There are conflicting results about the effect of neuroleptic drugs on the erythrocyte/plasma Li+ ratio and intraerythrocyte Li+ concentration, and methodological problems may be a reason for this. The effect of the concurrent use of neuroleptic drugs with Li+ on the Li+ ratio was studied in 66 patients with bipolar affective disorders during prophylactic Li+ therapy using the new direct method of measuring erythrocyte Li+ concentration. This new direct method has been shown to give much more precise and accurate results than the values obtained by other methods. No relationship was found between the Li+ ratio and sex, age, Li+ dosage, duration of treatment or plasma Li+ concentration. Results revealed that patients taking a combination of Li+ and neuroleptic drugs showed significantly lower Li+ ratios and intraerythrocyte Li+ concentrations as compared with those on Li+ alone. It is notable that this reducing effect of neuroleptic drugs was increased by the concurrent use of two types of neuroleptic drugs. The effect on neuroleptic drugs on the Li+ ratio may be mediated through a stabilizing effect of these drugs on the cell membrane and consequently Li+ transport in erythrocytes.

Alterations of bromocriptine-induced penile erection by chronic lithium in rats

In the present study, the effects of chronic lithium pre-treatment (30 days) on penile erection (PE) induced by bromocriptine were investigated in rats. Intraperitoneal administration of the dopamine receptor agonist, bromocriptine (4-32 mg/kg) induced PE in a biphasic manner. The maximum response was obtained with 8 mg/kg of bromocriptine and the effect was decreased with increasing doses of the drug from 8 to 32 mg/kg. When animals were pre-treated with different doses of the D-1 dopamine receptor antagonist, SCH 23390, or the D-2 dopamine receptor antagonist, sulpiride, the PE response was decreased. The response induced by bromocriptine (4-32mg/kg) was reduced in animals pre-treated with chronic lithium. SCH 23390 did not produce a larger inhibitory effect on the bromocriptine response in animals pre-treated with chronic lithium, but the inhibitory effect of sulpiride was increased in this condition. It is concluded that chronic lithium treatment may alter the D-1/D-2 receptor activity and inhibit bromocriptine-induced PE.

Conditions that lithium inhibits or potentiates vasopressin V1-receptor-mediated platelet aggregation and [Ca++]i mobilization

1. Besides clinical use, there are many explanations for the mechanism of action of lithium. Although it is shown that lithium may reduce the supply of inositol that is required to sustain phosphoinositide synthesis, evidence exists concerning the potentiating effect of lithium on this pathway. We therefore decided to evaluate conditions in which lithium inhibits or potentiates platelet aggregation and calcium response induced by vasopressin. 2. Platelet aggregation was measured by the photometric method, and changes in intracellular free calcium were measured using fura-2/AM. 3. We show an inhibitory action of neomycin on vasopressin-induced platelet aggregation. Lithium, according to the preincubation time, could both potentiate or inhibit platelet aggregation and calcium responses induced by vasopressin. The inhibitory effect of lithium on platelet aggregation is dependent on concentrations of both lithium and vasopressin and also the presence of indomethacin, for example, in the absence of indomethacin there was no clear inhibitory action of lithium on vasopressin-induced platelet aggregation. 4. These results show the importance of arachidonate metabolites concerning lithium effects on platelet V1-receptor signaling. In conclusion, because the arachidonate metabolites are responsible for the release of other active substances from platelets' granules, the aggregatory responses in the absence of indomethacin may be amplified, and this subsequently may change the net inhibitory action of lithium.

The effect of cyclosporine A and trifluoperazine on amylase secretion from rat parotid glands in vitro

In the present study the effects of trifluoperazine (TFP) and/or cyclosporine A (CsA) on the amylase secretion of rat parotid gland lobules were investigated. Cyclosporine A, in doses of 10(-6), 3 x 10(-6) and 10(-5) M, caused a dose-dependent reduction in amylase secretion. Trifluoperazine, a well-established calmodulin antagonist, also significantly reduced amylase secretion by the gland, confirming that the secretion is calmodulin dependent. Concurrent administration of CsA and TFP showed a marked positive interaction in reducing the secretion of amylase. Thus, the hypothesis that CsA may have Ca2+/calmodulin antagonistic properties is supported by the present study.

Effects of diltiazem and verapamil on ADP-induced rabbit platelet shape change and aggregation

1. The effects of diltiazem and verapamil (two structurally different calcium channel blockers) were examined on the rabbit platelets shape change and aggregation induced by adenosine-5'-diphosphate (ADP). 2. ADP was a much more potent stimulator on inducing platelet shape change (ED50 = 1 x 10(-7)) than platelet aggregation (ED50 = 1.78 x 10(-6)). 3. Both drugs similarly inhibited ADP-induced platelet shape change and aggregation at concentrations more than 300 microM. 4. There were no significant differences in inhibitory effects of either diltiazem or verapamil on ADP-induced platelet shape change and aggregation. 5. The inhibitory effects of diltiazem and verapamil on ADP-induced platelet shape change and aggregation at high concentrations may be due to their non specific properties.

Effects of chronic lithium pretreatment on apomorphine-induced penile erection

1. The effects of chronic lithium pretreatment (600 mg/l in drinking rats, 30 days) on penile erection (PE) induced by apomorphine were investigated in rats. This treatment resulted in a serum Li concentration after 30 days of 0.31 +/- 0.01 mmol/l. 2. Subcutaneous (s.c.) administration of mixed D1/D2 dopamine receptor agonist apomorphine (0.05-0.5 mg/kg) induced PE in a biphasic manner. The maximum effect was obtained with 0.1 mg/kg of the drug while the response decreased with increasing doses of apomorphine from 0.1 to 0.5 mg/kg. 3. Pretreatment of animals with 0.0125-0.1 mg/kg of D1 dopamine receptor antagonist SCH 23390 or D2 dopamine receptor antagonist sulpiride (12.5-100 mg/kg) decreased apomorphine-induced PE. Combination of SCH 23390 (0.025 mg/ kg) with sulpiride (12.5 mg/kg) caused a stronger inhibitory effect on apomorphine response. This indicates that both D1 and D2 dopamine receptors may be involved in PE induced by apomorphine. 4. The response induced by apomorphine (0.05-0.05 mg/kg) was decreased in animals pretreated with chronic lithium. The inhibitory effect of sulpiride on apomorphine response, increased in animals pretreated with lithium, in contrast the inhibitory effect of SCH 23390 did not change in this condition. However, a combination of SCH 23390 with sulpiride increased inhibitory effect on apomorphine response in lithium pretreated rats. 5. It is concluded that chronic lithium inhibits PE induced by dopaminergic mechanism(s).

Alteration by ouabain of rat submandibular glands function

1. Effects of various doses of intraperitoneal ouabain (1,2 and 5 mg/kg) on rat submandibular saliva were investigated in this study. 2. Potassium and calcium and their product (K+ x Ca2+) were found to be elevated in all groups. 3. Changes in salivary flow were not the major cause of the alterations in electrolytes. 4. Protein concentrations were elevated in the doses of 1 and 2 mg/kg of the drug and somewhat reduced in the dose of 5 mg/kg of ouabain but still above the base line. 5. The results show that there is an ouabain-induced close parallelism between magnesium and total protein secretion from rat submandibular glands.

The effect of lithium on endothelial-dependent relaxation in rat isolated aorta

1. In endothelium-containing rings of rat aorta, precontracted by phenylephrine, addition of acetylcholine (Ach), resulted in a concentration-dependent relaxation through the release of endothelial dependent relaxing factors, including nitric oxide (IC50 = 8.41 microM). 2. Pretreatment of the tissues with 20 microM indomethacin, significantly decreased the relaxation. 3. Preincubation of the preparations in medium solution in which sodium has been partially replaced by 0.5 mM lithium, significantly reduced Ach-induced endothelial dependent relaxation (EDR). 4. Lithium (2 mM) in medium, significantly increased Ach-induced relaxation. 5. As is shown in this study, lithium has two opposite actions of EDR, with the dose of 0.5 mM inhibiting, while the dose of 2 mM potentiates EDR. Thus it seems that the action of lithium on EDR is mediated through two separate mechanisms.

Effects of lithium on rat parotid and submandibulary gland functions

1. Pure submandibular and parotid saliva were collected intraorally by micro polyethylene canula from anesthetized lithium treated and control rats using pilocarpine as secretagogue. 2. Acute intraperitoneal injection of a single dose of lithium chloride (10 mg/kg), caused a significant decrease in protein, calcium, potassium and sodium concentrations of parotid saliva and also a significant decrease in protein, potassium and calcium concentrations of submandibular saliva. 3. Chronic treatment of rats for 10 days by LiCl solution (1200 mg/l) also caused some marked changes in saliva compositions similar to those observed in acute experiment. 4. The results of this study suggest that lithium as a drug used in the treatment of affective disorders can influence the secretory mechanisms of both submandibular and parotid glands. 5. These effects of lithium in composition of parotid and submandibular saliva are not related to duration of treatment.

Different calcium dependencies of contractile activity of prostatic and epididymal portions of rat vas deferens

1. The effects of some organic calcium entry blockers and different concentrations of extracellular calcium on electrically-evoked contractions of isolated epididymal and prostatic portions of rat vas deferens were investigated. 2. Both epididymal and prostatic parts of rat vas deferens responded to single pulse or train electrical field stimulation, with twitch contractions of submaximal amplitude. 3. Verapamil showed a biphasic action on the contractions produced by single pulse electrical stimulation. In concentrations < 10(-5) M, it potentiated the responses of both portions, but at higher concentrations, the excitatory action was overcome by a concentration-dependent inhibitory effect. 4. Nifedipine reduced the amplitude of electrically-evoked contractions of both portions in a concentration-dependent manner. The ED50 of nifedipine was 3.6 x 10(-8) M and 2.1 x 10(-6) M in prostatic and epididymal portions, respectively. 5. Dantrolene sodium reduced the amplitude of electrically-evoked contractions of both portions in a concentration-dependent manner. The ED50 of dantrolene was 1.55 x 10(-4) M and 9.1 x 10(-4) M in prostatic and epididymal portions, respectively. 6. Reduction of Ca2+ concentration in medium reduced the amplitude of contractions of both portions significantly. This calcium dependence was more apparent in low frequencies of electrical stimulation.

On the relation of calcium channel blockers to rat parotid and submandibular glands function in vivo

1. The effects of nifedipine, verapamil and diltiazem on rat parotid and submandibular glands function were studied. 2. Nifedipine (5 mg/kg), verapamil (5 mg/kg) and diltiazem (10 mg/kg) were injected intraperitoneally 15 min before saliva collection. 3. Animals were anesthetized with 50 mg/kg of sodium pentobarbital and 8 mg/kg of pilocarpine was used as secretagogue. 4. Submandibular saliva was analyzed for flow rate, protein and calcium concentrations; and parotid saliva for calcium and amylase contents. 5. In treated groups, flow rate and calcium of submandibular saliva were significantly lower than controls. Parotid calcium in the nifedipine group was decreased and in verapamil and diltiazem groups was increased. Parotid amylase was significantly decreased in both the nifedipine and diltiazem groups. 6. It is concluded that a blockade of calcium channels in salivary glands acinar cells by CCBs causes some alterations in salivary secretions.

Inhibition by lithium of neomycin-induced release of N-acetyl-beta-glucosaminidase in the rat heart

The effects of neomycin, lithium and concurrent therapy of these drugs on subcellular distribution of lysosomal enzyme, N-acetyl-beta-glucosaminidase (NAG) in the heart was studied. Released activity of NAG was used as a marker for assessing myocardial lysosomal integrity. The activity of NAG was determined in non-sedimentable and sedimentable fractions after centrifugation of the tissue extracted for assessment of the subcellular distribution of the lysosomal enzyme. Daily intraperitoneal injection of 100 mg/kg/day of neomycin increased the ratio of the non-sedimentable activity (free) to the non-sedimentable plus sedimentable activities (total) of NAG. Daily intraperitoneal injection of lithium decreased the total activity of NAG but did not affect the ratio of free: total activities of the enzyme. Lithium in doses of 2 and 4 mM/kg/day one hour prior to neomycin reduced the neomycin-induced enhancement of the ratio of free: total activity of NAG. Neomycin like other aminoglycosides altered the acidic phospholipid metabolism in lysosomal membranes and/or impairment of some important lysosomal functions. In this regard, the protective effects of lithium may be due to interference of this ion with phosphoinositide cycle.

Effects of vinca alkaloids on rat parotid and submandibular glands function in vivo

1. Vincristine (1 mg/kg) and vinblastine (2 mg/kg) were injected intraperitoneally into the rats, 24 hr before the experiments. 2. Animals were anesthetized with 50 mg/kg of sodium pentobarbital and saliva was collected from vincristine-treated, vinblastine-treated and control animals using 8 mg/kg of pilocarpine as secretagogue. 3. Parotid saliva was analyzed for protein, amylase and Ca2+ content, and submandibular saliva for flow rate, protein and Ca2+ concentration. 4. Saliva from two treated groups was significantly lower (P < 0.01) in flow rate, amylase and protein content than that of control group. Calcium level was significantly increased (P < 0.05) in treated animals. 5. It is concluded that the antisecretory effects of vinca alkaloids may be consistent with their actions on salivary cell microtubules.

Inhibition of the morphine withdrawal syndrome and the development of physical dependence by lithium in mice

Due to the claim that lithium (Li+) reduces morphine self-administration in dependent rats, the effects of acute and chronic Li+ treatments on naloxone-precipitated withdrawal syndrome and physical dependence development to morphine in mice chronically treated with morphine, were evaluated. Morphine dependency was induced by the ingestion of morphine through drinking water in increasing doses for 10 days. Physical dependence to morphine was observed by precipitating an abstinence syndrome with naloxone (2 mg/kg, i.p.). In the acute experiments, Li+ (1 and 10 mg/kg, i.p.) was administered 1 hr prior to challenge with naloxone to morphine-dependent mice whereas for chronic studies, mice received morphine concomitant with Li+ (1200 mg/l) as drinking fluid for 10 days. Results obtained indicate that acute Li+ administration significantly reduced the withdrawal signs, and we were unable to induce some degree of morphine dependency in co-administration of Li+ to mice receiving chronic morphine treatment as compared to chronic morphine administration alone. The present study revealed that even in mice with very much lower serum Li+ levels than the commonly accepted therapeutic range there was a significant reduction in the withdrawal signs. It has been shown that Li+ and morphine have diverse effects on the transmembrane signal control systems. The interaction of Li+ and morphine might be through these systems.

Comparison of various calcium channel blockers on guinea-pig isolated common bile duct

1. The inhibitory effects of various calcium channel blockers; nifedipine, verapamil, diltiazem and a heterogenous compound, dantrolene, have been investigated on isolated common bile duct from guinea-pig. 2. All the compounds tested induced a concentration-dependent reduction of the amplitude of contractile response to electrical stimulation or increasing the calcium concentration of the bathing media. 3. Nifedipine was the most potent compound whereas the least potent was dantrolene; verapamil and diltiazem had intermediate potency. 4. The IC50 values for these compounds were calculated as: nifedipine 3.68 x 10(-9) M; verapamil, 4.93 x 10(-8) M; diltiazem, 4.2 x 10(-7) M; and dantrolene 5.51 x 10(-5) M. 5. All the compounds displaced the concentration-response curve of calcium chloride to the right in a concentration-dependent manner. Among the compounds studied, nifedipine had the highest and dantrolene had the lowest potency. 6. These results indicate the striking pharmacological effects of the calcium channel blockers on the common bile duct and may indicate a possible role for these compounds in the treatment of biliary colic.

The effect of lithium on morphine-induced analgesia in mice

1. The effects of acute and chronic lithium (Li+) treatments on the antinociception caused by morphine were studied in mice using the tail-flick test. 2. Subcutaneous injection of morphine (10 mg/kg) caused significant antinociception. 3. Acute Li+ administration (0.05, 0.1, 0.3, 1, 5 and 10 mg/kg, i.p.) alone had no significant antinociceptive effect but changed morphine analgesia; low doses of Li+ (0.1, 0.3 and 1 mg/kg) were found to decrease the antinociception induced by morphine whereas higher doses of the drug (10 mg/kg) potentiated this effect. 4. The 6 day administration of Li+ with a serum level of 0.528 mM decreased the antinociceptive effect of morphine. 5. The effect of Li+ on morphine-induced analgesia persisted for 96 hr in spite of the fact that Li+ drinking was discontinued (the serum Li+ level decreased from 0.528 to 0.022 mM). 6. It has been reported that Li+ might change both the binding of opioids to their receptors and biosynthesis or release of endogenous opioids. There is also a considerable body of evidence which indicates that both Li+ and morphine affect phosphoinositide turnover, intracellular calcium content and cyclic AMP level. The interaction of two drugs may conceivably take place through these systems. 7. These data suggest that the biological effects of Li+ may exist at very much lower serum Li+ levels than the commonly accepted therapeutic range.

Effects of gentamicin on rat submandibulary gland functions

1. Submandibular saliva was collected from anesthetized gentamicin-treated and control rats using carbachol, isoproterenol and pilocarpine as secretagogue. 2. Intraperitoneal injection of a large single dose (80 mg/kg) of gentamicin caused marked changes in saliva flow rate, protein and electrolyte concentrations in the presence of parasympathetic or sympathetic agents used as stimulants. 3. The secretion of N-acetyl-beta-D-glucosaminidase in saliva was determined and there was a marked increase in the enzyme activity of saliva of gentamicin-treated rats in comparison to that of controls. 4. The results of this study suggest that gentamicin as an aminoglycoside antibiotic at the dose employed, can influence the secretory mechanisms of rat submandibular glands.

Effects of atropine, pirenzepine, clonidine, and morphine on biphasic response of rat gastric fundus to field stimulation

1. Electrically evoked contractions in isolated strips of rat gastric fundus were inhibited by atropine (IC50 = 2.5 x 10(-9) M), pirenzepine (IC50 = 2.3 x 10(-8) M), clonidine (IC50 = 3.9 x 10(-8) M) and morphine (IC50 = 3.2 x 10(-7) M) in a dose-dependent manner. 2. The inhibitory effect of morphine was antagonized by naloxone (10(-6) M). The inhibitory effect of clonidine not only was not reversed by yohimbine but also was enhanced. Yohimbine per se inhibited these contractions (IC50 = 6.4 x 10(-6) M). 3. In presence of atropine (2 x 10(-6) M) and guanethidine (5 x 10(-6) M), electrical stimulation of isolated strips of rat gastric fundus produced a non-adrenergic, non-cholinergic (NANC) inhibitory response. 4. The NANC inhibitory response was decreased by morphine (10(-8)-3 x 10(-6) M). In addition, morphine decreased the tone of the muscle. These effects of morphine was antagonized by naloxone (3 x 10(-6) M). 5. Clonidine up to 10(-6) M had no influence on the NANC inhibitory response but yohimbine per se (10(-7)-3 x 10(-5) M) blocked it (IC50 = 3 x 10(-6) M). 6. These findings indicate that electrically evoked contractions in the rat gastric fundus were mediated by muscarinic receptors. In addition, the NANC inhibitory response in the isolated 5-strips of rat gastric fundus was blocked by morphine and yohimbine.

Ultrastructural localization of calcium in neuromuscular junctions of smooth and skeletal muscles after aminoglycoside antibiotics treatment

Aminoglycoside antibiotics are all capable of producing clinically significant neuromuscular paralysis. Since part of the mechanism of action of these antibiotics at neuromuscular junction is a calcium-dependent inhibition of acetylcholine release, so this experiment was carried out in vitro on both somatic (isolated rat phrenic-nerve hemidiaphragm) and autonomic neuro-effector transmission (guinea-pig ileum) using gentamicin and amikacin, to determine the calcium contents at this level. Electron microscopic observations on gentamycin- and/or amikacin-treated materials, using potassium pyroantimonate method suggest a reduction of internal calcium in nerve terminals of both preparations.

Possible evidence for involvement of new subtype of P1-purinoceptors in rat isolated uterus

1. The effects of adenosine (Ado), 5'-N-ethylcarboxamidoadenosine (NECA), 2-chloro-adenosine, N6-phenylisopropyladenosine (L-PIA and D-PIA) and N6-cyclohexyladenosine (CHA) were examined on the rat isolated uterus. 2. All the analogues except NECA, in a concentration-dependent manner, inhibited electrically induced contractions. 3. 8-Phenyltheophylline (8-PT: P1 antagonist) did not antagonize adenosine and its analogues-induced relaxation. 4. Dipyridamole (Dipy: an adenosine uptake inhibitor) potentiated the relaxations to adenosine but had no significant effect on the relaxations induced by the analogues. 5. The agonist potency order for the relaxation of contractions elicited by direct muscle stimulation was: CHA > L-PIA > 2-chloroadenosine > D-PIA > Ado. 6. The present data may propose the presence of a new subtype of P1-purinoceptor.

The role of calcium and alpha-adrenoceptors in contractile response of chick expansor secundariorum muscle to field stimulation

1. The effects of some alpha-adrenergic agonists and antagonists on electrically-evoked contractions and tension of chick expansor secundariorum muscle (ESM), and dependence of these events on extracellular calcium was investigated. 2. Both train and continuous electrical stimulation can produce regular contractions in preparations obtained from 40-60 day old chicks. 3. Clonidine had a biphasic action on the contractions produced by train electrical stimulation. In concentrations ranging from 10(-8) to 3 x 10(-7) M, clonidine decreased the contraction amplitude, but in higher concentrations, it caused an increase in both the muscle tension and the contraction amplitude. These effects were reversed by application of yohimbine although yohimbine by itself had no effect on the contractions. 4. Introduction of calcium free isotonic high potassium medium decreased muscle tone which was followed by further dose-dependent increase in tension, along with the addition of cumulative doses of CaCl2 (ED50 = 2.8 x 10(-3) M). 5. Nifedipine reduced the amplitude of ESM contractions produced by continuous electrical stimulation in a dose dependent manner (IC50 = 6.7 x 10(-7) M). 6. Methoxamine induced a completely dose dependent increase in muscle tension which was dependent on extracellular calcium and was inhibited by nifedipine. In the presence of 10(-8) M nifedipine, ED50 of methoxamine stimulatory effect increased from the control value of 2.2 x 10(-7) to 8.4 x 10(-7) M).(ABSTRACT TRUNCATED AT 250 WORDS)

The protective effect of liquorice components and their derivatives against gastric ulcer induced by aspirin in rats

We have examined the protective effect of liquorice or its derivatives against gastric ulcer induced by aspirin. A granular mixture of aspirin alone and coated with liquorice or its derivatives including the deglycyrrhized form, a high glycyrrhized form, carbenoxolone, and enoxolone were studied. Aspirin coated with liquorice reduced the number and size of ulcers, reducing the ulcer index from 1.5 +/- 0.12 to 0.5 +/- 0.12 and the incidence from 96% to 46%. Coating with derivatives was less effective (ulcer index, 0.70-0.94; incidence 62-76%).

Diabetic rats show more resistance to neuromuscular blockade induced by aminoglycoside antibiotics

1. Neuromuscular blocking effect of gentamicin and neomycin evaluated in phrenic-nerve hemidiaphragm preparation in normal and diabetic rats and IC50 of both drugs determined from LDR curves. 2. IC50 of gentamicin was 0.91 +/- 0.05 and 1.67 +/- 0.08 mmol.l-1 for normal and diabetic rats respectively. 3. IC50 of neomycin was 0.42 +/- 0.02 and 0.61 +/- 0.06 mmol.l-1 for normal and diabetic rats respectively. 4. The results show diabetic rats are more resistant to neuromuscular blocking action of aminoglycoside antibiotics (AGs). 5. Replacement of sodium by lithium (1.5 and 5 mmol.l-1) in the media, reduced this effect of aminoglycosides (AGs) significantly. 6. It appears that the prevention of AGs induced-neuromuscular blockade by lithium is not significantly different in both groups.

Methoxamine-induced rhythmic activity in rabbit anococcygeus muscle

1. Methoxamine 0.5 microns induced an extremely regular rhythmic activity in isolated rabbit anococcygeus muscle. 2. Prazosin had an inhibitory effect on methoxamine-induced rhythmic contractions. IC50 of prazosin was 7.94 nM. 3. The methoxamine-induced contractions are dependent on extracellular calcium and can be inhibited by the omission of calcium from media or the introduction of verapamil (IC50 = 0.11 microM) or nifedipine (IC50 = 0.21 microM). 4. Application of reserpine made the preparations 40-fold more sensitive to methoxamine. 5. It can be concluded that rhythmic contractions produced by methoxamine are mediated through stimulatory action of methoxamine on alpha-I adrenoceptors and depend on extracellular calcium. 6. Lithium made the muscle more sensitive to methoxamine action. In preincubated muscles with 1, 3 and 5 mM lithium the initiation of contractions occurred at 1.5 x 10(-7), M, 5 x 10(-8) M and 1.5 x 10(-8) M of methoxamine, respectively.

Inhibition of gentamicin-induced nephrotoxicity by lithium in rat

Daily intraperitoneal injection of gentamicin in doses of 2, 4 and 10 mg/kg/day for 5 consecutive days produced proximal tubular necrosis in male albino rats as assessed by ultrastructural findings from electron microscopic observations. With respect to nephrotoxicity, aminoglycoside antibiotics (AGs) have been shown to concentrate in the lysosomes of kidney proximal tubular cells to inhibit the activities of phospholipases A and C, including a phospholipidosis, characterized by the formation of myeloid bodies. It has been suggested that the nephrotoxicity of AGs is related to the extent of this phospholipidosis. The concurrent therapy of lithium in doses of 5 and 10 mEq/kg/day, administered subcutaneously, 24 hours prior to gentamicin administration for the same period, proved effective in reducing the gentamicin-induced phospholipidosis in kidney as judged by reduction in lysosomal myeloid bodies to an amount of 26-45 percent. It is well known that lithium interferes with phosphatidylinositol turnover and reduces the cellular availability of myoinositol which is needed for the resynthesis of membrane polyphosphoinositides. Thus, the inhibitory effect of lithium on gentamicin-induced nephrotoxicity may be due to interference of lithium with phosphoinositide cycle.

Developmental changes in morphine and clonidine sensitivity of isolated chick oesophagus

1. Electrically evoked contractions of isolated newly-hatched and over 6 week-old chicks cervical oesophagus (pre-crop) were inhibited by morphine and clonidine in a dose-dependent manner. 2. The inhibitory effects of morphine and clonidine were antagonized by naloxone (3 x 10(-6) M) and yohimbine (10(-7) M), respectively. 3. IC50 for morphine was 1.01 x 10(-7) M for newly-hatched and 5.19 x 10(-6) M for adult chicks. 4. IC50 for clonidine was 2.34 x 10(-9) M for newly-hatched and 1.19 x 10(-8) M for adult chicks. 5. These findings indicate a significant decrease in inhibitory effect of morphine and clonidine during developmental stages.

Rabbit isolated vas deferens possess A1 and A2 adenosine receptors

1. The effects of adenosine, 5'-N-ethylcarboxamidoadenosine (NECA), 2-chloroadenosine, N6-phenylisopropyladenosine (L-PIA and D-PIA) and N6-cyclohexyladenosine (CHA) were examined on the rabbit isolated vas deferens. 2. All the analogues in a concentration-dependent manner inhibited contractile response to electrical stimulation. 3. 8-Phenyltheophylline caused a rightward shift of all the adenosine and its analogues' concentration-response curves. 4. The order of potency for the adenosine and its analogues on the rabbit isolated vas deferens was: CHA = NECA greater than L-PIA greater than 2-chloroadenosine greater than D-PIA greater than adenosine. 5. It is concluded that CHA, NECA, L-PIA, 2-chloroadenosine, D-PIA and adenosine mediate their inhibitory effects on the rabbit isolated muscle via both A1 and A2 adenosine receptors.

Inhibitory action of aminoglycoside antibiotics on the electrically induced release of opioid peptides in the guinea-pig ileum in vitro

The effect of aminoglycoside antibiotics upon the electrically induced release of endogenous opioid peptides from the guinea-pig ileum was studied in vitro. Stimulation of guinea pig ileum at 10 Hz in normal Tyrode solution resulted in the naloxone sensitive depression of the twitch contractions of this muscle. Addition of aminoglycosides during 10 Hz stimulation diminished this naloxone sensitive depression in a dose dependent manner. IC50s of this effect of streptomycin, neomycin, kanamycin and gentamicin were found to be 2.54, 2.29, 1.36 and 0.7 mg/ml respectively. A 3.5 fold increase in the calcium concentration of media during 10 Hz stimulation significantly reversed the effect of aminoglycosides. It is concluded that aminoglycoside antibiotics exert their effect by interfering with trans-membrane movements of calcium at the nerve endings which is required for the electrically induced release of opioid peptides.

In vitro binding of dantrolene to bovine serum albumin and rabbit red blood cell ghosts

The binding of dantrolene to rabbit red blood cell (RBC) ghosts and bovine serum albumin as models of receptor sites was studied using fluorescence techniques. Dantrolene upon binding to rabbit RBC ghosts and bovine serum albumin showed fluorescence with emission maxima at 495 and 500 nm, respectively. Dantrolene bound to rabbit RBC ghosts with an association constant of 6.06 X 10(4) M-1 and there were 2.4 X 10(6) dantrolene binding sites per ghost. The binding of dantrolene to bovine serum albumin showed an anomaly with respect to dantrolene concentration. Dantrolene at concentrations of 1.25-3.75 microM bound to bovine serum albumin with an association constant of 1.72 X 10(4) M-1 and there were 1.078 binding sites/mol bovine serum albumin. The higher affinity of dantrolene toward blood cells was confirmed by studying the distribution of dantrolene between blood cells and plasma after a single i.p. injection of dantrolene sodium (3 mg/kg) to albino rabbits. It was found that the concentration of dantrolene in rabbit blood cells was 2.76 times that of plasma.

In vitro binding of dantrolene to sarcoplasmic reticulum of rabbit skeletal muscle

Dantrolene upon binding to microsomes containing sarcoplasmic reticulum of rabbit thigh muscle exhibits a fluorescence with emission at 490 nm, which shows a blue shift of 35 nm compared with its fluorescence in ethylacetate. Using fluorescence techniques, dantrolene binding to microsomes isolated from rabbit thigh muscle was investigated. From Scatchard plots of binding studies, the association constant (Kass) and the number of binding sites of dantrolene to sarcoplasmic reticulum were calculated, which was found to be 9.6 X 10(4) M-1 and 1.71 mumole/g of membrane proteins, respectively. In the presence of verapamil (1.25 X 10(-4) M), another calcium antagonist, the binding of dantrolene to microsomes was enhanced. However, at a high concentration of verapamil (3.75 X 10(-4) M), the Scatchard plot of dantrolene binding was found to be biphasic.

Effect of dantrolene sodium on the contractility of rabbit jejunum in vitro

The effect of dantrolene sodium on the spontaneous contractions of rabbit jejunum was studied in vitro. Dantrolene sodium (4.5 x 10(6) to 4.5 10(4) M) reversibly decreased the amplitude of contractions in a dose-dependent manner. ED50 was found to be about 7.9 x 10(-5) M. Its effect was biphasic in that a period of potentiation preceded that of suppression of contractions. Lowering or increasing (2.5 fold in each direction) the calciumm concentration of bathing media did not affect the suppression of contraction caused by dantrolene sodium to any significant degree. Caffeine but not quinine was found to be able to restore the activity of the intestine to normal after a 50% inhibition caused by dantrolene sodium. Dantrolene sodium, verapamil and nifedipine were able to shift the dose-response curves of calcium in potassium-polarized rabbit jejunum to the right and pA2 values were found to be 4.18, 7.76 and 8.47 respectively. These data indicate that the effect of dantrolene on smooth muscle is mediated via inhibition of calciu movement across the membrane.

Pharmacological study of the anococcygeus muscle of the dog

1 The response of the dog anococcygeus muscle to field stimulation and to some drugs has been studied. The results are compared with those reported previously in the rat, cat and rabbit. 2 Field stimulation produced frequency-dependent contractions which were inhibited by guanethidine and phentolamine. When the tonus of the muscle was increased with guanethidine, field stimulation always produced frequency-dependent relaxation. The relaxation was not prevented by propranolol. 3 The muscle was contracted by noradrenaline, tyramine, acetylcholine, histamine (H1), 5-hydroxy-tryptamine, prostaglandin E2 and vasopressin. Phentolamine, atropine, promethazine (but not cimetidine) and methysergide inhibited the effect of the respective agonists. 4 After increasing the tonus of the muscle, it was relaxed by low concentrations of isoprenaline. The relaxation was antagonized by propranolol. 5 The response to adenosine triphosphate (ATP) was variable. In some preparations, it relaxed the muscle, in others it contracted the muscle prior to relaxation, in others still it only contracted the muscle. Indomethacin did not prevent ATP-induced contraction. 6 It is concluded that the anococcygeus of the dog, like that of rat, cat and rabbit, has an adrenergic motor innervation and an inhibitory innervation, the transmitter of which is not identified.