Inhibition of gastric acid secretion by a standardized aqueous extract of Cecropia glaziovii Sneth and underlying mechanism

Cecropia glazioui Sneth (Cecropiaceae) is used in folk medicine in tropical and subtropical Latin America as cardiotonic, diuretic, hypotensive, anti-inflammatory and anti-asthmatic. The hypotensive/antihypertensive activity of the plant aqueous extract (AE) and isolated butanolic fraction (BuF) has been confirmed and putatively related to calcium channels blockade in vascular smooth musculature [Lapa, A.J., Lima-Landman, M.T.R., Cysneiros, R.M, Borges, A.C.R., Souccar, C., Barreta, I.P., Lima, T.C.M., 1999. The Brazilian folk medicine program to validate medicinal plants - a topic in new antihypertensive drug research. In: Hostettman, K., Gupta, M.P., Marston, A. (Eds.), Proceedings Volume, IOCD/CYTED Symposium, Panamá City, Panamá, 23-26 February 1997. Chemistry, Biological and Pharmacological Properties of Medicinal Plants from the Americas. Harwood Academic Publishers, Amsterdam, pp. 185-196; Lima-Landman, M.T., Borges, A.C., Cysneiros, R.M., De Lima, T.C., Souccar, C., Lapa, A.J., 2007. Antihypertensive effect of a standardized aqueous extract of Cecropia glaziovii Sneth in rats: an in vivo approach to the hypotensive mechanism. Phytomedicine 14, 314-320]. Bronchodilation and antidepressant-like activities of both AE and BuF have been also shown [Delarcina, S., Lima-Landman, M.T., Souccar, C., Cysneiros, R.M., Tanae, M.M., Lapa, A.J., 2007. Inhibition of histamine-induced bronchospasm in guinea pigs treated with Cecropia glaziovi Sneth and correlation with the in vitro activity in tracheal muscles. Phytomedicine 14, 328-332; Rocha, F.F., Lima-Landman, M.T., Souccar, C., Tanae, M.M., De Lima, T.C., Lapa, A.J., 2007. Antidepressant-like effect of Cecropia glazioui Sneth and its constituents -in vivo and in vitro characterization of the underlying mechanism. Phytomedicine 14, 396-402]. This study reports the antiulcer and antisecretory gastric acid activities of the plant AE, its BuF and isolated compounds with the possible mechanism involved. Both AE and BuF were assayed on gastric acid secretion of pylorus-ligated mice, on acute models of gastric mucosal lesions, and on rabbit gastric H(+), K(+)-ATPase preparations. Intraduodenal injection of AE or BuF (0.5-2.0g/kg, i.d) produced a dose-related decrease of the basal gastric acid secretion in 4-h pylorus-ligated mice. At 1.0g/kg, BuF decreased the volume (28%) and total acidity (33%) of the basal acid secretion, and reversed the histamine (2.5mg/kg, s.c.)- or bethanecol (1.0mg/kg, s.c.)-induced acid secretion to basal values, indicating inhibition of the gastric proton pump. Pretreatment of mice with the BuF (0.05-0.5g/kg, p.o.) protected against gastric mucosal lesions induced by 75% ethanol, indomethacin (30mg/kg, s.c.) or restraint at 4 degrees C. BuF also decreased the gastric H(+), K(+)-ATPase activity in vitro proportionately to the concentration (IC(50)=58.8microg/ml). The compounds isolated from BuF, consisting mainly of cathechins, procyanidins and flavonoids [Tanae, M.M., Lima-Landman, M.T.R., De Lima, T.C.M., Souccar, C., Lapa, A.J., 2007. Chemical standardization of the aqueous extract of Cecropia glaziovii Sneth endowed with antihypertensive, bronchodilator, antacid secretion and antidepressant-like activities. Phytomedicine 14, 309-313], inhibited the in vitro gastric H(+), K(+)-ATPase activity at equieffective concentrations to that of BuF. The results indicate that C. glazioui constituents inhibit the gastric proton pump; this effect may account for the effective antisecretory and antiulcer activities of the standardized plant extract.

Antidepressant-like effect of Cecropia glazioui Sneth and its constituents - in vivo and in vitro characterization of the underlying mechanism

The present study aimed to characterize the antidepressant-like effect of a standardized aqueous extract (AE) of Cecropia glazioui Sneth and its purified fractions on in vivo (forced swimming test), ex vivo (hippocampal monoamines levels) and in vitro (serotonin, noradrenaline and dopamine uptake) tests, searching for the active principles and the underlying mechanisms of action. Treatment with AE, or with its butanolic fraction (BuF), the latter rich in catechins, procyanidins and flavonoids, reduced the immobility of rats in the forced swimming test indicating an antidepressant-like effect. Biochemical analysis of the hippocampal neurotransmitters in BuF-treated rats showed significant increase in monoamines levels. BuF and six of its purified constituents inhibited the uptake of [(3)H]-serotonin, [(3)H]-dopamine and [(3)H]-noradrenaline by synaptosomes of different brain regions. Catechin, catechin (4alpha-->8) ent-catechin (Procyanidin B3 isomer) and epicatechin (4beta-->8) epicatechin (Procyanidin B2) were the most active compounds. Comparatively, the uptake of [(3)H]-noradrenaline was the most affected. These results show that the antidepressant-like effect promoted by C. glazioui extract is most likely due to the blockade of the monoamines uptake in the CNS.

ACE activity during the hypotension produced by standardized aqueous extract of Cecropia glaziovii Sneth: a comparative study to captopril effects in rats

To evaluate the effect of the standardized aqueous extract (AE) of Cecropia glaziovii Sneth on the plasma angiotensin I converting enzyme (ACE-EC 3.4.15.1) activity, rats were treated with a single dose of AE (1 g/kg, p.o.) or repeatedly (0.5 g/kg/bid, p.o.) for 60 days. Captopril (50 mg/kg, p.o.) was used as positive control on the same animals. The effects on the blood pressure were recorded directly from the femoral artery (single dose), or indirectly by the tail cuff method (repeated doses) in conscious rats. The plasma ACE activity was determined spectrofluorimetrically using Hypuril-Hystidine-Leucine as substrate. The arterial blood pressure, heart rate and plasma ACE activity were not significantly modified within 24 h after a single dose administration of AE. Comparatively, blood pressure in captopril treated rats was reduced by 7-16% and heart rate was increased by 10-20% from 30 min to 24 h after drug administration. ACE activity after captopril presented a dual response: an immediate inhibition peaking at 30 min and a slow reversal to 32% up-regulation after 24 h. To correlate the drug effects upon repeated administration of either compound, normotensive rats were separated in three groups: animals with high ACE (48.8+/-2.6 nmol/min/ml), intermediate ACE (39.4+/-1.4 nmol/min/ml) and low ACE (23.5+/-0.6 nmol/min/ml) activity, significantly different among them. Repeated treatment with AE reduced the mean systolic blood pressure (121.7+/-0.5 mm Hg) by 20 mm Hg after 14 days. The hypotension was reversed upon washout 60 days afterwards. Likely, repeated captopril administration decreased blood pressure by 20 mm Hg throughout treatment in all groups. After 30 days treatment with AE (0.5 g/kg/bid, p.o.) the plasma ACE activity was unchanged in any experimental group. After captopril (50 mg/kg/bid, p.o.) administration the plasma ACE activity was inhibited by 50% within 1 h treatment but it was up-regulated by 120% after 12 h in all groups. It is concluded that the hypotension produced by prolonged treatment with AE of C. glaziovii is unrelated to ACE inhibition.

Chemical standardization of the aqueous extract of Cecropia glaziovii Sneth endowed with antihypertensive, bronchodilator, antiacid secretion and antidepressant-like activities

This study reports the extraction process and standardization of the aqueous extract (AE) of a Cecropia species aiming its pharmacological characterization as a phytomedicine to be used in primary health care. The plant was originally collected in its environment, and was thereafter specially cultivated for the present work. To standardize the plant AE, several 2.0% tea of the dried leaves were prepared under controlled conditions and freeze dried. The AE (20% yield) was partitioned with n-butanol yielding the butanolic fraction (BuF; 1% yield). The activity of AE on vital organ functions (cardiovascular, respiratory, gastrointestinal and central nervous system) was determined in vivo. The effects of AE were compared to those of BuF in the same models and the relative potency determined. BuF was further evaluated in representative in vitro models to assess possible mechanisms of action. Chemical constituents of BuF were isolated in preparative HPLC columns yielding 10 highly purified compounds chemically identified as catechins (2), procyanidins (4), flavonoids (2), mixed sugars (1) and chlorogenic acid. All the compounds were identified by chemical analytic instrumentation (13C-NMR, 1H-NMR, LC-MS). Their relative concentrations in AE were ca 12% catechins, 19% procyanidins and 19% flavonoids. The pharmacological activity of the standardized AE is reported in accompanying papers.

Inhibition of histamine-induced bronchospasm in guinea pigs treated with Cecropia glaziovi Sneth and correlation with the in vitro activity in tracheal muscles

A standardized aqueous extract (AE) and a purified fraction (BuF) of Cecropia glaziovi Sneth leaves were tested in unrestrained guinea pigs challenged with histamine. Changes of the respiratory pressure and rate were recorded in a whole body plethysmograph before and after treatment. The concentration of histamine necessary to produce bronchospasm was increased by five-fold following administration of AE (1.0 g/kg p.o.), and by two-fold after treatment with the semi-purified procyanidin/flavonoids enriched BuF (0.1 g/kg p.o.). Both effects were blocked by previous treatment with propranolol (10.0 mg/kg i.p.). In vitro incubation of BuF (0.1-1.0 mg/ml) decreased by 13-55% the maximal response of guinea pig tracheal muscle to histamine, without significant change of EC50. The results confirmed old reports on the useful pulmonary effects of Cecropia extracts. The bronchodilation observed in vivo seems to be related to beta-adrenergic activity observed in vitro only with high concentrations of the purified extract.

Antihypertensive effect of a standardized aqueous extract of Cecropia glaziovii Sneth in rats: an in vivo approach to the hypotensive mechanism

Cecropia glaziovii Sneth is a common tree at the Southeastern Brazilian coast. As many other species of the genus, it shares the reputed folk use to treat heart failure, cough, asthma and bronchitis. The plant has been cultivated under controlled conditions and the 2% aqueous extract (AE) prepared with the dried leaves was standardized by its chemical contents on catechins, flavonoids and procyanidins. The present paper reports the antihypertensive activity of AE and of n-butanol fraction (BuF), an enriched semi-purified butanolic fraction used to isolate the main chemical constituents. Oral administration of AE and BuF induced hypotension in normotensive rats. The effect of AE (0.5 g/kg/bi, p.o.) was time and dose-dependent peaking at 2-3 weeks after daily administration. BuF was faster but not more active than AE. Both extracts decreased the hypertension of spontaneous hypertensive rats, the hypertension induced in rats by L-NAME treatment and that induced by constriction of one renal artery. The antihypertensive effect was maintained for as long as 60 days of treatment and was reversible upon drug washout at the same rate of its establishment. Acute i.v. administration of BuF to anesthetized rats induced a fast short-lasting hypotension and inhibited the pressor responses to noradrenaline, angiotensin I and angiotensin II by 40%. These results were indirect indications that the hypotension induced by AE is not related to ACE inhibition, increased NO synthesis, or specific blockade of alpha1 and AT1 receptors. It can be suggested that BuF interferes with the calcium handling mechanisms in smooth muscle cells and neurons. Intravenous injection of five out of nine compounds isolated from BuF produced immediate but short-lasting hypotension that does not correlate with the onset of the hypotension after oral treatment. This finding suggests that they may not be the compounds directly responsible for the delayed and sustained hypotension after per os administration of AE. The many compounds isolated from AE are under evaluation to determine its pharmacokinetics, mechanisms of action and interactions necessary to yield the plant effect. Although its mechanism is still unknown, AE seems to be an effective and safe antihypertensive phytomedicine.

Pharmacological study of Stachytarpheta cayennensis Vahl in rodents

Freeze-dried aqueous extracts (AEs, 0.1-1g/kg body wt., p.o.) obtained from entire or selected parts of Stachytarpheta cayennensis were tested for their effects on gastric secretion, gastric motility, inflammation and pain in rodents, with the purpose of validating the plant's ethnomedical uses. The AE-Total, AE-Flowers and AE-Leaves but not AE-Stems inhibited the gastric acid secretion in pylorus-ligated rats with varying potency. Purification of AEs yielded the semipurifed fractions EtFs rich in iridoids. All the EtFs with exception of EtF-Stems inhibited gastric acid secretion of pylorus ligated mice. While AE-Total stimulated the intestinal transit of mice by 43%, AE-Leaves delayed it by 38%. These effects on intestinal transit were not observed when the EtFs were tested. Only AE-Leaves and AE-Flowers altered the gastric emptying of semisolids, increasing it by 45% and 69%, respectively. These results indicate that the compounds related to inhibition of gastric acid secretion and gastrointestinal motility are different. The AE-Total reduced abdominal writhing induced by acetic acid potently (ED50 value = 700 mg/kg, p. o.) without altering the writhes induced by acetylcholine. Attempts to identify the mechanism of analgesia were unsuccessful since the AE-Total did not show analgesic effects when tested in different models of pain such as formalin and capsaicin or the tail-flick test. Pretreatment of animals with AE-Total did not show antiinflammatory activity in any of the acute (paw edema induced by carrageenin, dextran or histamine, pleurisy induced by carrageenin and capsaicin-induced mouse ear edema) or chronic (air pouch) models used. No toxic signs were observed after administration of the different extracts up to 2 g/kg body wt., p.o. Collectively, the results confirmed folk information indicating presence of analgesic, mild laxative and potent inhibition of gastric secretion activities in the aqueous extracts of S. cayennensis. The results do not, however confirm the folk use of the plant as an antiinflammatory medicine.

Solanum paniculatum L. (Jurubeba): potent inhibitor of gastric acid secretion in mice

Solanum paniculatum L. is used commonly in Brazilian folk medicine for the treatment of liver and gastrointestinal disorders. The freeze-dried aqueous extracts (WEs) obtained from distinct parts of the plant (flowers, fruits, leaves, stems and roots) were tested to determine their antiulcer and antisecretory gastric acid activities using mice. The aqueous extracts of roots, stems and flowers inhibited gastric acid secretion in pylorus-ligated mice with ED50 values of 418, 777 and 820 mg/kg body wt. (i.d.), respectively. Extracts of leaves (0.5-2 g/kg body wt., i.d.) did not affect gastric secretion, whereas fruit extracts (0.5-2 g/kg body wt., i.d.) stimulated gastric acid secretion. The stimulatory effect of the fruit extract was inhibited by pretreatment with atropine (5 mg/kg body wt., i.m.) but not with ranitidine (80 mg/kg body wt., i.p.) suggesting that the fruit extract activates the muscarinic pathway of gastric acid secretion. In contrast, administration of the root extract into the duodenal lumen inhibited histamine- and bethanechol-induced gastric secretion in pylorus-ligated mice. In addition, the aqueous extract of roots (ED50 value, 1.2 g/kg body wt., p.o.) protected the animals against production of gastric lesions subsequent to the hypersecretion induced in mice by stress following cold restraint. This effect was not reproduced when the lesions were induced by blockade of prostaglandins synthesis via subcutaneous injection of indomethacin. Thus, antiulcer activity of the plant extracts appears to be related directly to a potent anti-secretory activity. No toxic signs were observed following administration of different extracts up to 2 g/kg body wt., p.o. Collectively, the results validate folk use of Solanum paniculatum L. plant to treat gastric disorders.

Nicotinic receptor/ionic channel complex (AChR) in androgen-dependent skeletal muscle cultures

The kinetic properties of the nicotinic receptor/ionic channel complex (AChR) were compared in cell cultures obtained from androgen-dependent skeletal muscles of the perineal complex (P) and from muscles less dependent upon sex hormones (the thigh musculature, T). Because the development of P is delayed compared to other skeletal muscles in the rat, cultures were performed taking into account the age of the donor (4- or 6-day-old rats), and the time interval the cells remained in culture (7 days and 15 days). The ionic channel conductance (gamma) and the mean channel open time (tau) were determined with the patch-clamp technique in the cell-attached configuration at room temperature. Cultures from P and T muscles were morphologically identical in size and shape, independent of the animals' age at plating or on the plating time. In all of them, the AChR was spread over the cell membrane. More than one AChR ionic channel conductance was observed in P and T cultures, and the prevalent value of gamma in either culture ranged from 30 pS to 35 pS. In P fibers from 4-day-old rats cultured for 7 days (P 4/7), the distribution of channel open times fitted a double exponential, while in T 4/7 they were fitted with a single exponential. In cultures from P and T muscles obtained from older rats (6 days old) and in those cells remaining in culture for a prolonged time (15 days), the channel open times also fitted a double exponential. Because P and T cultures lack trophic neuronal influences, the difference observed between the tau of P 4/7 and T 4/7 was thought to be the hormone requirement of P muscles to grow and differentiate. Likewise, the difference observed between T 4/7 and T 4/15 may indicate the need for neurotrophic influences to maintain higher tau values in older cultures. Since this requirement is not found in cultured fibers, tau would tend to assume slower values approaching those of P without hormone activation.

Evaluation of the anxiolytic-like effects of Cecropia glazioui Sneth in mice

Cecropia glazioui Sneth has been used in most Latin American countries as an antihypertensive, cardiotonic, and antiasthmatic folk medicine. In the cardiovascular studies to define its antihypertensive action it was noteworthy that animals treated with the aqueous extract (AE) of C. glazioui were much calmer than control animals. That observation prompted the present study, aimed at an investigation of the effects of AE and of two semipurified fractions on mouse behavior as evaluated in the elevated plus-maze test (EPM). Male adult Swiss mice were treated with AE (0.25-1 g/kg po) acutely (1 h) or repeatedly (24, 7, and 1.5 h before the test). After repeated administration of AE, the frequency of entries in the open arms of EPM was increased threefold. A similar profile of action was observed after treatment with the butanolic fraction (Fbut) but not with the aqueous fraction (Faq). These findings suggest that the AE of C. glazioui promotes an anxiolytic-like effect in mice. The active principles responsible for this action are present in the less polar fraction of the extract, the main constituents of which are flavonoids and terpenes, among other compounds.

Evaluation of the longitudinal musculature of segments of the distal colon interposed following extended jejunum-ileum resection

Several morbid conditions may necessitate extensive intestinal resection, leading to short-bowel syndrome. When clinical treatment becomes inefficient, a surgical approach is necessary. Distal colon interposition is one of the viable techniques. The interposition of colon segments between remnants of the small bowel improved lifestyle, increased transit time, and diminished diarrhea. The aim of this study is to observe the longitudinal muscular contractions after distal colon interposition. Sixteen male Wistar rats (EPM-1) were submitted to an 80% small bowel resection associated with a partial colectomy of the distal colon immediately after the bifurcation of the middle colic artery followed by a 3-cm isoperistaltic distal colon interposition. After 70 days, the animals were submitted to euthanasia and segments of the jejunum, ileum, remnant colon, and interposed colon were prepared for pharmacological tests. The isometric contractions were measured by a polygraph. After 30 minutes, the dose/effect curves were obtained for both metacholine and barium chloride stimulation through the extraluminal surface (serosa). After this period, we observed a significant increase in the length, diameter, and thickness of the intestinal wall. Regarding the sensibility (pD(2)), no difference was found (interposed colon = 7.21 +/- 0.2; remnant colon = 7.65 +/- 0.1; remnant jejunum 7.46 +/- 0.1; and remnant ileum 7.57 +/- 0.1), even though the animals were submitted to different procedures. In relation to the maximal effect (E(max)), the longitudinal muscle contraction responses (interposed colon = 11.79 +/- 0.1; remnant jejunum = 15.42 +/- 0.2; and remnant ileum = 11.48 +/- 0.2) were lower than those of the remnant colon (E(max) = 22.42 +/- 0.1). This means that there was a possible adaptation of colonic segments to their new location.

Diterpene from Baccharis trimera with a relaxant effect on rat vascular smooth muscle

A bioassay monitored fractionation of a chloroform extract from the aerial parts of Baccharis trimera yielded a mixture that blocked the Ca2+-induced contractions of KCl- depolarized rat portal vein preparations. Pharmacological tests of two pure compounds isolated from the mixture revealed the dilactonic clerodane diterpene as the active compound.

Natural probes for cholinergic sites: L-bebeerine actions on the neuromuscular transmission, the nicotinic receptor/ionic channel complex, and contraction of skeletal muscles

The mechanisms underlying the muscle relaxant activity of 1-bebeerine (BB), a tertiary alkaloid isolated from the roots of Chondrodendron platyphyllum, were examined in mammalian and amphibian skeletal muscles. Injections of BB (0.05-1 g/kg, i.p.) in rats caused a dose-related flaccid paralysis and respiratory arrest at high doses. In isolated rat diaphragm and toad sartorius muscles, BB depressed the indirectly elicited muscle twitches (IC50: 228 microM and 5.4 microM, respectively, at 22 degrees C) and blocked the nerve-elicited muscle action potential. The neuromuscular blockade was not reversed by neostigmine (10 microM). High concentrations of BB (170 and 340 microM) caused muscle contracture unrelated to the junctional blockade, and intensified by increasing the bath temperature. Analysis of the contraction properties showed that BB (40 and 80 microM) increased the twitch/tetanus ratio (46% and 125%) and prolonged the relaxation time; the falling phase of the directly elicited action potential in toad sartorius muscle fibers was slower probably by a decreased potassium conductance. BB (0.1-340 microM) reduced the binding of [125l]alpha--bungarotoxin to the junctional ACh receptor of the rat diaphragm (IC50: 47.7 microM, at 37 degrees C. At low concentrations BB (1.5-15 microM) induced either opening or blockade of the ACh receptor-ionic channel. The results showed that BB blocked noncompetitively the neuromuscular transmission through a mechanism that affects the ACh recognition site and the ionic channel properties. The alkaloid also produced muscle contracture and changed the contractile properties through its extra-junctional action at the calcium handling by the sarcoplasmic reticulum or the contractile machinery.

Ethnopharmacology, phytochemistry and pharmacology: a successful combination in the study of Croton cajucara

Phytochemical and pharmacological studies of Croton cajucara were oriented by traditional medicine. The stem bark of the mature plant is a rich source of clerodane-type diterpenes: trans-dehydrocrotonin (DCTN), trans-crotonin (CTN), cis-cajucarin B, cajucarin A, cajucarinolide and two novel clerodanes, trans-cajucarin B and sacacarin. In young (18-month-old) plants, the triterpene acetyl aleuritolic acid (AAA) was the major stem bark component and in these the diterpene DCTN was not present. The highest concentration of DCTN (1.4% of dry bark) was detected in 4-6 year-old plants, while 3-year-old plants contained only 0.26% of this diterpene. Three steroids (beta-sitosterol, stigmasterol and sitosterol-3-O-beta-glucoside), two flavonoids (kaempferol 3,4', 7-trimethyl ether and 3,7-dimethyl ether) and one diterpene (cajucarinolide) were isolated from the leaves of this Croton. The main pharmacological activity was correlated with DCTN. This clerodane produced anti-inflammatory and antinociceptive effects and a significant hypoglycemia in alloxan-induced diabetic rats. The compound also reduced the index of gastric lesions induced by restraint-in-cold. Dose-related DCTN and CTN inhibited in vivo the basal acid secretion in pylorus-ligature rats and oxyntic glands isolated from rabbit gastric mucosa, DCTN, CTN or AAA decreased in vitro uptake basal acid secretion induced by histamine and measured with the 14C-aminopyrine uptake method. Uniquely DCTN inhibited 14C-AP uptake induced by bethanechol. The terpenoids, DCTN and AAA, and the chloroform extract of 6-month-old plants reduced gastrointestinal transit in mice. The effects of DCTN and CTN on the survival of mice bearing Sarcoma 180 and Ehrlich carcinoma ascitic tumors, on the proliferation of cultured cells and TNFalpha were determined. DCTN was also evaluated for a possible antioestrogenic activity using the immature rat as a model system for bioassay of oestrogen and for an anti-implantation effect in regularly cycling rats. The biological experiments, using the plant extracts and the terpenoids DCTN, CTN and AAA, are herein discussed.

Anti-inflammatory activity of Urera baccifera (Urticaceae) in Sprague-Dawley rats

On a preliminary test, anti-inflammatory and analgesic dose-related activities on rats were observed for the aqueous fraction of Urera baccifera; this extract was bioassay-guided fractionated and the final aqueous fraction was used according the ethnobotanical use. Carrageenan-induced edema (n = 6), was used as an assay in the fractionating process. The anti-inflammatory and antinociceptive properties of the final aqueous fraction were studied using in vivo models. For the anti-inflammatory activity rat paw edema (n = 6), pleurisy induced by carrageenan (n = 6) and ear edema induced by topical croton oil (n = 6) models were used, and tail-flick test (n = 6), abdominal constrictions induced by acetic acid (n = 6), and formalin test (n = 6), were used for the antinociceptive activity. The tests performed showed an inhibition effect on leukocyte migration, and a reduction on pleural exudate, as well as dose-dependant peripheral analgesic activity, at a range of 25-100 mg/kg i.p. The final aqueous fraction contains most of the anti-inflammatory activity of the plant U. baccifera. A possible mechanism of action is discussed and based on the results we conclude that this plant has a potential for both anti-inflammatory and analgesic activity at the clinical level.

Evaluation of the antiurolithiatic activity of the extract of Costus spiralis Roscoe in rats

The antiurolithiatic activity of the water extract of Costus spiralis Roscoe was tested on formation of calculi on implants of calcium oxalate crystals or zinc disc in the urinary bladder of rats. The plant is a species from the family Zingiberaceae used in Brazilian folk medicine in urinary affections and for expelling urinary stones. Implantation of the foreign body in the urinary bladder of adult rats induced formation of urinary stones and hypertrophy of the smooth musculature. Oral treatment with the extract of Costus spiralis Roscoe (0.25 and 0.5 g/kg per day) after 4 weeks surgery reduced the growth of calculi, but it did not prevent hypertrophy of the organ smooth musculature. The contractile responses of isolated urinary bladder preparations to the muscarinic agonist bethanecol, in the presence and absence of the extract (0.3-3 mg/ml) or atropine (0.3-3 nM) did not differ among the experimental groups. The results indicate that the extract of Costus spiralis Roscoe is endowed with antiurolithiatic activity confirming thus folk information. The effect, however, was unrelated to increased diuresis or to a change of the muscarinic receptor affinity of the bladder smooth musculature to cholinergic ligands.

Gender does not influence neuromuscular properties in dimorphic skeletal muscles of the toad

The aim of this work was to study gender differences on the physiology of the dimorphic brachial musculature involved in the clasp reflex of the toad (Bufo marinus L.). The neuromuscular transmission, the sensitivity to acetylcholine (ACh) and the cholinesterase activity were compared on the forelimb sternoradialis muscles (SR) from male and female toads. The interosseous muscles of the first finger were used to compare the properties of the nicotinic receptor/ionic channel complex (AChR). All the muscles studied were dimorphic, i.e. significantly smaller in the female than in the male frog in otherwise similar size animals. The SR of either sex contracted to bath application of ACh with similar EC50. In physiological solution the frequency of the miniature end-plate potentials (mepps) was very low (0.1 s-1) and no gender difference was detected. The mepp amplitudes were 0.62 +/- 0.03 and 0.58 +/- 0.03 mV in SR from male and female toads, respectively. To increase exocytosis the muscles were incubated in hypertonic solution (158 mM NaCl). Under this condition mepp frequency was increased by five and seven times and mepp amplitude increased by 1.3 and 1.6 times in SR from male and female toads, respectively. The cholinesterase activity measured by the colorimetric method, did not differ in SR from male and female toads. In muscle fibers dissociated from the dimorphic interosseous muscles of male and female toads, the ionic channel conductance was 43 +/- 5.3 and 44 +/- 4.5 pS, respectively. The mean channel open time was voltage-dependent and not significantly different in preparations from both genders. These observations indicate that neither the ACh-nicotinic receptor interaction, nor the AChR complex kinetics and the nicotinic excitation-contraction coupling or the cholinesterase activity differ in dimorphic muscles from Bufo genders. No gender difference was detected in neuromuscular transmission of the studied muscle. Only a slight increase in mepp frequency and amplitude could be detected when the muscles were incubated in hypertonic solution.

Mechanism of neuromuscular blockade induced by phenthonium, a quaternary derivative of (-)-hyoscyamine, in skeletal muscles

1. The mechanisms underlying the postjunctional blockade induced by phenthonium [N-(4-phenyl) phenacyl 1-hyoscyamine] were investigated in mammalian and amphibian muscles. This muscarinic antagonist was previously shown to enhance specifically the spontaneous acetylcholine (ACh) release at concentrations that blocked neuromuscular transmission. 2. In both rat diaphragm and frog sartorius muscles, phenthonium (Phen, 1-100 microM) depressed the muscle twitches elicited by nerve stimulation (IC50: 23 microM and 5 microM, respectively), and blocked the nerve-evoked muscle action potential. The neuromuscular blockade was not reversed after incubation with neostigmine. 3. Equal concentrations of Phen decreased the rate of rise and prolonged the falling phase of the directly elicited action potential in frog sartorius muscle fibres, indicating that the drug also affects the sodium and potassium conductance. 4. Phen (50 and 100 microM) protected the ACh receptor against alpha-bungarotoxin (BUTX) blockade in the mouse diaphragm allowing recording of endplate potentials and action potentials after 5 h wash with physiological salt solution. 5. Phen (10-100 microM) produced a concentration- and voltage-dependent decrease of the endplate current (e.p.c.), and induced nonlinearity of the current-voltage relationship. At high concentrations Phen also shortened the decay time constant of e.p.c (tau(e.p.c.)) and reduced its voltage sensitivity. 6. At the same range of concentrations, Phen also reduced the initial rate of [125I]-BUTX binding to junctional ACh receptors of the rat diaphragm (apparent dissociation constant = 24 microM), the relationship between the degree of inhibition and antagonist concentration being that expected for a competitive mechanism. 7. It is concluded that Phen affects the electrical excitability of the muscle fibre membrane, and blocks neuromuscular transmission through a mechanism that affects the agonist binding to its recognition site and ionic channel conductance of the nicotinic ACh receptor.

Inhibition of gastric acid secretion by the aqueous extract and purified extracts of Stachytarpheta cayennensis

Stachytarpheta cayennensis Schauer (Verbenaceae) is used in folk medicine to treat gastric and intestinal disturbances. The freeze-dried aqueous extract of the whole plant tested to rodents up to the dose of 2 g kg-1, p.o., did not produce signs of toxicity. The extract (0.5-2 g kg-1, p.o.) increased the intestinal motility and protected mice against ulcers induced by restraintin-cold, ethanol or indomethacin. Injected into the duodenal lumen the extract inhibited the basal acid secretion as well as that induced by histamine and bethanecol in pylorus-ligated mice. Partition of the aqueous extract in organic solvents yielded semipurified fractions whose antiacid activity guided further chemical purification. All the fractions were chromatographically characterized, the main substances in the active extract being flavonoids and amines; some substances were revealed only under UV light. The most purified active fraction obtained presented a specific activity 5-10 times higher than that detected in the original extract. Data from pharmacological studies indicate that the antiulcer activity of S. cayennensis is related to a specific inhibition of gastric acid secretion. Cholinergic and histaminergic stimulation of acid secretion were similarly reduced by the extracts suggesting inhibition of common steps in both pathways, possibly at the level of histamine release/H2 receptor interaction, or at the proton pump. Whatever the mechanisms involved, the present data confirm the plant effectiveness as antiacid/antiulcer and laxative.

Sympathomimetic effects of Scoparia dulcis L. and catecholamines isolated from plant extracts

The herb Scoparia dulcis L. is used in Brazilian folk medicine to treat bronchitis, gastric disorders, haemorrhoids, insect bites and skin wounds, and in oriental medicine to treat hypertension. A previous study has shown that extracts of S. dulcis have analgesic and anti-inflammatory properties; in this work the sympathomimetic activity of an ethanolic extract of Scoparia dulcis L. has been investigated in rodent preparations in-vivo and in-vitro. Administration of the extract (0.5-2 mg kg-1, i.v.) to anaesthetized rats produced dose-related hypertension blocked by the alpha-adrenoceptor antagonist prazosin (1 mg kg-1). Partition of the extract in chloroform-water yielded an aqueous phase 20 times more potent than the extract; this produced hypertension in either reserpine-treated or pithed rats. In untreated and reserpine-treated rats the same fraction (1-3 x 10(3) micrograms mL-1) produced concentration-dependent contractions of the vas deferens musculature parallel to those obtained with noradrenaline (10(-8)-10(-4)M). Prazosin (10(-7)M) reduced the maximum contractile effect of the aqueous fraction, and shifted the concentration-response curves for noradrenaline to the right. The aqueous fraction (25 and 50 micrograms mL-1) increased the inotropism of electrically driven left atria of rats, the effect being blocked by propranolol (0.4 microgram mL-1). In preparations of guinea-pig tracheal rings the aqueous fraction (1-3 x 10(3) micrograms mL-1) relaxed the muscle contraction induced by histamine (10(-4) M) in proportion to the concentration. The effect was antagonized competitively by propranolol (1.5 microM). High-performance liquid-chromatographic analysis of the aqueous fraction revealed the presence of both noradrenaline and adrenaline in the plant extract. The results indicated that both catecholamines may account for the hypertensive and inotropic effects obtained after parenteral administration of S. dulcis extracts. This sympathomimetic activity is, however, unrelated to the previously reported analgesic and anti-inflammatory properties of the plant extract, but may explain its effectiveness upon topical application in the healing of mucosal and skin wounds.

Blockade of acetylcholine release at the motor endplate by a polypeptide from the venom of Phoneutria nigriventer

1. The mechanisms underlying the muscle relaxation effect of a fraction (PF3) isolated from the Phoneutria nigriventer spider venom were assessed on mouse diaphragm and chick biventer cervicis muscle preparations. 2. PF3 (0.25-4 micrograms ml-1) produced a concentration-dependent blockade of the nerve-elicited muscle twitch of the mouse diaphragm (IC50 = 0.8 micrograms ml-1) without affecting the directly induced muscle twitch. In similar preparations, the crude venom (1-10 micrograms ml-1) produced muscle contracture and blocked both the direct and indirectly induced muscle twitches. 3. In the chick biventer cervicis muscle, PF3 (1-5 micrograms ml-1) blocked the nerve stimulated muscle twitch (IC50 = 1.26 micrograms ml-1), but did not alter the postjunctional response to exogenous acetylcholine (ACh, 10 microM-10 mM). 4. PF3 (2-8 micrograms ml-1) reduced the frequency of miniature endplate potentials (m.e.p.ps) recorded intracellularly from the mouse diaphragm muscle fibers by 58 to 64%, and diminished the amplitude of m.e.p.ps by 20 to 40% of control. The relationship between log m.e.p.p. frequency and log [Ca2+]o was shifted rightwards in the presence of 4 micrograms ml-1 PF3. 5. Raising the frequency of m.e.p.ps with high K+ medium or theophylline (3 mM) did not prevent the toxin-induced depression of spontaneous ACh release. 6. The quantal content of e.p.ps (m), determined in cut-diaphragm muscle fibres, was reduced by 53% and 77% of control by 1 and 4 micrograms ml-1 PF3, respectively. At 1 microgram ml-1 the toxin shifted the relationship between log m and log [Ca2+]o towards higher values without apparent change of the slope. 7. E.p.p. trains elicited at 10 to 50 Hz in the presence of PF3 (1 microgram ml-1) exhibited irregular amplitudes and facilitation related to the frequency of nerve stimulation. 8. It is concluded that PF3 blocks neuromuscular transmission by acting prejunctionally and reducing the nerve-evoked transmitter release. The effect was related to a diminished Ca2+ entry into the nerve terminal associated with inhibition of exocytosis.

Prejunctional effect of quaternary derivatives of l-hyoscyamine at the rat neuromuscular junction. A structure-activity relationship study

1. The effects of phenthonium and related compounds on the spontaneous release of acetylcholine (ACh) were investigated with electrophysiological and radiolabelled techniques to correlate the prejunctional effect with their cholinolytic activities and to determine the structure-activity relationship. 2. Phenthonium and endophen are N-(4-phenyl)-phenacyl derivatives of l-hyoscyamine in "exo" and "endo" conformation, respectively. Tropol is N-(4-phenyl) phenacyl tropan-3-ol whereas ipratropium is 8-isopropyl-noratropine. 3. Only phenthonium increased the frequency of miniature endplate potentials and the resting efflux of spontaneous [3H]-ACh in rat diaphragm muscles. 4. The rank order of the antimuscarinic potency was: ipratropium > atropine > phenthonium = endophen > tropol. The rank order of the antinicotinic activity was: phenthonium = endophen > tropol > atropine > ipratropium. 5. It is concluded that the prejunctional facilitatory effect of phenthonium is associated with the N-phenyl-phenacyl group at "exo" conformation but the effect is unrelated to its cholinolytic properties.

Prejunctional regulatory actions of androgens on a hormone sensitive muscle

The influence of androgens and time course of effects induced by hormone deprivation were examined on the spontaneous transmitter release in the levator ani (LA) muscle of 30-180-day-old male rats. The resting membrane potential (RMP) and miniature endplate potentials (mepps) were recorded intracellularly from LA muscle fibers of intact animals or gonadectomized at different ages. In intact animals, the frequency of mepps increased proportionately to the muscle fiber growth up to 60 days, stabilizing thereafter. Gonadectomy at any age did not affect the RMP, but increased the frequency of mepps by 65% to 140%. The effect was detected after 15 days and was unrelated to the degree of muscle atrophy. Independently of the age of gonadectomy control values of mepp frequency were restored after 90 days, while the accompanying postjunctional changes persisted. These results indicate that androgens exert a prejunctional inhibitory influence on the spontaneous transmitter release in the rat LA muscle. The transient nature of the prejunctional effect induced by hormone deprivation indicates an adjustment of nerve terminals to persistent postjunctional alterations.

Testosterone control of endplate and non-endplate acetylcholinesterase in the rat levator ani muscle

The time course of effects of castration (5-60 days) and testosterone treatment (15-60 days) of adult male rats were examined on the endplate (+EP) and non-endplate (-EP) acetylcholinesterase (AChE) of the androgen-dependent levator ani (LA) muscle. The thiocholine method was used to determine the enzyme activity. Castration caused LA muscle atrophy within 5 days but reduced the -EP and +EP AChE after 10 and 20 days, respectively. Following 30 days castration -EP and +EP AChE reached respectively 41% and 35% of control activity. Testosterone retrieval restored the control values of both muscle weight and total AChE after 15 and 60 days, respectively. Recovery of the +EP AChE preceded that of -EP AChE by 30 days. The results showed that in the rat LA muscle, +EP and -EP AChE depend on a continuous testosterone regulation that predominates at +EP region spreading thereafter to -EP region. Those data suggest a hormone regulation of AChE exerted indirectly through the synthesis and release of neurotrophic substances.

Pharmacological evaluation of the anti-inflammatory activity of a citrus bioflavonoid, hesperidin, and the isoflavonoids, duartin and claussequinone, in rats and mice

Pretreatment of rats with hesperidin (50 and 100 mg kg-1, s.c.) reduced the paw oedema induced by carrageenan by 47 and 63%, respectively, within 5 h. The effect was equivalent to that produced by indomethacin (10 mg kg-1, p.o.), although unrelated to the administered dose, particularly at high doses. At 100 mg kg-1 hesperidin decreased the rat paw oedema induced by dextran by 33%, without influencing the histamine-induced paw oedema. Hesperidin also inhibited pleurisy induced by carrageenan, reducing the volume of exudate and the number of migrating leucocytes by 48 and 34%, respectively, of control values. Equal doses of duartin and claussequinone were ineffective in all the above tests. Pretreatment of mice with hesperidin (100 mg kg-1, s.c.) reduced acetic acid-induced abdominal constriction by 50%, but did not affect the tail flick response. Hyperthermia induced by yeast in rats was slightly reduced by hesperidin. No lesions of the gastric mucosae were detected in rats pretreated with hesperidin. The results indicate that hesperidin obtained from citrus cultures may present a potential therapeutical use as a mild anti-inflammatory agent, being also useful as a precursor of new flavonoids endowed with such activity.

Pharmacological screening of Ageratum conyzoides L. (Mentrasto)

The pharmacological activities of a water extract (WE) of Ageratum conyzoides L, a plant popularly known for its analgesic and anti-inflammatory properties, were studied in vivo and in vitro preparations. Oral administration (p.o.) of the water extract (WE, 0.1 to 5 g/kg) to rats and mice induced quietness and reduced the spontaneous motility. The sleeping time induced by sodium pentobarbital (50 mg/kg, i.p.) in mice was not altered by previous treatment with WE (2 g/kg, p.o.). The same treatment did not influence the paw edema induced by carrageenan or dextran, nor did it reduce the chronic paw edema induced by complete Freund's adjuvant or formaldehyde in rats. The tail flick response in immersion test and writhings induced by 0.8% acetic acid in mice were not altered by WE either. In isolated guinea-pig ilea WE (0.4 to 4 mg/ml) did not alter the EC50 values of histamine or acetylcholine, but reduced the maximal response to the agonists by 20 to 50%. WE (0.01 to 10 mg/ml) produced tonic contractions of the ileal smooth muscle proportional to the doses, reaching a maximum of 75% relatively to the maximum obtained with histamine. Those contractions were blocked by diphenhydramine (10 nM) and reduced by 32% in presence of atropine (10 nM). The results indicated that oral treatment of rodents with A. conyzoides L neither reduced the inflammatory edema nor did it decrease the reaction to pain stimuli. In vitro the extract presented an unexpected histamine-like activity characteristic of a partial agonist. The results did not confirm the popular medicinal indications of the plant.

Inhibition of gastric secretion by a water extract from Baccharis triptera, Mart

Baccharis triptera Mart, is a widespread Compositae used in Brazilian folk medicine to treat gastrointestinal disturbances, rheumatic disease, mild fever, diabetes and as an anti-helminthic. Water extract of small branches of the plant (WE) administered to mice and rats (0.1 to 2 g/kg, p.o.) did not alter spontaneous motor activity, sleeping time induced by barbiturates or the tail-flick response in mice. The extract decreased by 40% the number of writhings induced by 0.8% acetic acid, i.p., but did not influence paw edema induced by carrageenan or dextran in rats. WE (2 g/kg, p.o.) decreased the intestinal transit of charcoal in mice by 20%. Gastric secretion in pylorus ligated rats was reduced after treatment with WE (1 and 2 g/kg, i.p. or intraduodenal) and the gastric pH was raised. The extract (1 g/kg, p.o.) prevented gastric ulcers induced in rats by immobilization at 4 degrees C, but not those induced by indomethacin (10 mg/kg, s.c.). The results indicate that WE may relieve gastrointestinal disorders by reducing acid secretion and gastrointestinal hiperactivity. Neither analgesic nor anti-inflammatory activities were detectable.

Cardiac glycosides isolated from the Indian-snuff, Maquira sclerophylla Ducke

The hydroalcoholic extract of the powdered bark of the Indian-snuff Maquira sclerophylla Duck was purified by column chromatography in silica-gel and the major cardenolide isolated from preparative TLC was identified by 1H-NMR, 12C-NMR and IR analyses. The spectra showed that the active substance has strophanthidin as the aglycone.

Analgesic activity of a triterpene isolated from Scoparia dulcis L. (Vassourinha)

Analgesic and anti-inflammatory activities of water (WE) and ethanolic (EE) extracts of Scoparia dulcis L. were investigated in rats and mice, and compared to the effects induced by Glutinol, a triterpene isolated by purification of EE. Oral administration (p.o.) of either WE or EE (up to 2 g/kg) did not alter the normal spontaneous activity of mice and rats. The sleeping time induced by sodium pentobarbital (50 mg/kg, i.p.) was prolonged by 2 fold in mice pretreated with 0.5 g/kg EE, p.o. Neither extract altered the tail flick response of mice in immersion test, but previous administration of EE (0.5 g/kg, p.o.) reduced writhings induced by 0.8% acetic acid (0.1 ml/10 g, i.p.) in mice by 47%. EE (0.5 and 1 g/kg, p.o.) inhibited the paw edema induced by carrageenan in rats by respectively 46% and 58% after 2 h, being ineffective on the paw edema induced by dextran. No significant analgesic or anti-edema effects were detected in animals pretreated with WE (1 g/kg, p.o.). Administration of Glutinol (30 mg/kg, p.o.) reduced writhing induced by acetic acid in mice by 40% and the carrageenan induced paw edema in rats by 73%. The results indicate that the analgesic activity of S. dulcis L. may be explained by an anti-inflammatory activity probably related to the triterpene Glutinol.

The water extract of Coleus barbatus Benth decreases gastric secretion in rats

Coleus barbatus (Labiatae) Benth is popularly used in Brazil "for the healing of liver and stomach diseases". The water extract (WE 1 to 10 g/kg, p.o.) of stem and leaves given to rats and mice did not induce signs of intoxication. Previous treatment of mice with WE (1 g/kg, p.o.) shortened the sleeping time induced by pentobarbital (50 mg/kg, i.p.) by 37%, although the extract alone did not increase the spontaneous activity nor did it induce hyperexcitability. In mice WE (2 g/kg, p.o.) increased the intestinal transit of charcoal by 30%, while reduced gastric secretions in rats treated with WE (2 g/kg intraduodenal) (3.9 +/- 1.0 to 0.5 +/- 0.2 ml/4 h, respectively). The treatment also reduced the total acid secretion from 34.4 +/- 11.0 to 2.7 +/- 0.5 mEq/l and raised gastric pH from 2.2 +/- 0.3 to 6.5 +/- 0.8. Treatment with WE (2 g/kg, p.o.) protected against gastric ulcers induced by stress (5.3 +/- 1.6 and 1.5 +/- 0.5 ulcers/cm2), but it did not protect against indomethacin induced ulcers. The results show that the water extract of C. barbatus Benth produces mild stimulation of the central nervous system and increases intestinal movements. The extract also reduces gastric secretion indicating an antidyspeptic activity, and protects against gastric ulcers induced by stress.

Phenthonium, a quaternary derivative of (-)-hyoscyamine, enhances the spontaneous release of acetylcholine at rat motor nerve terminals

1. A quaternary derivative of (-)-hyoscyamine, phenthonium (Phen) induced a concentration-dependent increase in the rate of spontaneous quantal release of acetylcholine (ACh) at the mammalian neuromuscular junction, as shown by intracellular recordings of the miniature endplate potentials (m.e.p.ps) in rat diaphragm muscles. 2. The prejunctional effect of Phen (10-50 microM) was reversible, unrelated to temperature (22 degrees-35 degrees C), unaltered by either changes in [Ca2+]o or by high [Mg2+]o, and was not induced by membrane depolarization. 3. Simultaneously, Phen reduced the amplitude of m.e.p.ps by a postjunctional action. 4. The muscarinic agonist oxotremorine did not prevent the increase in m.e.p.p. frequency induced by Phen. Cholinesterase inhibition with neostigmine potentiated the prejunctional effect induced by a low (20 microM) but not a high (50 microM) concentration of Phen. 5. The increase in m.e.p.p. frequency induced by Phen was not influenced by previous incubation with either atropine (0.01-10 microM) or (+)-tubocurarine (0.05-0.1 microM). Each antagonist however, intensified the postjunctional effect of Phen. 6. Phen (20 microM) did not influence the quantal contents of e.p.ps in cut-muscle preparations or in the presence of high [Mg2+]o. A high concentration of Phen (50 microM) increased the rundown of e.p.p. trains evoked at 10-50 Hz. 7. The results indicate that the facilitatory prejunctional action of Phen cannot be explained by an antimuscarinic activity. A possible interaction of the antagonist with putative prejunctional nicotinic cholinoceptors however, was not excluded.

Trophic control of cholinesterase activity in a testosterone-dependent muscle of the rat. II. Effects of testosterone administration

The effects of testosterone on the weight, protein content, and acetylcholinesterase (AChE) activity were investigated in the hormone-dependent levator ani and nondependent extensor digitorum longus and soleus muscles from normal or castrated male rats. In either group some muscles were also chronically denervated. Testosterone propionate treatment (3 mg/week for 2 weeks, s.c.) of normal rats increased the weight and protein content of the levator ani, respectively, by 19% and 63%; the muscle AChE was not affected. Protein content, but not the weight of the normal extensor digitorum longus and soleus was also increased after testosterone; AChE was reduced by 20% in the extensor digitorum longus and unaltered in the soleus. In castrated rats, testosterone reversed the levator ani atrophy and slowed down the decay of AChE, but it did not restore the normal enzyme activity. Testosterone did not prevent the atrophy and AChE decrease induced by denervation of either muscle. The weight and protein content of the denervated levator ani from castrated rats were increased by testosterone to the values found in denervated muscles from normal rats; AChE in the same muscles was not increased. The results confirm that separate mechanisms regulate protein synthesis and AChE in the rat levator ani. AChE is mainly regulated by neural factors which in turn appear to be influenced by circulating androgens. Similar hormonal influence on the muscle AChE was not detected in the extensor digitorum longus and soleus muscles.

Influence of castration on the membrane reactivity of the guinea-pig vas deferens

The guinea-pig vas deferens is a quiescent muscle which after castration undergoes atrophy and shows spontaneous contractions preceded by membrane spike activity. The influence of castration on the spontaneous release of neurotransmitters and on the internal concentration of sodium and potassium ions was studied. Utilizing the microelectrode technique it was shown that castration induces a partial depolarization (10 mV) of the cell membrane, but did not change the frequency of spontaneous excitatory junction potentials (SEJPs) of guinea-pig vas deferens. However, the time-course and the amplitude of the SEJPs were increased after castration, probably because of changes in membrane properties related to organ atrophy. Castration probably promotes a change in the ionic permeability of the smooth muscle fibre, since the ratio pNa/pK was twice that of control muscles.

Trophic control of cholinesterase activity in a testosterone-dependent muscle of the rat: effects of castration and denervation

The effects of testosterone withdrawal and chronic denervation on muscle weight and acetylcholinesterase (AChE) activity were studied in the hormone-sensitive levator ani muscle of the rat. Castration of adult male rats for 7 to 60 days caused a linear decrease of the weight, protein content, and AChE activity of the muscle, which stabilized after 30 days. Muscle weight and protein content decreased 2.3% per day. The total AChE activity decreased 7 days later 3.2% per day, reaching 37% of control at day 30. AChE activity per unit weight was increased in all castrated groups. Muscle weights and AChE activity of the extensor digitorum longus and soleus muscles were not altered after castration. Denervation of all three muscles caused 50% reduction of the muscle weight and protein content after 15 days. Total AChE activity decayed exponentially with a rate of 0.12 per day to 15 to 18% of control values. AChE activity per unit weight in the denervated muscles was always lower than in the control muscles. Combined castration and denervation intensified only the levator ani protein loss. The different onset and time course of the effects induced by castration and denervation indicate distinct mechanisms involved in the trophic control of muscle proteins and AChE activity. Chronic muscle denervation decreased total AChE activity to 15% of normal, whereas castration reduced the enzyme to 40% of the control values. The results indicate that neuronal and hormonal influences on AChE activity of the levator ani are not additive but overlap.

Timbós: ichthyotoxic plants used by Brazilian Indians

The pharmacology of serjanosides, active principles isolated from the fish-poison plant Serjania lethalis St. Hil, a Sapindaceae, was investigated by comparing their actions in fishes and mammals with those of rotenone and certain saponins. The ichthyocid activity of the serjanosides was 2.5 times greater than that of the crude plant extract, approximately 10 times lower than the activity of rotenone, but from 10 to 50 times greater than the activity of the other saponins. When injected in mammals, the serjanosides induced deep prostration, dyspnea, cyanosis, ectopic heart beats, cardiovascular failure and respiratory arrest. These effects, leading to death that was not prevented by artificial respiration, indicated several mechanisms for the toxic action of the serjanosides. In vitro studies with these substances have shown that membrane depolarization and muscle contracture were probably due to unspecific surface actions. Rotenone, under the same experimental conditions induced hypotension, bradycardia and respiratory arrest. Death was prevented by artificial respiration. Ectopic foci, membrane depolarization, contractures and neuromuscular block were not observed after rotenone. Apparently, death from rotenone poisoning was a consequence of respiratory failure of central origin. The serjanosides are rather potent fish poison saponins. Mammals, however, are apparently insensitive to the same specific action since other toxic effects induced by those substances in rats and mice were also observed by employing saponins devoid of fish-killing activity.

The influence of testosterone on neuromuscular transmission in hormone sensitive mammalian skeletal muscles

The influence of testosterone on neuromuscular transmission was studied in levator ani (LA) and extensor digitorum longus (EDL) muscles taken from normal rats, castrated rats, and castrated rats treated with testosterone. Thirty days after castration LA muscle weights were reduced by 60%, but the frequency and amplitude of the miniature end-plate potentials (mepps) were increased by 40% and 50%, respectively. The weights and mepp frequencies of the EDL muscles were not altered after castration, but the mepp amplitudes increased by 30%. The quantal content of the endplate potentials was not affected in either muscle. Administration of testosterone to the castrated rats prevented such changes in the LA muscles. The results indicate that castration of adult rats affects the spontaneous transmitter release in both muscles, but the changes are more pronounced in the levator ani, which is a target muscle for testosterone.

Vasoconstriction induced by delta 9-tetrahydrocannabinol on the perfused rabbit ear artery

Periarterial incubation of delta 9-Tetrahydrocannabinol (THC, 15.0--30.0 mM) to the "in vitro" perfused central artery of the rabbit ear, induced sustained contractions related to the dose and reverted after washing. Simultaneously, the artery responses to transmural electrical stimulation were blocked and the effects of intravascular injection of noradrenaline were additive to the constriction induced by THC. Either reserpine treatment or chronic artery denervation blocked the vasoconstriction induced by THC. These results indicate that THC may induce vasoconstriction in the perfused artery of the rabbit through the release of noradrenaline from sympathetic nerve terminals.

Castration atrophy and pharmacological reactivity of the rat coagulating gland

1. The reactivity and sensitivity of the rat coagulating gland to acetylcholine, adrenaline, serotonin and barium chloride was studied 7, 15 and 30 days after castration. 2. The wet and the dry weight of the coagulating gland progressively decreased with time after castration. 3. Spontaneous contractions were observed in the coagulating gland 15 and 30 days after castration. 4. The maximum force developed per gram tissue was significantly higher than control for serotonin and barium chloride on the 7th day, while for acetylcholine and adrenaline the increase was observed only on the 15th day after castration. 5. The pD2 values for adrenaline, barium chloride and serotonin increased significantly 15 days after castration, whereas the change in sensitivity to acetylcholine was detected only 30 days after castration. 6. These results suggest that changes in reactivity and sensitivity of the rat coagulating gland caused by castration are not related only to muscle atrophy, since the time course of the development of the effects is different for the four agonists studied.

Spontaneous contractions and membrane activity of castrated guinea-pig vas deferens

Castration of the guinea pig was followed by atrophy of the vas deferens and appearance of spontaneous contractions. Testosterone replacement reversed those effects and diethylstilbestrol treatment increased them. A month after castration or castration and stilbestrol treatment (15 mg/30 days), the membrane exhibited depolarization and spontaneous spikes that were not seen with the normal groups. The spontaneous contractions observed with both groups reflected the occurrence of membrane spikes. Tetrodotoxin (3 c 10(-6) M) did not change the membrane potential in any organ studied nor did it affect the pattern of spontaneous contractions. Verapamil (5 x 10(-6) M) increased the membrane potential of the muscles from castrated and stilbestrol-treated castrated animals, abolished the membrane spikes and blocked the spontaneous contractions. The results suggest that castration increases calcium permeability through the membrane. The increase in calcium permeability would be responsible for muscle rhythmicity.

The triple effect induced by delta 9-tetrahydrocannabinol on the rat blood pressure

The intravenous injection of delta 9-tetrahydrocannabinol (2-10 mg/kg) produced dose-related changes in the rat blood pressure. Three effects were detected: (1) an immediate and short-lasting hypotension related to bradycardia, blocked after atropine, vagotomy hexamethonium and pithing; (2) A rise in blood pressure 30 seconds after injection, insensitive to yohimbine, hexamethonium, pithing and reserpine treatment; (3) a slow and persistent hypotension, 5 min later, insensitive to atropine and vagotomy but inhibited by hexamethonium, pithing and reserpine treatment. It was concluded that intravenous injection of THC in rats may induce vagal stimulation and hypotension. This effect was reversed and followed by hypertension due to direct vasoconstriction not dependent on sympathetic activity. After this action a central decrease in sympathetic tonus led to a persistent hypotension an effect which is commonly reported for mammals.

The inhibitory effect induced by delta9-tetrahydrocannabinol on the contractions of the isolated rat vas deferens

To analyse the influence of delta9-Tetrahydrocannabinol (THC) on the effects induced by sympathomimetic, parasympathomimetic and direct spasmogenic drugs, the isolated rat vas deferens preparation was chosen. Instead of the usual emulsifying agents, we have used 1% ethanol (ET-OH) to keep the cannabinoids in homogeneous dispersion in the bath. THC exerted a non-competitive inhibition of noradrenaline and of acetylcholine responses but no synergistic action nor competitive antagonism was seen on the dose range used. BaCl2 was potentiated by ethanol and this effect was abolished by THC. The water soluble derivative SP 111 showed actions similar to those of THC on noradrenaline and acetylcholine responses. It did not affect BaCl2 contractions, indicating that the cannabinoid might act by depressing early events of membrane activation.