Effect of a gel containing pilocarpine on vaginal atrophy in castrated rats

OBJECTIVES: To evaluate the effect of Carbopol gel formulations containing pilocarpine on the morphology and morphometry of the vaginal epithelium of castrated rats. METHODS: Thirty-one female Wistar-Hannover rats were randomly divided into four groups: the control Groups I (n=7, rats in persistent estrus; positive controls) and II (n=7, castrated rats, negative controls) and the experimental Groups, III (n=8) and IV (n=9). Persistent estrus (Group I) was achieved with a subcutaneous injection of testosterone propionate on the second postnatal day. At 90 days postnatal, rats in Groups II, III and IV were castrated and treated vaginally for 14 days with Carbopol gel (vehicle alone) or Carbopol gel containing 5% and 15% pilocarpine, respectively. Next, all of the animals were euthanized and their vaginas were removed for histological evaluation. A non-parametric test with a weighted linear regression model was used for data analysis (p<0.05). RESULTS: The morphological evaluation showed maturation of the vaginal epithelium with keratinization in Group I, whereas signs of vaginal atrophy were present in the rats of the other groups. Morphometric examinations showed mean thickness values of the vaginal epithelium of 195.10±12.23 μm, 30.90±1.14 μm, 28.16±2.98 μm and 29.84±2.30 μm in Groups I, II, III and IV, respectively, with statistically significant differences between Group I and the other three groups (p<0.0001) and no differences between Groups II, III and IV (p=0.0809). CONCLUSION: Topical gel formulations containing pilocarpine had no effect on atrophy of the vaginal epithelium in the castrated female rats.

Effects of milk curd on saliva secretion in healthy volunteer compared to baseline, 2% pilocarpine and equivalent pH adjusted acetic acid solutions.

Background: Dry mouth is a common clinical problem, and different products have been proposed to improve it. In this investigation, the effects of "milk curd" on the amount of saliva secretion were studied. Materials and Methods: A total of 32 patients (aged 20-30) were selected from healthy volunteers. Milk curd concentrations of 0.5, 1, 2 and 4%, and 2% pilocarpine were prepared as drops. The impact of the drugs on the saliva weight was assessed after 1-5 min. To determine the effects of the pH of the milk curd on the amount of saliva secretion, different concentrations of acetic acid were used. Results: At the end of the first minute, the differences between the data for all groups were statistically significant, and the difference between the 2% and 4% milk curd groups was higher than the others (P < 0.0001). The differences in the amount of the saliva secreted at the end of the second minute between the baseline and 4% milk curd groups and between the 0.5% and 4% MC groups were significant (P = 0.006 and P = 0.025, respectively). In total, there was no significant difference between the effect of various pH treatments and the amount of baseline saliva secretion. Conclusion: Milk curd has a significant local impact, and the saliva increase depends on the dose. It seems that this effect is not only related to its acidic taste. As a result, factors other than pH are involved in the effect.

The effects of antidepressants and pilocarpine on rat parotid glands: an immunohistochemical study

OBJECTIVES: To evaluate the effects of antidepressants and pilocarpine on the quantity of myoepithelial cells and on the proliferation index of the epithelial cells of rat parotid glands. INTRODUCTION: Hyposalivation, xerostomia, and alterations in saliva composition are important clinical side effects related to the use of antidepressants. METHODS: Ninety male Wistar rats were allocated to nine groups. The control groups received saline for 30 (group C30) or 60 days (group C60) or pilocarpine for 60 days (group Pilo). The experimental groups were administered fluoxetine (group F30) or venlafaxine for 30 days (group V30); fluoxetine (group FS60) or venlafaxine (group VS60) with saline for 60 days; or fluoxetine (group FP60) or venlafaxine (group VP60) with pilocarpine for 60 days. Parotid gland specimens were processed, and the immunohistochemical expression of calponin and proliferating cell nuclear anti-antigen on the myoepithelial and parenchymal cells, respectively, was evaluated. Analysis of variance (ANOVA), Tukey HSD and Games-Howell tests were applied to detect differences among groups (p<0.05). RESULTS: Compared with the controls, chronic exposure to antidepressants was associated with an increase in the number of positively stained cells for calponin. In addition, venlafaxine administration for 30 days was associated with an increase in the number of positively stained cells for proliferating cell nuclear anti-antigen. Fluoxetine and pilocarpine (group FP60) induced a significant decrease in the number of positively stained cells for calponin compared with all other groups. CONCLUSIONS: The number of positively stained cells for calponin increased after chronic administration of antidepressants. The proliferation index of the epithelial cells of rat parotid glands was not altered by the use of antidepressants for 60 days.

Participation of the cholinergic system in the ethanol-induced suppression of paradoxical sleep in rats

Sleep disturbance is among the many consequences of ethanol abuse in both humans and rodents. Ethanol consumption can reduce REM or paradoxical sleep (PS) in humans and rats, respectively. The first aim of this study was to develop an animal model of ethanol-induced PS suppression. This model administered intragastrically (by gavage) to male Wistar rats (3 months old, 200-250 g) 0.5 to 3.5 g/kg ethanol. The 3.5 g/kg dose of ethanol suppressed the PS stage compared with the vehicle group (distilled water) during the first 2-h interval (0-2 h; 1.3 vs 10.2; P < 0.001). The second aim of this study was to investigate the mechanisms by which ethanol suppresses PS. We examined the effects of cholinergic drug pretreatment. The cholinergic system was chosen because of the involvement of cholinergic neurotransmitters in regulating the sleep-wake cycle. A second set of animals was pretreated with 2.5, 5.0, and 10 mg/kg pilocarpine (cholinergic agonist) or atropine (cholinergic antagonist). These drugs were administered 1 h prior to ethanol (3.5 g/kg) or vehicle. Treatment with atropine prior to vehicle or ethanol produced a statistically significant decrease in PS, whereas pilocarpine had no effect on minutes of PS. Although the mechanism by which ethanol induces PS suppression is not fully understood, these data suggest that the cholinergic system is not the only system involved in this interaction.

Methacholine and PDGF activate store-operated calcium entry in neuronal precursor cells via distinct calcium entry channels

Neurons are a diverse cell type exhibiting hugely different morphologies and neurotransmitter specifications. Their distinctive phenotypes are established during differentiation from pluripotent precursor cells. The signalling pathways that specify the lineage down which neuronal precursor cells differentiate remain to be fully elucidated. Among the many signáis that impinge on the differentiation of neuronal cells, cytosolic calcium (Ca2+) has an important role. However, little is known about the nature of the Ca2+ signáis involved in fate choice in neuronal precursor cells, or their sources. In this study, we show that activation of either muscarinic or platelet-derived growth factor (PDGF) receptors induces a biphasic increase in cytosolic Ca2+ that consists of reléase from intracellular stores followed by sustained entry across the plasma membrane. For both agonists, the prolonged Ca2+ entry occurred via a store-operated pathway that was pharmacologically indistinguishable from Ca2+ entry initiated by thapsigargin. However, muscarinic receptor-activated Ca2+ entry was inhibited by siRNA-mediated knockdown of TRPC6, whereas Ca2+ entry evoked by PDGF was not. These data provide evidence for agonist-specific activation of molecularly distinct store-operated Ca2+ entry pathways, and raise the possibility of privileged communication between these Ca2+ entry pathways and downstream processes.

Assessment of the progressive nature of cell damage in the pilocarpine model of epilepsy

Pilocarpine-induced (320 mg/kg, ip) status epilepticus (SE) in adult (2-3 months) male Wistar rats results in extensive neuronal damage in limbic structures. Here we investigated whether the induction of a second SE (N = 6) would generate damage and cell loss similar to that seen after a first SE (N = 9). Counts of silver-stained (indicative of cell damage) cells, using the Gallyas argyrophil III method, revealed a markedly lower neuronal injury in animals submitted to re-induction of SE compared to rats exposed to a single episode of pilocarpine-induced SE. This effect could be explained as follows: 1) the first SE removes the vulnerable cells, leaving behind resistant cells that are not affected by the second SE; 2) the first SE confers increased resistance to the remaining cells, analogous to the process of ischemic tolerance. Counting of Nissl-stained cells was performed to differentiate between these alternative mechanisms. Our data indicate that different neuronal populations react differently to SE induction. For some brain areas most, if not all, of the vulnerable cells are lost after an initial insult leaving only relatively resistant cells and little space for further damage or cell loss. For some other brain areas, in contrast, our data support the hypothesis that surviving cells might be modified by the initial insult which would confer a sort of excitotoxic tolerance. As a consequence of both mechanisms, subsequent insults after an initial insult result in very little damage regardless of their intensity.

Intestinal ischemia/reperfusion induces bronchial hyperreactivity and increases serum TNF-alpha in rats

INTRODUCÃO: A isquemia/reperfusão intestinal ou hepática induz lesão pulmonar aguda em modelos animais de falência de múltiplos órgãos. O fator de necrose tumoral (TNF-a) está envolvido no mecanismo inflamatório da síndrome da angústia respiratória aguda. Embora a cascata inflamatória que leva à síndrome da angústia respiratória aguda tenha sido extensamente investigada, os componentes mecânicos desta ainda não são completamente compreendidos. Nós levantamos a hipótese de que a isquemia/reperfusão esplâncnica provoca aumento da reatividade contráctil das vias aéreas, bem como aumento do TNF-a sérico. OBJETIVO: avaliar a reatividade da musculatura lisa brônquica sob estimulação com metacolina, e medir os níveis séricos de TNF-a após isquemia/reperfusão intestinal e/ou hepática em ratos. MÉTODO: Ratos Wistar foram submetidos a 45 min de isquemia intestinal, ou 20 minutos de isquemia hepática, ou a ambas (isquemia dupla), ou controle, seguidos por 120 min de reperfusão. A resposta brônquica a concentrações molares (10-7 to 3x10-4) de metacolina foi avaliada usando-se uma preparação ex-vivo de musculatura brônquica. RESULTADOS: A resposta brônquica (g/100mg de tecido) mostrou reatividade aumentada a concentrações crescentes de metacolina na isquemia intestinal e isquemia dupla, mas não na isquemia hepática. Similarmente, o TNF-a sérico aumentou na isquemia intestinal e isquemia dupla, mas não na isquemia hepática. CONCLUSÃO: Isquemia intestinal, quer isolada ou associada à hepática, provocou hiper-reatividade da musculatura brônquica, sugerindo um possível papel da constrição brônquica na disfunção respiratória conseqüente à isquemia/reperfusão esplâncnica. Este aumento foi simultâneo ao do TNF-a sérico, porém o possível efeito causal do TNF-a na contractilidade brônquica permanece a ser determinado.

Expression of Ca2+-dependent Synaptotagmin Isoforms in Mouse and Rat Parotid Acinar Cells

Synaptotagmin is a Ca2+ sensing protein, which triggers a fusion of synaptic vesicles in neuronal transmission. Little is known regarding the expression of Ca2+ - dependent synaptotagmin isoforms and their contribution to the release of secretory vesicles in mouse and rat parotid acinar cells. We investigated a type of Ca2+ - dependent synaptotagmin and Ca2+ signaling in both rat and mouse parotid acinar cells using RT-PCR, microfluorometry, and amylase assay. Mouse parotid acinar cells exhibited much more sensitive amylase release in response to muscarinic stimulation than did rat parotid acinar cells. However, transient [Ca2+]i increases and Ca2+ influx in response to muscarinic stimulation in both cells were identical, suggesting that the expression or activity of the Ca2+ sensing proteins is different. Seven Ca2+ - dependent synaptotagmins, from 1 to 7, were expressed in the mouse parotid acinar cells. However, in the rat parotid acinar cells, only synaptotagmins 1, 3, 4 and 7 were expressed. These results indicate that the expression of Ca2+ - dependent synaptotagmins may contribute to the release of secretory vesicles in parotid acinar cells.

Comparison of sweat rate during graded exercise and the local rate induced by pilocarpine

Centrally stimulated sweat rate produced by graded exercise until exhaustion was compared to the local sweat rate induced by pilocarpine, often used as a sweating index for healthy individuals. Nine young male volunteers (22 ± 4 years) were studied in temperate environment in two situations: at rest and during progressive exercise with 25 W increases every 2 min until exhaustion, on a cycle ergometer. In both situations, sweating was induced on the right forearm with 5 ml 0.5 percent pilocarpine hydrochloride applied by iontophoresis (1.5 mA, 5 min), with left forearm used as control. Local sweat rate was measured for 15 min at rest. During exercise, whole-body sweat rate was calculated from the body weight variation. Local sweat rate was measured from the time when heart rate reached 150 bpm until exhaustion and was collected using absorbent filter paper. Pharmacologically induced local sweat rate at rest (0.4 ± 0.2 mg cm-2 min-1) and mean exercise-induced whole-body sweat rate (0.4 ± 0.1 mg cm-2 min-1) were the same (P > 0.05) but were about five times smaller than local exercise-induced sweat rate (control = 2.1 ± 1.4; pilocarpine = 2.7 ± 1.2 mg cm-2 min-1), indicating different sudorific mechanisms. Both exercise-induced whole-body sweat rate (P < 0.05) and local sweat rate (P < 0.05) on control forearm correlated positively with pilocarpine-induced local sweat rate at rest. Assuming that exercise-induced sweating was a result of integrated physiological mechanisms, we suggest that local and whole-body sweat rate measured during graded exercise could be a better sweating index than pilocarpine.

Increased oxygen consumption caused by cAMP- and Ca2+-mediated chloride secretion in rat distal colon

El transporte iónico epitelial exige aporte de ATP provisto por el metabolismo aeróbico. En el colon distal de rata, la secreción de cloruro explica la mayor parte del transporte electrogénico medido como corriente de cortocircuito (ISC). La inhibición de la secreción basal de cloruro reduce el consumo epitelial de oxígeno (QO2), mientras que la serotonina aumenta proporcionalmente ISC y QO2. El efecto de la serotonina es mediado por receptores 5HT4 acoplados a adenilato ciclasa medianteproteína G estimulante (GS). En este trabajo seestudió si el aumento del QO2 asociado con la secreción de cloruro es un efecto común a otros agentes que actúan sobre cAMP o Ca2+. Los efectos del inhibidor de la fosfodiesterasa, 3-isobutil-1-metilxantina (IBMX) y del agonista muscarínico carbacol (ambos a 0.1 mmol/L) se evaluaron en la mucosa aislada del colon distal de rata montado en una cámara de Ussing modificada para determinación continua de la concentración de oxígeno, permitiendo medir QO2. Se compararon la ISC y el QO2 basales con las resultantes del añadido de serotonina (control activo), IBMX, carbacol, o IBMX y carbacol. Todos aumentaron proporcionalmente ISC y QO2. Aunque el efecto de IBMX solo fue modesto y el del carbacol fue breve, se observó una sinergia cuando fueron agregados simultáneamente. El análisis de regresión lineal mostró una correlación significativa entre los incrementos de ISC y de QO2 (r2 = 0.746; P menor que 0.0001). Por tanto, la estimulación de la secreción de cloruro aumenta el QO2 independientemente de la vía efectora intracelular involucrada. Estos resultados corroboran el estrecho acoplamiento entre secreción de cloruro y QO2 en este epitelio.

Epithelial ion transport is dependent on ATP supply provided by aerobic metabolism. In the rat distal colon chloride secretion accounts for the largest portion of electrogenic transport measured as the short-circuit current (ISC). Inhibition of basal chloride secretion decreases epithelial oxygen consumption (QO2) in this tissue, while serotonin (5-hydroxytryptamine) proportionally increases both Isc and QO2. The effect of serotonin in this tissue is mainly mediated by 5HT4 receptors linked to adenylate cyclase through a stimulant G protein (GS). This work assessed whether the chloride secretion-induced increase in QO2 is a common characteristic of secretagogues, which act through either cAMP-dependent or Ca2+-dependent mechanisms. The effects of phosphodiesterase inhibitor 3-isobutyl-1- methylxantine (IBMX) and muscarinic agonist carbachol (both 0.1 mmol/L) were studied in rat distal colon isolated mucosa mounted in an Ussing chamber adapted for continuous measurement of oxygen concentration, allowing determination of QO2. Baseline ISC and QO2 were compared with ISC and QO2 after addition of either serotonin as an active control, IBMX, carbachol or IBMX plus carbachol. Each drug increased proportionally Isc and QO2. Although the effect of IBMX alone was modest and that of carbachol was short-lived, a synergic effect on Isc and QO2 was seen when both drugs were simultaneously added. Linear regression analysis showed a significant correlation between increases in ISC and QO2 (r2 = 0.746; P < 0.0001). Thus, stimulation of chloride secretion increases QO2 regardless of the intracellular pathway involved. These results extend previous findings, corroborating the close coupling between chloride secretion and QO2 in this epithelium

Cystic Fibrosis in Korean Children: A Case Report Identified by a Quantitative Pilocarpine Iontophoresis Sweat Test and Genetic Analysis

Cystic fibrosis (CF) is inherited as an autosomal recessive trait, and the mutations in cystic fibrosis transmembrane conductance regulator (CFTR) gene contributes to the CF syndrome. Although CF is common in Caucasians, it is known to be rare in Asians. Recently, we experienced two cases of CF in Korean children. The patients were girls with chronic productive cough since early infancy. Chest computed tomography showed the diffuse bronchiectasis in both lungs, and their diagnosis was confirmed by the repeated analysis of a quantitative pilocarpine iontophoresis test (QPIT). The sweat chloride concentrations of the first patient were 108.1 mM/L and 96.7 mM/L. The genetic analysis revealed that she was the compound heterozygote of Q1291X and IVS8 T5 -M470V. In the second case, the sweat chloride concentrations were 95.0 mM/L and 77.5 mM/L. Although we performed a comprehensive search for the coding regions and exonintron splicing junctions of CFTR gene, no obvious disease-related mutations were detected in the second case. To our knowledge, this is the first report of CF in Korean children identified by a QPIT and genetic analysis. The possibility of CF should be suspected in those patients with chronic respiratory symptoms even in Korea.

Supersensitivity of the cholinergic muscarinic system in the rat's brain is induced by high concentrations of Cu+2

Transition metals have been described as regulators of receptor's function. here, we studied the effects of chronic administration of Cu2+ or the Cu2+ chelator penicillamine (PA) on the functional and binding properties of the muscarinic receptors (MR) on selected areas of rat's brain. Groups of 10 Sprague-Dawley rats were treated daily, for 45 days with either 1) 1 mg/Kg CuSO4 (Cu2+), 2) 100 mg/Kg PA, or 3) saline solution. Double T-maze and motility cages were used for behavioral testing and the binding assays were performed using [3H]-QNB or [3H]-N-MSCP as MR's ligands. Cu2+ brain levels were measured in the cerebral cortex by atomic absorption spectrophotometer. Results showed that PA treated rats displayed a significant decrease of locomotor's activity (LA) and rearing behavior (RB), but a significant increases in memory efficiency (ME). Cu2+ treated rats displayed diminished RB with no significant changes in LA. Cu2+ treated rats displayed higher MR's density (Bmax) in cortex (C), striatum (S), and hippocampus (H). An increase in Bmax was also observed in PA treated rats, but only in C and S. Finally, Cu2+ tissue concentration was significantly higher in C of both Cu2+ and with PA treated animals. In conclusion, 45 days of Cu2+ or PA treatment induced brain hypercuprosis, which was associated with MR binding supersensitivity; however, change in ME was only observed in PA treated rats suggesting that might be still another factor in these experiments besides Cu2+ (i.e., Zn2+ or PA itself) involved in memory modulation.

Effect of pilocarpine mouthwash on salivary flow

Pilocarpine is a cholinergic agonist that increases salivary flow and has been used to treat xerostomia. Oral intake is the most frequent route of administration. Adverse effects are dose-dependent and include sudoresis, facial blushing and increased urinary frequency. The objective of the present study was to evaluate the effects of topical pilocarpine solutions as mouthwashes on salivary flow and their adverse effects on healthy subjects. Forty volunteers received 10 ml 0.5, 1 and 2 percent pilocarpine solutions or 0.9 percent saline in a randomized, double-blind, placebo-controlled manner. Salivation was measured before and 45, 60 and 75 min after mouth rinsing for 1 min with 10 ml of saline or pilocarpine solutions. Vital signs were measured and ocular, gastrointestinal and cardiovascular symptoms, anxiety and flushing were estimated using visual analog scales. There was a dose-dependent increase in salivation. Salivation measured after 1 and 2 percent pilocarpine (1.4 +/- 0.36 and 2.22 +/- 0.42 g, respectively) was significantly (P<0.001) higher than before (0.70 +/- 0.15 and 0.64 +/- 0.1 g), with a plateau between 45 and 75 min. Cardiovascular, visual, gastrointestinal and behavioral symptoms and signs were not changed by topical pilocarpine. Mouth rinsing with pilocarpine solutions at concentrations of 1 to 2 percent induced a significant objective and subjective dose-dependent increase in salivary flow, similar to the results reported by others studying the effect of oral 5 mg pilocarpine. The present study revealed the efficacy of pilocarpine mouthwash solutions in increasing salivary flow in healthy volunteers, with no adverse effects. Additional studies on patients with xerostomia are needed

Heart rate responses to a muscarinic agonist in rats with experimentally induced acute and subacute chagasic myocarditis

We administered arecoline to rats, with experimentally induced chagasic myocarditis, in order to study the sinus node sensitivity to a muscarinic agonist. Sixteen month old rats were inoculated with 200,000 T. cruzi parasites ("Y" strain). Between days 18 and 21 (acute stage), 8 infected rats and 8 age-matched controls received intravenous arecoline as a bolus injection at the following doses: 5.0, 10.0, 20.0, 40.0, and 80.0 mug/kg. Heart rate was recorded before, during and after each dose of arecoline. The remaining 8 infected animals and 8 controls were subjected to the same experimental procedure during the subacute stage, i.e., days 60 to 70 after inoculation. The baseline heart rate, of the animals studied during the acute stage (349 Ý 68 bpm, mean Ý SD), was higher than that of the controls (250 Ý 50 bpm, p < 0.005). The heart rate changes were expressed as percentage changes over baseline values. A dose-response curve was constructed for each group of animals. Log scales were used to plot the systematically doubled doses of arecoline and the induced-heart rate changes. The slope of the regression line for the acutely infected animals (r = - 0.99, b =1.78) was not different from that for the control animals (r = - 0.97, b = 1.61). The infected animals studied during the subacute stage (r = - 0.99, b = 1.81) were also not different from the age-matched controls (r = - 0.99, b = 1.26, NS). Consequently, our results show no pharmacological evidence of postjunctional hypersensitivity to the muscarinic agonist arecoline. Therefore, these results indirectly suggest that the postganglionic parasympathetic innervation, of the sinus node of rats with autopsy proved chagasic myocarditis, is not irreversibly damaged by Trypanosoma cruzi.

Antispasmodic action of propinox on the isolated human gallbladder: possible mechanism of action

Propinox is an antispasmodic drug frequently used in the treatment of disorders of the gastrointestinal tract, the uterus and the galbladder, but little is known about its relaxing activity in gallbladder tissue. The main objective of this study was to determine the antispasmodic activity of propinox, compared to other antispasmodics, in the gallblader and to assess its binding affinity to receptor sites which may be involved in its mechanism of action. Antispasmodic activity of propinox, (-) scopolamine-n-butyl bromide, atropine and verapamil was determined in human gallbladders to reduce the risk of interspecies variability. Inhibitory activities (ED50) of carbachol-induced contraction were: atropine 5.03x10(-8) M>propinox 1.25x10(-7) M> verapamil 6.63x10(-6)M> (-) scopolamine-n-butyl1 bromide 5.4x10(-5) M. pD'2 for propinox was 6.94, indicating non competitive inhibition of carbachol action. Radioligand binding studies were performed to determine if the antisplasmodic action of the drug involved binding to muscarinic receptors or calciumatagonist sites. The inhibition constant (Ki) of proponix for muscarinic receptors of guinea pig ileum smoth muscle, which contains a mixed M2-M3 receptor population, was 1.6x10(-6) M. Ki for brain muscarinic receptors (M1) was 1.0x10(-4) M, for cardiac receptors (M1) was 1.0x10(-4)M, for receptors (M2) 1.2x10(-6)M and from salivary gland receptors (M3) 1.5x10(-6)M. For binding to the dihidropiridine calcium antagonist binding sites, Ki were: 4.9x10(-5)M for propinox and 2.2x10(-7)M for verapamil. For the phenylakylamine binding sites Ki were: 5.0x10(-6)M for propinox and 3.5x10(-8)M for verapamil. For the benzothiacepine binding sites, Ki for propinox was 5.2x10(-6)M. The following may be concluded: 1- The antispasmodic activity of propinox in isolated human galbladder was was comparatively less potent than of atropine and more potent than those verapamil and (-) scopolamine-n-butyl bromide. 2- Propinox showed binding to muscarinic and calcium receptors that can be related to its antisplasmodic activity; suggesting that the drug is an antispasmodic with anticholinergic and musculotropic activity. 3.- The dual mechanism of action, anticholinergic and calcium-blocking, would induce synergism of pharmacodynamic effects and minimize adverse events of pure antimuscarinic drugs or calcium antagonists.

Inhibition of carbachol-induced inositol phosphate accumulation in the embryonic retina promoted by kainate and veratridine

In the present study, we report that low concentrations of the glutamate ionotropic agonist kainate decreased the turnover of [3H]-phosphoinositides ([3H]-InsPs) induced by muscarinic receptors in the chick embryonic retina. When 100 muM carbachol was used, the estimated IC50 value for kainate was 0.2 muM and the maximal inhibition of ~50 percent was obtained with 1 muM or higher concentrations of the glutamatergic agonist. Our data also show that veratridine, a neurotoxin that increases the permeability of voltage-sensitive sodium channels, had no effect on [3H]-InsPs levels of the embryonic retina. However, 50 muM veratridine, but not 50 mM KCl, inhibited ~65 percent of the retinal response to carbachol. While carbachol increased [3H]-InsPs levels from 241.2 + 38.0 to 2044.5 + 299.9 cpm/mg protein, retinal response decreased to 861.6 + 113.9 cpm/mg protein when tissues were incubated with carbachol plus veratridine. These results suggest that the accumulation of phosphoinositides induced by activation of muscarinic receptors can be inhibited by the influx of Na+ ions triggered by activation of kainate receptors or opening of voltage-sensitive sodium channels in the chick embryonic retina.

La estimulación colinérgica central en la desnervación sinoaórtica. Efecto de la administración i.c.v. de agentes colinomiméticos / The central cholinergic stimulation in the sinoaortic denervation. Effect of the intracerebroventricular administration of cholinomimetic agents

Se decidió encarar el estudio farmacológico de la participación colinérgica en el modelo de desnervación sinoaórtica analizando los efectos cardiovasculares de agonistas muscarínicos diversos y del anticolinesterásico neostigmina administrados por vía endovenosa o por la vía intracerebroventricular. También se evaluó la actividad de la enzima acetilcolinesterasa en diversas estructras del sistema nervioso central luego de la a inhibición por administración intracerebral de neostigmina pero disminuye el efecto bradicardizante. Sin embargo no alteraría las respuestas cardiovasculares correspondientes a la inyección i.v. del agonista oxotremorina y a la i.c.v. del agonista McNeil-A-343. Luego de la administración i.c.v. de neostigmina, la actividad enzimática remanente osciló entre 24 por ciento a 30 por ciento en las estructuras hipotalámicas y entre 42 por ciento a 52 por ciento en los restantes tejidos, sin diferencias entre las ratas con operación simulada y aquellas con desnervación sinoaórtica. Los resultados sugieren que en los efectos cardiovasculares de la estimulación colinérgica central posiblemente no estarían involucrados receptores muscarínicos del subtipo M1. Por otra parte, no estaría afectada la degradación de la acetilcolina en el sistema nervioso central, lo que apoyaría la idea de un compromiso de receptores muscarínicos en los cambios observados. Por la ruta de administración utilizada de neostigmina, se observa un mayor grado de inhibición de la acetilcolinesterasa hipotalámica, sugiriendo entonces que las estructuras hipotalámicas podrían estar comprometidas en los efectos cardiovasculares inducidos por la administración intracerebral del anticolinesterásico.