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Ocusert P 20/P 40 was tested on 53 outpatients with glaucoma for 5 weeks. In 27 patients good results and compatibility could be seen. The therapy had to be stopped with 26 patients, due to bad compatibility in 16 patients, and due to insufficient effectiveness in 10 patients.
Male Holtzman rats weighting 200-250 g were anesthetized with zoletil 50 mg/Kg (tiletamine chloridrate 125.0 mg and zolazepan chloridrate 125.0 mg) into quadriceps muscle and stainless steel cannulas were implanted into their supraoptic nucleus (SON). We investigated the effects of the injection into the supraoptic nucleus (SON) of FK 409, a nitric oxide donor, and NW-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor (NOS), on the salivary secretion, arterial blood pressure, sodium excretion and urinary volume induced by pilocarpine, which was injected into SON. The drugs were injected in 0.5 microl volume over 30-60 s. Controls was injected with a similar volume of 0.15 M NaCl. FK 409 and L-NAME were injected at doses of 20 microg/0.5 microl and 40 microg/0.5 microl respectively. The amount of saliva secretion was studied over a five-minute period after injection of pilocarpine into SON. Injection of pilocarpine (10, 20, 40, 80, 160 microg/microl) into SON produced a dose-dependent increase in salivary secretion. L-NAME was injected into SON prior to the injection of pilocarpine into SON, producing an increase in salivary secretion due to the effect of pilocarpine. FK 409 injected into SON attenuating the increase in salivary secretion induced by pilocarpine. Mean arterial pressure (MAP) increase after injections of pilocarpine into the SON. L-NAME injected into the SON prior to injection of pilocarpine into SON increased the MAP. FK 409 injected into the SON prior to pilocarpine attenuated the effect of pilocarpine on MAP. Pilocarpine (0.5 micromol/0.5 microl) injected into the SON induced an increase in sodium and urinary excretion. L-NAME injected prior to pilocarpine into the SON increased the urinary sodium excretion and urinary volume induced by pilocarpine. FK 409 injected prior to pilocarpine into the SON decreased the sodium excretion and urinary volume induced by pilocarpine. All these roles of pilocarpine depend on the release of nitric oxide into the SON. In summary the present results show: a) SON is involved in pilocarpine-induced salivation; b) that mechanism involves increase in MAP, sodium excretion and urinary volume.
Our studies have focused on the effect of injection of L-NAME and sodium nitroprussiate (SNP) on the salivary secretion, arterial blood pressure, sodium excretion and urinary volume induced by pilocarpine which was injected into the medial septal area (MSA). Rats were anesthetized with urethane (1.25 g/kg b. wt.) and a stainless steel cannula was implanted into their MSA. The amount of saliva secretion was studied over a five-minute period after injection of pilocarpine into MSA. Injection of pilocarpine (10, 20, 40, 80, 160 microg/microl) into MSA produced a dose-dependent increase in salivary secretion. L-NG-nitro arginine methyl-esther (L-NAME) (40 microg/microl), a nitric oxide (NO) synthase inhibitor, was injected into MSA prior to the injection of pilocarpine into MSA, producing an increase in salivary secretion due to the effect of pilocarpine. Sodium nitroprussiate (SNP) (30 microg/microl) was injected into MSA prior to the injection of pilocarpine into MSA attenuating the increase in salivary secretion induced by pilocarpine. Medial arterial pressure (MAP) increase after injections of pilocarpine into the MSA. L-NAME injected into the MSA prior to injection of pilocarpine into MSA increased the MAP. SNP injected into the MSA prior to pilocarpine attenuated the effect of pilocarpine on MAP. Pilocarpine (40 ug/ul) injected into the MAS induced an increase in sodium and urinary excretion. L-NAME injected prior to pilocarpine into the MSA increased the urinary sodium excretion and urinary volume induced by pilocarpine. SNP injected prior to pilocarpine into the MSA decreased the sodium excretion and urinary volume induced by pilocarpine. All these roles of pilocarpine depend on the release of nitric oxide into the MSA. We may also conclude that the MSA is involved with the cholinergic excitatory mechanism that induce salivary secretion, increase in MAP and increase in sodium excretion and urinary volume.
High-dose treatment with pilocarpine hydrochloride, a cholinergic muscarinic agonist, induces seizures in rodents following systemic or intracerebral administration. Pilocarpine seizures are characterized by a sequential development of behavioral patterns and electrographic activity. Hypoactivity, tremor, scratching, head bobbing, and myoclonic movements of the limbs progress to recurrent myoclonic convulsions with rearing, salivation, and falling, and status epilepticus. The sustained convulsions induced by pilocarpine are followed by widespread damage to the forebrain. The amygdala, thalamus, olfactory cortex, hippocampus, neocortex, and substantia nigra are the most sensitive regions to epilepsy-related damage following convulsions produced by pilocarpine. Spontaneous seizures are observed in the long-term period following the administration of convulsant doses of pilocarpine. Developmental studies show age-dependent differences in the response of rats to pilocarpine. Seizures are first noted in 7-12 day-old rats, and the adult pattern of behavioral and electroencephalographic sequelae of pilocarpine is seen in 15-21-day-old rats. During the third week of life the rats show an increased susceptibility to the convulsant action of pilocarpine relative to older and younger animals. The developmental progress of the convulsive response to pilocarpine does not correlate with evolution of the brain damage. The adult pattern of the damage is seen after a delay of 1-2 weeks in comparison with the evolution of seizures and status epilepticus. The susceptibility to seizures induced by pilocarpine increases in rats aged over 4 months. The basal ganglia curtail the generation and spread of seizures induced by pilocarpine. The caudate putamen, the substantia nigra, and the entopeduncular nucleus govern the propagation of pilocarpine-induced seizures. The antiepileptic drugs diazepam, clonazepam, phenobarbital, valproate, and trimethadione protect against pilocarpine-induced convulsions, while diphenylhydantoin and carbamazepine are ineffective. Ethosuximide and acetazolamide increase the susceptibility to convulsant action of pilocarpine. Lithium, morphine, and aminophylline also increase the susceptibility of rats to pilocarpine seizures. The pilocarpine seizure model may be of value in designing new therapeutic approaches to epilepsy.
We investigated the effect of L-NAME, a nitric oxide (NO) inhibitor and sodium nitroprusside (SNP), an NO-donating agent, on pilocarpine-induced alterations in salivary flow, mean arterial blood pressure (MAP) and heart rate (HR) in rats. Male Holtzman rats (250-300 g) were implanted with a stainless steel cannula directly into the median preoptic nucleus (MnPO). Pilocarpine (10, 20, 40, 80, 160 g) injected into the MnPO induced an increase in salivary secretion (P<0.01). Pilocarpine (1, 2, 4, 8, 16 mg/kg) ip also increased salivary secretion (P<0.01). Injection of L-NAME (40 g) into the MnPO prior to pilocarpine (10, 20, 40, 80, 160 g) injected into the MnPO or ip (1, 2, 4, 8, 16 mg/kg) increased salivary secretion (P<0.01). SNP (30 g) injected into the MnPO or ip prior to pilocarpine attenuated salivary secretion (P<0.01). Pilocarpine (40 g) injection into the MnPO increased MAP and decreased HR (P<0.01). Pilocarpine (4 mg/kg body weight) ip produced a decrease in MAP and an increase in HR (P<0.01). Injection of L-NAME (40 g) into the MnPO prior to pilocarpine potentiated the increase in MAP and reduced HR (P<0.01). SNP (30 g) injected into the MnPO prior to pilocarpine attenuated (100%) the effect of pilocarpine on MAP, with no effect on HR. Administration of L-NAME (40 g) into the MnPO potentiated the effect of pilocarpine injected ip. SNP (30 g) injected into the MnPO attenuated the effect of ip pilocarpine on MAP and HR. The present study suggests that in the rat MnPO 1) NO is important for the effects of pilocarpine on salivary flow, and 2) pilocarpine interferes with blood pressure and HR (side effects of pilocarpine), that is attenuated by NO.
1. Pilocarpine administration has been used as an animal model for temporal lobe epilepsy since it produces several morphological and synaptic features in common with human complex partial seizures. Little is known about changes in extracellular neurotransmitter concentrations during the seizures provoked by pilocarpine, a non-selective muscarinic agonist. 2. Focally evoked pilocarpine-induced seizures in freely moving rats were provoked by intrahippocampal pilocarpine (10 mM for 40 min at a flow rate of 2 microl min(-1)) administration via a microdialysis probe. Concomitant changes in extracellular hippocampal glutamate, gamma-aminobutyric acid (GABA) and dopamine levels were monitored and simultaneous electrocorticography was performed. The animal model was characterized by intrahippocampal perfusion with the muscarinic receptor antagonist atropine (20 mM), the sodium channel blocker tetrodotoxin (1 microM) and the N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 (dizocilpine maleate, 100 microM). The effectiveness of locally (600 microM) or systemically (10 mg kg(-1) day(-1)) applied lamotrigine against the pilocarpine-induced convulsions was evaluated. 3. Pilocarpine initially decreased extracellular hippocampal glutamate and GABA levels. During the subsequent pilocarpine-induced limbic convulsions extracellular glutamate, GABA and dopamine concentrations in hippocampus were significantly increased. Atropine blocked all changes in extracellular transmitter levels during and after co-administration of pilocarpine. All pilocarpine-induced increases were completely prevented by simultaneous tetrodotoxin perfusion. Intrahippocampal administration of MK-801 and lamotrigine resulted in an elevation of hippocampal dopamine levels and protected the rats from the pilocarpine-induced seizures. Pilocarpine-induced convulsions developed in the rats which received lamotrigine perorally. 4. Pilocarpine-induced seizures are initiated via muscarinic receptors and further mediated via NMDA receptors. Sustained increases in extracellular glutamate levels after pilocarpine perfusion are related to the limbic seizures. These are arguments in favour of earlier described NMDA receptor-mediated excitotoxicity. Hippocampal dopamine release may be functionally important in epileptogenesis and may participate in the anticonvulsant effects of MK-801 and lamotrigine. The pilocarpine-stimulated hippocampal GABA, glutamate and dopamine levels reflect neuronal vesicular release.
The interaction between pilocarpine and hexobarbital was studied in male rats. Hexobarbital was infused continously. The dose needed to obtain an EEG criterion (the "silent second") was determined. The ensuing anesthesia times after these equi-anesthetic doses were also recorded. At different times prior to the hexobarbital threshold determination the rats were pretreated with 25-200 mg/kg of pilocarpine. In most experimental series pretreatment with methylatropine (2 mg/kg s.c.) was also given to reduce the effects of pilocarpine on peripheral cholinergic sites. In the dose-response study pilocarpine was given 1 h prior to the hexobarbital threshold determination. Pilocarpine in doses of 25-50 mg/kg increased the amount of hexobarbital needed to obtain the "silent second". With higher doses of pilocarpine, increases in hexobarbital thresholds were seen if no convulsion had been induced by the pilocarpine treatment. If a convulsion was recorded the dose of hexobarbital was reduced. Similar results were obtained in the time-effect studies where more convulsions tended to appear if the time between the dose of pilocarpine and the dose of hexobarbital was increased. In animals without convulsions the effect of pilocarpine on the dose of hexobarbital was counteracted by atropine (8 mg/kg i.p.). The ensuing anesthesia times were increased in the pilocarpine pretreated animals, which could be due to either the pilocarpine dose, the increased dose of hexobarbital needed to obtain the "silent second", or both. No regression between body temperature and dose of hexobarbital was found, but there was a regression with the ensuing anesthesia times. The effects of pilocarpine with an increase in hexobarbital threshold is similar to the changes seen in the threshold in the abstinence after chronic barbital treatments. More important, however, is that both increases are reduced by convulsions. Could pilocarpine be a model for the changes in the abstinence after barbital?
Our studies have focused on the effect of L-NG-nitroarginine methyl ester (L-NAME), an inhibitor of nitric oxide synthase (NOS), and L-arginine, the substrate of NOS, on salivary secretion induced by the administration of pilocarpine into the lateral cerebral ventricle (LV) of rats. The present study has also investigated the role of the beta-adrenergic agonists and antagonist injected into LV on the salivary secretion elicited by the injection of pilocarpine into LV. Male Holtzman rats with a stainless-steel cannula implanted into the LV were used. The amount of salivary secretion was studied over a 7-min period after injection of pilocarpine, isoproterenol, propranolol, salbutamol, salmeterol, L-NAME and L-arginine. The injection of pilocarpine (10, 20, 40, 80 and 160 microg/microl) into LV produced a dose-dependent increase in salivary secretion. The injection of L-NAME (40 microg/microl) into LV alone produced an increase in salivary secretion. The injection of L-NAME into LV previous to the injection of pilocarpine produced an increase in salivary secretion. L-Arginine (30 microg/microl) injected alone into LV produced no change in salivary secretion. L-Arginine injected into LV attenuated pilocarpine-induced salivary secretion. The isoproterenol (40 nmol/microl) injected into LV increased the salivary secretion. When injected previous to pilocarpine at a dose of 20 and 40 microg/microl, isoproterenol produced an additive effect on pilocarpine-induced salivary secretion. The 40-nmol/microl dose of propranolol injected alone or previous to pilocarpine into LV attenuated the pilocarpine-induced salivary secretion. The injection of salbutamol (40 nmol/microl), a specific beta-2 agonist, injected alone into LV produced no change in salivary secretion and when injected previous to pilocarpine produced an increase in salivary secretion. The 40-nmol/microl dose of salmeterol, a long-acting beta-2 agonist, injected into LV alone or previous to pilocarpine produced no change in salivary secretion. The results have shown that central injections of L-NAME and L-arginine interfere with the salivary secretion, which implies that might participate in pilocarpine-induced salivary secretion. The interaction between cholinergic and beta-adrenergic receptors of the central nervous system (CNS) for the control of salivary secretion can also be postulated.
PURPOSE: To retrospectively compare subjective postirradiation xerostomia scores of patients who received concomitant oral pilocarpine during radiotherapy for head and neck cancer and 3 months thereafter with those of similar cohorts who did not receive pilocarpine. METHODS AND MATERIALS: Subjective xerostomia was assessed using a visual analog scale xerostomia questionnaire that measured oral dryness, oral comfort, difficulty with sleep, speech, and eating. The concomitant pilocarpine group had both parotid glands in the initial field treated to at least 45 Gy and received 5 mg pilocarpine hydrochloride four times per day (q.i.d.) beginning on the first day of radiotherapy and continuing for 3 months after completion of radiation. The control cohort had also received at least 45 Gy to both parotid glands and had not received pilocarpine at the time of evaluation. Scores on the visual analog scale were averaged and compared using the Student's t-test. RESULTS: Seventeen patients who received concomitant pilocarpine during head and neck irradiation and 18 patients who had not been treated with pilocarpine were available for follow-up. The mean intervals between completion of radiation and evaluation of xerostomia were 17 months and 16 months, respectively. Only one of the pilocarpine-treated patients was still taking pilocarpine at the time of evaluation. For each of the individual components of xerostomia scored on the visual analog scale, as well as the composite of all components, the group that had received oral pilocarpine during radiation had significantly less xerostomia (p < 0.01 for each). CONCLUSIONS: The use of 5 mg oral pilocarpine q.i.d. during radiotherapy for head and neck cancer and 3 months thereafter was associated with significantly less subjective xerostomia than that reported by a similar cohort of patients who had not received pilocarpine. The continued use of pilocarpine does not appear to be necessary to maintain this benefit in most patients.
Pilocarpine, a widely used antiglaucoma drug, was incorporated into a newly developed submicron emulsion (pilocarpine emulsion) suitable for local ocular administration. Pilocarpine-Emulsion effect on the intraocular pressure (IOP) was studied following a single dose application in normotensive rabbits. Membrane filtration (steam autoclaving) was found not to affect particle size distribution, zeta potential or pH of the pilocarpine emulsion preparation. A single dose application of pilocarpine emulsion 1.7% (equivalent to 2% pilocarpine hydrochloride) induced a prolonged progressive decrease in IOP in normotensive rabbits, which started at eleven hours post instillation and reached its maximal value of 6.0 +/- 0.2 mmHg at 29 hours. The pressure decreasing effect induced by pilocarpine emulsion treatment followed a pattern different from that generated by generic pilocarpine (Pilocarpine Hydrochloride 2% eye drops); In the latter group, IOP reduction (starting at two hours) persisted during the initial five hours post-instillation, while in the former, the hypotensive effect started at a later stage, and was maintained during a twenty nine hour follow-up causing a greater IOP decrease than in the generic group (% delta IOP of 28.5% and 18%, respectively). In the contralateral eyes of Pilocarpine Emulsion treated rabbits, an ocular hypotensive effect was noted late after application (11 hours through 29 hours post-instillation), while this effect was negligible in rabbits-treated with aqueous pilocarpine. Our findings point to the possibility that the novel preparation of pilocarpine incorporated into submicron emulsion might serve as a long-acting form of pilocarpine which might require a single daily application. Further studies are required to elucidate the mechanism and action of this preparation.
BACKGROUND: Xerostomia (dry mouth) is a clinical symptom due to a number of factors, including Sjögren syndrome and radiation treatment to the head and neck region. It has been reported that acupuncture increases the salivary flow rate (SFR) in healthy subjects and in patients with xerostomia. A prognostic tool that would allow the care provider to identify patients who may respond to acupuncture treatment will aid in early intervention and thus lead to normalized SFR or relief of symptoms. OBJECTIVES: To determine the prognostic value of a test using pilocarpine chloride to identify those patients with xerostomia who may achieve a long-term increase in SFR in response to acupuncture. DESIGN: Cohort clinical study of 10 months' duration. SETTING: School of dentistry in a large, urban, research institute. PATIENTS: Thirty-two consecutive patients with xerostomia due to radiation treatment (n = 21) or Sjögren syndrome (n=11). INTERVENTION: Salivary flow rates for unstimulated whole saliva and paraffin-chewing stimulated whole saliva were measured before and after the administration of individualized doses of pilocarpine. All patients were then given 24 acupuncture treatments and followed up at 1 and 6 months. The effects of acupuncture treatment on SFR were recorded and response compared with the results of the pilocarpine test. MAIN OUTCOME MEASURES: Sensitivity, specificity, and positive and negative predictive value of the pilocarpine test based on changes in SFR, defined as a 20% increase or greater, following acupuncture treatment, compared with response to the pilocarpine test. RESULTS: At the 1-month follow-up, 18 (72%) of 25 patients with a positive pilocarpine test result had defined significant changes in SFR; 4 (67%) of 6 patients with a negative pilocarpine test result had an unchanged SFR. At this point, the sensitivity of the pilocarpine test was 0.90 (95% confidence interval [CI], 0.68-0.99) and the specificity was 0.36 (95% CI, 0.11-0.69). The positive predictive value was 0.72 (95% CI, 0.51-0.88), and the negative predictive value was 0.67 (95% CI, 0.22-0.96). At the 6-month follow-up, 17 (74%) of 23 patients with a positive pilocarpine test result had defined significant changes in SFR; 3 (60%) of 5 patients with a negative pilocarpine test result had an unchanged SFR. At this point, the sensitivity of the pilocarpine test was 0.89 (95% CI, 0.67-0.99), and the specificity was 0.33 (95% CI, 0.07-0.70). The positive predictive value was 0.74 (95% CI, 0.52-0.90), and the negative predictive value was 0.60 (95% CI, 0.15-0.95). CONCLUSION: The pilocarpine test was found to have a high sensitivity and good positive predictive value in identifying patients who may respond to acupuncture for the treatment of xerostomia.
Systemic administration of pilocarpine in rats can result in a chronic behavioral state that is similar to human temporal lobe epilepsy. The pilocarpine model of epilepsy is widely used for studying the factors that contribute to the development of epilepsy as a consequence of status epilepticus (SE). For this purpose, pilocarpine is either administered alone at a high systemic dose or in combination with lithium, which markedly potentiates the convulsant effect of pilocarpine. Both experimental protocols, however, are associated with high mortality rates. In the present study, we evaluated whether mortality rate in rats can be decreased by repeated administration of low doses of pilocarpine. The time the rats spent in SE was limited by diazepam. Preliminary experiments in lithium-free rats indicated that repeated low-dose administration of pilocarpine is too time-consuming to produce SE compared to single high-dose administration. All subsequent experiments were performed in lithium-pretreated rats. Single-dose injection of 30 mg/kg pilocarpine produced SE in approximately 70% of the animals, but 45% of the rats died although SE was interrupted by diazepam after 90 min. Repeated i.p. administration of 10 mg/kg pilocarpine at 30-min intervals resulted in SE after 2-4 injections; the mean dose of pilocarpine needed to induce SE was 26 mg/kg. When SE was interrupted after 90 min, mortality rate was below 10%, which was significantly lower compared to the protocol with one single administration of 30 mg/kg pilocarpine. In contrast to mortality rate, the development of spontaneous recurrent seizures did not differ between experimental protocols. Almost all rats which had experienced a SE of at least 60 min developed chronic epilepsy. Average latency to the first spontaneous seizure was approximately 40 days. The frequency and severity of spontaneous seizures was not significantly different between protocols, although animal groups with repeated low-dose treatment tended to have higher frequencies of spontaneous seizures compared to single-dose administration. The present study demonstrates that systemic treatment of lithium-pretreated rats with several low doses of pilocarpine efficiently produces SE and chronic epilepsy with much lower mortality rates than single-dose pilocarpine.
1. In the present study, we investigated the prophylactic effects of pilocarpine hydrochloride on xerostomia models induced by either single (15 Gy) or repeated (8.6 Gy x3 days) X-ray irradiation in rats. Pilocarpine hydrochloride was administered orally 90 min before each irradiation session. Then, 7 days later, salivary volume, amylase activity and protein concentration in the saliva secreted from the right parotid gland were measured before and after a subsequent administration of pilocarpine hydrochloride (intraduodenal). 2. In irradiated no-pretreatment rats, irradiation induced a significant reduction in both spontaneous and pilocarpine hydrochloride-stimulated secretion (both total salivary volume and flow rate), regardless of the protocol used for X-ray exposure. In irradiated, pilocarpine hydrochloride-pretreated rats, salivary secretion was increased after stimulation by pilocarpine hydrochloride (intraduodenal) to a degree that depended on the pretreatment dose of pilocarpine hydrochloride (p.o.) in both xerostomia models. 3. There were no differences in amylase or protein concentrations between irradiated rats pretreated with pilocarpine hydrochloride and irradiated no-pretreatment control rats. 4. A decrease in the weight of the parotid gland was observed in rats exposed to either the single dose or repeated irradiation protocols. Changes in the submandibular gland were less marked than those in the parotid gland. These changes in gland weight were not affected by pilocarpine hydrochloride pretreatment. 5. The responsiveness of the parotid gland to subsequent stimulation with pilocarpine hydrochloride was apparently preserved in both xerostomia models by pretreatment with pilocarpine hydrochloride, which itself increased salivary secretion. This suggests that pilocarpine hydrochloride may exert functional protective effects against xerostomia that occurs following irradiation therapy through a stimulation of salivary secretion.
OBJECTIVE: To compare the pharmacokinetics of 0.5% pilocarpine containing sodium hyaluronate with 1% generic pilocarpine solution. METHODS: One hundred albino rabbits were divided into 20 groups, each consisting of 5 animals. Ten groups received 0.5% pilocarpine containing sodium hyaluronate and 10 groups received 1% generic pilocarpine solution as control. The aqueous humor was withdrawn at 5, 10, 20, 30, 40, 60, 90, 120, 150, and 180 min after instillation. The drug was extracted from aqueous humor with dichloromethane and was detected by reversed phase high performance liquid chromatography (HPLC). RESULTS: The average recovery rate of pilocarpine from aqueous humor was 98.2%. The minimum detectable concentration was 0.025 micro g/ml. The peak concentration and half-life of pilocarpine in aqueous humor were 4.46 micro g/ml at 10 min and 31.83 min, respectively, in the experimental group. Whereas, the peak concentration and half-life of pilocarpine in aqueous humor were 2.25 micro g/ml at 20 min and 22.98 min, respectively, in the control group. The peak concentration of pilocarpine in aqueous humor in the experimental group was 1.98 (P < 0.05) times higher than the control group. The area under curve of the drug concentration-time (AUC(0 - 180)) in the experimental group was 1.75 times higher than the control group. CONCLUSION: Pilocarpine (0.5%) containing sodium hyaluronate significantly increased the peak concentration of pilocarpine, shortened the time of reaching peak concentration and prolonged the half-life in aqueous humor. These results indicate that 0.5% pilocarpine with sodium hyaluronate significantly increases ocular bioavailability of pilocarpine.
The effect of 7-days BID (twice in a day) or TID (three times in a day) administration of the eye-drop combinations of timolol and pilocarpine (0.5% and 2%, respectively), metipranolol and pilocarpine (0.1% and 2%, respectively) or placebo on intraocular pressure (IOP) and heart rate (HR) of conscious rabbits were studied in order to assess the pharmacological potency of the combinations and their heart side effects. TID administration of both pharmacological combinations was followed by similar decrease of IOP as measured over 24 h (at 4.00 and 20.00 h). After the BID administration, a reduction in IOP was observed only twice with the timolol-pilocarpine combination. In contrast, a constant reduction in IOP was seen with the metipranolol-pilocarpine combination. Furthermore, the TID administration of the timolol-pilocarpine combination exerted a decrease of IOP that appeared to be more pronounced than that observed after the BID administration of the same combination, while no difference was found between the TID and BID administration of the metipranolol-pilocarpine treatment. Heart rate, when measured after 7 days of treatment, appeared to be constantly decreased only in the group of animals which received the TID administration of timolol-pilocarpine combination. The present results suggest that the BID or TID administration of metipranolol-pilocarpine combination was fully effective in reducing IOP without influencing HR. The timolol-pilocarpine association appeared to be fully active in reducing IOP only under the TID administration schedule. However, this rate of administration was followed by a constant reduction of HR. Thus, on a dose basis the metipranolol-pilocarpine combination appeared to be more effective in reducing IOP and less effective in inducing bradycardia than the timolol-pilocarpine association.
Binding of [3H]-pilocarpine to synaptic membranes in rat cerebral cortex was investigated, pilocarpine binding was also studied by competition of unlabelled pilocarpine with the [3H]-labelled muscarinic antagonist, [3H]-N-methyl-4-piperidinyl benzilate. 1. [3H]-pilocarpine binding sites are of protein nature, and the highest specific activity of binding is found in the synaptosomal fraction of all subcellular fractions. 2. Competition studies show that only muscarinic drugs inhibit [3H]-pilocarpine binding in their pharmacologically active concentration range. 3. Binding of [3H]-pilocarpine is influenced by GMPP-(NH)P (0.1 mM) similarly to the binding of other muscarinic agonists. 4. Examination of pilocarpine binding with [3H]-pilocarpine and the competition experiments with unlabelled pilocarpine indicate the presence of three sites with different affinities: 5 nM, 0.2 microM and 30 microM respectively. 5. Experiments with [3H]-4-NMPB and [3H]-pilocarpine indicate that there are more [3H]-pilocarpine binding sites than [3H]-4-NMPB binding sites in rat cerebral cortex.
We determined the effects of moxonidine and rilmenidine 20 nmol (alpha(2)-adrenergic and imidazoline receptor agonists) injected into the medial septal area (MSA) on the pilocarpine-induced salivation, when injected intraperitoneally (i.p.), of male Holtzman rats weighing 250-300 g, with stainless-steel cannula implanted into the MSA. The rats were anesthetized with zoletil 50 mg kg(-1) b.wt. (tiletamine chloridrate 125.0 mg and zolazepan chloridrate 125.0 mg) into quadriceps muscle intramuscularly (IM), saliva was collected using pre-weighed small cotton balls inserted in the animal's mouth. The pre-treatment with moxonidine injected into the MSA reduced the salivation induced by pilocarpine (1 mg kg(-1)) injected i.p. (12+/-3 mg min(-1)) vs. control (99+/-9 mg min(-1)). The pre-treatment with rilmenidine 40 nmol also reduced the salivation induce by pilocarpine injected i.p. (20+/-5 mg min(-1)) vs. control (94+/-7 mg min(-1)). Idazoxan 40 nmol (imidazoline receptor antagonist) injected into the MSA previous to moxonidine and rilmenidine partially blocked the effect of moxonidine and totally blocked the rilmenidine effect in pilocarpine-induced salivation injected i.p. (60+/-8 and 95+/-10 mg min(-1), respectively). Yohimbine 40 nmol (alpha(2)-adrenergic receptor antagonist) injected into the MSA previously to moxonidine and rilmenidine partially blocked the moxonidine effect but produced no change on the rilmenidine effect on i.p. pilocarpine-induced salivation (70+/-6 and 24+/-6 mg min(-1), respectively). Injection of these alpha(2)-adrenergic and imidazoline agonists and antagonists agents i.p. produced no change on i.p. pilocarpine-induced salivation. These results show that central, but not peripheral, injection of alpha(2)-adrenergic and imidazoline agonists' agents inhibit pilocarpine-induced salivation. Idazoxan, an imidazoline receptor antagonist, totally inhibits the rilmenidine effect and partially inhibits the moxonidine effect on pilocarpine-induced salivation. Yohimbine produced no change on rilmenidine effect but partially inhibited the moxonidine effect. Both of these antagonists when injected into the MSA previous to pilocarpine i.p. potentiated the sialogogue effect of pilocarpine. The results suggest that alpha(2)-adrenergic/imidazoline receptor of the MSA when stimulated blocked pilocarpine-induced salivation in rats when injected intraperitonially. These receptors of the medial septal area have an inhibitory mechanism on salivary secretion.