Pilocarpine-induced Salivary Secretion Research Articles

Age-related alteration of the involvement of CD36 for salivary secretion from the parotid gland in mice

This in vivo mouse model study was conducted to investigate the temporal alteration of the function of CD36 in salivary secretion. CD36 was highly expressed in the parotid gland of BALB/c mice. No significant variations were shown in the CD36 levels in the 8-, 48-, and 72-week-old animals. However, pilocarpine-induced salivary secretion was reduced in an age-dependent manner, showing a significantly low level at the age of 72 weeks. Pilocarpine-induced salivary secretion was significantly reduced by pretreatment with a CD36 inhibitor at 8 and 48 weeks, but not at 72 weeks. In senescence-accelerated mice (SAM), the pilocarpine-induced salivary secretion was significantly reduced at the age of 56 weeks, and a significantly lower amount of CD36 was demonstrated in the parotid gland, compared with the control. These results suggest that the involvement of parotid CD36 in mouse salivary secretion is altered with age.

Local anesthetics inhibit muscarinic acetylcholine receptor-mediated calcium responses and the recruitment of β-arrestin in HSY human parotid cells

ObjectivesLocal anesthetics act on G protein-coupled receptors (GPCRs); thus, their potential as allosteric modulators of GPCRs has attracted attention. Intracellular signaling via GPCRs involves both G-protein- and β-arrestin-mediated pathways. To determine the effects of local anesthetics on muscarinic acetylcholine receptors (mAChR), a family of GPCRs, we analyzed the effects of local anesthetics on mAChR-mediated Ca2+ responses and formation of receptor–β-arrestin complexes in the HSY human parotid cell line. MethodsCa2+ responses were monitored by fura-2 spectrofluorimetry. Ligand-induced interactions between mAChR and β-arrestin were examined using a β-arrestin GPCR assay kit. ResultsLidocaine reduced mAChR-mediated Ca2+ responses but did not change the intracellular Ca2+ concentration in non-stimulated cells. The membrane-impermeant lidocaine analog QX314 and procaine inhibited mAChR-mediated Ca2+ responses, with EC50 values of 48.0 and 20.4 μM, respectively, for 50 μM carbachol-stimulated Ca2+ responses. In the absence of extracellular Ca2+, the pretreatment of cells with QX314 reduced carbachol-induced Ca2+ release, indicating that QX314 reduced Ca2+ release from intracellular stores. Lidocaine and QX314 did not affect store-operated Ca2+ entry as they did not alter the thapsigargin-induced Ca2+ response. QX314 and procaine reduced the carbachol-mediated recruitment of β-arrestin, and administration of procaine suppressed pilocarpine-induced salivary secretion in mice. ConclusionLocal anesthetics, including QX314, act on mAChR to reduce carbachol-induced Ca2+ release from intracellular stores and the recruitment of β-arrestin. These findings support the notion that local anesthetics and their derivatives are starting points for the development of functional allosteric modulators of mAChR.

D-Serine Increases Release of Acetylcholine in Rat Submandibular Glands.

d-serine has been observed in submandibular gland tissue in rats, but its functions remain to be clarified. Oral administration of d-serine, but not l-serine, increased its concentrations in the submandibular gland and pilocarpine-induced salivary secretion. In vivo microdialysis was used to collect the d- and l-enantiomers of amino acids from local interstitial fluid in the rat submandibular gland. The proportion of the d-form of serine in interstitial fluid was higher than that in plasma or saliva. Perfusion of the rat submandibular gland with d-serine and l-glutamic acid via the submandibular gland artery resulted in a significant increase in salivary secretion after stimulation of muscarinic receptors with carbachol. In vivo microdialysis applied to the submandibular glands of rats showed that infusion of d-serine along with l-glutamate through the microdialysis probe significantly elevated acetylcholine levels in local interstitial fluids in the submandibular glands of anesthetized rats as compared to that with l-glutamate alone in an N-methyl-d-aspartate receptor glycine site antagonist-sensitive manner. These results indicate that d-serine augments salivary secretion by increasing acetylcholine release in the salivary glands.

Analysis of salivary flow rate, biochemical composition, and redox status in orchiectomized spontaneously hypertensive rats

ObjectiveThis study aimed to analyze the salivary flow rate, biochemical composition, and redox status in orchiectomized spontaneously hypertensive rats (SHR) compared to normotensive Wistar rats. DesignThirty-two young adult male SHR and Wistar (3-months-old) rats were randomly distributed into four groups; either castrated bilaterally (ORX) or underwent fictitious surgery (SHAM) as Wistar-SHAM, Wistar-ORX, SHR-SHAM, and SHR-ORX. Two months beyond castration, pilocarpine-induced salivary secretion was collected from 5-month-old rats to analyze salivary flow rate, pH, buffer capacity, total protein, amylase, calcium, phosphate, sodium, potassium, chloride, thiobarbituric acid reactive substances (TBARs), carbonyl protein, nitrite, and total antioxidant capacity. ResultsThe salivary flow rate was higher in the Wistar-ORX compared to the Wistar-SHAM group, while remaining similar between the SHR-SHAM and SHR-ORX groups. ORX did not affect pH and salivary buffer capacity in both strains. However, salivary total protein and amylase were significantly reduced in the Wistar-ORX and SHR-ORX compared to the respective SHAM groups. In both ORX groups, salivary total antioxidant capacity and carbonylated protein were increased, while lipid oxidative damage (TBARs) and nitrite concentration were higher only in the Wistar-ORX than in the Wistar-SHAM group. In the Wistar-ORX and SHR-ORX, the salivary calcium, phosphate, and chloride were increased while no change was detected in the SHAM groups. Only salivary buffering capacity, calcium, and chloride in the SHR-ORX adjusted to values similar to Wistar-SHAM group. ConclusionHypertensive phenotype mitigated the orchiectomy-induced salivary dysfunction, since the disturbances were restricted to alterations in the salivary biochemical composition and redox state.

Effects of orchiectomy and testosterone replacement therapy on redox balance and salivary gland function in Wistar rats

The objective of this study was to investigate the effects of orchiectomy (ORX) and testosterone replacement therapy (TRT) on redox balance and function of salivary glands. Forty-five young adult male Wistar rats (3 months old) were either castrated bilaterally or underwent fictitious surgery (SHAM) and were subsequently distributed into 3 groups: SHAM, ORX, and TRT (castrated rats that received an intramuscular injection of testosterone cypionate 10 mg/kg/weekly). All treatments started 4 weeks after castration (4 months old) and lasted 4 weeks (5 months old). At the end of treatment, pilocarpine-induced salivary secretion was collected to analyze salivary flow rate and biochemistry composition, and the parotid (PG) and submandibular (SMG) glands were sampled for redox balance markers and histomorphometric analyses. ORX increased salivary flow rate, calcium, phosphate, and chloride, and decreased total protein and amylase, while not changing the salivary buffer capacity, pH, sodium, and potassium compared to SHAM. TRT restored all salivary parameters to SHAM values. ORX increased oxidative lipid and protein damage, total antioxidant capacity, and uric acid in both salivary glands compared to SHAM. Superoxide dismutase, catalase, and glutathione peroxidase activities were greater only in the SMG of the ORX group in relation to SHAM. ORX decreased duct and acini area, while increasing connective tissue in the PG. On the other hand, ORX reduced duct area and increased acini area in the SMG compared to SHAM. TRT restored the redox balance and histomorphometric parameters to close to SHAM values in both salivary glands. Orchiectomy-induced salivary gland dysfunction was characterized by an increase in the salivary flow rate and changes in the secretion of total protein, amylase, and electrolytes, which are key factors, considered important for maintaining oral health status. To sum up, orchiectomy impaired the redox balance of the salivary glands. Our results also showed that TRT reversed the oxidative damage, morphological alterations, and salivary gland dysfunction induced by orchiectomy. Therefore, these results suggest an important action of testosterone on the redox balance and secretory ability of salivary glands.

Pilocarpine-Induced Effects on Salivary Secretion as a Pharmacological Biomarker for Cholinergic Parasympathetic Activation.

Pilocarpine-induced salivary secretion could serve as a nontherapeutic target engagement biomarker in a clinical setting to test the activity of an M3 positive allosteric modulator (PAM). The potentiating effect on the reactivity of the M3 receptor to the agonistic effect of pilocarpine would support the mechanism of action of an M3 PAM in a variety of therapeutic areas. The aim of this study was to determine the optimal pilocarpine dose needed for evaluation of this potentiating effect. Therefore, the effects of pilocarpine on salivary secretion rate and its pharmacokinetics were explored at single doses of 2.5, 5, and 10mg of pilocarpine or placebo. The study also explored the test-retest variability of the pilocarpine-induced effects on salivary secretion. Pilocarpine caused a reproducible, dose-related increase in overall and maximum salivary secretion rate, in line with pilocarpine exposure. Oral doses of pilocarpine from 2.5 to 10mg were safe and well tolerated, consistent with the published safety profile. These results support the use of pilocarpine in single-dose pharmacological challenge studies. The recommended dose for evaluating M3 PAM activity would be between 2.5 and 5mg, showing a small increase in salivary secretion rate with room for further increase due to PAM activation.

Effect of testosterone replacement therapy and mate tea (Ilex paraguariensis) on biochemical, functional and redox parameters of saliva in orchiectomized rats

ObjectiveEvaluate the effects of testosterone replacement therapy (TRT) and mate tea (MT) [Ilex paraguariensis] on biochemical, functional, and redox parameters of saliva in orchiectomized rats (ORX) DesignSixty young adult male Wistar rats (3 months old) were either castrated bilaterally or underwent fictitious surgery (SHAM) and were distributed into 5 groups: SHAM, ORX, TU (castrated rats that received a single intramuscular injection of testosterone undecanoate 100 mg/kg), MT (castrated rats that received MT 20 mg/kg, via intragastric gavage, daily), and TU + MT. All treatments started 4 weeks after castration (4 months old) and lasted 4 weeks (5 months old). At the end of treatment, pilocarpine-induced salivary secretion was collected to analyze salivary flow rate (SFR) and biochemistry composition through determination of total protein (TP), amylase (AMY), electrolyte, and biomarkers of oxidative stress. ResultsORX increased SFR, salivary buffering capacity, calcium, phosphate, chloride, total antioxidant capacity, thiobarbituric acid reactive substances (TBARs), and carbonyl protein, reduced TP and AMY activity, and did not change pH, sodium, and potassium compared to SHAM. TU and TU+MT restored all salivary parameters to values of SHAM, while only TBARs and AMY returned to SHAM levels in the MT group. ConclusionsTRT with long-acting TU restored the biochemical, functional, and redox parameters of saliva in orchiectomized rats. Although MT did not have a TRT-like effect on salivary gland function, the more effective reduction in lipid oxidative damage in the MT and TU + MT groups could be considered as adjuvant to alleviate the salivary oxidative stress induced by orchiectomy.

Changes of salivary functions in experimental periodontitis model rats

ObjectiveThis study was designed to investigate the mechanism of salivary dysfunction in an experimental periodontitis rat model and to examine the improvements in salivary secretion following treatment of the experimental periodontitis. MethodsIn the experimental periodontitis rat model, which included a unilateral ligature for 4 weeks around the second upper molar, several salivary functions were investigated. Changes in the salivary function were evaluated 4 weeks after removal of the ligature in some rats. ResultsThe periodontitis model showed significant reductions in the weight of the bilateral major salivary glands and pilocarpine-induced salivary secretion. The model also showed an increase in the number of apoptotic cells in bilateral salivary glands. According to Ca2+ imaging and Western blotting, there were no differences in the muscarine-induced intracellular Ca2+ mobilization in acinar cells or in the M3 receptor and AQP5 expression levels in the salivary glands between the sham and the periodontitis model. Following removal of the ligature, differences in the weights of salivary glands and pilocarpine-induced salivary secretion between the sham and the periodontitis model animals were not found. ConclusionThese results suggest that experimental periodontitis leads to hyposalivation and that relief from it improves salivary function. It is likely that lower levels of salivary secretion are caused by the decrease of functional acinar cells in salivary glands in the experimental periodontitis model, and the bilateral gland effects in the unilateral periodontitis model are caused by systemic rather than by local effects.

Rat Submandibular Gland Perfusion Method for Clarifying Inhibitory Regulation of GABAA Receptor

GABA is an inhibitory transmitter found in rat salivary gland. However, the inhibitory potential of GABA on salivary secretion is unclear. Using an in vivo cannulation method, intraperitoneal administration of GABA was ineffective in the absence of gabaculine, a GABA transaminase inhibitor, on pilocarpine-induced salivary secretion, suggesting that GABA was rendered metabolically inactive before reaching the salivary gland. We hypothesized that the action of a drug on the salivary glands could be measured directly using a submandibular gland perfusion system. The submandibular gland artery, veins, and duct were cannulated in situ so that physiological functions such as innervation would not be compromised. Hank's balanced salt solution (pH 7.4) was perfused at a rate of 0.5 ml/min together with 1 μM carbachol (CCh) over a 5-min period every 30 min. Amount of secreted saliva showed no change to the recurrent addition of CCh to the perfusate. GABA or muscimol dose-dependently inhibited CCh-induced salivary secretion. This effect was blocked by bicuculline, a GABA(A)-receptor (GABA(A)-R) antagonist, and enhanced by clonazepam, a central-type benzodiazepine-receptor agonist. These results suggest that salivary secretion is suppressed by GABA(A)-R in rat salivary gland and that the perfusion method used was effective in clarifying inhibitory regulation of GABA(A)-R.

Role of the medial septal area on pilocarpine-induced salivary secretion and water intake

Peripheral injection of pilocarpine, a cholinergic muscarinic agonist, induces salivation, water intake and hypertension. The medial septal area (MSA) is involved in cardiovascular control and fluid–electrolyte balance. Therefore, the effects of lesions or muscarinic cholinergic blockade in the MSA on the salivation, water intake and pressor responses induced by peripheral pilocarpine (4 μmol/kg of body weight) were investigated. Male Holtzman rats with stainless steel cannulas implanted in the MSA or submitted to electrolytic lesion of MSA were used. MSA lesion (1 day) reduced the salivation (262 ± 45 vs. sham: 501 ± 30 mg/7 min) and water intake (2.6 ± 0.4 vs. sham: 4 ± 0.4 ml/1 h) induced by intraperitoneal pilocarpine, whereas 15-day MSA lesion reduced only the pilocarpine-induced water intake (2.3 ± 0.5 ml/1 h). Pre-treatment with the muscarinic cholinergic antagonist atropine methyl bromide (4 nmol/0.5 μl) into MSA also reduced the pilocarpine-induced salivation (420 ± 33 mg/7 min) and water intake (1.4 ± 0.4 ml/1 h). Conversely, MSA lesions or the blockade of muscarinic receptors in the MSA did not change the pressor response induced by intravenous pilocarpine. The results show that MSA and its muscarinic receptors are part of the forebrain circuitry activated by peripheral pilocarpine that induce salivary secretion and water intake. Moreover, they suggest that different central mechanisms are involved in the salivatory, dipsogenic and cardiovascular effects of peripheral pilocarpine in rats.

In vivo demonstration of M 3 muscarinic receptor subtype selectivity of darifenacin in mice

A novel muscarinic receptor antagonist, darifenacin, inhibited specific binding of [ N-methyl- 3H]scopolamine ([ 3H]NMS) in the mouse bladder, submaxillary gland and heart in a concentration-dependent manner. The inhibitory effect was most potent in the submaxillary gland, followed by the bladder and heart. In addition, darifenacin inhibited specific [ 3H]NMS binding in the membranes of CHO-K1 cell lines expressing muscarinic M 2 and M 3 receptor subtypes, and the potency was significantly (22-fold) greater at the M 3 than at the M 2 subtype. At 0.5 to 12 h after oral administration of darifenacin, a significant increase in K d values for specific [ 3H]NMS binding was seen in the bladder, submaxillary gland and lung of mice, compared with control values. Also, there was a sustained decrease in the B max values in the submaxillary gland. These data suggest that muscarinic receptor binding of oral darifenacin is rapid in onset and of a long duration. On the other hand, oral darifenacin exerted only temporary or little binding of muscarinic receptors in the heart and colon. Pilocarpine-induced salivary secretion in mice was continuously suppressed by oral darifenacin. The time-course of suppression coincided well with that for the muscarinic receptor binding in the submaxillary gland. The antagonistic effect of darifenacin against the dose–response curves for pilocarpine appeared to be insurmountable. In conclusion, the present study has shown that oral darifenacin may exert a pronounced and long-lasting binding of muscarinic receptors in tissues expressing the M 3 subtype.

Damage of the medial preoptic area impairs peripheral pilocarpine-induced salivary secretion

The existence of neural connections between the medial preoptic area (MPOA) and the salivary glands and the increase in salivation by thermal or electrical stimulation of the MPOA have suggested an important role of MPOA in the control of salivary gland function. Although direct cholinergic activation of the salivary glands induces salivation, recent studies have suggested that salivation produced by i.p. pilocarpine may also depend on the activation of central mechanisms. Therefore, in the present study, we investigated the effects of bilateral electrolytic lesions of the MPOA on the salivation induced by i.p. pilocarpine. Adult male Holtzman rats ( n = 11–12/group) with bilateral sham or electrolytic lesions of the MPOA were used. One, five, and fifteen days after the brain surgery, under ketamine anesthesia, the salivation was induced by i.p. pilocarpine (1 mg/kg of body weight), and saliva was collected using preweighted small cotton balls inserted into the animal's mouth. Pilocarpine-induced salivation was reduced 1 and 5 days after MPOA lesion (341 ± 41 and 310 ± 35 mg/7 min, respectively, vs. sham lesions: 428 ± 32 and 495 ± 36 mg/7 min, respectively), but it was fully recovered at the 15th day post-lesion (561 ± 49 vs. sham lesion: 618 ± 27 mg/7 min). Lesions of the MPOA did not affect baseline non-stimulated salivary secretion. The results confirm the importance of MPOA in the control of salivation and suggest that its integrity is necessary for the full sialogogue effect of pilocarpine. However, alternative mechanisms probably involving other central nuclei can replace MPOA function in chronically lesioned rats allowing the complete recovery of the effects of pilocarpine.

Comparative Evaluation of Exocrine Muscarinic Receptor Binding Characteristics and Inhibition of Salivation of Solifenacin in Mice

Anticholinergic agents such as oxybutynin are clinically useful in the treatment of overactive bladder. However, oral administration of oxybutynin is frequently accompanied by side effects such as dry mouth, and novel bladder-selective anticholinergic agents such as solifenacin and tolterodine are now under development. The aim of the present study was to characterize the suppression of cholinergic salivation and exocrine muscarinic receptor binding of solifenacin on oral administration to mice in comparison with those of oxybutynin. Results showed that both drugs produced a significant increase in K(d) values for specific [N-Methyl-(3)H]scopolamine methyl chloride ([(3)H]NMS) binding in the mouse submaxillary gland, compared with control values. However, this enhancement in K(d) values was significantly smaller with solifenacin than with oxybutynin. Moreover, the inhibitory effect of solifenacin on pilocarpine-induced salivary secretion was significantly weaker than that of oxybutynin. Solifenacin dissociated more readily from muscarinic receptors in the mouse submaxillary gland than oxybutynin. In conclusion, the present study indicates that the weak suppression of cholinergic salivation by solifenacin compared with oxybutynin may be partially attributed to its relatively fast dissociation kinetics from exocrine muscarinic receptors.

Characterization of muscarinic receptor binding and inhibition of salivation after oral administration of tolterodine in mice

The current study was undertaken to characterize the effects of oral administration of tolterodine on muscarinic receptor binding in the bladder and submaxillary gland and on salivation in mice. In the in vitro experiment, tolterodine and its metabolite (5-hydroxymethyl metabolite: 5-HM) competed concentration-dependently with [ N-methyl- 3H]-scopolamine ([ 3H]NMS) in the mouse bladder, submaxillary gland and heart, and the potencies of both agents were greater than that of oxybutynin. After oral administration of tolterodine (6.31, 21.0 μmol/kg) and oxybutynin (76.1 μmol/kg), there was a dose and time-dependent increase in K d values for specific [ 3H]NMS binding in the bladder, prostate, submaxillary gland, heart, colon and lung, compared with control values, suggesting significant muscarinic receptor binding in each tissue. The K d increase in each tissue by oral oxybutynin reached a maximum value of 0.5 h after oral administration and then rapidly declined, while that by tolterodine was greatest 2 h after the administration and it was maintained for at least 6 or 12 h, depending on the dose and on the tissue. Thus, muscarinic receptor binding of oral tolterodine was slower in onset and of a longer duration than that of oxybutynin. Also, oral oxybutynin showed relatively greater receptor binding in the submaxillary gland as compared with other tissues, but such high selectivity to the exocrine gland muscarinic receptors was not observed by oral tolterodine. Oral administration of tolterodine and oxybutynin reduced significantly the pilocarpine-induced salivary secretion in mice, and the attenuation of oral tolterodine appeared more slowly and it was more persistent than that of oral oxybutynin. The antagonistic effect of oral tolterodine on the dose–response curves to pilocarpine was significantly weaker than that of oxybutynin. These data suggest that oral tolterodine, compared with the case of oral oxybutynin, binds more selectively to muscarinic receptors in the mouse bladder than in the submaxillary gland, which may be advantageous in treating patients with overactive bladder.

Muscarinic receptor binding, plasma concentration and inhibition of salivation after oral administration of a novel antimuscarinic agent, solifenacin succinate in mice

1 A novel muscarinic receptor antagonist, solifenacin succinate, inhibited specific binding of [N-methyl-(3)H]-scopolamine ([(3)H]-NMS) in the mouse bladder, submaxillary gland and heart in a concentration-dependent manner. This inhibitory effect was greatest in the submaxillary gland, followed by the bladder and heart. 2 After oral administration of oxybutynin (76.1 micromol kg(-1)) or solifenacin (62.4, 208 micromol kg(-1)), a significant dose- and time-dependent increase in K(D) values for specific [(3)H]-NMS binding was seen in the bladder, prostate, submaxillary gland, heart, colon and lung, compared with control values. The increase in K(D) induced by oxybutynin in each tissue reached a maximum 0.5 h after oral administration and then rapidly declined, while that induced by solifenacin was greatest 2 h after administration and was maintained for at least 6 or 12 h, depending on the dose. The muscarinic receptor binding of oral solifenacin was slower in onset and of a longer duration than that of oxybutynin. 3 Plasma concentrations of oxybutynin and its active metabolite (N-desethyl-oxybutynin, DEOB) were maximum 0.5 h after its oral administration and then declined rapidly. Oral solifenacin persisted in the blood for longer than oxybutynin. 4 Pilocarpine-induced salivary secretion in mice was significantly reduced by oral administration of solifenacin and was completely abolished 0.5 h after oral oxybutynin. Although the suppression induced by solifenacin was more persistent than that due to oxybutynin, the antagonistic effect of solifenacin on the dose-response curves to pilocarpine was significantly weaker than that of oxybutynin. It is concluded that oral solifenacin persistently binds to muscarinic receptors in tissues expressing the M(3) subtype, such as the bladder.

In vivo demonstration of muscarinic receptor binding activity of N-desethyl-oxybutynin, active metabolite of oxybutynin

The present study was undertaken to characterize in vivo muscarinic receptor binding of N-desethyl-oxybutynin (DEOB), active metabolite of oxybutynin (anticholinergic agent), in the bladder, submaxillary gland, heart and colon of rats, in relation to the plasma concentrations and inhibition of salivation. In the in vitro experiment, DEOB, as well as oxybutynin, inhibited the concentration-dependently specific [ 3H]N-methylscopolamine (NMS) binding in rat tissues and the affinity of DEOB in the rat bladder, submaxillary gland and colon was significantly (about 2 times) greater than that of oxybutynin. Following i.v. injection of DEOB (2.73–27.3 μmol/kg), there were dose- and time-dependent increases in the apparent dissociation constant (Kd) for specific [ 3H]NMS binding in the bladder, submaxillary gland, heart and colon of rats, compared with control values, and the effect was similar to that by i.v. injection of oxybutynin (2.54–25.4 μmol/kg). Plasma concentrations of DEOB and oxybutynin in these rats showed dose- and time-dependent increases. The pilocarpine-induced salivary secretion in rats was equipotently reduced by the i.v. injection of DEOB and oxybutynin. In conclusion, it has been shown that intravenously injected DEOB, as well as oxybutynin, binds significantly to muscarinic receptors in rat tissues including the bladder and salivary gland and the receptor binding activity of DEOB is roughly similar to that of oxybutynin.

Role of nitric oxide and β-adrenoceptors of the central nervous system on the salivary flow induced by pilocarpine injection into the lateral ventricle

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 β-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 μg/μl) into LV produced a dose-dependent increase in salivary secretion. The injection of l-NAME (40 μg/μl) 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 μg/μl) injected alone into LV produced no change in salivary secretion. l-Arginine injected into LV attenuated pilocarpine-induced salivary secretion. The isoproterenol (40 nmol/μl) injected into LV increased the salivary secretion. When injected previous to pilocarpine at a dose of 20 and 40 μg/μl, isoproterenol produced an additive effect on pilocarpine-induced salivary secretion. The 40-nmol/μl dose of propranolol injected alone or previous to pilocarpine into LV attenuated the pilocarpine-induced salivary secretion. The injection of salbutamol (40 nmol/μl), a specific β-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/μl dose of salmeterol, a long-acting β-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 β-adrenergic receptors of the central nervous system (CNS) for the control of salivary secretion can also be postulated.

Effects of .ALPHA.-D-N-acetylneuraminyl cholesterol on the pilocarpine-induced salivary response and salivary gland acetylcholine and choline levels in mice.

It has been suggested that α-D-N-acetylneuraminyl cholestero1 (α-SC) affects the activation of nerve cells. In the present study, the effects of α-SC (1 and 10mg/kg, p. o.) on the sublingual and submandibular glands of naive and reserpinized mice were examined. In naive mice, α-SC increased ACh levels in the sublingual gland and decreased Ch levels in the sublingual and submandibular glands. In mice treated with reserpine (0.5 and lmg/kg, s. c.), which induces the depletion of norepinephrine storage in terminals of sympathetic neurons, ACh and Ch levels in the sublingual and submandibular glands increased.α-SC (1mg/kg) inhibited this increase in ACh levels in reserpinized mice, but did not affect the increase in Ch levels. In naive and reserpinized mice, α-SC further enhanced pilocarpine-induced salivary secretion. These findings suggest that α-SC exerts some influence on the parasympathetic nervous system and promotes the salivary response.

Pilocarpine-induced salivary secretion, kinin system and nitric oxide in rats

In anaesthetized rats, intraperitoneal injection of pilocarpine (0.1 to 1 mg.Kg-1) induced a dose-dependent flow of saliva. During salivation by pilocarpine (0.5 mg.Kg-1), the blood content of submaxillary glands was not significantly increased but the blood volume of the animals was reduced. The salivary flow rate induced by pilocarpine was similar in normal and kininogen-deficient rats. L-NG-nitro-arginine (L-NOARG, 35 mg.Kg-1), a nitric oxide synthesis inhibitor, increased the salivary flow elicited by pilocarpine (0.5 mg.Kg-1). L-NOARG did not modify the blood volume loss but decreased the blood content of the submaxillary glands. The volume of salivary secretion induced by isoproterenol (250 mg.Kg-1) was lower in kininogen-deficient rats than in normal rats. It was significantly reduced by HOE 140 (2 mg.Kg-1), a bradykinin antagonist. L-NOARG increased the salivary flow induced by isoproterenol during the ten first minutes of collection but suppressed it thereafter. We concluded that kinins are not involved in the stimulating effect of pilocarpine on rat salivary glands but these peptides would participate to the development of the salivation induced by isoproterenol in rats. Nitric oxide contributes to the control of the vascular tone in rat salivary glands. The influence of L-NOARG on salivation would be explained by its effects on blood pressure and vascular resistances.