OBJECTIVE[corrected] To characterize the insulinotropic action of hippocampal cholinergic neurostimulating peptide (HCNP) and analyze the role of type 3 muscarinic receptor (M(3)R) pathway in the action of HCNP.

METHODSINS-1 cells were incubated in routine RPMI 1640 medium (control group), RPMI 1640 supplemented with 50 pg/ml synthetic HCNP (HCNP group), or HCNP-containing medium with the addition of PMA 18 h prior to insulin release assay. The insulin levels in the medium was measured using radioimmunoassay following stimulation with different concentrations of glucose. Real-time quantitative PCR was used for detecting the gene expression of HCNP-pp, choline acetyltransferase (ChAT) and M(3)R in HCNP group and control group.

RESULTSAfter stimulation with different concentrations of glucose (5.6 and 16.7 mmol/L), HCNP group showed significantly higher insulin levels than the control and HCNP+ PMA groups. Compared with those in the control group, the mRNA levels of HCNP-pp, ChAT, and M(3)R were all lowered in HCNP group.

CONCLUSIONHCNP can promote insulin release in INS-1 cells by increasing ChAT activity and activating M(3)R, and this effect is inhibited by PMA.

Animals ; Cell Line ; Insulin ; secretion ; Neuropeptides ; pharmacology ; Rats ; Receptor, Muscarinic M3 ; metabolism

OBJECTIVETo investigate the effect of diabetic autonomic neuropathy on the seminal vesicle and search for the theoretical evidence for the prevention and treatment of diabetic infertility by observing changes in the contents of the nerve growth factor (NGF) and muscarinic M3 receptor in the seminal vesicle of diabetic rats.

METHODSDiabetic models were established in 10 of the 15 male adult SD rats by intraperitoneal injection of streptozotocin (STZ), and the other 5 were included in a normal control group. Eight weeks after modeling, seminal vesicles were collected from the rats for HE and immunohistochemical staining.

RESULTSCompared with the normal controls, the diabetic models showed a decreased number of smooth muscle cells, thinner cytoplasm of glandular epithelial cells and disordered structure in the seminal vesicle. The intensity of NGF-positive staining was significantly enhanced, but that of M3 markedly reduced in the diabetic group. There were statistically significant differences in the mean integrated optical density (IA) of muscarinic M3 receptors and NGF between the control and diabetic groups (0.0187 +/- 0.0024 vs 0.0100 +/- 0.0015 and 0.0209 +/- 0.0085 vs 0.0412 +/- 0.0117, P<0.01).

CONCLUSIONThe changes in the expressions of NGF and M3 receptors in the seminal vesicle of diabetic rats suggest that diabetes mellitus may induce autonomic neuropathy of the seminal vesicle.

Animals ; Diabetes Mellitus, Experimental ; metabolism ; Male ; Nerve Growth Factor ; metabolism ; Rats ; Rats, Sprague-Dawley ; Receptor, Muscarinic M3 ; metabolism ; Seminal Vesicles ; metabolism

Animals ; Arecoline ; pharmacology ; Cholinergic Agonists ; pharmacology ; Female ; Guinea Pigs ; In Vitro Techniques ; Male ; Muscle Contraction ; drug effects ; Muscle, Smooth ; physiology ; Pyloric Antrum ; physiology ; Receptor, Muscarinic M3 ; metabolism

OBJECTIVE: To investigate the expression of M3 subtype of muscarinic receptors (M3R) during the incised wound healing of the skin in mice and the characteristics of its time-dependent. METHODS: The change of M3R in skin incised wound was detected by immunohistochemical staining and Western blot. RESULTS: M3R-positive cells were detected in epidermis, hair follicle, sebaceous glands, sweat glands, dermomuscular layer in normal mouse skin. Expression of M3R was mainly detectable in polymorphonuclear cells (PMNs) in the wound specimens aged from 6h to 12h after injury. Afterwards, the M3R-positive cells were mostly mononuclear cells (MNCs) and fibroblastic cells (FBCs) at 1 d to 3d post-injury, whereas the M3R-positive cells were mostly FBCs aged from 5 d to 14d. Morphometrically, the ratio of the M3R-positive cells increased aged from 6h to 12h after injury, with a peak at 12h. The ratios kept a high relatively level aged from 1 d to 5 d, but significantly that lowered as compared with aged 12h after injury. The ratio reached the peak at 7 d again after injury, and then decreased gradually. The M3R protein also revealed a time-dependent tendency with double peaks at 12h and 7 d after injury as detected by Western blotting. CONCLUSION M3R is time-dependently expression in PMNs, MNCs and FBCs suggesting that it may play roles during the skin incised wound healing, and M3R may be used as a marker for wound age determination.
Animals ; Blotting, Western ; Fibroblasts/metabolism* ; Immunohistochemistry ; Male ; Mice ; Monocytes/metabolism* ; Neutrophils/metabolism* ; Receptor, Muscarinic M3/metabolism* ; Skin/metabolism* ; Time Factors ; Wound Healing ; Wounds and Injuries/metabolism*

AIMAcetylcholine(ACh) is a neurotransmitter and a potent vasodilator in many vascular beds. ACh hyperpolarizes the smooth muscle cells(SMCs) of arteries including the cochlear spiral modiolar artery(SMA) via an endothelium-dependent mechanism, but the biochemical and biophysical basis of the hyperpolarization and vasodilation remain unclear and controversial.

METHODSUsing intracellular recording techniques and an in vitro preparation of the SMA, the ionic mechanism of the hyperpolarization and a possible role of nitric oxide(NO) were investigated.

RESULTSWith 5 mmol/L K(+) in the bathing solution and a minimum longitudinal tension, ACh (0.1-10 micromol/L) induced a robust hyperpolarization in low RP cells but caused a depolarization in the high RP cells. The ACh hyperpolarization was fast in onset and offset and the amplitude was concentration-dependent(22 and 30 mV by 1 micromol/L and 10 micromol/L ACh, respectively, n = 7 ). ACh also hyperpolarized the cells that initially had a high resting potential (RP) but were pre-depolarized by Ba(2+) (50-100 micromol/L). The onset time courses of the hyperpolarization were often slower in these cases than those without the presence of Ba(2+) . The ACh-induced hyperpolarization was blocked by atropine (0.1- 1 micromol/L, n = 6) or DAMP (50 -100 nmol/L, n = 6, a selective M3 antagonist) and also by BAPTA-AM (10 micromol/L, n = 7, a membrane-permeable Ca(2+)-chelator), or charybdotoxin plus apamin (50-100 nmol/L, n= 4, Ca(2+) -activated K(+) -channel blockers), but not by Nomega-nitro-L-arginine methyl ester (L-NAME, 300 micromol/L, n = 8, an inhibitor of NO-synthase), glipizide (10 micromol/L, n = 4, ATP-sensitive K(+) -channel blocker) and indomethacin (10 micromol/L, n = 4, cyclo-oxygenase inhibitor).

CONCLUSIONIt is concluded that ACh-induced hyperpolarization in the arterial SMCs is primarily due to an activation of calcium-activated potassium channels via M3 receptors of endothelial cell and is independent of NO-release in the spiral modiolar artery.

Acetylcholine ; physiology ; Animals ; Arteries ; Cell Polarity ; physiology ; Cochlea ; blood supply ; physiology ; Guinea Pigs ; Membrane Potentials ; physiology ; Muscle, Smooth, Vascular ; metabolism ; physiology ; Nitric Oxide ; metabolism ; Potassium Channels, Calcium-Activated ; metabolism ; Receptor, Muscarinic M3 ; metabolism

To detect the function and expression of ventricular M3 receptor (M3R) in cerebral-cardiac syndrome (CCS) model rats and to explore the relationship between the expression of M3R and the arrhythmia resulted from CCS, CCS model rats were induced by occluding right middle cerebral artery. ECG was monitored. Intracellular calcium ([Ca2+]i) changes after agitating M3R were recorded by laser scanning confocal microscope. Changes of M3R expression in the ventricular tissue were detected by Western blotting. QRS and QT intervals in CCS group were remarkably longer than that in sham group. According to the results of Western blotting, the level of M3R expression was remarkably lower in CCS group compared with that in the normal group. KCl induced [Ca2+]i increasing in CCS group could be depressed by choline and the effect of choline could be blocked by 4-DAMP. The lower expression of M3R in CCS group may be one of important reasons of arrhythmia resulted from CCS. M3R that depressed the [Ca2+]i increasing agitated by choline may become a new target to cure arrhythmia resulted from CCS.
Animals ; Arrhythmias, Cardiac ; etiology ; metabolism ; pathology ; physiopathology ; Calcium ; metabolism ; Choline ; pharmacology ; Electrocardiography ; Heart Ventricles ; metabolism ; Infarction, Middle Cerebral Artery ; complications ; Male ; Muscarinic Antagonists ; pharmacology ; Myocardium ; metabolism ; ultrastructure ; Myocytes, Cardiac ; metabolism ; Piperidines ; pharmacology ; Potassium Chloride ; pharmacology ; Random Allocation ; Rats ; Rats, Wistar ; Receptor, Muscarinic M3 ; antagonists & inhibitors ; metabolism

OBJECTIVE: To observe the expression of Muscarinic receptor M1, M3, M5 subunits in rat flocculus following left unilateral labyrinthectomy (UL). METHOD: The RT-PCR was used to observe the expression of Muscarinic receptor M1, M3, M5 subunits post-unilateral labyrinthectomy and investigate its effect on vestibular compensation. RESULT: Muscarinic receptor M1, M3, M5 subunits were induced decrease in both side flocculus after unilateral labyrinthectomy. The expression was the least in the 1 d flocculus of following UL. The expression is rising from the 3-7 d flocculus of following UL. No difference was observed in the 7 d and sham operation flocculus following UL. No difference was observed in the ipsilateral and contralateral flocculus at any group. CONCLUSION Muscarinic receptor M1, M3, M5 subunits were induced decrease in the flocculus after unilateral labyrinthectomy. But the significance of the change of Muscarinic receptor M1, M3, M5 subunits in the vestibular compensation is still unknown.
Animals ; Cerebellum ; metabolism ; Functional Laterality ; Gene Expression ; Male ; Postoperative Period ; Rats ; Receptor, Muscarinic M1 ; metabolism ; Receptor, Muscarinic M3 ; metabolism ; Receptor, Muscarinic M5 ; metabolism ; Vestibule, Labyrinth ; metabolism ; surgery

This study is to explore whether the protective effect of resveratrol on ischemia-reperfusion injury is correlated with the structural and functional association between M3 receptor (M3 subtype of muscarinic acetylcholine receptor) and Cx43 (connexin 43 gap junction proteins). Immunoprecipitation, immunoblotting and immunofluorescence were applied to investigate whether resveratrol has an effect on structural and functional association between M3 and Cx43. The effect of resveratrol on electrocardiogram Lead II ex vivo in rats, SOD (superoxide dismutase) activity and MDA (malondialdehyde) content was also observed in order to evaluate the protective effect of resveratrol on ischemia-reperfusion injury. Resveratrol could restore the structural and functional association between M3 receptor and Cx43 gap junction proteins that was partially destroyed under ischemia-reperfusion injury. The phosphorylation and spatial distribution disturbances in Cx43 expression caused by ischemia-reperfusion injury were also restored. Also, the QRS duration, SOD activity and MDA content were restored. Resveratrol could restore the structural and functional association between M3 receptor and Cx43 gap junction proteins.
Animals ; Connexin 43 ; metabolism ; Electrocardiography ; Heart ; drug effects ; physiopathology ; In Vitro Techniques ; Male ; Malondialdehyde ; metabolism ; Myocardial Reperfusion Injury ; metabolism ; physiopathology ; Myocardium ; metabolism ; Phosphorylation ; drug effects ; Protective Agents ; pharmacology ; Random Allocation ; Rats ; Rats, Wistar ; Receptor, Muscarinic M3 ; metabolism ; Stilbenes ; pharmacology ; Superoxide Dismutase ; metabolism

The modulation of ACh on delayed rectifier-like potassium currents (I(K)) was studied in freshly dissociated cerebral cortical neurons using the whole-cell patch-clamp technique. Wistar rats between 10- and 14-day old of both sexes were used. After rats were decapitated, their brains were quickly removed, iced, and then manually cut into 400 mum slices. Slices were then incubated for 0.5 h at 32 degrees C in a buffered artificial cerebrospinal fluid (ACSF) bubbled with 95% O2, 5% CO2. Slices were then removed into buffered ACSF containing protease (0.5 mg/ml) at 32 degrees C. After 30 min of enzyme digestion, tissue was rinsed three times in the buffered saline. Then the enzyme-treated slices were mechanically dissociated with a graded series of fire-polished Pasteur pipettes. The cell suspension was then plated into a 35 mm dish and placed on the stage of a Olympus inverted microscope. For whole-cell recordings of currents, standard voltage-clamp techniques were used. Neurons were held at -80 mV, and the I(K) was evoked by 2 000 ms depolarizing voltage commands to potential between -40 mV and +60 mV in 10 mV steps applied at a frequency of 0.5 Hz. It was found that the inhibitory effect of ACh (0.1, 1, 10, 100 mumol/L) on I(K) was dose-dependent. It was also found that ACh affected the activation process of I(K) significantly, i.e., the activation curve of I(K) was characterized by half-activation potential of (-41.8+/-9.7) mV and a slope factor of (30.7+/-7.2) mV in the cortical neurons and they were changed to (-122.4+/-38.6) mV and (42.4+/-7.0) mV, respectively, after giving ACh (10 mumol/L). Tubocurarine (100 mumol/L) antagonized the inhibitory effect of ACh on I(K), and the drop of currents varied from the control value of (36.5+/-7..8)% to (16.9+/-13.8)% (n=8, P<0.01). 4-DAMP (10 mumol/L) blocked the inhibitory effect of ACh on I(K), and the currents reduced from the control value of (36.5+/-7.8)% to (26.8+/-4.7) % (n=6, P<0.05). Pirenzepin did not antagonize the inhibition of ACh on I(K) (n=7, P>0.05). Chelerythrine (20 mumol/L) blocked the inhibitory effect of ACh on I(K) and the currents reduced from the control value of (36.5+/-7.8)% to (11.7+/-17.3)% (n=6, P<0.05). On the contrary, PDBu (10 mumol/L) strengthened the inhibition of ACh on I(K) and the drop of currents changed from the control value of (36.5+/-7.8)% to (59.2+/-14.0)% (n=5, P<0.05). PDBu abolished the antagonism of chelerythrine on ACh in cortical neurons. It is suggested that the ACh-induced depolarization of neurons in the cortex is attributed to the inhibition of I(K) that is most likely evoked by the activation of nicotinic ACh receptors and muscarinic M3 receptor via protein kinase C (PKC) signal transduction pathway.
Acetylcholine ; physiology ; Animals ; Cell Separation ; Delayed Rectifier Potassium Channels ; antagonists & inhibitors ; Female ; Male ; Neurons ; metabolism ; physiology ; Patch-Clamp Techniques ; Protein Kinase C ; metabolism ; physiology ; Rats ; Rats, Wistar ; Receptor, Muscarinic M3 ; metabolism ; Receptors, Nicotinic ; metabolism ; Signal Transduction ; physiology ; Somatosensory Cortex ; cytology ; physiology

AIMTo optimize the method of investigating structural integration between proteins and study the integration between arrhythmia related proteins in molecular level.

METHODSImmunostaining the normal ventricular myocytes was used to observe the distribution of connexin 43 and muscarinic acetylcholine receptor (mAChR). The five mAChR subtypes were precipitated using immunoprecipitation. Then, SDS-PAGE and Western blotting with the anti-connexin 43 antibody were performed to observe whether they were structurally integrated. Further, different concentrations of detergent were used to observe whether this relationship could be broken.

RESULTSThe five subtypes of mAChR existed in the cardiac myocyte of the rat, and all the five mAChR subtypes combined with connexin 43. In the normal rat ventricular myocyte membrane, connexin 43 and M3 receptor are co-located. When adding certain concentration of detergent to the membrane protein, the integration between M3 receptor and connexin 43 was broken, and the phosphorylated form of connexin 43 integrated with M3 receptor.

CONCLUSIONThe results indicated that the structural integration between mAChR and phosphorylation of connexin 43 existed in rat ventricular myocardium, and this integration could be broken by certain concentration of detergent.

Animals ; Cell Membrane ; metabolism ; Connexin 43 ; metabolism ; Heart Ventricles ; Immunoprecipitation ; Male ; Microscopy, Confocal ; Myocytes, Cardiac ; metabolism ; Phosphorylation ; drug effects ; Rats ; Rats, Wistar ; Receptor, Muscarinic M3 ; metabolism ; Receptors, Muscarinic ; metabolism ; Sodium Dodecyl Sulfate ; pharmacology