Nucleus raphe obscurus participates in regulation of gallbladder motility through vagus and sympathetic nerves in rabbits

The aim of the present study is to investigate if the nucleus raphe obscurus (NRO) participate in regulating the gallbladder motility in rabbits. Rabbits were fasted for about 20-24 hours. After anesthetization with urethane, an incision was made at the middle of the abdomen and the gallbladder was exposed. A frog bladder connected with force transducer was inserted into the gallbladder through a small incision at the funds to record gallbladder motility (tonic contraction and phasic contraction). Glutamate and other chemicals were microinjected into NRO through a vitreous tube attached to a microsyringe. We found both the tonic contraction and phasic contraction of the gallbladder were enhanced after the glutamate was injected into NRO. GABA inhibited gallbladder motility if administrated in the same way. Microinjection of ketamine, NMDA (N-methyl-D-aspartate) receptor antagonist, into NRO inhibited the phasic contraction of gallbladder. Administration of CNQX (6-cyano-7-nitroquinoxaline-2, 3-dione), a non-NMDA receptor antagonist, enhanced the gallbladder tonic contraction. Pretreatment of ketamine into NRO attenuated the effect of glutamate, while pretreatment of CNQX had no effect on it. Intravenous injection of atropine or vagotomy completely abolished the effect of glutamate on gallbladder phasic contraction, while intravenous injection of phentolamine or transecting the spinal cord at T3-4 inhibited that on tonic contraction. Intravenous injection of propranolol did not influence the glutamate effect. These results suggested that glutamate in NRO participates in regulating the motility of the gallbladder through NMDA receptor. When excited, the NMDA receptors in NRO enhance the phasic contraction of the gallbladder through vagus nerve and peripheral M-receptors, and enhance the tonic contraction of the gallbladder through sympathetic nerve and peripheral alpha-receptors. GABA in NRO is also involved in the regulation of gallbladder motility.     

Endogenous oxytocin excites phasic contraction of gallbladder in rabbits through oxytocin receptor

These experiments were performed to study the effect of oxytocin (OT) and it's specific receptor on gallbladder motility in rabbits. The fasted New Zealand white rabbits (2.0-2.5 kg) were anaesthetized by urethane (1 g/kg). The gallbladder pressure was recorded continuously to monitor the gallbladder motility. Systemic OT (0.01, 0.02, 0.04 mg/kg, iv) did not affect the gallbladder pressure, but dose-dependently increased the frequency of phasic contraction. Five min after OT administration (0.04 mg/kg, iv), the strength of phasic contraction increased to 0.23 +/- 0.08 mmHg/min (P < 0.01, n = 6). The gallbladder motility returned to normal 15 min later after OT treatment. Intravenous injection of atosiban (0.04 mg/kg, iv), an OT receptor antagonist, decreased the strength of gallbladder phasic contraction but did not affect gallbladder pressure. Pretreatment of atosiban (0.04 mg/kg, iv) completely abolished the systemic OT effect on gallbladder. Vasopressin (VP) (0.1 - 0.5 IU/kg, iv) dose-dependently decrease the gallbladder pressure but did not affect the phasic contraction. MK-329 (0.4 mg/kg, iv), the CCK-A receptor antagonist, L-365, 260 (0.4 mg/kg, iv), the CCK-B receptor antagonist and atropine (0.2 mg/kg, iv), the M receptor antagonist, did not affect the OT effect on gallbladder motility. We suggest that endogenous OT regulates gallbladder phasic contraction through specific OT receptor. This effect is independent of the peripheral CCK and M receptors.     

Contractile effects of endothelins on isolated human ureter

The aim of our study was to investigate mechanism of action of endothelins 1, 2 and 3 on spontaneous activity, tone and intraluminal pressure of human ureter. Both longitudinal tension and intraluminal pressure were recorded from the isolated segments of proximal human ureter. Endothelins 1, 2 and 3 (5.35x10(-11) M - 5.05x10(-8) M) produced concentration-dependent tonic contraction and sustained increase in intraluminal pressure of isolated preparations of human ureter. Endothelins 1 and 3 produced also concentration-dependent inhibition of spontaneous, phasic contractions of the isolated preparations. Selective antagonist of ET(A) receptors BQ123 and selective antagonist of ET(B) receptors BQ788 produced significant inhibition of endothelin-1-induced tonic contraction (pA(2)=8.80 and 6.55, respectively) and increase in intraluminal pressure (pA(2)=8.68 and 7.02, respectively), while they did not affect endothelin-1-induced inhibition of spontaneous activity. Endothelin 1 produces increase in tone and intraluminal pressure of isolated human ureter acting on both ET(A) and ET(B) receptors, the first one being functionally more important. Only endothelins 1 and 3 inhibit spontaneous, phasic activity of human ureter, but this effect was not blocked by selective antagonists of ET(A) and ET(B) receptors.     

Muscarinic receptors on nerves and muscles in opossum esophagus muscularis mucosa

The muscarinic receptors of muscularis mucosa have some recognition properties that suggest they resemble receptors of the M1 subtype. The nerves of these tissues also contain muscarinic receptors which inhibit tonic contractions caused by release of a substance-P-like material by field stimulation. These receptors also appear to be M1 in type as they are maximally activated by McNeil A343 as well as by carbachol (pD2, 5.5 and 7.5, respectively). They are also inhibited by pirenzepine, as well as by atropine (negative logarithms of the required dose for 50% inhibition or potentiation, 6.6-6.7 compared with 8.2-8.3). Hexahydrosiladifenidol, an antagonist selective or M2 receptors of guinea pig ileum, had a low (approximately 7.1) pA2 value for antagonism of both agonists in smooth muscle in this tissue. However, it was closer to atropine in potency with respect to potentiating tonic responses to field stimulation or to inhibiting phasic responses to field stimulation than it was to antagonizing smooth muscle contractions. Thus, atropine was about 40 times more potent than pirenzepine and 2-5 times more potent than hexahydrosilafenidol. There were some quantitative differences in the effectiveness of these three antagonists in blocking the phasic (acetylcholine-mediated) response to field stimulation. Atropine was 70-100 times more potent than pirenzepine and 8-25 times more potent than hexahydrosiladifenidol. This greater potency difference for inhibition of phasic contractions compared with potentiation of tonic contractions was discussed. This tissue appears to be one of the first smooth muscles in which both nerves and muscles contain muscarinic receptors with some recognition properties resembling those of the M1 subtype.     

Muscarinic receptors in the neostriatum--participation in the operant behavior regulation in dogs

Exposure of the dogs to signals, data collection and processing were accomplished using a special PC software. Bilateral microinjections of the muscarinic receptors agonists (oxotremorine) into the neostriatum enhanced the tonic component of instrumental movements, suppressed the phasic component and increased the postural component's amplitude. These changes were much more obvious in microinjections of the non-selective muscarinic receptor agonist carbachol due, probably, to its effect on both the M1 and M4 muscarinic receptors of the neostriatum efferent neurones.     

Endothelium-independent and -dependent contractions induced by endothelin-1 in canine basilar arteries

Endothelium-dependence of contractile responses to endothelin-1 was examined in isolated canine basilar arteries. Within 2 hrs after mounting tissue preparations, endothelin-1 (10(-9) M) caused a monophasic tonic contraction that developed very slowly and was sustained in intact and endothelium-removed arteries. More than 5 hrs after tissue mounting, endothelin-1 (10(-9) M) caused a biphasic contraction consisting of phasic and tonic components in intact arteries, and caused a monophasic tonic contraction in endothelium-removed arteries. This phasic component was significantly decreased by aspirin (5 x 10(-5) M,), OKY-046 (10(-5) M) (a TXA2 synthetase inhibitor) and ONO-3708 (10(-8) M) (a TXA2 antagonist). The present experiments demonstrate that endothelin-1 causes an endothelium-independent tonic contraction and an endothelium-dependent phasic contraction in canine basilar arteries, and suggest that TXA2 plays a role as an endothelium-derived contracting factor.     

中缝隐核对兔奥迪氏括约肌肌电活动的影响

实验用电生理学和微量注射法观察了兔中缝隐核（NRO）对奥迪氏括约肌肌电活动的影响,动物禁食但自由饭水,18－24h手用乌拉坦（1.0g/kg)静脉麻醉,用双极康铜丝电极引导奥迪氏括约肌肌电,发现NRO内微注射谷氨酸（340mmol/L,0.4ul)可使奥迪氏括约肌肌电活动加强,与在NRO内微量注射生理盐水或者将谷氨酸（340mmol/L,0.4ul)注射到NRO以外的地方相比,具有显著差异（P＜0．01）,NRO 微量注射N-methy-D-aspartate(NM-DA)受体阻断剂氯胺酮（180mmol/L,0.1ul),可消除谷氨酸的效应,而将微量非NMDA受体阻断剂CNQX（2mmol/L,0.1ul)注入NRO,可使奥迪氏括约肌肌电加强,外周应用M－受体阻断剂阿托品（0.2mg/kg)或双侧颈部迷走神经切断,可阻断微量谷氨酸注射到NRO内所引起的效应,静脉注射α－受体阻断剂酚妥拉明（1.5mg/kg),心得安（1.5mg/kg)或自T3－4处切断脊髓,对NRO内微量注射谷氨酸的效应没有影响,结果提示,NRO对奥迪氏括约肌运行有调节作用,其中谷氨酸主要通过NMDA受体兴雷奥迪氏括约肌肌电活动,其传出途径是迷走神经和外周M受体。     

The influence of prostaglandin E2 (PGE2) on the acetylcholine-initiated contractions of isolated gastric muscularis muscle of Bufo marinus

Acetylcholine (ACh) (1.5 X 10(-5) M) elicited three different types of tonic and phasic contraction of muscularis muscle from different parts (cardiac, middle and pyloric) of the stomach of Bufo marinus. Prostaglandin E2 (PGE2) (10(-9)-10(-6) M) induced a concentration-dependent relaxation of tonic contractions elicited by ACh (1.5 x 10(-5) M) of strips from the cardiac part while potentiating the phasic contractions from the middle part of the stomach. PGE2 (10(-7) M) relaxed tonic contraction and potentiated phasic contraction concomitantly in preparations in which tonic and phasic contractions were elicited by ACh (1.5 x 10(-5) M). The effects of PGE2 on the preparation are related to the part of the stomach from where the strips are prepared and the muscle tone of the preparation.     

NO对家兔Oddi括约肌肌电活动和血压的影响

应用３２只家兔观察一氧氮对Ｏｄｄｉ括约肌肌电和血压的影响。静脉注射ＮＯ合酶抑制剂Ｎ＾Ｇ－硝基－Ｌ－精氨酸,可见ＳＯ肌电振幅增大和血压升高,Ｌ－ＮＮＡ所致的肌电活动增强可Ｌ－精氨酸反转。     

兔迷走神经在协调消化间期胆囊与奥迪氏括约肌运动方面的作用

目的：探讨兔迷走神经在协调消化间期胆囊（ＧＢ）与奥迪氏括约肌（ＳＯ）运动方面的作用。方法：运动禁食但自由饮水１５￣１８ｈ，乌拉坦静脉麻醉。蛙膀胱置入ＧＢ内，测ＧＢ内压，双极康铜丝电极引ＳＯ肌电。结果：消化间期ＧＢ位相性收缩（ＧＢＰＣ）与ＳＯ锋电位簇（ＣＳＰＳＯ）间存在１：１对应关系，迷走复合区（ＤＶＣ）内微量注射谷氨酸钠（ＭＳＧ）或促甲状腺素释放激素（ＴＲＨ）后ＰＣＧＢ及ＳＯ锋电位活动增强，ＧＢＰ     

Modulation of laryngeal and respiratory pump muscle activities with upper airway pressure and flow.

The hypothesis that upper airway (UA) pressure and flow modulate respiratory muscle activity in a respiratory phase-specific fashion was assessed in anesthetized, tracheotomized, spontaneously breathing piglets. We generated negative pressure and inspiratory flow in phase with tracheal inspiration or positive pressure and expiratory flow in phase with tracheal expiration in the isolated UA. Stimulation of UA negative pressure receptors with body temperature air resulted in a 10--15% enhancement of phasic moving-time-averaged posterior cricoarytenoid electromyographic (EMG) activity above tonic levels obtained without pressure and flow in the UA (baseline). Stimulation of UA positive pressure receptors increased phasic moving-time-averaged thyroarytenoid EMG activity above tonic levels by 45% from baseline. The same enhancement of posterior cricoarytenoid or thyroarytenoid EMG activity was observed with the addition of flow receptor stimulation with room temperature air. Tidal volume and diaphragmatic and abdominal muscle activity were unaffected by UA flow and/or pressure, whereas respiratory timing was minimally affected. We conclude that laryngeal afferents, mainly from pressure receptors, are important in modulating the respiratory activity of laryngeal muscles.     

Action of colchicine on cholinergic and adrenergic mechanisms in guinea pig vas deferens

Guinea pig vas deferens responds to externally applied acetylcholine (ACh) or noradrenaline (NA) by a small rapid contraction (phasi phase) and then a large contraction (tonic phase). The phasic phase was not affected by removal of external Ca²⁺, but tonic phase depended on external Ca²⁺. At lower temperatures the two components became larger and detectable separately. The tonic phase induced by ACh at low temperature (at 20°C) was greatly depressed by brief treatment with colchicine (0.5 μM – 5 μM), although the tonic phase at high temperature (at 37°C) was not affected. Na-induced contraction (phasic or tonic phase) was not changed by the colchicine-treatment. High K⁺ (40 mM)-contracture, which in many cases consisted of a single phase and depended on external Ca²⁺, was also not affected by brief treatment with colchicine. Culture of vas deferens for 3 days in the presence of colchicine, increased the phasic phase of ACh- and NA-induced contractions significantly, but reduced the tonic phase of contractions induced by ACh and NA. Colchicine also reduced high K⁺-contracture, the decrease depending on the period of culture with colchicine. Organ culture with colchicine did not affect the amounts of m-ACh and α-Ad receptors or the IC₅₀ value of ACh and NA on ³H-ligand binding. These results suggest that colchicine specifically interacts with some steps in m-ACh and α-Ad receptor-responsor (e.g. ionophore) coupling without affecting the receptor number or affinity of the receptors for agonists. The mechanisms of action of colchicine are discussed in relation to m-ACh and α-Ad receptor functions.     

Cholecystokinin induced gallbladder contraction is influenced by nicotinic and muscarinic receptors

Effects of pirenzepine, known as a muscarinic receptor antagonist, on the contraction of dog gallbladder elicited by cholecystokinin (CCK) were examined in comparison with atropine and hexamethonium ones. Intraluminal gallbladder pressure in an in situ anaesthetized dog model was chosen for studying gallbladder motility. The intravenous administration of pirenzepine (0.75 mg/kg b.wt.), atropine (3 mg/kg b.wt.) or hexamethonium (5 mg/kg b.wt.) elicited a marked decrease in the increase of intraluminal gallbladder pressure induced by intravenous bolus injections of CCK (0.25-2 Ivy dog unit/kg b.wt.) and by continuous infusion of CCK (0.025-0.4 Ivy dog unit/kg b.wt./min). It was concluded that CCK induced gallbladder contractions were influenced by both nicotinic and muscarinic receptors.     

Tonic contractions allow metabolic recuperation of the adductor muscle during escape responses of giant scallop Placopecten magellanicus

To escape from starfish predators, giant scallops, Placopecten magellanicus, swim using series of strong phasic contractions interrupted by tonic contractions. To investigate whether these tonic contractions allow metabolic recuperation of the adductor muscle, we sampled scallops at rest (Control), after an initial series of phasic contractions (Phasic) and after 1 min of tonic contraction following their initial phasic contractions (Phasic + Tonic) and compared muscle levels of phosphoarginine, adenylate nucleotides (ATP, ADP and AMP) and adenylate energy charge (AEC). Scallops in the two active groups did not differ in the numbers of phasic contractions or the mean phasic force production. Phosphoarginine concentrations in the adductor muscle decreased with phasic activity and remained low after 1 min of tonic contraction. ATP and ADP and total adenylate levels did not differ between the three groups, but AMP levels were higher in the scallops sampled after phasic contractions than in control scallops. The AEC was reduced by phasic contractions but returned to control levels after 1 min of tonic contraction. A significant negative correlation between AEC and the number of claps in the Phasic group disappeared in the Phasic + Tonic group. Thus, tonic contractions following phasic contractions allow partial metabolic recovery of the adductor muscle by returning AEC to control levels. However, phosphoarginine levels did not recover during tonic contractions, and a negative correlation between the number of claps and phosphoarginine levels remained in the Phasic + Tonic group. By interspersing tonic contractions between series of phasic contractions, scallops improved muscle energetic status, which should help maintain phasic force production during the remainder of the escape response.     

Central muscarinic control of the pattern of small intestinal motility in rats

The effects of central and peripheral administration of muscarinic agonists and antagonists on small intestinal motility were examined in conscious rats chronically fitted with electrodes implanted in the duodeno-jejunal wall and a cannula in a cerebral lateral ventricle. Intracerebroventricular (i.c.v.) administration of either atropine or pirenzepine at doses from 1 to 10 micrograms, 15 min before a 3 and 6 g lab chow meal significantly reduced the duration of the postprandial disruption of the migrating myoelectric complexes (MMC). The reduction was significantly greater for atropine, a mixed M1 and M2 muscarinic receptor antagonist, than for pirenzepine, an antagonist with a high affinity for M1 receptors. At a higher dose (10 micrograms) intra peritoneal (i.p.) administration of atropine or pirenzepine did not modify the postprandial disruption of MMC. Oxotremorine (10 ng) a M2 agonist, but not McNeil A343 (5 micrograms), a selective M1 agonist, given i.c.v. in fasted rats disrupted for 1.5 h the MMC pattern. At the same doses given i.p. oxotremorine and McNeil A343 disrupted the MMC for 15 and 45 min respectively. We conclude that the postprandial changes in the small intestinal motility involve muscarinic receptors, mainly of M2 subtype, at the level of the central nervous system.     

Cholinergic stimulation enhances colonic motor activity, transit, and sensation in humans

The cholinesterase inhibitor neostigmine indirectly stimulates muscarinic M(1)/M(2)/M(3) receptors, thereby reducing colonic distension in acute colonic pseudo-obstruction. We investigated the dose-response profile for the colonic sensorimotor effects of neostigmine and bethanechol, a direct muscarinic M(2)/M(3) agonist in humans. A barostat-manometric assembly recorded phasic pressures, tone, and pressure-volume relationships (compliance) in the descending colon and rectum of 30 healthy subjects who received intravenous neostigmine (0.25, 0.75, or 1.5 mg; n = 15) or subcutaneous bethanechol (2.5, 5, or 10 mg; n = 15). Sensation to luminal distension was also assessed. Thereafter, the effects of neostigmine and bethanechol on colonic transit (geometric center) were compared with those of saline by scintigraphy in 21 subjects. Both drugs increased colonic phasic pressure activity, reduced rectal compliance, and enhanced urgency during rectal distension. Neostigmine also reduced colonic and rectal balloon volumes, reflecting increased tone by an average of 12% and 25% for the highest dose, respectively. Only neostigmine reduced colonic compliance, accelerated colonic transit [mean geometric center at 90 min 2.5 vs. 1.0 (placebo)], and increased pain perception during colonic distension. We conclude that neostigmine has more prominent colonic motor and sensory effects than bethanechol. Moreover, neostigmine induces coordinated colonic propulsion, perhaps by stimulating muscarinic M(1) receptors in the myenteric plexus.     

Relative magnitude of tonic and phasic synaptic excitation of medullary inspiratory neurons in dogs

The relative contribution of phasic and tonic excitatory synaptic drives to the augmenting discharge patterns of inspiratory (I) neurons within the ventral respiratory group (VRG) was studied in anesthetized, ventilated, paralyzed, and vagotomized dogs. Multibarrel micropipettes were used to record simultaneously single-unit neuronal activity and pressure microejected antagonists of GABAergic, glycinergic, N-methyl-D-aspartate (NMDA) and non-NMDA glutamatergic, and cholinergic receptors. The discharge patterns were quantified via cycle-trigger histograms. The findings suggest that two-thirds of the excitatory drive to caudal VRG I neurons is tonic and mediated by NMDA receptors and the other third is ramp-like phasic and mediated by non-NMDA receptors. Cholinergic receptors do not appear to be involved. The silent expiratory phase is produced by phasic inhibition of the tonic activity, and approximately 80% of this inhibition is mediated by gamma-aminobutyric acid receptors (GABA(A)) and approximately 20% by glycine receptors. Phasic I inhibition by the I decrementing neurons does not appear to contribute to the predominantly step-ramp patterns of these I neurons. However, this decrementing inhibition may be very prominent in controlling the rate of augmentation in late-onset I neurons and those with ramp patterns lacking the step component.     

Functional role of M2 muscarinic receptors in the guinea pig ileum

Muscarinic agonists elicit contraction in the standard guinea pig ileum bioassay through activation of M3 muscarinic receptors that are also linked to phosphoinositide hydrolysis. Surprisingly, the most abundant muscarinic receptor in the ileum is the M2 which causes a specific inhibition of cyclic AMP accumulation elicited by the beta-adrenergic receptor. After most of the M3 receptors are inactivated, the ileum still retains high sensitivity to muscarinic agonists provided that the contractile responses are measured in the presence of histamine and forskolin, which together, have no effect on contraction. Under these conditions, the potencies of antagonists for blocking the contractile response are consistent with those expected for an M2 response. Moreover, the muscarinic contractile response measured in the presence of histamine and forskolin after inactivation of M3 receptors is pertussis toxin sensitive. In contrast, muscarinic contractions in the standard bioassay are pertussis toxin insensitive. These results demonstrate that the M2 muscarinic receptor can cause an indirect contraction of the guinea pig ileum by preventing the relaxing effect of agents that increase cAMP.     

Centrally administered bombesin modulates gastric motility

Intracerebroventricular bombesin alters arterial pressure and gastrointestinal transit in rats. In order to evaluate the influence of bombesin on arterial and gastric intraluminal pressure in a specific site in the central nervous system, we microinjected bombesin into the medial subnucleus of the nucleus tractus solitarius (mNTS) in 28 rats anesthetized with choralose. Bombesin (78 pmole in 25 nl), but not vehicle, caused an increase of tonic gastric intraluminal pressure (2.6 +/- 0.5 cm H2O) and of phasic gastric intraluminal pressures but did not acutely alter arterial pressure. The effect on tonic and phasic gastric intraluminal pressure was dose-dependent. The threshold dose was 7.8 pmole. Intravenous bombesin caused a similar dose-dependent rise in tonic gastric intraluminal pressure but did not significantly change the mean amplitude of phasic gastric intraluminal pressures. Transection of the cervical spinal cord and both cervical vagus nerves blocked the effect of centrally but not peripherally administered bombesin. We conclude that bombesin microinjected into the mNTS does not influence arterial pressure but does raise tonic and phasic gastric intraluminal pressures. Bombesin may act in the NTS as a central modulator of gastric motility.     

Oviductal isthmic motility patterns as monitored by polyview in unrestrained sows around ovulation

A method for monitoring oviductal isthmic motility in sows incorporating a computer programme (Polyview) was developed. This method was found to be reliable and easy for recording and analysing data. Isthmic motility patterns were monitored from 11 h prior to and up to 36 h after ovulation in 13 unrestrained multiparous sows during their second oestrus after weaning. The amplitudes and frequencies of phasic pressure fluctuations in relation to the hormonal profiles were also calculated. The isthmic motility patterns were regular before ovulation changing to wave patterns during the peri-ovulatory period and eventually to irregular patterns after ovulation. The amplitudes and frequencies of phasic pressure fluctuations were significantly higher (p<0.05) prior to and soon after ovulation than afterwards. Plasma oestradiol-17beta levels significantly (p<0.05) decreased before ovulation while plasma progesterone levels increased significantly (p<0.05) after ovulation. Despite a significant decrease in the plasma levels of oestradiol-17beta prior to ovulation, the amplitudes and frequencies of phasic pressure fluctuations remained high until shortly after ovulation. This could have been due to the endogenous levels of oestradiol-17beta bound to the nuclear oestradiol-17beta receptors that might still have been present in the isthmus. Conversely, the irregular isthmic motility patterns, the decline in the frequencies of phasic pressure fluctuations and amplitudes seen after ovulation may have been due to the rising plasma levels of progesterone. The amplitudes and frequencies of phasic pressure fluctuations were highest at the time when oestradiol-17beta levels were highest and when progesterone levels were low. It can be concluded that the changes in the isthmic motility patterns, amplitudes and frequencies of phasic pressure fluctuations in relation to the changes in the plasma levels of oestradiol-17beta and progesterone seen in the present study prior to and after ovulation indicate a possible role of the oviduct in regulating gamete transport.