Influence of strip size and location on contractile responses of rat urinary bladder body strips.

1. We investigated the influence of strip length and dorsal or ventral location of rat urinary bladder strips on contractile responsiveness. 2. No differences occurred in the contractile responses of 0.5, 1.0 and 2.0 cm strips to field stimulation, carbachol, ATP, substance P or to KCl when the data were expressed as either absolute tension or as tension per cross-sectional area. However, correction for strip mass resulted in significant decreases in the contractile responses of the 2.0-cm strips compared with the 0.5-cm strips. 3. No differences occurred in length-tension curves for ventral and dorsal bladder strips, even though the strips from the dorsal surface appeared thinner than those from the ventral surface. 4. Strips from the ventral surface exhibited more variability in response to field stimulation and were less sensitive to atropine pre-treatment than were those from the dorsal surface. They were also less sensitive to the contractile effects of carbachol than dorsal strips. Dorsal and ventral strips were equally responsive to ATP, substance P and KCl. 5. Our data indicate that the contractile responsiveness of rat urinary bladder strips is independent of strip length. Although there are some differences between the cholinergic responsiveness of strips from the ventral and dorsal surfaces of the bladder, the differences are so small that for most studies they will probably have no influence on data interpretation.

A clinical trial of bethanechol in patients with xerostomia after radiation therapy. A pilot study.

The effects of bethanechol in the treatment of dry mouth were assessed in patients with xerostomia after radiation therapy to the head and neck. Bethanechol possesses muscarinic and nicotinic-cholinergic activity that likely accounts for its mode of action. Bethanechol (25 mg, three times daily) was not associated with significant side effects. Statistically significant increases in whole resting saliva (p = 0.003) and whole stimulated saliva (p = 0.001) were seen. In patients with pretreatment stimulated saliva volumes greater than resting saliva volumes, a positive response to subsequent use of the sialagogue was seen.

Differential effects of Na+, K(+)-ATPase inhibition by ouabain on acid secretory responses to histamine and bethanechol in the mouse isolated stomach.

1. The effect of Na+,K(+)-ATPase inhibition by ouabain on gastric acid secretion was studied in the mouse isolated whole stomach preparation. 2. Ouabain caused a transient enhancement of histamine-induced gastric acid secretion followed by an inhibitory phase. On the other hand, ouabain caused a rapid reduction of bethanechol-stimulated acid secretion without an enhancement phase. 3. In dibutyryl cyclic AMP-induced acid secretion, ouabain led to a transient increase in acid secretion followed by a fall, as was seen with the histamine stimulation. Ouabain caused a rapid reduction of A23187-induced acid secretion. 4. Ouabain by itself increased basal acid secretion, and thereafter slowly suppressed the acid secretion. 5. Atropine inhibited both the ouabain-induced enhancement of the stimulated gastric acid secretion and the ouabain-induced stimulation of basal acid secretion. 6. The present study showed that Na+,K(+)-ATPase inhibition by ouabain caused a phasic enhancement of the stimulated gastric acid secretion through release of endogenous acetylcholine when the secretagogues act via an intracellular cyclic AMP pathway. It also inhibited the stimulated acid secretion irrespective of secretagogues, probably through its inhibitory effect on Na+,K(+)-ATPase in the gastric parietal cell.

Ventricular arrhythmias induced by chemically modified intrinsic cardiac neurones.

OBJECTIVE: The aim was to investigate whether intrinsic cardiac neurones can be involved in the genesis of ventricular arrhythmias. METHODS: Nicotinic, muscarinic, beta adrenergic, peptidergic, and amino acidergic agonists, as well as purinergic compounds, were individually administered in microliter quantities adjacent to spontaneously active in situ right atrial neurones in 57 anaesthetised dogs before and after acute decentralisation. RESULTS: Ventricular arrhythmias were induced in one third of the dogs following neurochemical administration. Ventricular arrhythmias are induced much less frequently when intrathoracic extracardiac neurones are modified chemically. Salvos of ventricular premature contractions or ventricular tachycardias were elicited when intrinsic cardiac neurones were modified locally applied nicotine, bethanechol, isoprenaline, angiotensin II, bradykinin, substance P, vasoactive intestinal polypeptide, glutamate, or adenosine. In 60% of those instances in which intrinsic cardiac neuronal activity was modified by a neurochemical, ventricular arrhythmias were elicited. When arrhythmias were induced, activity generated by chemically modified intrinsic cardiac neurones increased from 0.7(SD 0.2) to 2.2(0.4) impulses.s-1 (p < 0.05). Following decentralisation of the intrinsic cardiac nervous system, repeat administration of the same neurochemicals into the same loci elicited ventricular arrhythmias in 42% of those dogs in which ventricular arrhythmias had been elicited previously. Neuronal activity increased [0.8(0.5) to 2.1(0.6) impulses.s-1; p < 0.05] in 86% of these instances. CONCLUSIONS: Intrinsic cardiac neurones can be involved in the genesis of ventricular arrhythmias.

Comparative studies on the ontogeny and autonomic responses of the fetal calf bladder at different stages of development: involvement of nitric oxide on field stimulated relaxation.

This initial study correlates the passive length-tension relationship, contractile and relaxant responses to field stimulation and contractile responses to specific autonomic agonists and antagonists with gestational age. Fetal bovine bladders were separated into three groups based on the head-rump length (FL): 30 to 45 cm. (early gestation), 50 to 65 cm. (middle gestation) and 70 to 85 cm. (late gestation). Each bladder was separated into upper and lower bladder segments; longitudinal strips of smooth muscle were isolated and placed in individual muscle baths. Passive length-tension studies demonstrated that compliance was greatest in the bladder of late gestation and lowest in the bladder of early gestation period. Field stimulation (FS) elicited frequency-dependent contractile responses in all strips. In the upper bladder, the maximal response and maximal rate of tension generation to FS was lowest in the youngest fetuses and increased in proportion to the gestational age. In the lower bladders, there were no gestational age-related differences in the maximal response or maximal rate of tension generation in response to field stimulation. The maximal response of the upper bladder to bethanechol increased significantly from the youngest gestational age to mid-gestation, with no further changes between mid- and late gestation. The maximal response to field stimulation and bethanechol were equal between upper and lower bladder segments for the youngest gestational bladders, whereas for the oldest gestational ages, the maximal response of the upper bladder to FS and bethanechol were significantly greater than the responses of the lower bladder. In the presence of maximal precontraction with bethanechol, FS induced a rapid and marked decrease in tension. The magnitude of the relaxation was substantially greater for the strips of lower bladder than for the strips of upper bladder at late gestation. In lower bladders, the magnitude of the field stimulated relaxation was greater in the strips from the older fetuses than in the strips from younger fetuses. In all strips, field stimulated relaxations were completely inhibited by pretreatment with L-NAME (an inhibitor of nitric oxide synthesis), indicating that the FS-induced relaxation was due to nitric oxide. In addition to nitric oxide-induced relaxation, beta adrenergic stimulation also induced a significant relaxation of the isolated strips. In summary, these data suggest that, in the tubular shaped fetal bovine bladder, there were distinct differences in the autonomic responses between the upper bladder segment and the lower bladder segment in the late gestation period.

Temporal changes in rabbit urinary bladder function and DNA synthesis during chronic treatment with furosemide.

In a preliminary study we showed that 14 days of furosemide infusion in rabbits caused increases in bladder mass and contractile responses of bladder body strips to field stimulation, bethanechol, ATP and KCl. The present study investigated the temporal effects of furosemide-induced diuresis on micturition, bladder mass, bladder wall proliferation activity and DNA synthesis. In addition, contractile responses of bladder body strips were monitored. Furosemide-containing osmotic pumps were implanted in male New Zealand White rabbits. Micturition was monitored for 7 days. Biochemical analyses were done 3, 7 and 14 days after implantation. Contractile responses were measured at 3 and 7 days. Polyuria and polydipsia started within 1 day after implantation of furosemide-containing osmotic pumps and continued at the same level for 7 days. Bladder mass was significantly increased at 3 and 7 days. Diuresis stimulated 3H-thymidine uptake and caused an increase in bladder DNA concentration at 3 days. However, both DNA concentrations and 3H-thymidine levels returned to control levels by 7 days. Contractile responses to field stimulation and agonists were increased at 7 days but unchanged at 3 days. The data confirm that modest increases in bladder mass and the ensuing increases in contractile function are a normal and beneficial physiological response to diuresis.

Depletion of secretory granules from the feline parotid gland: action of NANC transmitters per se.

A parotid acinar degranulation of approximately 60 and 40% was observed in cats under pentobarbitone anaesthesia after a 90-min period of continuous stimulation of the parasympathetic auriculo-temporal nerve at 10 Hz in the absence and presence of atropine, respectively. Atropine completely abolished the large fluid response of the gland to the nerve stimulation. In the non-atropinized cats, bethanechol, infused into the carotid artery at a dose rate evoking a salivary flow similar to that in response to parasympathetic nerve stimulation, caused an acinar degranulation of approximately 25% and acinar vacuolation. Vasoactive intestinal peptide (VIP; 0.5 microgram kg-1 min-1 also infused into the carotid artery for 90 min) caused an acinar degranulation of the same magnitude as the parasympathomimetic drug but the peptide did not give rise to any fluid secretion or vacuole formation. The experiments were performed in the presence of alpha- and beta-adrenoceptor blockers. Thus, in parotid glands of the cat, producing no overt secretion of fluid, non-adrenergic, non-cholinergic (NANC) mechanisms may be at work causing exocytosis of the acinar granules. These mechanisms are also likely to contribute to the secretion of granules in response to parasympathetic nerve activity in the absence of blockade of the classical autonomic receptors.

Effects of 17 beta-estradiol on endothelium-dependent relaxation induced by acetylcholine in female rat aorta.

Estrogens have been postulated to play an important role in modulation of vascular responses to endogenous reactive substances. The effects of chronic in vivo treatment with 17 beta-estradiol on relaxant responses to acetylcholine were investigated in the rat aorta isolated from prepubertal female rats. The selectivity of effects of 17 beta-estradiol on acetylcholine-induced relaxation was evaluated using histamine, another endothelium-dependent relaxant in the rat aorta. 17 beta-Estradiol significantly enhanced endothelium-dependent relaxation induced by acetylcholine, but did not alter the vascular responses to acetylcholine in endothelium-denuded aortic rings isolated from prepubertal female rats. In contrast, 17 beta-estradiol did not change endothelium-dependent relaxation induced by histamine in endothelium-intact aortic rings. The results of the present study demonstrate that 17 beta-estradiol selectively enhances acetylcholine-induced endothelium-dependent relaxation in the rat aorta.

Decreased electromechanical activity of guinea pig circular muscle during pregnancy.

BACKGROUND: Delayed gastric emptying has been reported during pregnancy; however, its underlying mechanism is poorly understood. The purpose of this study was to determine if electromechanical activity of antral circular muscle is decreased during pregnancy. METHODS: Antral muscle strips from third-trimester pregnant and age-matched control virgin female guinea pigs were studied in vitro. RESULTS: Spontaneous and bethanechol-induced phasic antral contractions from pregnant guinea pigs were reduced significantly in force compared with control virgin animals. Although the resting membrane potentials were similar, the electric slow waves of pregnant animals displayed significant decreases in upstroke amplitude, plateau amplitude, and number of spikes during the plateau potential compared with control animals. The voltage-tension relationship was similar in pregnant and control animals. CONCLUSIONS: This study indicates that (1) the force of antral circular muscle contractions is decreased during pregnancy and (2) this decreased force is secondary to a diminished slow wave depolarization. The results suggest that a change in electromechanical activity of gastric muscle is a cause of altered gastric motility in pregnancy.

Pathological changes in frontal cortex from biopsy to autopsy in Alzheimer's disease.

We evaluated the change in density of total senile plaques, plaque subtypes, and neurofibrillary tangles, from biopsy to autopsy in left frontal cortical sections from four patients with clinically typical Alzheimer's disease (AD). Comparisons were made on sections stained with modified Bielschowsky and Thioflavin S. In two cases, comparisons were also made on tissue stained with a monoclonal Alz-50 antibody and an antiserum to A beta (beta-amyloid protein). Despite a marked decline in mental status over several years of follow-up clinical evaluations, there was no consistent significant change in numerical density of plaques or tangles among the four cases. However, we did find fewer primitive plaques in the autopsy specimens. These results from longitudinally evaluated persons with typical AD suggest that although plaques and tangles may serve as adequate markers of the presence of AD, their numerical density within a single neocortical region may not reflect dementia severity. This conclusion supports the results of recent cross-sectional studies on the progression of pathology among persons with AD.

Electrical communication between glomus cells of the rat carotid body.

Glomus cells of rat carotid bodies can be electrotonically coupled. This was determined by simultaneous intracellular recording and stimulation of two neighboring cells. Voltage applied into one cell (V1), was detected in the other cell as E2. The ratio E2/V1 or coupling coefficient (KC), varied from 0.003 to 1. R0 or input resistance (24.1-3,500 M omega), was calculated from the voltage elicited in the injected cell by current injection (V1/I1). The coupling resistance (RC) was estimated by using Bennett's model and was inversely related to KC. It ranged from 8.5 to 46,112 M omega. Values for KC are provisional since we may not have always recorded from immediately adjacent cells. Similarly, calculations of R0 and RC may not be accurate since, in all probability, there is a multicellular network. Stimulation by hypoxia (100% N2 or Na2S2O4), acidity (lactic acid or 100% CO2), dopamine, ACh, nicotine and bethanechol depolarized the majority of glomus cells, their input resistance decreased and cells became uncoupled. Fewer cells were either unaffected or coupling increased. There was a significant and negative correlation between changes in coupling coefficient and in coupling resistance.

Effects of partial outlet obstruction of the rat urinary bladder on micturition characteristics, DNA synthesis and the contractile response to field stimulation and pharmacological agents.

Partial outlet obstruction is one of the major urological complications induced by benign prostatic hypertrophy (BPH). The current study describes the time course of the effect of mild partial outlet obstruction (in rats) on in vivo micturition parameters, DNA synthesis, and on the in vitro response of the bladder to field stimulation, bethanechol, methoxamine, ATP, and KCl. Mild partial outflow obstruction was created by placing a catheter (outside diameter: 1.70 mm.) transabdominally in front of the urethra, tying a ligature (2-zero silk) around both the urethra and catheter, and then removing the catheter. The micturition pattern was monitored for 2 days prior to surgery, and then continuously for 14 days following the surgery. The changes in bladder weight and the in vitro detrusor function of control (sham operated) and obstructed bladders (1, 3, 5, 7, 14 and 28 days after surgery) were examined. Micturition frequency in the dark cycle decreased immediately after the operation, and then increased linearly reaching a maximum at the 5th day, and stabilized at this increased level for the duration of the micturition study. The frequency of the dark cycle was also decreased immediately after the sham surgery and then gradually increased over the period of observation. Bladder weight increased by day 1 following surgery, and remained high throughout the 28 day study. The contractile response of the obstructed bladder base to field stimulation was reduced at days 1 and 3. The response then increased above control for day 5, reached a maximum response at day 7 and remained at this level for days 14 and 28. A similar pattern was observed for the contractile response of the bladder body to bethanechol and KCl, and for the bladder base to methoxamine and KCl. Both obstructed and sham surgeries increased bladder DNA content and 3H-thymidine incorporation, which reached maximal values on days 5 and 3, respectively. DNA content and 3H-thymidine incorporation of obstructed bladders were greater than those of sham operated bladders. In conclusion, partial outlet obstruction in the rat resulted in a progressive increase in bladder mass, an increase in micturition frequency, increases in the in vitro contractile response to field stimulation, bethanechol, methoxamine, and KCl, and increases in bladder DNA content and 3H-thymidine incorporation.

Peptide YY inhibits pancreatic secretion via cholinergic pathways.

The influence of extrapancreatic nerves and intrapancreatic cholinergic activity on the inhibition of pancreatic exocrine secretion by peptide YY (PYY) was studied in conscious dogs. Chronic pancreatic fistulae were created in five mongrel dogs while a second group of five dogs also underwent complete pancreatic denervation. After recovery, a continuous infusion of secretin (62 ng/kg/hr) and cholecystokinin (50 ng/kg/hr) was administered over 2 hr. An infusion of PYY (400 pm/kg/hr) was then given randomly, during either the first or second experimental hour. The experiments were then replicated with a continuous background infusion of (90 micrograms/kg/hr) bethanechol, a cholinergic agonist. The secretin/cholecystokinin-induced bicarbonate and protein outputs were significantly inhibited by PYY in both the innervated and denervated animals. In the denervated animals, bethanechol eliminated the inhibitory effects of PYY. We conclude that extrapancreatic nerves do not mediate the inhibitory effects of PYY. The results suggest that PYY inhibits secretin/cholecystokinin-induced pancreatic response by an intrapancreatic cholinergic mechanism.

The effect of furosemide-induced diuresis on rabbit micturition and bladder contractile function.

The morphology and contractile function of the urinary bladder can be significantly altered in response to specific forms of physiological and pathophysiological stress placed upon it. For example, partial outlet obstruction results in a marked increase in bladder mass (weight) with associated alterations in the contractile response to specific forms of stimulation. Diabetes and its associated diuresis also induce significant alterations in bladder weight and contractile function. The current study was designed to determine if the increase in bladder weight induced by diuresis is associated with contractile alterations similar to those observed following partial outlet obstruction. Diuresis was induced by continual slow-infusion of furosemide using osmotic pumps. The results can be summarized as follows: 1) After two weeks of furosemide treatment the bladder mass was significantly greater than in the controls. 2) Furosemide-treated rabbits consumed and excreted three times more fluid than did the controls. 3) In vivo cystometric capacity and bladder compliance of the furosemide-treated rabbits were significantly increased. 4) Diuresis induced a significant increase in the contractile response of isolated bladder body strips to field stimulation, ATP, bethanechol, and KCl. 5) Furosemide treatment had no effects on the contractile responses of bladder base strips to any form of stimulation. Diuresis resulted in a significant increase in bladder weight and an associated increase in the contractile state of the bladder body, presumably through an increase in smooth muscle.

The influence of diabetes mellitus on glucose utilization by the rat urinary bladder.

Streptozocin-induced diabetes in rats causes changes in urinary bladder function and increases the responsiveness of isolated bladder strip preparations to contractile agents and field stimulation. We monitored the role of extracellular glucose in the contractile responsiveness of bladder body strips from control, 2-month diabetic, and sucrose-drinking rats to the muscarinic agonist bethanechol. Consumption of sucrose and induction of diabetes caused increases in bladder mass compared with that of controls. In the presence of normal glucose levels (5.6 mmol/L), bladder strips from diabetic rats responded to bethanechol with significantly larger responses than those from control or sucrose-drinking rats. Removal of glucose from the bathing medium caused time-dependent decreases in contractile response of bladder strips from all groups; there were no differences in the percent decrease in response between the three groups. The presence of insulin (100 mU/mL) had no effects on contractile responsiveness or the rate of decline of response. Following return of glucose to the medium, there were progressive increases in contractile responsiveness in all groups, which returned to original contractile values within 60 minutes and were unaffected by insulin. Pyruvate (9.1 mmol/L) was able to substitute for glucose in maintaining the contractile responses. Increasing the glucose concentration of the medium to 30 mmol/L had no effects on contractile responses. Unstimulated bladder adenosine triphosphate (ATP) and creatine phosphate concentrations were similar in control, diabetic, and sucrose-drinking rats. In conclusion, changes in glucose utilization and high-energy phosphate levels cannot explain the increased contractile responsiveness of bladder body strips from diabetic rats to contractile agents.

Role of calcium in mediating the biphasic contraction of the rabbit urinary bladder.

1. The response of the urinary bladder to field stimulation is biphasic in nature consisting of an initial phasic contraction followed by a prolonged tonic phase which lasts for the duration of the stimulation. 2. The phasic response is mediated by the release of neurohumoral transmitters, primarily acetylcholine (via muscarinic receptor stimulation) and ATP (via purinergic receptor stimulation). The tonic component is mediated entirely via muscarinic receptor stimulation. 3. The present study investigates the dependence on extracellular calcium of the phasic and tonic contractile responses to field stimulation, bethanechol, and ATP. The results can be summarized as follows: 4. Field stimulation (2 and 32 Hz) and bethanechol evoke a biphasic contractile response whereas ATP evokes only a phasic response. 5. There were no significant effects of either calcium channel blockers or calcium fee EGTA medium on either spontaneous contraction or basal tension of muscle strips. 6. The calcium channel antagonists diltiazem and verapamil inhibited both the phasic and tonic responses induced by field stimulation (both 2 and 32 Hz) in a dose dependent manner. 7. For both 2 and 32 Hz stimulation, the ED50 s for the inhibition of the tonic phases of the responses to field stimulation were significantly lower than the ED50s for the inhibition of the phasic responses. 8. The tonic phase of the responses to field stimulation were inhibited to a significantly greater degree than the phasic responses by incubation in calcium-free medium containing EGTA. 9. Both the phasic and tonic components of the response to bethanechol stimulation were inhibited equally, and followed a similar time course as the tonic component of field stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of subcutaneous bethanechol on bladder sensation during cystometry.

Bethanechol has been shown to produce a pharmacologic effect on the urinary bladder, although the clinical efficacy of this response is controversial. The measured response has been an increase in detrusor pressure, although sensory effects may occur also. In this study, 10 neurologically intact men had cystometry before subcutaneous administration of 5 mg bethanechol chloride and thirty minutes after bethanechol. The sensation of desire to void and the maximum cystometric capacity occurred at a higher intravesical pressure and a smaller bladder capacity following bethanechol. Subcutaneous bethanechol appears to alter the bladder pressure and capacity at which the perception of desire to void and the sensation of maximum fullness occurs.

Adenosine and cholinergic-induced gastric contraction in rats.

Adenosine is known for its modulatory effects on gastric secretory function and mucosal blood flow in rats. However, its action on gastric motility has not been defined. The influence of adenosine on gastric contractions provoked by cholinergic drugs and direct vagal stimulation have, therefore, been examined. Bethanechol (25, 50 or 100 micrograms/kg i.v.) and electrical vagal stimulation dose and voltage dependently increased the number and the amplitude of gastric contractions. An adenosine-A1-receptor agonist, L-phenylisopropyladenosine (10 or 50 micrograms/kg s.c.), given 30 min beforehand, did not affect the changes in gastric parameters but decreased the basal mean blood pressure and lessened the reduction in blood pressure evoked by bethanechol. The adenosine-A2-receptor agonist N-ethylcarboxaminoadenosine (1 or 5 micrograms/kg s.c.), 30 min beforehand, however, significantly increased the number but not the force of gastric contractions; a lower dose of this drug increased the basal blood pressure and potentiated the depressive action of bethanechol on systemic blood pressure. Adenosine administration (7.5 mg/kg s.c.) significantly increased its plasma levels at 30 and 60 min after injection; pretreatment with it (2.5, 7.5 or 12.5 mg/kg s.c.), 30 min beforehand, did not affect the gastric and vascular actions of bethanechol. The highest dose of adenosine potentiated the contractile response of vagal stimulation. In the isolated fundus preparation, adenosine added to the organ bath (10(-6), 10(-4), 10(-2) M) also did not affect the contractions induced by acetylcholine.(ABSTRACT TRUNCATED AT 250 WORDS)

Beta-receptor responsiveness after desipramine treatment.

To examine whether a tricyclic antidepressant affects the functional response to a beta-receptor agonist in man, the response of heart rate, blood pressure, and plasma cAMP to isoproterenol was measured in 14 normal controls taking 75 mg desipramine daily. Desipramine significantly increased the bolus dose of isoproterenol needed to increase heart rate by 25 bpm at 14-30 days but not at 3-8 days. During infusions of isoproterenol, the increase in systolic blood pressure was blunted at both 3-8 days and 14-30 days, while the decrease in diastolic blood pressure was unaffected. Blood pressure findings were not affected by preadministration of bethanechol. In ten controls, isoproterenol infusions increased plasma cAMP, but this was unaffected by desipramine treatment. These findings suggest a decrease in the functional response of beta 1, but not beta 2, receptors after treatment with desipramine.

Galanin activates an inwardly rectifying potassium conductance in mudpuppy atrial myocytes.

Galanin- and bethanechol-activated K+ currents have been studied in mudpuppy atrial myocytes. The galanin and bethanechol K+ currents were time-dependent and inwardly rectifying. In GTP gamma S, the galanin and bethanechol currents were reduced progressively as G-protein gated K+ channels became activated. GDP beta S inhibited agonist-induced outward currents. We conclude that galanin and bethanechol activate the same or a very similar inwardly rectifying K+ conductance and that activation of a G protein is required.