A study of morphine-induced urinary retention in anesthetized rats capable of micturition

The nature of morphine-induced urinary retention was studied in anesthetized rats in which the bladder contraction accompanying micturition could be observed. Morphine (0.1 mg/kg, i.v.) prolonged the micturition interval and increased the level of micturition threshold. Morphine (1 mg/kg, i.v.) completely inhibited bladder contraction and bladder pressure was elevated until solution leaked from the penis, but the bladder pressure after inhibition by morphine (1 and 5 mg/kg, i.v.) did not significantly rise over the peak pressure level during micturition before injection of morphine. The inhibitory effect of morphine (1 and 5 mg/kg, i.v.) was reversed by naloxone (0.1 mg/kg, i.v.). Morphine (5 mg/kg, i.v.) did not increase the pressure induced by infusion of solution from near the bladder neck to the urethra. After intracerebroventricular (i.c.v.) and intrathecal (i.t.) administration of morphine (1 microgram), the micturition interval was prolonged and the level of micturition threshold was increased. Morphine (5 micrograms, i.c.v. and i.t.) inhibited bladder contraction and naloxone (5 micrograms, i.c.v. and i.t.) reversed the inhibitory effect of morphine injected by the same administration route. From these results, urinary retention induced by systematically injected morphine was considered to result from inhibition of bladder function mediated via opioid receptors of the micturition centers in the supraspinal and spinal regions.     

The effect of baclofen on the urinary bladder contraction accompanying micturition in anesthetized rats

We studied the effects of baclofen on the bladder contraction induced by infusion of Tyrode's solution into the urinary bladder in anesthetized rats. Baclofen (5 mg/kg, i.v.) completely inhibited bladder contraction and abolished the efferent discharges recorded from the left pelvic nerve, causing the bladder pressure to rise until solution leaked from the penis. The inhibitory effect of baclofen (5 mg/kg, i.v.) could not be reversed by picrotoxin (1 mg/kg, i.v., twice with an interval of 10 min) or naloxone (1 mg/kg, i.v.). In parallel with convulsion, strychnine (1 mg/kg, i.v.) contracted the bladder which had been inhibited by baclofen and generated electrical activities consisting of efferent discharges and electromyograms. The dose of intracerebroventricularly or intrathecally injected baclofen which completely inhibited the bladder contraction was 0.1 or 10 micrograms, respectively. After the inhibition of bladder contraction by i.v. injection of baclofen, electrical stimulation of the sacral cord could contract the bladder and cause a fall in bladder pressure to around the level existing after micturition. From these results, the active site of baclofen which is related to the inhibition of bladder contraction is thought to be the micturition center in the brain stem.     

In vivo effects of gamma-aminobutyric acid on the urinary bladder contraction accompanying micturition

We studied the effects of the gamma-aminobutyric acid (GABA) receptor agonists, diazepam and muscimol, on the urinary bladder contraction induced by infusion of Tyrode's solution into the bladder in anesthetized rats. Diazepam (1 mg/kg, i.p.) completely inhibited bladder contraction, causing the bladder pressure to rise until solution leaked from the penis. The inhibitory effects of diazepam were reversed by picrotoxin (1 mg/kg, i.v., twice with an interval of 10 min), and the effects were potentiated and attenuated by pretreatment with aminooxyacetic acid (AA, 10 mg/kg, i.v.) and semicarbazide (200 mg/kg, i.v.), respectively. Only pretreatment with AA inhibited the bladder contraction induced by infusion of Tyrode's solution into the bladder in six out of eight rats. Diazepam abolished efferent discharges recorded from the left pelvic nerve, but hexamethonium facilitated the generation of efferent discharges after inhibition of bladder contraction. After complete inhibition of bladder contraction by diazepam, electrical stimulation of the left pelvic nerve at 5 Hz for 30 sec was able to induce bladder contraction, and this resulted in micturition. Intracerebroventricular injection or intrathecal injection into the sacral part of the spinal cord of 1 microgram muscimol completely inhibited the bladder contraction. It was considered that the inhibitory effects of GABA receptor agonists on bladder contraction were mainly induced through the GABA receptors in the micturition center of the sacral cord, as well as the brain stem.     

Effect of terodiline hydrochloride on the function of urinary bladder in rats

The effect of terodiline on the function of urinary bladder was investigated in anesthetized rats. When saline was infused continuously into the urinary bladder of rats, terodiline (1-10 mg/kg, i.v.) prolonged the time to micturition in a dose-dependent manner. When enough saline was infused into the urinary bladder to induce the voiding contraction in urethra-ligated rats, terodiline (1-10 mg/kg, i.v.) and verapamil (1 mg/kg, i.v.) abolished the contraction, of which amplitude and frequency were partially inhibited by atropine (1 mg/kg, i.v.). Efferent discharge from the pelvic nerve on the micturition reflex was inhibited by terodiline (3 mg/kg, iv.v.). Both of the bladder contractions evoked by the electrical stimulation of the peripheral or central cut end of the pelvic nerve were dose-dependently inhibited by terodiline (1-10 mg/kg, i.v.). At 3 mg/kg or more, terodiline significantly inhibited the contraction, and the effects were long lasting. The effect of atropine (1 mg/kg, i.v.) was similar to that of terodiline (3 mg/kg, i.v.). Increase in frequency of urination and decrease in total urinary volume per micturition after the bilateral transection of the hypogastric nerve were improved after on oral administration of terodiline (1-10 mg/kg).     

Effects of central nervous system-acting drugs on urinary bladder contraction in unanesthetized rats

We studied the effects of drugs on urinary bladder contraction in unanesthetized (UA) rats using the same method as that previously employed to investigate similar effects in urethane and alpha-chloralose-anesthetized (A) rats. The surgical procedure was performed under halothane anesthesia, and after the recovery, the rats were restricted in a Ballman cage during the experiment. The pattern of the cystometrogram obtained in UA rats was very similar to that in A rats, and almost the same pattern was maintained for at least three hours. Baclofen (10 mg/kg, i.p.), morphine (10 mg/kg, i.p.) and pentobarbital (20 mg/kg, i.p.) completely inhibited the bladder contraction at doses only double those at which the same drugs inhibited the bladder contraction in A rats when i.v. injected. When the bladder pressure rose almost to the level of the peak pressure existing before injection of these drugs, the instilled solution leaked from the penis. On the other hand, even after injection of diazepam (5 mg/kg, i.p.) at a dose five times greater than the minimum amount necessary for complete inhibition of bladder contraction in A rats, the bladder contraction accompanying micturition continued in UA rats. It appears that the inhibitory effect of diazepam on bladder contraction in rats is potentiated by anesthesia.     

Effects of apomorphine on urinary bladder motility in anesthetized rats

We studied the effects of apomorphine (AM) on bladder motility in anesthetized rats in which Tyrode's solution was continuously infused into the bladder at a constant rate, including an almost constant rate of bladder contraction accompanying micturition. AM at a dose of 1 mg/kg, i.v., caused a hyperactive bladder response, during which micturition disappeared. AM (12.5 micrograms for intracerebroventricular (i.c.v.) injection or 50 micrograms for intrathecal (i.t.) injection also caused a hyperactive response in about half of the rats. Supersensitization to AM appeared in reserpine-treated rats (2.5 mg/kg, i.p., 48 and 24 hr before the experiment). Haloperidol (1 mg/kg, i.v.) or SCH 23390 (5 mg/kg, i.v.) completely suppressed the hyperactive bladder response induced by AM (5 mg/kg, i.v.), and then the bladder contraction accompanying micturition reappeared after administration of these drugs. Pretreatment with sulpiride (100 mg/kg, i.p.) for 60 min, which hardly affected the bladder contraction induced by infusion of Tyrode's solution, suppressed the hyperactive bladder response induced by AM. These results suggest that the hyperactive bladder response induced by i.v.-injected AM results from synchronous stimulation of the micturition reflex centers in the brain stem and sacral cord and that the hyperactive bladder response is elicited via both D1 and D2 receptors.     

Effects of oxybutynin hydrochloride on the urinary bladder and urethra in in situ preparations

Effects of oxybutynin on the urinary bladder and urethra were studied in comparison with atropine and flavoxate in cats and rabbits. Oxybutynin at 10 mg/kg, i.v., significantly inhibited the bladder contractions induced by electrical stimulation of the peripheral end in pelvic nerve. Oxybutynin was about one half the potency of atropine. On the contrary, 10 mg/kg of flavoxate, i.v., showed both effects of potentiation and inhibition. The bladder contractions induced by acetylcholine (ACh) and AHR-602 were markedly inhibited by oxybutynin and atropine. Oxybutynin was about one-fifteenth the potency of atropine. DMPP-induced contractions were inhibited by oxybutynin and atropine in a high dose, but oxybutynin was about two-fifths the potency of atropine. In addition, 3 mg/kg of oxybutynin, i.v., inhibited the contraction induced by hypogastric nerve stimulation, but 10 mg/kg of oxybutynin, i.v., significantly inhibited this contraction following initial potentiation. Oxybutynin showed an inhibitory effect on spontaneous rhythmical contraction, bladder tone and pelvic nerve discharge, similar to the effects of atropine. On the contrary, flavoxate potentiated this contraction and increased the bladder tone and pelvic and hypogastric nerve discharge. Urethra contractions induced by norepinephrine, ACh and hypogastric nerve stimulation were inhibited by oxybutynin, but not markedly. Oxybutynin and atropine dose-dependently increased the infusion volume, bladder volume capacity and micturition threshold pressure in the cystometrogram in rabbits. Flavoxate also increased them. From these results, it si suggested that oxybutynin is therapeutically a useful agent for pollakisurea nervosa.     

Effects of adrenergic agonists on an experimental urinary incontinence model in anesthetized rabbits.

We have developed an experimental urinary incontinence model in anesthetized female rabbits, in order to study the effects of alpha-adrenergic receptor agonists on it in vivo. Micturition was induced artificially by electrical stimulation of the abdomen of rabbits receiving a continuous infusion of glucose-free. Tyrode's solution into the urinary bladder. Alpha-1 adrenergic agonists, phenylephrine (1 mg/kg, i.v.) and the newly synthesized agent ST-1059 (1 mg/kg, i.v.) and its prodrug midodrine (10 mg/kg), which was intraduodenally administered, elevated the bladder pressure and arrested micturition induced by electrical stimulation. Prazosin (0.1 mg/kg, i.v.) inhibited these effects of phenylephrine. The effect of an alpha-2 agonist, clonidine (1 mg/kg, i.v.), on micturition induced by electrical stimulation was not clearly defined. This study demonstrates that alpha-1 adrenergic agonists can arrest artificially-induced micturition via urethral contraction. This method may be useful for evaluating the effect of a drug on urethral leakage in vivo.     

Pharmacological studies of loperamide, an anti-diarrheal agent. II. Effects on peristalsis of the small intestine and colon in guinea pigs (author's transl)

Effects of loperamide on peristalsis in the guinea pig intestines were investigated in comparison with those of morphine and atropine. The following results were obtained. The ejection of intraluminal fluid produced by the peristaltic contraction of the isolated ileum was suppressed by loperamide at a concentration of 10(-8) or 2 X 10(-8) g/ml. Peristalsis in the intestinal loop of anesthetized guinea pigs was inhibited by i.v. administration of loperamide at a dose of 0.03 mg/kg. Morphine (0.03 mg/kg i.v.) and atropine (0.05 mg/kg i.v.) also inhibited the peristaltic contraction. The effect of loperamide continued longer than that of morphine. Peristalsis in the colonic loop of anesthetized guinea pigs was inhibited by i.v. administration of loperamide at a dose of 0.01 or 0.03 mg/kg. Morphine (0.1 mg/kg i.v.) and atropine (0.03 mg/kg i.v.) also inhibited the peristaltic contraction of the colonic loop. Loperamide (0.01 or 0.03 mg/kg i.v.) and morphine (0.1 mg/kg i.v.) caused a slight and temporary increase of resting level of intraluminal pressure with inhibition of peristalsis in the colonic loop. These results suggest that loperamide suppresses the peristaltic contraction caused by distension of the intestinal lumen.     

In vivo inhibitory effects of stimulation at the central end of the pelvic nerve severed from urinary bladder on urinary bladder contraction in rats

Two- or five-Hz electrical stimulation of the central end of the left pelvic nerve severed from the urinary bladder in rats inhibited bladder contraction induced by intravesical infusion of Tyrode's solution. Inhibition of bladder motility by 2-Hz nerve stimulation appeared after pretreatment with strychnine (0.3 mg/kg, i.v.), naloxone (1 mg/kg, i.v.) and picrotoxin (1 mg/kg, i.v.). Hypogastric nerve stimulation, however, did not affect bladder contraction. These results suggest the presence of an inhibitory mechanism on the pelvic motoneuron activated by contralateral pelvic nerve stimulation in rats.     

Effect of K+ channel openers, KRN2391 and Ki1769, and nitroglycerin on the urinary tract of rats in vivo.

The effects of KRN2391 (N-cyano-N'-(nitroxyethyl)-3-pyridine carboximidamide methane-sulfonate), which possesses ATP-sensitive potassium (K+) channel opening (KCO) activity and nitrate activity; Ki1769 (N-cyano-N'-(phenylethyl)-3-pyridinecarboximidamide methanesulfonate), which possesses only KCO activity; and nitroglycerin (NG) were determined on the motility of the ureter, urinary bladder and urethra of rats. Bladder contraction was induced by infusion of fluid into the bladder of conscious rats and recorded on a cystometrogram. KRN2391 and Ki1769 (both 0.3 mg/kg, i.v.) prolonged the micturition interval immediately after the injection, but NG (5 mg/kg, i.v.) did not. Peristaltic movement of the ureter, recorded in anesthetized rats, was inhibited by i.v. injection of KRN2391 and Ki1769 (both 0.03 mg/kg). However, when NG, NaNO2, N-nitro L-arginine methylester and methylene blue were applied directly to the ureter, no change in movement of the ureter was detected. KRN2391 (0.03 mg/kg, i.v.) and Ki1769 (0.3 mg/kg, i.v.) reduced the resistance to fluid infusion through the urethral lumen in anesthetized rats, whereas NG (0.5 mg/kg, i.v.) only reduced this resistance transiently. These results indicate that KCO activity had an inhibitory effect on the motility of the ureter, bladder and urethra. On the other hand, nitrate activity had an inhibitory effect on urethral tonus, corresponding to that induced by KCO activity.     

Evaluation of drugs for treatment of urinary bladder dysfunction in conscious rats with intact pelvic nerve and after resection of the left pelvic nerve

We studied the effects of drugs used for treatment of bladder dysfunction in conscious rats with intact pelvic nerves and also in rats at one or two weeks after nerve decentralization on the left side. Bladder contraction accompanying micturition was continuously induced by infusion of solution at a constant rate. When the effects of oxybutynin (3 mg/kg, i.p.) and terodiline (3 and 10 mg/kg, i.p.) on the cystometrogram were studied for about 2 hr, these drugs shortened and then prolonged the micturition interval (MI), but atropine (1 and 5 mg/kg, i.p.), butylscopolamine (20 mg/kg, i.p.) and nifedipine (3 mg/kg, i.p.) exhibited only a shortening effect on the MI. After injection of oxybutynin (10 mg/kg, i.p.), solution dribbled from the urethra for about 30 min. Terodiline (3 mg/kg) caused ischuria in the rats one week after resection of the left pelvic nerve, but not in the rats two weeks after surgery. Physostigmine (0.3 mg/kg, i.p.) improved micturition in the rats one week after surgery, but the effect was not evident in the rats with intact pelvic nerves. It was found that the drugs used for treating failure to store or expel urine exhibited a beneficial effect on micturition in rats with intact pelvic nerves and also in rats one week after nerve decentralization, respectively.     

Effects of 3-methyl-4-oxo-2-phenyl-N-[2-piperidinyl) ethyl]-4H-1-benzopyran-8-carboxyamide hydrochloride monohydrate (FL-155), a new anti-pollakiuria agent, on rhythmic bladder contractions in anesthetized rats

The effects of FL-155, which was synthesized to develop a new orally-active anti-pollakiuria agent, on the rhythmic bladder contractions were studied in anesthetized rats. At a pressure exceeding 10 cm H2O in the bladder, a rhythmic bladder contraction was observed up to at least 120 min. This response was abolished by a spinal (C1 level) cut, cuts of both pelvic nerves, thiopental (3.0 mg/kg, i.v.) or lidocaine (1.0 mg/kg, i.v.); and atropine (0.01 mg/kg, i.v.) strongly inhibited the amplitude of the response. FL-155 and flavoxate, in intravenous (0.3-3.0 mg/kg and 1.0-3.0 mg/kg, respectively) and intraduodenal (12.5-100 mg/kg and 200-400 mg/kg, respectively) administrations, dose-dependently abolished the rhythmic bladder contractions, and FL-155 was 8-16 times more potent than flavoxate in intraduodenal administrations. These results suggest that the rhythmic bladder contraction in anesthetized rat may be a polysynaptic reflex through pelvic nerves and the central nervous system (supraspinal level), and FL-155 appears to be a candidate for an orally active anti-pollakiuria agent.     

Pharmacological evaluation of the role of cyclooxygenase isoenzymes on the micturition reflex following experimental cystitis in rats

Prostanoids, generated from cyclooxygenase (COX) isoenzymes, play a role in the physiological function of the lower urinary tract and are important mediators of inflammatory hyperalgesia. The present work evaluates the effects of the COX-1/COX-2 inhibitor dexketoprofen as well as of a selective COX-2 inhibitor, NS-398, on urodynamic function following endotoxin (LPS) or cyclophosphamide (CYP)-induced inflammation of the urinary bladder. The application of arachidonic acid (330 microgram rat(-1)) onto the serosal surface of the urinary bladder in control rats elicited bladder contractions which could be blocked in a dose-dependent manner by dexketoprofen (0.1 - 3 mg kg(-1), i.v.) but not by NS-398 (0.2 - 6 mg kg(-1), i.v. ). Dexketoprofen (3 mg kg(-1), i.v.) decreased the micturition frequency and increased the pressure threshold for triggering the micturition either when administered within 15 min or 3 h following surgery in control animals. NS-398 (6 mg kg(-1), i.v.) decreased the micturition frequency and increased the pressure threshold when administered 3 h but not 15 min following surgery. Administration of LPS (2 mg kg(-1), i.v., 90 - 120 min) increased both the micturition frequency and the pressure threshold for triggering the micturition reflex. Changes in urodynamic parameters induced by LPS were prevented by doses of either dexketoprofen (1 mg kg(-1), i.v.) or NS-398 (2 mg kg(-1), i.v.) which were ineffective in control animals. Pretreatment with CYP (150 mg kg(-1), i.p., 48 h) increased the micturition frequency, pressure threshold, and the minimal intravesical pressure but decreased the mean amplitude of micturition contractions. In CYP-treated rats, dexketoprofen (1 mg kg(-1), i.v.) or NS-398 (2 mg kg(-1), i.v.) blocked the CYP-induced urodynamic changes with exception of the micturition contraction amplitude. These results indicate that COX-1 may be involved in modulating the threshold for activating the micturition reflex in the normal rats and also demonstrates that inhibition of COX-2 prevents or reverses the urodynamic changes associated with bladder inflammation induced either by surgery, LPS or CYP treatments.     

Effects of (+/-)-4'-ethyl-2-methyl-3-(l-pyrrolidinyl) propiophenone hydrochloride (HY-770) on the bladder function

The effects of HY-770 on micturition reflexes in rats, dogs and cats and urethral pressure in dogs were compared with those of flavoxate.HC1 (flavoxate), terodiline.HCl (terodiline) and oxybutynin.HCl (oxybutynin). 1) HY-770, in intravenous (2 and 4 mg/kg) and intraduodenal (12.5 and 25 mg/kg) administrations, dose-dependently abolished the rhythmic bladder contractions in anesthetized rats. The activity of HY-770, in intravenous administration (i.v.), was almost equal to those of flavoxate, terodiline and oxybutynin; and the activity of HY-770, like terodiline, was more potent than that of flavoxate in intraduodenal administration (i.d.). 2) In the cystometrograms, HY-770 (3, 4 or 8 mg/kg, i.v.) dose-dependently increased the time to micturition (capacity of bladder) without decreasing the amplitude of micturition contraction in anesthetized rats, dogs and cats, and HY-770 (25 mg/kg, i.d.) also increased the capacity in anesthetized cats. 3) HY-770 (4 and 8 mg/kg, i.v.) dose-dependently increased the capacity of the bladder in the cystometrograms of pollakiuria induced by either transection of both the hypogastric nerves or chronic cannulation to the bladder in anesthetized or conscious rats, respectively. 4) HY-770 (25 mg/kg, i.d.) slightly decreased the urethral pressure in anesthetized dogs. These results suggest that HY-770 is a promising drug for the treatment of pollakiuria induced by a neurogenic bladder or unstable bladder, etc.     

Inhibitory effect of inaperisone hydrochloride (inaperisone), a new centrally acting muscle relaxant, on the micturition reflex.

We examined the effects of inaperisone hydrochloride (inaperisone), a new centrally acting muscle relaxant, on bladder function in anesthetized rats and isolated rat tissues. We also investigated its mechanism of action. When a balloon inserted into the bladder was expanded, rhythmic bladder contractions were observed; inaperisone (4 mg/kg i.v.) abolished these contractions, in both normal and decerebrated rats. The bladder tonus or bladder contraction induced by peripheral stimulation of the pelvic nerve was barely inhibited by inaperisone (4 mg/kg i.v.), but this dose of inaperisone abolished the efferent discharge from the pelvic nerve that accompanied the rhythmic bladder contractions. The doses of intracerebroventricularly (i.c.v.) and intrathecally injected inaperisone which abolished the rhythmic bladder contractions were 10 and 100 micrograms, respectively. The inhibitory effects of inaperisone (4 mg/kg i.v.) were not diminished by naloxone (1 mg/kg i.v.) or by bicuculline (0.5 mg/kg i.v.), but were diminished by phaclofen (30 mg/kg i.v. or 300 micrograms i.c.v.). The specific binding of [3H]baclofen to rat brain synaptosomal membranes was barely inhibited by inaperisone (up to 1 mM). From these results, it is speculated that, among other possible mechanisms, inaperisone inhibits the micturition reflex by acting indirectly on GABAB receptors in the brainstem.     

Inhibition mechanism of Gosha-jinki-gan on the micturition reflex in rats

We investigated the actions of Gosha-jinki-gan, a traditional Japanese medicine containing processed Aconiti tubers, on urinary bladder function in anesthetized rats. In cystometrical investigations, Gosha-jinki-gan (1.0 g/kg, i.d.) increased bladder capacity as well as micturition threshold pressure. In addition, it decreased the frequency of distension-induced rhythmic bladder contractions. However, it did not influence the amplitude of bladder contractions induced by electrical stimulation of the pontine micturition center. The inhibitory effect of Gosha-jinki-gan on bladder motility was abolished by pretreatment with nor-binaltorphimine (10 mg/kg, s.c.), and was diminished by the concomitant use of anti-dynorphin A antiserum (10 microg, i.t.), yohimbine (10 microg, i.t.), or methysergide (20 microg, i.t.). Processed Aconiti tuber extract (27 mg/kg, i.d.) also suppressed bladder motility, and the effect was abolished by nor-binaltorphimine. These results suggest that Gosha-jinki-gan attenuates bladder sensation via the kappa-opioid receptor-stimulating action of processed Aconiti tuber. Gosha-jinki-gan may be a useful anti-pollakiuria agent that does not influence bladder contractility at micturition.     

The effect of MK-801 on the micturition reflex in anesthetized rats

We studied the effect of MK-801, a potent non-competitive NMDA receptor antagonist, on the micturition reflex in anesthetized rats. Pretreatment with MK-801 (0.1-1 mg/kg i.v.) dose dependently increased the bladder capacity and reduced the micturition contraction. The ability of MK-801 to inhibit bladder voiding was confirmed in additional experiments in which the compound (30-50 micrograms/kg i.v.) transiently suppressed established bladder voiding produced by continuous bladder filling. MK-801 (1 microM) did not affect nerve-mediated contractions of the rat bladder or inhibit the response to capsaicin. These findings provide pharmacological evidence for an involvement of NMDA receptors in the micturition reflex pathways.     

Hypotensive actions of ephedradines, macrocyclic spermine alkaloids of ephedra roots*.

Ephedradines A, B, C and D (3 mg/kg, i.v.) elicited hypotensive effects in Wistar rats. Administration of ephedradine B (EB) (0.1-3 mg/kg, i.v.) to Wistar rats and to spontaneously hypertensive rats reduced blood pressure in a dose-dependent manner. EB (1 mg/kg, i.v.) slightly potentiated the pressor action of norepinephrine (1 microg/kg, i.v.) and significantly reduced that of 1,1-dimethyl-4-phenylpiperazinium (50 microg/kg, i.v.). The hypotensive activity of EB (1 mg/kg, i.v.) was inhibited by pretreatment with atropine (5 mg/kg, i.v.) or diphenhydramine (5 mg/kg, i.v.). In the hypogastric nerve-vas deferens of guinea pig, application of EB (3 x 10 (-7)-10 (-5) g/ml)to the ganglion inhibited the contraction of the vas deferens induced by electrical preganglionic nerve stimulation and by acetylcholine (10 (-4)-10 (-3) g/ml) applied to the ganglion. It is thus concluded that the hypotensive activity of ephedradine B is exerted mainly by ganglion block.