Nagoya J. med. Sci. 39: 37-42,1976

37

RESPONSE OF URINARY BLADDER TO CHOLINERGICAND ADRENERGIC AGENTS*
ATSUO KONDO

Department of Urology Nagoya University School of Medicine(Director: Prof Hideo Mitsuya)

ABSTRACTThe pharmacologic response of bladder muscle strip of albino rabbits was studied in vitro.
The effect of cholinergic and adrenergic agents and their antagonists were demonstrated witha log dose-response curve. Cholinergic receptors were abundant in detrusor muscle. While theexcitory alpha adrenergic receptors existed in bladder neck, the inhibitory beta adrenergic
receptors were predominant in detrusor muscle. The role of cholinergic and adrenergic
receptors in detrusor muscle and bladder neck was discussed.

INTRODUCTION

Despite the morphological evidence of both cholinergic and adrenergic innervation at
the mammalian urinary bladder 1)2)3), the role of adrenergic nerve regarding micturition has
been a matter of constant dispute. Parasympathetic pelvic nerve facilitates micturition,
elevating bladder tonus and iTJcreasing contraction force. Torbey and Leadbetter4 ) could
not observe any appreciable change in bladder activity by electrical stimulation of sympathetic hypogastric nerve. Boyarsky et al. 5) noted that stimulation of beta adrenergic
receptors impaired the micturition by increasing bladder capacity and lowering the voidingpressure.
Ahlquist 6 ) demonstrated in 1948 that adrenergic receptor sites were composed of bothalpha and beta receptors. Alpha receptor is associated with excitatory response of thesmooth muscle and beta receptor mediates relaxation of smooth muscle, with some exceptions. The aim of the present article is to study the pharmacologic response of the bladder
strip to cholinergic and adrenergic agents in vitro.
MATERIALS AND METHODS

Twenty albino rabbits were killed by a blow in the neck. The bladder was excised at
the level of both ureteral orifices and the proximal portion was used as a detrusor specimen.
The mucosa was peeled off with a small scissors. The specimen, 50 mm X 5 mm, wasprepared at the random direction and mounted in a small organ bath. The muscle wasallowed to equilibrate to Krebs Ringer solution for 30 min warmed at 3rC and aerated
with 95 per cent oxygen and 5 per cent carbon dioxide. The activity of the muscle strip
was registered with force-displacement transducer (Grass Co., FT-03), then fed to a 4channel polygraph.
'" Part of the work has been conducted at University of Alberta, Alberta, and University of Sherbrooke,Quebec, Canada.

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Received for publication June 16,1976

A. KONDO

38

Norepinephrine and isoproterenol were used as adrenergic stimulant. They work at
both alpha and beta receptors. However, the former is generally more potent on alphareceptors and the latter has its main action on beta receptors. Phenoxybenzamine andpropranol act as specific blockade of alpha and beta receptors, respectively. Drugs tested
are as follows: acetylcholine chloride, hexamethonium bromide, physostigmine, atropine
sulfate, L-norepinephrine, DL-isoproterenol hydrochloride, phenoxybenzamine hydrochloride, and proprano!.
RESULTS

1. Spontaneous contraction
Regular spontaneous contractions were observed after 30 min equilibration to Krebs
Ringer solution; frequency of 4 to 5 per min with amplitude of 1.5 to 2.5 g (Fig. I). TheGram432Io432Ioo2345( Min)
FIG. 1. Spontaneous contraction of rabbit detrusor muscle. Muscle strip resected longitudinally (upper recording) and horizontally (lower recording).

contraction pattern was the same whether the muscle strip was excised longitudinally or
horizontally from the detrusor muscle.

2. Response of detrusor muscle to cholinergic agentsThe log dose-response curve of acetylcholine and other agents is shown in Fig. 2. The
rabbit muscle strip responded to acetylcholine at as low as I ng/m!. Muscle tonus waselevated with diminished amplitude and fast contractions (Fig. 3A). Presence of I Jlg/ml
atropine, a competitive antagonist at receptor site of smooth muscle, completely inhibitedthe action of acetylcholine. Physostigmine in a concentration of I IJg/ml, which inhibitedthe action of cholinesterase, facilitated the effect of acetylcholine, shifting the doseresponse curve to the left. Hexamethonium in a concentration of I Jlg/ml, a ganglion

RESPONSE OF URINARY BLADDER TO CHOLINERGIC AND ADRENERGIC AGENTS

39

blockade, did not give any effect on actylcholine.
3. Response of detrusor muscle to adrenergic agents
Administration of norepinephrine caused relaxation of muscle specimen (Fig. 4).

,.

100_o~• Ach• Atr + Achu Hexa + Ach• Physo + Ach

20o~L
9876Concentration of Ach [-log lOX]

105FIG.2. The effect of acetylcholine and other agents on detrusor muscle is demonstrated witha log dose-response curve. Ach: acetylcholine, Atr: atropine, Hexa: hexamethonium,
and Physo: physostigmine.

FIG. 3. A, response of detrusor
muscle strip to acetylcholine (Ach), 1 ,ug/ml.
Band C, activation ofbeta adrenergic receptors by norepinephrine(NE), 1 ,ug/ml and isoproterenol (ISO), 10,ug
1m! at detrusor muscle
strip. D, activation ofalpha adrenergic receptors by norepinephrine(NE), 100 mg/m! atbladder neck.

B.

c.

D.

o2(Min)3

40

A. KONDO~

0~100..·0c

080

u~

C
060

c..>

....
040>.

• NE
• PBZ • NE'iiic 20Q)-•c

PRO + NE
PRO + PBZ + N E

o01089of

567ConcentrationNE[- log lOx]

FIG.4. The effect of norepinephrine and its antagonists on detrusor muscle is shown with alog dose-response curve. NE: norepinephrine, PBZ: phenoxybenzamine, and PRO:
propranol.

Frequency and amplitude were the first to be affected, then followed by fall of muscle
tonus (Fig. 3B). While phenoxybenzamine in a concentration of I /lg/ml exerted littlechange, propranol of the same concentration exerted a strong inhibitory action and shifted
the curve to the right. Administration of both phenoxybenzamine and propranol resulted
in the same effect as with propranol alone.
Isoproterenol also inhibited muscle contraction in a concentration of I ng/ml (Fig. 5).
This inhibitory action was prevented by propranol alone and by both propranol andphenoxybenzamine, shifting the curve to the right. Blockade of alpha receptor, phenoxybenzamine slightly facilitated the action of isoproterenol.

4.

Response of bladder neck strip
Spontaneous rhythmic contraction was observed in Krebs Ringer solution.

~ 100g 80-...

.'0~:~40u•cco60c..>.... 40···0>.

en20cQ)

c0010150
PBZ+ ISOPRO + ISO
PRO + PBZ + ISO

9.~:~
8Concentration

7ofISO.0\"065[ - log lOX]

FIG.5. The effect of isoproterenol and its antagonists on detrusor muscle is demonstrated
with a log dose-response curve. ISO: isoproterenol, PBZ: phenoxybenzamine, andPRO: propranol.

TheRESPONSE OF URINARY BLADDER TO CHOLINERGIC AND ADRENERGIC AGENTS

41

excitatory response of specimen to acetylcholine was weak and irregular. The effect ofnorepinephrine and isoproterenol was excitatory (Fig. 3D), quite different from thatobserved in detrusor muscle. This action could be inhibited by phenoxybenzarnine but notby propranol, indicating the predominance of alpha adrenergic receptors in this portion.
DISCUSSION

Since excitatory action of detrusor muscle is solely mediated through parasympathetic
nerve, the acetylcholine derivative which possesses the least side effect on other organs
should be chosen for the hypotonic or atonic bladder dysfunction 7)8). Atropine derivatives
such as methantheline (Banthine)9) and propantheline (Pro-Banthine) have been successfully
used for the treatment of uninhibited and reflex type of neurogenic bladder dysfunction.
Physostigmine has a great affinity for cholinesterase, ten thousand times more than thatof acetylcholine, which, in turn, augumented the actylcholine action. Hexamethonium,
ganglion blockade, was of no effect at the post synapse in the detrusor muscle.
Figures 4 and 5 obviously demonstrated that inhibitory beta adrenergic receptors arepredominant but the excitatory alpha adrenergic receptors are very few in the detrusor
muscle. At the bladder neck, on the contrary, the alpha adrenergic receptors are abundantly
present (Fig. 3D). Naturally, one can not substitute alpha adrenergic stimulant for cholinergic drug. Distribution of alpha and beta receptors and cholinergic receptors in urinary
bladder can be schematically demonstrated as in Fig. 6.
What role do these cholinergic and adrenergic receptors play upon the function of thebladder from the clinical point of view?

Parasympathetic
Nerve

Sympathetic
Nerve

FIG. 6. The schematic presentation of cholinergic and adrenergic receptors found in detrusor
muscle and bladder neck in vitro.

42A. KONDOURINE ACCUMULATION PHASE: The intrinsic characteristic, which the bladder muscle
possesses, allows to accumulate urine without an appreciable increase in intravesical pres~sure 10 ). Besides, the detrusor muscle would be allowed to relax and its tonus to fall dueto the effect of beta receptors S). It is probable that the alpha receptors would close thebladder outlet tight and be involved in the mechanism of urinary continence.
MICTURITION PHASE: Contraction of detrusor muscle and resultant elevation of intravesical pressure are the most important factors to initiate the micturition. Subsequently, theopening of the inner urethral orifice and relaxation of voluntary muscle of the external
urethral sphincter are to be followed. Activation of cholinergic receptors via pelvic nerve
yields a strong contraction throughout the detrusor muscle, which would easily overcome
the antagonistic effect of beta receptors. The transformation of so-called flat base plate
into a funnel shape at bladder neck is achieved by the contraction of Bell's muscle, andinner and outer longitudinal detrusor muscles l l ). Since the burst of electric discharge isrecorded from hypogastric nerve before and during micturition I2 ), it is possible that thealpha adrenergic receptors would more or less take part in opening the inner urethral orifice
by increasing muscle tonicity. Recently Krane and Olsson l3 ) have reported the clinical trialof phenoxybenzamine, an alpha adrenergic blocking agent. The micturition disturbanceowing to bladder neck dysfunction was successfully treated by the oral administration ofthis agent in 52 paraplegics.
ACKNOWLEDGEMENT

Many thanks are due to professors H. Mitsuya, J. G. Susset and D. M. Paton for theirsupport.
REFERENCES
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