Bladder PharmacologyBladder PharmacologyCampbell-WalshCampbell-Walsh

Ch. 56: 1948-1972Ch. 56: 1948-1972

Stephen Miller, DOStephen Miller, DO

Peripheral Peripheral PharmacologyPharmacology

Muscarinic Muscarinic

4 different receptor subtypes based 4 different receptor subtypes based on Pharmacology (M1-M5)on Pharmacology (M1-M5)

Human Bladder Human Bladder – M1M1– M2 (Predominate)M2 (Predominate)– M3:M3:

Mediate cholinergic contractionsMediate cholinergic contractions

Key roles in:Key roles in:– Salivary secretionSalivary secretion– Pupillary constrictionPupillary constriction– Digestive tractDigestive tract

MM33R ActionR Action

Acetylcholine Acetylcholine M M33R R IP IP33 hydrolysis (PLC) hydrolysis (PLC) Intracellular Intracellular CaCa2+2+ Release = Smooth Muscle Release = Smooth Muscle ContractionContraction

L- type CaL- type Ca2+2+ channels have also channels have also been indicated in Mbeen indicated in M33R mediated R mediated detrusor contractionsdetrusor contractions

MM22RR

Coactivation could enhance Coactivation could enhance response to M3:response to M3:

1.1. Inhibition of adenylate cyclase = Inhibition of adenylate cyclase = suppressing sympathetic mediated suppressing sympathetic mediated depression of detrusordepression of detrusor

2.2. Inactivation of K+ channelsInactivation of K+ channels

3.3. Activation of nonspecific cation Activation of nonspecific cation channelschannels

Prejunctional Muscarinic Prejunctional Muscarinic ReceptorsReceptors

M1R facilitate Acetylcholine releaseM1R facilitate Acetylcholine release M2-M4R inhibit releaseM2-M4R inhibit release

Purinergic MechanismsPurinergic Mechanisms Parasympathetic stimulationParasympathetic stimulation ATP acts on 2 ReceptorsATP acts on 2 Receptors

– P2X (ion channel) with 7 subtypesP2X (ion channel) with 7 subtypes– P2Y (G-Protein coupled receptor) with eight subtypesP2Y (G-Protein coupled receptor) with eight subtypes

May play a role in Pathological conditionsMay play a role in Pathological conditions– Unstable bladdersUnstable bladders– BOOBOO– Increased amount of P2X1R in obstructed bladdersIncreased amount of P2X1R in obstructed bladders– P2X3R in small diameter afferent neurons of the DRG P2X3R in small diameter afferent neurons of the DRG

are also found in the wall of bladder and ureterare also found in the wall of bladder and ureter Mechanosensory and Nociceptive signalingMechanosensory and Nociceptive signaling

Adrenergic MechanismsAdrenergic Mechanisms Isoproterenol, TerbutilineIsoproterenol, Terbutiline ββ- Adrenergic- Adrenergic

– ββ 22 and and ββ 33 Receptors results in direct relaxation Receptors results in direct relaxation of detrusor smooth muscleof detrusor smooth muscle

3 main receptor3 main receptor Mediated through stimulation of Adenylate Mediated through stimulation of Adenylate

cyclase and accumulation of cyclic AMPcyclase and accumulation of cyclic AMP PDE inhibitors?PDE inhibitors?

– Selective inhibition of bladder PDE Selective inhibition of bladder PDE Increase Increase cAMPcAMP Relax detrusor and/or enhance the sensitivity/efficacy Relax detrusor and/or enhance the sensitivity/efficacy

of of adrenergic agonists adrenergic agonists

– Bladder Isoform of PDE?Bladder Isoform of PDE?

-Adrenergic-Adrenergic Ephedrine, Phenylpropanolamine, Midodrine, Ephedrine, Phenylpropanolamine, Midodrine,

PsuedoephedrinePsuedoephedrine

Bladder: (Not prominate in nml bladder)Bladder: (Not prominate in nml bladder) -adrenergic density is increased in pathological -adrenergic density is increased in pathological

conditionsconditions– NE induced responses convert from relaxation to NE induced responses convert from relaxation to

contractioncontraction 1dR subtype1dR subtype

Urethra:Urethra: Promote urine storage by increasing Urethral Promote urine storage by increasing Urethral

resistanceresistance– Hypogastic nerve stimulation and Hypogastic nerve stimulation and -adrenergic agonists -adrenergic agonists

produce a rise in intraurethral pressure produce a rise in intraurethral pressure – blocked by blocked by 1- adrenergic antagonists1- adrenergic antagonists 1a major subtype in Urethra/Prostate1a major subtype in Urethra/Prostate

Nitric OxideNitric Oxide Major inhibitory transmitter mediating Major inhibitory transmitter mediating

relaxation of the urethral smooth muscle relaxation of the urethral smooth muscle during micturationduring micturation

Involved in controlling bladder afferent Involved in controlling bladder afferent nerve activitynerve activity

Increase production of intracellular cGMP Increase production of intracellular cGMP = Smooth muscle relaxation= Smooth muscle relaxation– Inactivated by PDE’sInactivated by PDE’s– Role for PDE-inhibitors?Role for PDE-inhibitors?

Afferent NeuropeptidesAfferent NeuropeptidesSubstance PSubstance PNeurokinin ANeurokinin ACalcitonin gene- related peptide (CGRP) Calcitonin gene- related peptide (CGRP) Vasoactive Intestinal polypeptide (VIP)Vasoactive Intestinal polypeptide (VIP)Pituitary adenylate cyclase-activating peptide (PACAP)Pituitary adenylate cyclase-activating peptide (PACAP)EnkephalinsEnkephalins

Contained in capsaicin-sensitive, C-Fiber Contained in capsaicin-sensitive, C-Fiber bladder afferentsbladder afferents– Released in bladder by noxious stimulation Released in bladder by noxious stimulation – Inflammatory response Inflammatory response plasma extrav., plasma extrav.,

vasodilation, and alter bladder smooth muscle vasodilation, and alter bladder smooth muscle activityactivity

– transmitters at afferent terminals of the spinal transmitters at afferent terminals of the spinal cordcord

Receptors of TachykininsReceptors of Tachykinins– NK1R NK1R blood vessels to induce plasma extrav. blood vessels to induce plasma extrav.– NK2R NK2R bladder contractions bladder contractions– NK2R NK2R increase excitability during bladder filling increase excitability during bladder filling

or inflammationor inflammation

ProstanoidsProstanoids Prostaglandins, ThromboxaneProstaglandins, Thromboxane Manufactured throughout the lower urinary Manufactured throughout the lower urinary

tracttract Bladder Mucosa Contains:Bladder Mucosa Contains:

– PGI2, PGE2, PGE2a, Thromboxane APGI2, PGE2, PGE2a, Thromboxane A– PGF2PGF2, PGE, PGE2 = Contraction, PGE, PGE2 = Contraction

Mediated by specific receptors on cell Mediated by specific receptors on cell membranesmembranes– DP, EP, FP, IP, and TPDP, EP, FP, IP, and TP

Slow onset of actionSlow onset of action– Modulatory roleModulatory role– Affect neural release of transmitters or inhibit Affect neural release of transmitters or inhibit

acetylcholinesterase activityacetylcholinesterase activity

EndothelinsEndothelins 21 amino acid peptides produced in 21 amino acid peptides produced in

endothelial cellsendothelial cells ET-1 (ET-2, ET-3)ET-1 (ET-2, ET-3)

– Control of bladder smooth muscle toneControl of bladder smooth muscle tone– Regulation of local blood flowRegulation of local blood flow– Bladder wall remodeling in pathological conditionsBladder wall remodeling in pathological conditions

involved in detrusor hyperplasia and involved in detrusor hyperplasia and overactivity seen in pts with BOO resulting overactivity seen in pts with BOO resulting from BPH from BPH

Receptors: ETA , ETBReceptors: ETA , ETB Also have a role in nociceptive mech. in Also have a role in nociceptive mech. in

peripheral and Central Nervous Systemperipheral and Central Nervous System– Peripheral = induce detrusor activityPeripheral = induce detrusor activity– Spinal Cord = inhibit micturition through Opioid’sSpinal Cord = inhibit micturition through Opioid’s

Parathyroid Hormone Related Parathyroid Hormone Related PeptidePeptide

Manufactured by bladder smooth Manufactured by bladder smooth musclemuscle

Detrusor relaxationDetrusor relaxation

Sex SteroidsSex Steroids Do not directly affect bladder Do not directly affect bladder

contractility, but modulate receptors contractility, but modulate receptors and influence growth of bladder and influence growth of bladder tissuestissues

Estrogen: Effect on urinary continence Estrogen: Effect on urinary continence in females probably reflects multiple in females probably reflects multiple actions on adrenergic receptors, actions on adrenergic receptors, vasculature, and urethral morphologyvasculature, and urethral morphology– Increasing adrenergic receptorsIncreasing adrenergic receptors– NOSNOS

Progesterone: increases electrical and Progesterone: increases electrical and cholinergic contractions of bladdercholinergic contractions of bladder

Transducer function of Transducer function of UrotheliumUrothelium

Urothelial cells display Urothelial cells display properties of nociceptors and properties of nociceptors and mechanoreceptorsmechanoreceptors– Release NO, ATP, Acetylcholine, Release NO, ATP, Acetylcholine,

Substance P, ProstaglandinsSubstance P, Prostaglandins local chemical/mechanical stimuli local chemical/mechanical stimuli

chemical signals to bladder chemical signals to bladder afferentsafferents CNS CNS

Serotonin (5-HT)Serotonin (5-HT)

Neuroendocrine cells along urethra Neuroendocrine cells along urethra and prostateand prostate

Contraction in concentration Contraction in concentration dependent mannerdependent manner

C-Fiber PharmacotherapyC-Fiber Pharmacotherapy Unmyelinated C-fibers are normally silentUnmyelinated C-fibers are normally silent

– Activated by noxious stimuliActivated by noxious stimuli– Irritated state they become responsive to low Irritated state they become responsive to low

pressure bladder distentionpressure bladder distention Capsaicin and Resiniferatoxin (RTX)Capsaicin and Resiniferatoxin (RTX)

– Vanilloids that stimulate and desensitize Vanilloids that stimulate and desensitize C fibers to produce pain and release C fibers to produce pain and release neuropeptidesneuropeptides

TRPV1 (transient receptor potential)TRPV1 (transient receptor potential) Spinal cord, DRG, bladder, Urethra, Colon Spinal cord, DRG, bladder, Urethra, Colon Activated Activated calcium/Na influx calcium/Na influx afferent terminals afferent terminals

CNSCNS Capsaicin selectively excites and Capsaicin selectively excites and

subsequently desensitizes C-fiberssubsequently desensitizes C-fibers RTX causes desensitization without prior RTX causes desensitization without prior

excitationexcitation

Normal ConditionsNormal Conditions

Pathologic ConditionsPathologic Conditions

Botulinum ToxinBotulinum Toxin Inhibit acetylcholine release at the presynaptic Inhibit acetylcholine release at the presynaptic

cholinergic nerve terminal = Inhibiting striated cholinergic nerve terminal = Inhibiting striated and smooth muscle contractionsand smooth muscle contractions

Also shown to inhibit afferent nerve activityAlso shown to inhibit afferent nerve activity 4 steps required for Paralysis4 steps required for Paralysis

1.1. Toxin heavy chain Toxin heavy chain Nerve terminal receptor(?) Nerve terminal receptor(?)2.2. Internalization of toxin into nerve terminalInternalization of toxin into nerve terminal3.3. Translocation of light chain into the cytosolTranslocation of light chain into the cytosol4.4. Inhibition of neurotransmitter releaseInhibition of neurotransmitter release

Urological uses (BTX-A)Urological uses (BTX-A) Spinal cord injury suffering from detrusor-external Spinal cord injury suffering from detrusor-external

sphincter dyssynergia and detrusor overactivitysphincter dyssynergia and detrusor overactivity Pelvic floor spasticityPelvic floor spasticity BPHBPH

Actions of Drugs on Smooth Actions of Drugs on Smooth MuscleMuscle

Calcium Channel BlockersCalcium Channel Blockers Potassium Channel OpenersPotassium Channel Openers TCATCA

Calcium Channel BlockersCalcium Channel Blockers Diltiazem, VerapamilDiltiazem, Verapamil Spontaneous and evoked contractileSpontaneous and evoked contractile

properties are mediated by membrane properties are mediated by membrane depol. And movement of calcium into the depol. And movement of calcium into the smooth muscle cell through L-type Ca smooth muscle cell through L-type Ca channelschannels

Less effective in suppressing nerve-Less effective in suppressing nerve-mediated contractionsmediated contractions– Dependent on both Extracellular Ca and Dependent on both Extracellular Ca and

Intracellular CalciumIntracellular Calcium Develop a selective Ca channel blocking Develop a selective Ca channel blocking

agent to eliminate spontaneous contractions agent to eliminate spontaneous contractions without effecting micturition contractions?without effecting micturition contractions?

K channel OpenersK channel Openers

Cromakalim, PinacidilCromakalim, Pinacidil Move K+ out of cell Move K+ out of cell membrane membrane

hyperpolarization = reduction in hyperpolarization = reduction in spontaneous contractile activityspontaneous contractile activity

3 K channels identified3 K channels identified– Katp, SKCa, BKCaKatp, SKCa, BKCa

Intravesicular instillation of bladder Intravesicular instillation of bladder selective Katp = reduced detrusor selective Katp = reduced detrusor activity in rats with BOOactivity in rats with BOO

TCATCA

Imipramine, AmitriptylineImipramine, Amitriptyline– Antimuscarinic activityAntimuscarinic activity– Inhibition of Ca translocationInhibition of Ca translocation– Direct smooth muscle relaxantDirect smooth muscle relaxant

Spinal Ascending/Descending Spinal Ascending/Descending PathsPaths

GlutamatergicGlutamatergic Inhibitory Amino AcidsInhibitory Amino Acids Adrenergic Adrenergic SerotonergicSerotonergic OpioidOpioid PurinergicPurinergic

GlutamatergicGlutamatergic

Glutamate Glutamate – Bladder ContractionBladder Contraction– Excitatory transmitter in afferent limb of Excitatory transmitter in afferent limb of

micturation reflexmicturation reflex Suppressed by NMDA receptor Suppressed by NMDA receptor

antagonistsantagonists

Inhibitory Amino AcidsInhibitory Amino Acids

Intrathecal injection of GABAa or Intrathecal injection of GABAa or GABAb agonists increases bladder GABAb agonists increases bladder capacity and decreases voiding capacity and decreases voiding pressures pressures (rats)(rats)

BaclofenBaclofen Glycine levels low in rats with chronic Glycine levels low in rats with chronic

spinal cord injuriesspinal cord injuries– Increasing dietary stores of glycine can Increasing dietary stores of glycine can

restore bladder functionrestore bladder function

AdrenergicAdrenergic

adrenoceptors can mediate adrenoceptors can mediate excitatory and inhibitory influences excitatory and inhibitory influences on the lower urinary tracton the lower urinary tract

Efferent and Afferent limbs of the Efferent and Afferent limbs of the Micturition reflex receive excitatory Micturition reflex receive excitatory and inhibitory input, respectively and inhibitory input, respectively from spinal noradrenergic systemsfrom spinal noradrenergic systems

SerotonergicSerotonergic

Raphe nucleus of the caudal brainstem Raphe nucleus of the caudal brainstem autonomic and sphincter motor nuclei in autonomic and sphincter motor nuclei in the lumbosacral spinal cordthe lumbosacral spinal cord

InhibitoryInhibitory DuloxetineDuloxetine

– Combined Norepinephrine/5 HT reuptake Combined Norepinephrine/5 HT reuptake inhibitorinhibitor

– Increase neural activity to external urethral Increase neural activity to external urethral sphincter and decreases bladder activity sphincter and decreases bladder activity through the CNSthrough the CNS

OpioidsOpioids

Inhibitory action of reflex pathways Inhibitory action of reflex pathways in the spinal cordin the spinal cord

PurinergicPurinergic

Adenosine A1Adenosine A1 Inhibitory actionInhibitory action

PMC and Supraspinal PMC and Supraspinal Mech.Mech.

GlutamateGlutamate

Excitatory in Micturition pathwayExcitatory in Micturition pathway

CholinergicCholinergic

Excitatory/InhibitoryExcitatory/Inhibitory M1R and Protein Kinase CM1R and Protein Kinase C

GABAGABA

InhibitoryInhibitory Acts on GABAa/GABAb ReceptorsActs on GABAa/GABAb Receptors

DopaminergicDopaminergic

Inhibitory Reflex Inhibitory Reflex – D1D1– D5D5– Substantia nigraSubstantia nigra

FacilitatoryFacilitatory– D2D2– D3D3– D4D4

OpioidsOpioids

InhibitoryInhibitory and and δδ Receptors Receptors

Mechanisms of Detrusor Mechanisms of Detrusor OveractivityOveractivity

Spinal Cord Injury/Neurogenic Spinal Cord Injury/Neurogenic Detrusor OveractivityDetrusor Overactivity

Damage above the Sacral level = detrusor Damage above the Sacral level = detrusor overactivityoveractivity– reorganization of synaptic connections in spinal reorganization of synaptic connections in spinal

cordcord– Alteration of bladder afferentsAlteration of bladder afferents

Nml Micturition by lightly myelinated ANml Micturition by lightly myelinated Aδδ afferentsafferents

Post injuryPost injury– Capsaicin-sensitive C- fiber mediated spinal Capsaicin-sensitive C- fiber mediated spinal

reflex = Detrusor overactivityreflex = Detrusor overactivity UMN: MS, PDUMN: MS, PD

– NGF (nerve growth factor) : Implicated as NGF (nerve growth factor) : Implicated as Chemical mediator of disease-induced changesChemical mediator of disease-induced changes

– NGF Antibodies?NGF Antibodies?

Bladder Outlet ObstructionBladder Outlet Obstruction Changes:Changes:

– Detrusor hypertrophyDetrusor hypertrophy– No change of myofilamentsNo change of myofilaments– Axonal degenerationAxonal degeneration– Decrease in percentage volume of MitochondriaDecrease in percentage volume of Mitochondria– Increase in sarcoplasmic reticulumIncrease in sarcoplasmic reticulum– Gap junctions are absentGap junctions are absent– Enlarged density of afferent and efferent nerve fibersEnlarged density of afferent and efferent nerve fibers

Unstable ContractionUnstable Contraction Obstruction-Induced detrusor overactivity with Obstruction-Induced detrusor overactivity with

irritative voiding symptoms has been attributed irritative voiding symptoms has been attributed to denervation supersensitivity.to denervation supersensitivity.

CNS alterationsCNS alterations – New spinal circuitsNew spinal circuits

NGFNGF– Increase precedes enlargement of bladder neurons and Increase precedes enlargement of bladder neurons and

development of urinary frequencydevelopment of urinary frequency

AgingAging

ContractilityContractility– αα – adrenergic stimulation increase and – adrenergic stimulation increase and

decrease in decrease in ββ – adrenergic inhibitory – adrenergic inhibitory responses?responses?

– Innervation and development of Gap Innervation and development of Gap Junctions?Junctions?

– Low energy production?Low energy production?

FutureFuture

PharmacogeneticsPharmacogenetics Tissue EngineeringTissue Engineering Gene TherapyGene Therapy