11School of Pharmaceutical Sciences, School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800 Penang, MalaysiaUniversiti Sains Malaysia, 11800 Penang, Malaysia

22Department of Pharmacology, Faculty of Medicine, Department of Pharmacology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia University of Malaya, 50603 Kuala Lumpur, Malaysia

33Department of Physiology, Aras Windle, University Department of Physiology, Aras Windle, University College Cork, College Road, Cork, IrelandCollege Cork, College Road, Cork, Ireland

INTERACTION OF SYMPATHETIC NERVOUS INTERACTION OF SYMPATHETIC NERVOUS SYSTEM AND RENIN ANGIOTENSIN SYSTEM: SYSTEM AND RENIN ANGIOTENSIN SYSTEM:

ROLE OF SYMPATHECTOMY IN RENAL ROLE OF SYMPATHECTOMY IN RENAL HAEMODYNAMIC OF RENAL FAILURE WITH HAEMODYNAMIC OF RENAL FAILURE WITH

HYPERTENSIONHYPERTENSION

B Fathihah1, AS Munavvar1, NA Abdullah 2, D Aidiahmad1, AH Khan1, HA Rathore1,

N Raisa1, MH NurJannah1, K Anand Swarup1, IM Salman1, MH Abdulla1 and EJ Johns3

Hypertension is considered as the most common presenting feature in renal diseases. Among the several factors known to be involved in the renal hypertension, the role of exaggerated sympathetic activity and a possible involvement of interaction between sympathetic nervous (SNS) and renin angiotensin (RAS) systems in the pathophysiology have not yet been fully elucidated.

Introduction

Introduction

Sympathetic overactivity triggering factor of hypertension

In hypertension increased spill over of sympathetic neurotransmitter, namely nor- epinephrine from the heart and kidney

Introduction

Renal failureRenal insufficiency

Life-threatening disease

Acute or chronic progression leading to endstage renal disease (ESRD)

Accompanied by hypertensionit has been reported that afferent stimuli arising from the scared and diseased kidneys into the central nervous system may activate the sympathetic nervous system and contribute in the genesis of hypertension

Introduction Activation of SNS

leads to enhanced tubular sodium reabsorption, vasoconstriction of renal arterioles mainly through 1 and release of renin via 1 from the juxtaglomerular cells.

Activation of RASthrough the angiotensin II (Ang II) bind to angiotensin receptor type 1 (AT1)

induce vasoconstriction and increased tubular sodium reabsorption (direct or through aldosterone).

The predominant receptors in the kidney are 1-adrenoceptor subtypes, play a pivotal role in the mediation of sympathetic nervous system (SNS) response and AT1.

Introduction Interaction between both systems:

Adrenergic systemrelease of renin, which will increase angiotensin II through a cascade system (enzymes).

RASi) intrarenal (ANGII on AT1):

- Direct ganglionic adrenergic stimulation- Terminal presynaptic release of

noradrenaline (endogenous adrenergic

neurotransmitter)

ii) extrarenal- Act centrally on CNS centres that regulate

sympathetic systems outflow (area postrema and rostral ventrolateral medulla)

Introduction

Sympathectomy or destruction of sympathetic nervous systems (SNS) has been widely used in assessing the role of peripheral and central sympathetic nervous system in various physiological processes. As nearly all organ systems are innervated by the SNS, any such attempt of disrupting the noradrenergic nerves may cause global loss of sympathetic tone following chemical sympathectomy and provide animal model with impaired SNS activity. One current model for denervation is chemical sympathectomy by the use of the neurotoxin 6-hydroxydopamine.

Introduction

6-hydroxydopamine (6OHDA) is an isomer of noradrenaline which produced a destructive phenomenon of the terminal ground plexus of pheripheral sympathetic (noradrenergic) neurons, called “ chemical sympathectomy”.6OHDA has the potential to produce adrenergic receptor blockade or destruction, but only after administration of toxic doses of 6OHDA or after the sympathetic neurons have been completely abolished.In the periphery, destructive process by 6OHDA is reversible in that new sympathetic plexus are formed from the relatively intact preterminal processes

Objectives

To verify the concept that exaggerated SNS is involved in the pathophysiology of renal diseases related hypertension.To determine if there is any alterations in renal haemodynamics after sympathectomy in renal failure and in renal failure in combination with hypertension.To examine the interaction of renin-angiotensin (RAS) and sympathetic nervous (SNS) systems in renal haemodynamics of rats with renal failure (RF) in combined state of essential hypertension.

Methodology

AnimalSpontaneously hypertensive rat (SHR)

Adult, male 200 - 310g.

Group 1, 2: Non renal failure SHR (NRFSHR) with and without sympathectomy (n=6)

Group 3, 4: Renal failure SHR (RFSHR) with and without sympathectomy (n=6)

Schematic diagram of experimental groups

SHR

Control (NRFSHR) Renal failure (RFSHR)

Sympathectomized (NRFSHR6OHDA)

Renal failure +Sympathectomized

(RFSHR6OHDA)

Non renal failure Renal failure

Methodology

Sympathectomy of the animals6-OHDA (6-Hydroxydopamine, Sigma Chemicals, USA). The doses used were 50 mg kg-1 (day 1, days 5 and 8) and 100 mg kg-1 ( day 2). 6-OHDA was dissolved in 0.9% NaCl and 0.1% ascorbic acid (Sigma Chemicals, USA)

Experimental protocol

Acclimatization3 days

Day 0

Acute study

Day 2 Day 6 Day 10 Day 12

Day 46OHDA50mg/kg

Day 56OHDA

100mg/kg

Day 86OHDA50mg/kg

Day 116OHDA50mg/kg

Cisplatin administration

5mg/Kg i.p.

Acute study

•Tracheotomy•Right jugular vein•Carotid artery•Midline abdominal incision•Bladder•Iliac artery •Isolation of renal artery

Surgical set-up

Anaesthetized (sodium pentobarbitone, 60 mg/kg, i.p.)

Renal Vasoconstrictor responses

2 ml saline

Saline (6 ml/hr) + Sodium Pentobarbitone (12.5 mg/kg/hr)

Stabilization period

1 hour

RNS + bolus doses of agonists

Acute Study(Simplified)

Renal vasoconstrictor Renal vasoconstrictor responsesresponses

Treatment Frequency/Dose

Renal Nerve Stimulation (RNS)

1-10 Hz at 15V, 2 ms for 15 seconds

Noradrenaline 25, 50, 100 and 200 ng

Phenylephrine 0.25, 0.50, 1.0 and 2.0 g

Methoxamine 0.5, 1, 2, and 4 g

Angiotensin II 2.5, 5.0, 10 and 20 ng

Result

1 2 4 6 8 10

0

10

20

30

40

50

60

70

80

SHR Control

RfSHRControl

RfShr6OHDA

NRFSHR6OHDA

RNS (Hz)

% d

rop o

f R

BF

**

Figure 1: Vasoconstrictor responses following renal nerve stimulation (RNS) in SHR treated with and without renal failure in combination with 6OHDA. * indicates significant (p<0.05) changes between experimental groups (n=6)

Result

25 50 100 200

10

20

30

40

50

60

70

80

90

RfShrControl

RfShr6OHDA

NRFSHR6OHDA

normal SHR

NA (ng)

**

% d

rop o

f R

BF

Figure 2: Vasoconstrictor responses following NA administration in SHR treated with and without renal failure in combination with 6OHDA. * indicates significant (p<0.05) changes between experimental groups (n=6)

Result

.25 .50 1.00 2.000

10

20

30

40

50

60

70

80

90

100

shr control

RfShrControl

RfShr6OHDA

NRFSHR6OHDA

PE (ug)

**

% d

rop o

f R

BF

*

Figure 3: Vasoconstrictor responses following PE administration in SHR treated with and without renal failure in combination with 6OHDA. * indicates significant (p<0.05) changes between experimental groups (n=6)

Result

.50 1.00 2.00 4.00

0

10

20

30

40

50

60

70

80

90

shr control

RfShrControl

RfShr6OHDA

NRFSHR6OHDA

ME (ug)

*

% d

rop o

f R

BF

*

Figure 4: Vasoconstrictor responses following ME administration in SHR treated with and without renal failure in combination with 6OHDA. * indicates significant (p<0.05) changes between experimental groups (n=6)

Result

Figure 1: Vasoconstrictor responses following Ang II administration in SHR treated with and without renal failure in combination with 6OHDA. * indicates significant (p<0.05) changes between experimental groups (n=6)

2.50 5.00 10.00 20.00

0

10

20

30

40

50

60

70

shr control

RfShrControl

RfShr6OHDA

NRFSHR6OHDA

Ang II (ng)

% d

rop o

f R

BF

2.50 5.00 10.00 20.00

0

10

20

30

40

50

60

70

shr control

RfShrControl

RfShr6OHDA

NRFSHR6OHDA

Ang II (ng)

% d

rop o

f R

BF

***

Conclusion

These results reiterate the importance of SNS in the pathogenesis of hypertension.In renal failure rats, there is an exaggeration of sympathetic activity but with a lower input of 1A

Collectively it is suggested that there was a cross talk between SNS and RAS in perspective of renal failure with hypertension.

Thank you