131 www. ajbrui. net Full length Research Article Blood Pressure Reducing Effect of Bitter Kola

131

www.

ajbrui.

net

Full length Research Article

Blood Pressure Reducing Effect of Bitter Kola

(

Garcinia

kola

,

Heckel

)

in Wistar Rats

Naiho A.O. &

*

Ugwu A.C.

Department of Physiology, Delta State University & University of Benin

ABSTRACT:

In this study the effect

of

Garcinia kola

(GK)

on blood pressure was investigated.

Albino wistar

rats were

divided into three groups

.

Groups A rats had normal rat chow and water ad

-

libitum while groups B and C rats had

Garcinia

kola

diet of 10% w/w and 15% w/w respectively, their

blood pressures were monitored weekly for a period of 6 weeks.

Secondly, inbred wistar rats weighing on the average 185g were anaestezized with thiopentone sodium 100mg/kg body weight

(b.wt) intraperitoneally and prepared for injection and for blood pressu

re measurements on a recording device (Ugo Basile

Itlay).

S

ignificant reduction in blood pressure (P<0.05) was observed in

rats given

G

K

-

enriched diets

,

in the third week. During

preliminary investigations it was observed that 5.0mg/kg b.wt dose of extract

was lethal after 6 minutes, while 3.0mg/kg b.wt

of the extract was tolerated for upwards of four hours. Based on these findings, graded doses of the extract. (0.5

–

3.0mg/kg)

were used and these doses produced statistically significiant (P<0.05) fall in m

ean arterial pressure and also significant

(P<0.05) increase in heart rate. Cholinergic blockade produced no significant attenuation on the effect of extract. However

there was a significant (P<0.05) attenuation to extract effect after Histaminergic blocka

de. This study shows that

Garcinia kola

contains in its alcohol extract, a v

a

soactive substance that has a blood pressure reducing effect.

KEY WORDS:

blood pressure,

Garcinia kola

, Vasoactive, Heart rate

INTRODUCTION

1

These agents usually act through electrical or non

-

electrical pathways. It is known that agents such as

Hypertensive disorders are the m

ost common causes of

adult morbidity and mortality in Africa. Many workers

have discovered many vasoactive substances capable of

reducing blood pressure. These include studies on the

blood pressure lowering ability of some natural plant

materials, such as

extracts of garlic, seed of pawpaw

(carica papaya), calyx of hibiscus and petals of

hibiscus.

Vasoactivie agents are considered to be any

physiologically occurring or exogenously administered

hormonal substance that alters the activity of vascular

smooth

muscle i.e. that cause its contraction, relaxation,

or both. (Bohr et al 1979).

1

Address for correspondence (

acugwu@yahoo.com

)

acetylcholine, alters membrane permeability and hence

change the net

diffusion potential, hyperpolarizing the

membrane and bringing about relaxation of vascular

smooth muscles (Nakajima and Hom 1967).

Cholingergic agents, also alters the frequency and other

characteristics of the action potential and these

alterations cause

changes in the mechanical

performance of the portal vein (Von Loh, 1971). The

cyclic AMP pathway is another process by which some

vasodilators bring about relaxation of vascular smooth

muscle supportive of this mechanism and this is

because the fact that

cyclic AMP itself, causes

vasodilatation. Anderson (1992) has presented

extensive evidence that suggest cyclic AMP stimulates

an energy requiring Ca

2+

binding mechanism that leads

to a decreased concentration of sarcoplasmic calcium,

and hence relaxation.

G

arcinia kola, known as

“false” kola, belongs to

the order of guterferae and contains pharmacologicall