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Ethnobotanical Leaflets 14: 108- 2010. Central
Nervous System Depressant Properties of Treculia africana Decne A. O.
Aderibigbe1*, 1Department of Pharmacology and
Toxicology, Faculty of Pharmacy, Bayelsa, 2Department of Pharmacology,
Faculty of Pharmacy, 3Department of Pharmacognosy, Faculty of Pharmacy, Issued
February 1, 2010 Abstract The study was carried
out to investigate the central nervous system activity of Treculia africana. The central nervous
system depressant properties of Treculia africana were determined using: Novelty –Induced
Rearing and Grooming, Locomotor activity, Ketamine-induced sleeping time and effect on rectal body
temperature. The crude extract produced decrease in rearing, grooming and locomotor activity. It also potentiated ketamine-induced sleeping time and produced hypothermic
effect in mice. The crude extract possessed sedative effect, which may be
through increase in the activity of GABA in the brain. Key
words: Treculia africana, Ketamine-induced
sleeping time, Hypothermia, Central depressant effect. Introduction Treculia africana
Decne is native to many parts of West and Tropical
Africa. It is a breadfruit species. The bread fruit is of the family Moraceae and is one of the four members of the genera Treculia. It
grows commonly in evergreen and deciduous forests, often by streams but may
sometimes be planted as in Nigeria where it is common in the Western and
Eastern states (Hatchinson, 1973). It is one of the
most cherished economic plants that have both food and medicinal value. The crude extract
from different parts of the plant has been used in the folk medicine in the
treatment of various ailments. It is used either singly or in combination
with other herbs in the traditional herbal preparation by different
communities to treat various diseases. Decoction from different parts of the
plant is used as an anti-inflammatory agent and in the treatment of whooping
cough. The crushed leaves juice is applied on the tongue as a treatment for
thrush in children; the latex is applied as an antibacterial agent in
eardrops and as chewing stick. The sap of the male tree is applied locally on
cotton wool to carious tooth for its removal. The root, immature leaves and
bark are part of the concoction used locally for treating cough,
constipation, edema and rheumatism. A decoction of the root has been used in
Nigeria as a vermifuge and also in Ghana as a tonic
after illness by villagers. The pulps of Treculia africana
have been shown to be useful in the treatment of ascaris
and guinea worm (Ogunleye and Parakoyi,
1992). Proximate chemical composition of the fruit and seed showed that it
contains high level of carbohydrate and protein but is relatively low in fat,
ash and fibre (Osabor et al., 2009). Treculia africana leaves decoctions were
reportedly used in Trinidad and Bahamas to lower blood pressure. The water
soluble and ethylacetate fractions have been shown
to reduce the fasting blood sugar levels (Oyelola et al., 2007). Three compounds were
isolated from Treculia africana and
they are identified as Phyllocoumarin; Catechin and 6,9 – dihydroxy-megastigmane
-3 –one with antibacterial and antifungal properties (Ogbonnia
et al., 2008). The plant was
claimed to be useful in the treatment of mental illness by local herbalists,
this led to the present investigation.
Material
and Methods Plant
Materials Treculia africana
stem barks were collected from the campus of the Obafemi
Awolowo University (OAU) in March, 2009. It was
scientifically identified at the Department of Pharmacognosy,
Faculty of Pharmacy, and the Department of Botany, OAU, Ile- Ife, Nigeria. It
was later deposited at the Herbarium, Department of Botany, OAU where it was
assigned Herbarium Specimen No. UHI 4225A. Preparation
of Plant Materials The plant was air
dried for two weeks at room temperature. The dried stem bark was pulverized
and 200g of the powder was extracted with 0.6 liters of 70% ethanol for 48
hr. The marc was re-extracted twice and the combined extract was concentrated
in vacuo at
a temperature of 40oC to yield 15 g crude extract. The crude
extract was prepared by dissolution in normal saline. Animals The animals used for
this experiment were mice of both sexes. All the animals were bred and housed
in well lit and aerated room in the Animal House, College of Medicine, Niger
Delta University, Amassoma. They were maintained
under natural daylight/night condition. All animals had free access to
drinking water and standard commercial diet (Guinea feeds brand, Bendel Feeds Nigeria). All experiment was carried out in
accordance with NIH guide for the care and use of laboratory animals. Drugs Ketamine
(Rotexmedica, Germany), Diazepam (Roche, Basel,
Switzerland). Methodology Toxicity
Test The method described by Lorke (1983) was used to determine the LD50,
which is the index of acute toxicity. Albino mice (20-25 g) of either sex
were used. This method involved an initial dose finding procedure, in which
the animals were divided into three groups of three animals per group. Doses
of 10,100 and 1000 mg/kg were administered intraperitonealy
(i.p.), one dose for each group. The treated
animals were monitored for 24 h mortality and general behaviour.
From the results of the above step, four different doses of (140, 225, 370
and 600 mg/kg) were chosen and administered i.p.
respectively to four groups of one mouse per group. The treated animals were
monitored for 24 h. The LD50 was then calculated as the geometric
mean of the lowest dose showing death and the highest dose showing no death. BEHAVIOURAL
ASSAYS Novelty-Induced Rearing and Grooming The behavioural
profiles of albino mice under the influence of the crude extract were
assessed singly in a plexiglas cage measuring (45
cm x 25 cm x 25 cm) containing wood shavings. The animals were divided into six
groups (n=5-7). Group one was given normal saline (0.2 ml/20 g, i.p.), while the remaining four groups (2-5) were given
crude extract (12.5-100 mg/kg, i.p.). Thirty minutes after a single i.p. injection of extract and control, Behavioural measurements were carried by placing the
animal directly from home cage into an opaque plexiglas
observation cage with only one side transparent for observation. Each animal
was used only once, with the sawdust bedding changed after each assessment to
remove olfactory cue from previous animal to the other. The time of the
experiment was kept constant (9.00 am -1.00 pm) daily to avoid changes in
biological rhythm. The behavioural component
employed in this observational analysis were rearing and grooming (Ajayi and Ukponmwan, 1994: Onigbogi et al.,
2000). Diazepam (2 mg/kg, i.p.) group (6) served as
reference drug. The frequency of episodic
rearing was quantified by using a manual counter and a stop watch. The total
frequency was summed up for each animal and totaled for the 30 min of
observation time. Rearing was taken as the number of times the mouse was
standing on its hind limb or with its forelimbs against the wall of the
observation cage or in the free air (Ajayi and Ukponmwan, 1994). Grooming was taken as the number of
body cleaning with mouth and face washing with forelimbs. Locomotor Activity Motor activity was
measured in an open field apparatus consisting a white plexiglas
box (28 cm x 28 cm x 25 cm) with a painted black grid dividing the floor into
16 (7 x 7 cm) equal squares. The animals were divided into six groups
(n=5-7). Group one was given normal saline (0.2 ml/20 g, i.p.),
while the remaining four groups (2-5) were given crude extract (12.5-100
mg/kg, i.p.). Thirty minutes after a single i.p. injection of extract and control, the animals were
placed singly in one of the corners of the box, the number of squares crossed
with all four paws was counted for 5 min (Brocco et al., 2002). The cages were cleaned
with seventy percent (70%) ethanol at intervals when the animal is removed (Haque et al.,
2001). Diazepam (2 mg/kg, i.p.) group (6) served as
reference drug. Ketamine - Induced Sleeping Time The effect of crude
extract on ketamine-induced sleeping time was
measured as described by Erden et al., 2001. The
mice were divided into five groups (n=5-7). The first group served as control
and was given normal saline (0.2ml/20 g, i.p.)
group (1), while groups (2-4) were given different doses of the extract
(50-200 mg/kg, i.p.). This was followed 30 min
later by i.p. administration of Ketamine
(100 mg/kg). The sleep latency and sleeping time were recorded. The sleep
latency was measured as time in minute after treatment with ketamine and the loss of righting reflex. While the time
in minute between losses and regaining of righting reflex was taken as
sleeping time (Erden et al., 2001). Diazepam (2 mg/kg, i.p.)
group (5) served as reference drug. Monitoring
of Body Temperature The recording of the body
temperature was carried out using a thermoprobe.
The effect of crude extract on the body temperatures was performed in five
groups of male mice (n=5-7). Groups one was given normal saline (0.2 ml/20 g,
i.p.), while groups (2-4) were given different
doses of the extract (50-200 mg/kg, i.p.). The
probe of the thermometer was inserted 1.5 cm into the rectum. The temperature
of the animals was recorded immediately before the test and 30, 60, 90, 120
and 180 min after the administration of control and extract. The pre-drug
recording served as the reference point for the determination of temperature
changes (Parimaladevi et al., 2003). Diazepam (2 mg/kg, i.p.)
group (5) served as reference drug. Statistical
Analysis Results are expressed
as mean ± S.E.M. The significance of different between groups were analysed using one way analysis of variance (ANOVA),
followed by post hoc analysis using the Student- Newman-keuls
test. Results
and Discussion Acute
toxicity: The LD50 of the crude extract of Treculia africana
was found to be 450 mg/kg i.p. Effect
of crude extract of Treculia africana on
novelty induced rearing and grooming The administration of
crude extract of Treculia africana
(12.5-100 mg/kg, i.p.) reduced novelty induced
rearing and grooming in mice. A significant [F (5, 25) = 47.8, P < 0.001]
reduction in the frequency of rearing episodes and a significant [F (5, 25) =
55.0, P < 0.001] reduction in grooming was observed dose dependently in
mice when compared to normal saline. Maximal inhibition of novelty induced
rearing and grooming was observed at 100 mg/kg (Table 1). Table
1: Effect of crude extract of Treculia africana on novelty induced rearing, grooming and locomotor activity in mice.
NIR: Novelty-Induced Rearing; NIG:
Novelty-Induced Groming; LA: Locomotor
activity. *indicate significant
difference from control. P < 0.05. The results are expressed as mean ±
S.E.M, (n = 5 – 7). One way ANOVA revealed that there is significant
difference between various treatment groups. Diazepam was used as standard
reference drug. Effect
of crude extract of Treculia africana on
locomotor activity The
administration of crude extract of Treculia africana (12.5 – 100 mg/kg, i.p.)
showed a significant reduction [F (5, 25) = 24.01, P < 0.001] in the locomotor activity of mice when compared to normal saline
(Table 1). Effect
of the crude extract of Treculia africana on ketamine –
induced sleeping time and sleep latency in mice The
administration of crude extract of Treculia africana (50 – 200 mg/kg, i.p.)
produced a significant [F (4, 20) = 140.5, P < 0.001] and moderate dose
dependent prolongation of sleeping time in mice when compared to normal
saline (Table 2). The crude extract also produced a significant [F (4, 20) =
52.0, P < 0.001] reduction in sleep latency when compared to normal saline
(Table 2). Table 2: Effect of the crude
extract of Treculia africana on
ketamine – induced sleeping time and sleep latency
in mice.
The results are
expressed as mean ± S.E.M, (n = 5 – 7). *indicate
significant difference from control. P < 0.05 . One way ANOVA revealed that there is
significant difference between various treatment groups. Diazepam was used as
standard reference drug. Effect
of the crude extract of Treculia africana on rectal body temperature in mice The administration of
crude extracts of Treculia africana
(50 – 200 mg/kg, i.p.) reduced rectal body
temperature dose dependently in mice. The reduction was significant [F (4,
20) = 24.44, P < 0.001] when compared to normal saline (Table 3). Table
3: Effect of the crude extract of Treculia africana on
rectal body temperature in mice
The results are expressed as mean ±
S.E.M, (n = 5 – 7). *indicate significant difference from
control. P < 0.05. One way ANOVA
revealed that there is significant difference between various treatment
groups. Diazepam was used as standard reference drug. The study established the
acute toxicity of the crude extract of Treculia africana by the determination of LD50.
Acute toxicity test was carried out in order to determine the dose of the
crude extract that will be administered to the mice. LD50 is the
dose at which mortality occur in 50% population of the experimental animals.
The higher the value of the LD50 for a substance, the relatively
safe the substance is assumed to be. The value obtained is not toxic to the
animal. The crude extract of Treculia africana
was examined for novelty - induced rearing (NIR) in mice. NIR is a behaviour of rodents in novel environments. The behaviour is employed by rodents as one of the survival
strategies in assessing the environment for food, protection and possibly
escapes (Blanchard et al., 2001).
Measurement of the frequency of rearing in rodents and the modification can
therefore be employed in assessing the crude extracts for both sedative
property and central nervous system stimulation (Vogel, 2002). Rearing has
been described as the vertical locomotion activity when the animal stands on
its hind leg while raising up its forearm in the air or placed on the wall of
the cage (Onigbogi et al., 2000). Drugs that stimulate the CNS increase rearing
behavior, while those that depress the CNS inhibit rearing behavior. In this
study, the crude extract inhibited NIR showing that it has sedative effect. The crude extract was
examined for novelty - induced grooming (NIG) in mice. Grooming is an
important behavioural component in animals and is
associated with de - arousal state of the central nervous system (CNS). De -
arousal indicates absence of stimulation. Drugs that have depressant effect
inhibit grooming behaviour. Grooming is described
in animals (rat or mice) as face or head washing with forearm or body
grooming with mouth (Ukponmwan et al., 1985). The crude extract reduced NIG this suggests that
the crude extract have depressant effect on the CNS. The
novelty - induced rearing and grooming behaviour
response is regulated by multiple neurotransmitter system; such transmitters
include gamma-aminobutyric acid (GABA),
cholinergic, adrenergic, opioid, serotonin,
glutamate and dopamine receptors (Walting, 1998).
The crude extract inhibit rearing and grooming behaviours
suggesting that it might be acting by blockade of dopamine, potentiation of GABA, inhibition of serotonin, inhibition
of cholinergic neurotransmission and inhibition of the stimulation of the
excitatory neurotransmitter in the CNS. (Jones et al., 1981; Strange, 1993). The crude extract
produced a reduction in locomotor activity. This
reduction in locomotor activity follows the pattern
obtained for NIR and NIG. The decrease of locomotor
activity further confirms the depressant activity of the crude extract.
Locomotion is mediated mainly through dopaminergic
pathway (Rang et al., 1999) but
other neurochemical pathways have been reported to
modulate locomotor activities in animals.
Generally, CNS depressants have inhibitory effects on locomotor
activities and other exploratory or inquisitiveness of animals (Haque et al.,
2001). A decrease in locomotor activity in rodents
is suggestive of a possible CNS – depressant activity (Cooper et al., 1996). Alteration of body
temperature can be interpreted as an index of alteration of various central
neurotransmitters acting on the receptor in the hypothalamus. Dopamine,
Acetylcholine, GABA and Opioid are some of the
receptors implicated in hypothalamic effect of drug in animal (Rang et al., 1999). Hypothermia is an
effect usually observed with benzodiazepine receptor agonist that produces
this effect at relatively low doses (Jackson and Nutt, 1990), hence diazepam
was used as positive control. The crude extract reduced normal rectal
temperature in mice when compared to control. The reduction in rectal
temperature of mice was highest at 30 min after administration of crude
extract and thereafter gradually returned to pretreatment temperature. The
hypothermia observed in this study suggests an implication of both central
and peripheral mechanisms. The effect may be due to the decreased levels of
metabolic heat production and or vasodilatation (N’gouemo
et al., 1996). Thus, the preoptic anterior hypothalamus is critical in the
neuronal network of thermoregulation (N’gouemo et al., 1996). The role of dopaminergic system in thermoregulation in mice has been
highlighted and it’s believed to act through D2 receptor sites.
Benzodiazepines cause hypothermia in animals even al low doses and they are
thought to act through benzodiazepine receptor (Jackson and Nutt, 1990). Ketamine
– induced sleeping time is an experiment normally carried out to determine
the effect of test agent on CNS depression resulting in sleep by ketamine injection. Two parameters are measured in this
experiment, latency of sleep and total sleeping time. The latency of sleep is
defined as the time in minute from injection time to loss of righting reflex
(unconsciousness) while total sleeping time is defined as the total time in
minute from loss of righting reflex (loss of consciousness) to regain of
righting reflex (recovery of consciousness) (Haque et al., 2001; Ayoka
et al., 2006). The crude extract
produced a significant reduction in sleep latency and an increase in total
sleeping time induced by ketamine in a dose
dependent manner when compared to control. This result suggests that the
crude extract possessed sedative activity. The
study concluded that the crude extract possessed central depressant
properties. The sedative effect may be due to increase in the activity of
GABA in the brain. It may also be due to the effect of the extract on the
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