Journal of Medicine and Medical Sciences Vol. 2(3) pp. 763 –767, March 2011
Available online@ http://www.interesjournals.org/JMMS
Copyright © 2011 International Research Journals
Full Length Research Paper
Effect of Excitatory Amino acid antagonist on
haloperidol induced Parkisonian Symptom in Rat
Peter I. Aziba and Ojo Ifedayo O.
Department of Pharmacology and faculty of Pharmacy, Olabisi Onabanjo University, Ago Iwoye, Nigeria.
Accepted 20 March, 2011
This study investigated the effect of ketamine, a selective non competitive antagonist of N-methyl-DAspartate (NMDA) on haloperidol (0.25 mg/kg) induced parkisonian symptoms in Wistar rats of both
sexes, average weight 150g. The aim of the study focused on the hypothesis that blockade of NMDA
receptor could have beneficial effect on haloperidol induced parkinsonian symptoms.Hypolocomotion
was induced intraperitoneally (i.p) with 0.25mg/kg haloperidol, a neuroleptic. The open field test was
used for assessment. Albino rats were divided into 5 groups of 6 animals each (group i, was not treated
(Control), group ( ii and iii) were treated with 0.25mg/kg and 0.5mg/kg, respectively, group( iv) received
2.5mg/kg ketamine and group (v) received 0.25mg/kg of haloperidol and 2.5mg/kg of ketamine
concomitantly. Results obtained showed ketamine in the concentration used significantly (P<0.01)
improved locomotor activity in haloperidol induced hypolocomotion, similarly exploration, (rearing and
rearing against the wall) was significantly unaltered, furthermore, the result seem to unveil the
protective effect of ketamine in the concentrations used in this work.
Keywords: Haloperidol, Ketamine, Locomotion, exploration Rats
INTRODUCTION
Excitatory neurotransmission in the brain and spinal cord
is mediated mainly by the acidic amino acid, L-glutamate.
Glutamate is the most abundant free amino acid in the
central nervous system (CNS) and is capable of inducing
an excitatory response in almost all CNS neurons.
Besides its role in excitatory neurotransmission,
glutamate is involved in the molecular mechanisms
underlying learning processes and synaptic plasticity.
Glutamate is stored in synaptic vesicles within nerve
terminals, from which it is released in a Ca++-dependent
manner upon depolarization. Glutamate's action is
+
terminated mainly by high-affinity, Na -dependent uptake
into neurons and glia. Once in the glial cell, glutamate is
converted to glutamine, which diffuses into nerve
*Corresponding author Email: peteraziba@yahoo.com; Tel:
+2348037234145.
terminals. Within the terminal, glutamine is converted to
glutamate (Stewart et al., 2002). Glutamate activates
several types of receptors that have been grouped into
two distinct classes: ionotropic and metabotropic
receptors. The family of ionotropic receptors includes
three subgroups: NMDA (N-methyl-D-aspartate), AMPA
(α-amino-3-hydroxy-5-methylisoxazole propionic acid),
and KA (kainic acid) receptors, according to their
preferred agonist.
Parkinson’s disease is primarily caused by
degeneration of dopaminergic neurons in the substantia
nigra pars compacta, which results in a dramatic
decrease in dopamine content in the corpus striatum.
This effect triggers a number of secondary neuronal
alterations which contribute to the complex mechanisms
underlying parkinsonian symptoms. Dopaminergic
terminals of the nigrostriatal pathway end on mediumsize spiny GABAergic neurons which form striopallidal
(“indirect”) and strionigral (“direct”) pathways (Gerfen,
764 J. Med. Med. Sci.
1992; Blandini et al., 2000). It has been postulated that a
loss of dopamine in the course of Parkinson’s disease
leads to functional imbalance between these two
efferents (the “indirect” pathway is disinhibited and the
“direct” one is inhibited) (Gerfen, 1992; Blandini et al.,
2000), and finally to over activation of glutamatergic
neurotransmission (Klockgether and Turski, 1989). In
accordance with this view, glutamate released in excess
from corticostriatal or thalamostriatal terminals activates
the striopallidal GABAergic pathway, which successively
leads to inhibition of pallidosubthalamic GABA-ergic
neurons,
activation
of
subthalamopallidal
and
subthalamonigral
glutamatergic
projections,
and
overstimulation of GABA-ergic basal ganglia outputs: the
nigro- and pallidothalamic pathways (Klockgether and
Turski, 1989; Gerfen, 1992; Blandini et al., 2000).
This degenerative process that characterizes PD
causes a functional rearrangement of basal ganglia
circuitry. Thereby resulting into the impairment of the
nigrostriatal pathway and increased activity of the basal
ganglia output nuclei, as a result of enhanced
glutamatergic drive from the subthalamic nucleus
Excessive stimulation of the NMDA receptor, because
of increased levels of glutamate or to decreased removal
from the synaptic cleft of the transmitter, results in direct
excitotoxicity which contributes to Parkinson symptoms.
MATERIAL AND METHOD
made of durable non-absorbent material. Open-field
experiments allow the evaluation of animal’s basal
activity and its evolution, in response to novelty or
anxiogenic environment,
and in response
to
pharmacological treatment, lesion or genetic modification.
Locomotor activity refers to the movement from one
location to another. In rodents, one of the most important
components of exploration, a prominent activity of the
rat’s repertoire of spontaneous activity, is locomotion.
Moreover, locomotor activity and exploration are involved
in many behavioural and physiological functions and are
influenced by many external factors, such as
environmental conditions (light, temperature, noise)
Animals and Experimental procedures
Albino rats of wistar strain grouped into (i-vi) of average
weight150g were used in this study. The group (i) was
used as a control which means no drug was administered
to the rats. Haloperidol 0.25mg/kg and 0.5mg/kg were
administered to the rat group (ii and iii) respectively.
Ketamine 2.5mg/kg was administered to group (iv).
Ketamine 2.5mg/kg and Haloperidol 0.25mg/kg were coadministered in group ( iv) experiments . The locomotor
activity of these animals were examined at hourly
intervals , for 5h using an open field test apparatus. The
open field activity tests are used to measure locomotor
activity in rodents and serves as good preliminary test to
determine motor deficits induced by the Haloperidol.
Drugs and Chemicals
Haloperidol (Hadol®) and Ketamine Hydrochloride
injection
USP.
were
obtained
from
Janssen
Pharmaceutical and Rotexmedica respectively.
Animals
Albino rats of the Wistar strain of (both sexes) were
purchased from an in-breed private colony, in Ibadan,
Oyo-State, Nigeria. The rats were housed in the
experimental animal house, in the Department of
Pharmacology, Faculty of pharmacy Olabisi Onabanjo
University, Sagamu Campus, Ogun State, Nigeria, under
controlled conditions with a 12 h light/12 h dark schedule
and fed with commercially available rat pelleted diet and
water ad libitum throughout the period of the experiment.
(ii) Open Field Apparatus: The open field apparatus
was constructed with plywood and measured 72 x 72cm
with 36cm walls. Lines were drawn on the floor with a
marker into sixteen 18x18cm squares. The arena was
Maintenace of animals
The open field was cleaned between each rat using 70%
ethyl alcohol to avoid odour cues. Rats were handled by
the base of their tails at all times. Rats were placed
randomly into one of the four corners of the open field
facing the centre and allowed to explore the apparatus for
5min. After 5min test, rat were returned to their cages
and the open field was cleaned between tests.
(iii) Measurements: The behavioural score measured in
this experiment includes:
• Line crossing: Frequency with which the rat crossed
one of the grid lines with all four paws
• Rearing: Frequency with which the rat stood on their
hind limb in the maze
• Rearing against a wall: Frequency with which the rat
stood on their hind limb against a wall of the open field.
Frequency of line crossing =
Numbers of grid lines
crossed within5min
(5x60) s
Aziba and Ifedayo 765
Table 1: The Mean Scores of the Line Crossing Frequency in Open Field Test for control and treatment groups of wistar rats.
Treatment
Control
Haloperidol
(0.25mg/kg)
Haloperidol
(0.5mg/kg)
Ketamine
(2.5mg/kg)
Haloperidol
(0.25mg/kg)+
ketamine
(2.5mg/kg)
1
0.113±0.001
0.006±0.001*
(94.7)
0.004±0.001*
a
(96.4)
0.068±0.001*
a
(39.8)
0.03±0.005**
(-400)b
Time of observation after administration (h)
2
3
4
0.113±0.001
0.113±000
0.113±000
0.003±0.001*
0.003±0.001*
0.006±0.001*
a
a
a
(97.3)
(97.3)
(94.7)
0.004±0.001*
0.006±0.001*
0.004±0.001*
a
a
a
(96.4)
(94.6)
(96.4)
0.060±0.005*
0.070±0.005*
0.100±0.006*
a
a
a
(46.9)
(38.1)
(11.5)
0.017±0.001**
0.017±0.001**
0.02±0.006**
(-466.6)b
(-466.6)b
(-233)b
5
0.113±0.000
0.040±0.006*
a
(64.6)
0.037±0.001*
a
(67.6)
0.123±0.001*
a
(-8.8)
0.053±0.001**
(*32.5)b
Result expressed as Mean ± Standard Error, values in parenthesis represent % change; (-) = increase, (+) = decrease, (a) % change in
relative to control group, (b) % change relative to haloperidol (0.25mg/kg) treated group.*p<0.001 when compare to control, **p<0.001
when compare to haloperidol (0.25mg/kg), n=6
Frequency of Rearing = Numbers of rearing within 5min
(5x60) s
Frequency of Rearing against the wall=
Rearing against the wall within 5min
Numbers of
(5x60) s
Statistical Analysis
The value obtained from the control and treatments
groups were recorded and compared statistically using
the statistical package for social sciences (SPSS).
RESULTS
The results of the study are shown in the tables below
(Tables 1-3).
DISCUSSION
The result reported in this study suggest a protective
effect of ketamine a selective non competitive antagonist
of NMDA receptor antagonist against haloperidol a
neuroleptic drug, however, ketamine may not produce a
selective hypoglutamate state, but more likely produce a
non selective multi- system neurochemical perturbation
via direct or indirect effects (Kapur and seemen, 2002) .
The overall alteration as seen in the behavioural score
of line crossing , rearing and rearing against the wall
frequencies in the above table when haloperidol treated
group was compared with the control ( group to which no
drug was administered). This is an indication of the
suitability of haloperidol as an agent to produce
hypolocomotion, a parkinsonian-like effect in wistar rats
(Ossowaka et al., 1995).
The frequency of line crossing, rearing and rearing
against the wall are usually used to express locomotor
activity, and other gait disturbances that have been
implicated with such drug as the neuroleptics,
benzodiazepines, opiates, and psychostimulants ( Eweka
et al and Om'Iniabohs et al., 2008). Development of
behavioural measurements of locomotor activity and
exploration was in part relevant in various rodent models
as an initial screen for pharmacological effects predictive
of therapeutic efficacy of a drug in humans. Indeed,
locomotion and exploration are mediated by
neurotransmitters affected by many drugs, such as
neuroleptics, benzodiazepines, opiates, and psychostimulants, and consequently are changed in response to
these drugs administration. Moreover, alterations of
locomotor activity and exploration can have important
consequences for paradigms that aim to study more
specific processes, such as learning, memory reward,
anxiety… Thus it is imperative to verify if a drug, lesion,
strain difference or genetic manipulation influences
general
motor
activity.
Furthermore,
locomotor
abnormalities are associated with several human
diseases such as Parkinson’s disease.The open field
apparatus result showed a significant (p< 0.001)
reduction in locomotor activity of haloperidol treated rats
compared with the negative control groups. This
decrease in locomotor activities has been reported to be
766 J. Med. Med. Sci.
Table 2: Mean Scores of the Rearing Frequency in Open Field Test for control and treatment groups of wistar rats.
Treatment
Control
Haloperidol
(0.25mg/kg)
Haloperidol
(0.5mg/kg)
Ketamine
(2.5mg/kg)
Haloperidol
(0.25mg/kg)+
ketamine
(2.5mg/kg)
1
0.013±0.001
0.000±0.000*
a
(100)
0.000±0.000*
a
(100)
0.010±0.001*
a
(2301)
0.000±0.000
(0)b
Time of observation after administration (hrs)
2
3
0.013±0.000
0.013±0.001
0.000±0.000*
0.000±0.000*
a
a
(100)
(100)
0.000±0.000*
0.000±0.000*
a
a
(100)
(100)
0.003±0.001*
0.007±0.001*
a
a
(76.9)
(46.2)
0.000±0.000
0.000±0.000
(0)b
(0)b
4
0.013±0.001
0.000±0.000*
a
(100)
0.000±0.000*
a
(100)
0.013±0.001
a
(0)
0.000±0.000
(0)b
5
0.013±0.001
0.000±0.000*
a
(100)
0.000±0.000*
a
(100)
0.01±0.001*
a
(23.1)
0.000±0.000
(0)b
Result expressed as Mean ± Standard Error, values in parenthesis represent % change; (-) = increase, (+) = decrease, (a) % change in
relative to control group, (b) % change relative to haloperidol (0.25mg/kg) treated group.*p<0.001 when compare to control, **p<0.001 when
compare to haloperidol (0.25mg/kg), n=6
Table 3: Mean Scores of the Frequency of Rearing Against the Wall in Open Field Test for control and treatment groups of wistar rats.
Treatment
Control
Haloperidol
(0.25mg/kg)
Haloperidol
(0.5mg/kg)
Ketamine
(2.5mg/kg)
Haloperidol
(0.25mg/kg)+
ketamine
(2.5mg/kg)
1
0.027±0.001
0.000±0.000*
(100)a
0.000±0.000*
(100)a
0.017±0.001*
(37.0)a
0.000±0.000
(0)b
Time of observation after administration (hrs)
2
3
0.027±0.001
0.027±0.001
0.000±0.000*
0.000±0.000
(100)a
(100)a
0.000±0.000*
0.000±0.000*
(100)a
(100)a
0.023±0.001*
0.013±0.001*
(14.8)a
(51.9)a
0.000±0.000
0.000±0.000
(0)b
(0)b
4
0.027±0.001
0.000±0.000*
(100)a
0.000±0.000*
(100)a
0.017±0.001*
(37.0)
0.000±0.000
(0)b
5
0.027±0.001
0.000±0.000*
(100)a
0.000±0.000*
(100)a
0.020±0.006
(25.9)a
0.000±0.000
(0)b
Result expressed as Mean ± Standard Error, values in parenthesis represent % change; (-) = increase, (+) = decrease, (a) % change in relative
to control group, (b) % change relative to haloperidol (0.25mg/kg) treated group.*p<0.001 when compare to control, **p<0.001 when compare to
haloperidol (0.25mg/kg). n=6
related to blockade of dopamine transmission at
nigrostratial pathway.
The result showed variation in the locomotor activity
and exploration among the control group, haloperidol
treated group (0.25mg/kg and 0.5mg/kg), ketamine
treated group (2.5mg/kg), group to which 0.25mg/kg
haloperidol and 2.5mg/kg ketamine are co-administered
in a time dependent manner.We have shown in this
studythat deficits in locomotor activity which are
associated with administration of dopamine antagonist
are improved where both drugs coadministered with an
NMDA antagonist ,this could the antipsychotic induced
extra pyramidal symptons.
Haloperidol (0.25mg/kg) treatment in the rat induced a
strong hypolocomotion state within 1 h of injection,
reaching a maximal plateau after 2 h and lasting for 4 h
subsequent
hours thereafter
showed improved
locomotor activity.
2.5mg/kg ketamine, a non competitive NMDA receptor
blocker,
when
co-administered
with
0.25mg/kg
haloperidol in wistar rats, showed a significant (p<0.001)
improvement in line crossing when compared with the
haloperidol treated group as seen in table 1. However
there was no significant improvement in rearing and
rearing against the wall (exploration) as shown in table 2
and table 3 respectively.
Aziba and Ifedayo 767
It is important to state that 2.5mg/kg Ketamine
administered alone does not significantly (p<0.001)
increase the locomotor activity of the wistar rats.
This experiment agreed to the hypothesis that both
nigrostriatal dopamine systems and corticostiatal
glutamate systems participate in the regulation of striatal
function (Fuxe et al., 1977, Fonnum et al., 1981) and
represent major afferents to the striatum. It is therefore
suggested
that
pharmacologic
manipulation
of
glutamatergic neurotransmission at the level of NMDA
implication of this study could involve the antipsychotic –
induced extrapyramidal symptoms not necessarily
Parkinson disease.
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