Indian Journal of Experimental Biology
Vol. 38, November 2000, pp. 1172-1174
Role of ATP sensitive potassium channel on 7 -hydroxy flavone induced
antinociception and possible association with changes in glycaemic status
P E Venkataramanan, S.Parvathavarthini & S Viswanathan
Institute of Pharmacology, Madras Medical College, Chennai 600 003 , Indi a
and
S Ramaswamy*
Department of Pharmacology, Jawaharlal Institute of Postgraduate, Medical Education and Research , Pondicherry 605 006, India
Received 3 March 2000; revised 6 July 2000
Opioid type of analgesics open ATP sensitive potassium channel at the cellular level to produce antinocicepti ve
response. These channels have also been show n to modulate insulin secretion by the pancreas. 7-hydroxy flavone, an
anti nociceptive agent shown to act through opioid pathways was investigated for its effect on glycaemic state and associated
algesic state. The involvement of ATP sensitive potassium channel in the action was examined by using glybenclamide. The
result reveal that 7-HF per se did not elicit any sign ificant change in the glycae mic state simultaneously eliciting
antinociceptive response as tested by aceti c acid induced abdominal constriction assay procedure. G!ibenclamide treatment
attenuated the ant inoc iceptive effect of 7-HF and while maintained its hypoglycaemic response. The present finding suggest
that 7-HF induces antinociception like morphin e, utili se ATP sensitive potassium channel at the cellular level and do not
suggest a cause-effect relationship between the changes in the glycaemic and algesic state. Possibly, insulin which is
controlled by ATP sensitive potassium channel at the cellular level might also modulate antinociccption exhib iting a causeeffect relationship between them.
The cause-effect relationship between changes in the
glycaemic and algesic state remains debatable. While
a few reports support such a relationship, most of
1
them oppose this contention - 3 • An earlier stud/
suggested that use of chemical diabetic mod els which
causes functional and structural changes in the
neuronal system4 may be the contributing factor for
these varied results.
At the cellular level, one of the important
mechanisms utili sed by opioid like antinociceptive
agents is ATP sensitive potassium channels. Earlier
studies established that opioid receptors in the central
nervous system elicit antinociception by opening ATP
senstttve potassium channel 5-7 . ATP senstttve
potassium channel opener pinnacidil has been shown
8
to potentiate morphine analgesia . It is noteworthy
that aradrenergic receptors mediated antinociception
which ts considered independent of opioid
mechanism also utilised these ATP sensitive
potassium channel at the cellular level to elicit
antinociception 9 . Additionally agents like prolactin
which has been shown to elicit opioid mediated
antinociception also utilises such mechanism 10 .
*Correspondent author
Interestingly ATP sensitive potassium channel has
been documented to modulate insulin release from the
9 11
~-isl ets of pancreas " . Considering these available[
literature, there appears to be a link between
antinociception, changes in the glycaemic state and
ATP sensitive potassium channel. The present study
investigated the cause-effect relationship between
changes in glycaemic state and algesic state using
physiological manoeuvres instead of chemical models
as suggested earlier. 7-hydroxy flavone (7-HF) was
used to elicit antinociception since it is almost non12
toxic, utilized opioid pathways sans adverse effects •
The possible role of A TP sensitive potassium
channels was also examined.
Healthy male Swiss albino mice (25-30 g) were
housed in polypropylene cages with free access to
food and water.
The antinociception was assayed using acetic acid
13
induced abdominal constriction assay procedure .
The number of abdominal constrictions for 15 mil"\
following intraperitoneal injection of 0.6% acetic acid
(10 ml/kg) was recorded. A significant reduction in
the number of abdominal constrictions when
compared with vehicle treated animals was
considered as antinociceptive response.
NOTES
The blood glucose was measured from a drop of
blood collected by cutting the tip of the tail of the
mouse using AMES glucometer with appropriate
glucostick. This was measured prior to any drug
exposure and just before acetic acid challenge
throughout the study. The results were expressed as
percentage considering the initial blood glucose level
of that animal as 100%.
Drug treatment -7-HF was used in the dose of
100 mg/kg;s.c. (as 1% suspension in carboxy methyl
cellulose) 60 min prior to acetic acid challenge.
Glibenclamide, an ATP sensitive potassium channel
blocker, was administered 10 min prior to acetic acid
challenge in vehicle treated animal or 50 min after 7HF administration.
Drugs used-7-HF (synthesized and gifted by
Research Organics, Chennai), glibenclamide (gift
from Dr.Reddy's Laboratory, Hyderabad) acetic acid
(IDPL), carboxy methyl cellulose sodium salt (Glaxo
Laboratory, Bombay) and tween 80 (BDH, Mumbai).
7-HF was prepared as a suspension of I %
carboxymethyl cellulose and glibenclamide in 0.05 %
tween 80. Appropriate vehicles were used as control.
7-HF, in the dose employed, (selected based on
earlier studies) elicited a significant reduction in the
number of acetic acid induced abdominal constriction
without significantly modifying the blood glucose
level. In contrast, glibenclamide per se induced
significant hypoglycaemia without modifying the
number of abdominal constriction. Glibenclamide
treatment in 7 -HF pretreated animals still elicited
hypoglycaemia, however, the degree was significantly
Jess. In contrast, it almost attenuated the 7-HF
induced inhibition of acetic acid induced abdominal
constriction (Table 1).
The present findings confirm the earlier reported
antinociceptive effect of 7-HF which has been shown
to act through opioid pathways 12 . However, it was
without any effect on the glycaemic state. This
observation
indicates
that
7 -HF
induced
antinociception and alterations in glycaemic state are
not cause effective. Glibenclamide treatment
attenuated 7-HF induced antinociceptive response
similar to that of morphine thus confirming that 7-HF
also utilizes ATP sensitive potassium channels at the
cellular . level like morphine. The dissociated
relationship suggested earlier between 7-HF induced
antinociception and glycaemic state is supported by
the observation that though glibenclamide attenuated
7-HF antinociception it was still able to elicit
1173
Table !-Effect of glibenclamide on the blood glucose and acetic
acid induced abdominal constrictions in mice (n=7)
[Values are mean± SE]
Treatment
(mg/kg; ip)
Vehicle
Glibenclamide, I 02
7-HF, 100
7-HF 100 +
Glibenclamide, I 0
Blood glucose 1
(%change)
No. of abdominal
constrictions
104.3 ± 0.5
25.0 ± 1.4
55.1 ± 5.6**
30. 1 ±2.7
110.8 ± 8.3
15 .7 ± 1.4**
73.7 ± 2.2**"
21.7 ±0.9**"
1
8lood glucose was expressed as the percentage considering the
initial value as I 00%.
2
G!ibenclamide was inj ected i.p. I 0 min prior to acetic ac id
challenge
3
7-HF was administered s.c. 60 min prior to acetic acid challenge
** P < 0.01 when compared with vehicle treatment
"P < 0.05 when compared with their respective 7-HF value.
significant hypoglycaemia. These observations tempt
to suggest that the cellular mechanism involving ATP
sensitive potassium channels in the elicition of
antinociception does not reflect in the metabolic
parameter, i.e. the blood glucose changes. Recently,
Takashita and Yamaguichi 14 reported an inherent
antinociceptive response for insulin independent of
its
hypoglycaemic
response.
Taking
into
consideration the findings of this report, a new
hypothesis relating insulin, antinociception and ATP
sensitive potassium channel function could be
proposed. A possible cause-effect relation ship
between algesic and insulinaemic state rather than
glycaemic state deserves investigation. This is
because at the cellular level ATP sensitive potassium
channels
have
been
shown
to
modulate
a ntinociceptive response and insulin release from ~­
11
cells of pancreas . The present study also prove that
like morphine, 7-HF utilises ATP sensitive potassium
channel.
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j