35
Pharmacological Research, Vol . 25, Supplement 1, 1992
OF PAIRED
PULSE
INHIBITION
ON
HYPOXIA-INDUCED
CHANGES IN HIPPOCAMPAL CAI FIELD POTENTIALS Sagratella S ., Zeng Y .C .
and scotti de Carolis A .
Pharmacology Department, Istituto Superiore di Sanital, Viale Regina Elena 299, 00161, Rome, Italy . Key words : paired pulse inhibition, hypoxia, hippocampus
The hippocampus is one of the brain areas most vulnerable to ischemic or anoxic
damage . i n
slices of rat hippocampus,
hypoxia induced a clear disappearance of the CAI population spike within a few mimutes . Many pharmacological studies have
been performed in order
to
un derstand the mechanisms
underlying hypoxia-induced synaptic
and
extrasynaptic
disturbances- in particular, a role has been established for adenosine- and NNIA
(N-methyl-D-aspartate)-agonist
antagonist drugs in
the treatment of hypoxia-induced
electrical changes- in this paper the
and
influence of calcium
concentration changes on hypoxia-induced electrophysiological alterations on the CAI field potential in slices of rat hippocampus has been examined . since calcium ions facilitate CAI paired pulse inhibition 11), the influence of this kind of inhibition on the hypoxia-induced changes was also studied_ Slices of rat hippocampus, prepared according to a technique described elsewhere (I), were subjected to hypoxia by varying
superfusion from 95%.
OZ - 5%
C02
to
95%. N2 -5% C02 . The
hypoxic period was maintained until a 50% reduction of the
1043-6618/92/2510035-02/$03 .00/0
© 1992 The Italian Pharmacological Society
36
Pharmacological Research, Vol. 25, Supplement 1, 1992 amplitude of the prima
population spike was achieved .
Experiments were performed at concentrations of 2 and 4 mid calcium . At the lower concen pulse stimulation induced a t
ation, a paired (15
esec}l
population spike with an
amplitude ratio of 1_1 + 0 .2 between the primary and the secondary population spike_ At 4 mM calcium, a ratio of 1 .8 +0 .2 was registered, revealing a high degree of paired pulse inhibition . No significant difference in time was recorded between both concentrations before a 50% reduction of the amplitude of the
primary
1 population spike occurred
(9 .3+0 .3 min at 2mH calcium ; 9_1+0 .2 min at 4 nH calcium),, nor was there any significant time difference in the achievement of a full recovery, of the
primary
(S_0+1 .1 min in 2mH calcium ; 7_3+1,2 min in
responses
4mm calcium) .
However, the decrease percentage of the amplitude of the secondary population spike, if any,
was
lower at 4 mM
22+10%) than at 2 mM calcium (-52+5%)our results indicate a protective role of paired inhibition against the
pulse
hypoxia-induced electrophysiological
changes of the CAI population spike . This suggests that those drugs which increase synaptic inhibition or reduce synap transmission -such as G 6ergic or adenosinergic drugs- could be successfully used for the treatment of anoxic-ischemic damage . I .Stringer JL, Lohnan _ in vitro effects calcium concentrations on hippocampal response . &xp Meurol 1998 ; 101 : 1 .32-146 .
e racer alar pyramidal c
Pharmacological Research, Vol . 25, Supplement 1, 1992
OF PAIRED
PULSE
INHIBITION
ON
HYPOXIA-INDUCED
CHANGES IN HIPPOCAMPAL CAI FIELD POTENTIALS Sagratella S ., Zeng Y .C .
and scotti de Carolis A .
Pharmacology Department, Istituto Superiore di Sanital, Viale Regina Elena 299, 00161, Rome, Italy . Key words : paired pulse inhibition, hypoxia, hippocampus
The hippocampus is one of the brain areas most vulnerable to ischemic or anoxic
damage . i n
slices of rat hippocampus,
hypoxia induced a clear disappearance of the CAI population spike within a few mimutes . Many pharmacological studies have
been performed in order
to
un derstand the mechanisms
underlying hypoxia-induced synaptic
and
extrasynaptic
disturbances- in particular, a role has been established for adenosine- and NNIA
(N-methyl-D-aspartate)-agonist
antagonist drugs in
the treatment of hypoxia-induced
electrical changes- in this paper the
and
influence of calcium
concentration changes on hypoxia-induced electrophysiological alterations on the CAI field potential in slices of rat hippocampus has been examined . since calcium ions facilitate CAI paired pulse inhibition 11), the influence of this kind of inhibition on the hypoxia-induced changes was also studied_ Slices of rat hippocampus, prepared according to a technique described elsewhere (I), were subjected to hypoxia by varying
superfusion from 95%.
OZ - 5%
C02
to
95%. N2 -5% C02 . The
hypoxic period was maintained until a 50% reduction of the
1043-6618/92/2510035-02/$03 .00/0
© 1992 The Italian Pharmacological Society
36
Pharmacological Research, Vol. 25, Supplement 1, 1992 amplitude of the prima
population spike was achieved .
Experiments were performed at concentrations of 2 and 4 mid calcium . At the lower concen pulse stimulation induced a t
ation, a paired (15
esec}l
population spike with an
amplitude ratio of 1_1 + 0 .2 between the primary and the secondary population spike_ At 4 mM calcium, a ratio of 1 .8 +0 .2 was registered, revealing a high degree of paired pulse inhibition . No significant difference in time was recorded between both concentrations before a 50% reduction of the amplitude of the
primary
1 population spike occurred
(9 .3+0 .3 min at 2mH calcium ; 9_1+0 .2 min at 4 nH calcium),, nor was there any significant time difference in the achievement of a full recovery, of the
primary
(S_0+1 .1 min in 2mH calcium ; 7_3+1,2 min in
responses
4mm calcium) .
However, the decrease percentage of the amplitude of the secondary population spike, if any,
was
lower at 4 mM
22+10%) than at 2 mM calcium (-52+5%)our results indicate a protective role of paired inhibition against the
pulse
hypoxia-induced electrophysiological
changes of the CAI population spike . This suggests that those drugs which increase synaptic inhibition or reduce synap transmission -such as G 6ergic or adenosinergic drugs- could be successfully used for the treatment of anoxic-ischemic damage . I .Stringer JL, Lohnan _ in vitro effects calcium concentrations on hippocampal response . &xp Meurol 1998 ; 101 : 1 .32-146 .
e racer alar pyramidal c
