Mj. O'Neill et al., LY377770, a novel iGlu5 kainate receptor antagonist with neuroprotective effects in global and focal cerebral ischaemia, NEUROPHARM, 39(9), 2000, pp. 1575-1588
We have evaluated the neuroprotective effects of the decahydroisoquinoline
LY377770, a novel iGlu5 kainate receptor antagonist, in two models of cereb
ral ischaemia.
Global ischaemia, induced in gerbils by bilateral carotid artery occlusion
(BCAO) for 5 min, produced a large increase in locomotor activity at 96 hr
post-occlusion and a severe loss of CA1 cells in the hippocampus histologic
ally at 120 hr post-occlusion. LY377770 (80 mg/kg i.p. 30 min before or 30
min after BCAO followed by 40 mg/kg i.p. administered at 3 and 6 hr after t
he initial dose) attenuated the ischaemia-induced hyperactivity and provide
d (92%) and (29%) protection in the CA1 cells respectively. This protection
was greater than that seen with maximally tolerated doses of other glutama
te receptor antagonists (CGS19755, CPP, MK-801, ifenprodil, eliprodil, HA-9
66, ACEA1021, L701,324, NBQX, LY293558, GYKI52466 and LY300164).
Focal ischaemia was induced by infusing 200 pmol of endothelin-1 (Et-1) adj
acent to the middle cerebral artery and LY377770 was administered at 80 mg/
kg i.p. immediately, 1 or 2 hr post-occlusion followed by 40 mg/kg i.p. 3 a
nd 6 hr after the first dose. The infarct volume, measured 72 hr later, was
reduced by LY377770 when given immediately (P<0.01), at 1 hr (P<0.05) but
not significantly at 2 hr post-occlusion. Reference compounds, LY293558 (20
mg/kg i.p. and then 10 mg/kg as above) and MK-801 (2.5 mg/kg i.p.), both a
dministered immediately post-occlusion produced significant (P<0.05) but so
mewhat less neuroprotection. In parallel microdialysis studies, LY377770 (7
5 mg/kg i.p.) attenuated ischaemia-induced increases in extracellular level
s of glutamate, but not of dopamine.
In conclusion, these results indicated that iGlu5 kainate receptors play a
central role in ischaemic brain damage following global and focal cerebral
ischaemia. LY377770 is a novel, soluble, systemically active iGlu5 antagoni
st with efficacy in global and focal ischaemia, even when administered post
-occlusion. LY377770 may therefore be useful as a neuroprotectant in man. (
C) 2000 Elsevier Science Ltd. All rights reserved.