Is. Xu et al., The effect of intrathecal selective agonists of Y-1 and Y-2 neuropeptide Yreceptors on the flexor reflex in normal and axotomized rats, BRAIN RES, 833(2), 1999, pp. 251-257
We have examined the effects of intrathecal (i.t.) administration of [Leu(3
1),Pro(34)]-neuropeptide Y (NPY) or NPY-(13-36), selective agonists of NPY
Y-1 or Y-2 receptors, respectively, on the excitability of the flexor refle
x in normal rats and after unilateral transection of the sciatic nerve. In
rats with intact and sectioned sciatic nerves, i.t. [Leu(31),Pro(34)]-Npy i
nduced a similar biphasic effect on the flexor reflex with facilitation at
low doses and facilitation followed by depression at high doses. In contras
t, i.t. NPY-(13-36) only facilitated the flexor reflex in normal rats, and
at high dose it caused ongoing discharges in the electromyogram. NPY-(13-36
) caused dose-dependent depression of the flexor reflex in rats after sciat
ic nerve transection, in addition to its facilitatory effect. Topical appli
cation of [Leu(31),Pro(34)]-NPY or NPY-(13-36) caused a moderate and brief
reduction in spinal cord blood flow. No difference was noted between the va
soconstrictive effect of [Leu(31),Pro(34)]-NPY and NPY-(13-36). It is sugge
sted that activation of Y-1 receptors may be primarily responsible for the
reflex depressive effect of i.t. neuropeptide Y in rats with intact sciatic
nerves, whereas both Y-1 and Y-2 receptors may be involved in mediating th
e depressive effect of NPY after axotomy. (C) 1999 Elsevier Science B.V. Al
l rights reserved.