The Journal of Neuroscience, May 1, 2001, 21(9):2983-2991
Substance P Abolishes the Facilitatory Effect of ATP on
Spontaneous Glycine Release in Neurons of the Trigeminal Nucleus Pars
Caudalis
Zhi-Ming
Wang,
Shutaro
Katsurabayashi,
Jeong-Seop
Rhee,
Malcolm
Brodwick, and
Norio
Akaike
Cellular and System Physiology, Graduate School of Medical
Sciences, Kyushu University, Fukuoka, 812-8582, Japan
Glycine release was facilitated by the activation of presynaptic
ATP receptors (P2X-type) in a preparation of dissociated trigeminal nucleus pars caudalis neurons in which the native synaptic boutons were preserved. The action of ATP was completely blocked by
substance P (SP) without alteration of the miniature IPSC (mIPSC) amplitude distribution. SP itself had no effect on mIPSC
frequency or amplitude. The inhibitory effect of SP on ATP action was
blocked by CP99994, indicating that the SP receptors are of the
neurokinin-1 type. The ATP-induced facilitation of the mIPSC
frequency was unaffected by Cd2+. Moreover, SP did
not inhibit the increase in mIPSC frequency induced high
K+ application, suggesting that SP did not modulate
voltage-dependent calcium channels or subsequent steps in the release process.
KT5720 and phorbol 12-myristate 13-acetate did not block SP
action, indicating that neither the cAMP-protein kinase A nor the protein kinase C pathway mediates the SP effects. However, in the presence of N-(6-aminohexyl)-5-chloro-1-naphthalene
sulphonamide (W-7), SP was no longer able to inhibit the
ATP-induced stimulation of mIPSC frequency.
1-[N,O-bis(5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperazine also suppressed the SP action, suggesting that SP modulates
P2X receptors via a Ca2+/calmodulin-dependent
protein kinase II-mediated pathway. In conventional whole-cell
mode, the presence of W-7 in the patch pipette did not affect the SP
inhibitory action. Thus, SP is not likely to be generating its
modulation through the production of a retrograde signal (involving
calmodulin) from the postsynaptic cell to the presynaptic boutons.
These results are the first demonstration of the modulation of one
presynaptic receptor by another. Because SP inhibits the ATP
stimulation of glycine release, SP may play a significant role in
hyperalgesia or chronic pain.
Key words:
dissociated neurons; substantia gelatinosa neuron; glycinergic nerve terminal; ATP and substance P receptors; calmodulin; CAM kinase II; glycinergic mIPSC; modulation; pain
Copyright © 2001 Society for Neuroscience 0270-6474/01/2192983-09$05.00/0