Details

Autor(en) / Beteiligte

• Chaban, V V
• Li, J
• Ennes, H S
• Nie, J
• Mayer, E A
• McRoberts, JA

Titel

N-methyl-D-aspartate receptors enhance mechanical responses and voltage-dependent Ca super(2+) channels in rat dorsal root ganglia neurons through protein kinase C

Ist Teil von

• Neuroscience, 2004-01, Vol.128 (2), p.347-357

Erscheinungsjahr

2004

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• N-methyl-D-aspartate (NMDA)receptors (NMDARs) located on peripheral terminals of primary afferents are involved in the transduction of noxious mechanical stimuli. Exploiting the fact that both NMDARs and stretch-activated channels are retained in short-term culture and expressed on the soma of dorsal root ganglia (DRG) neurons, we examined the effect of NMDA on mechanically mediated changes in intracellular calcium concentration ([Ca super(2+)] sub(i)). Our aims were to determine whether NMDARs modulate the mechanosensitivity of DRG neurons. Primary cultures of adult rat lumbosacral DRG cells were cultured for 1-3 days. [Ca super(2+)] sub(i) responses were determined by Fura-2 ratio fluorescence. Somas were mechanically stimulated with fire-polished glass pipettes that depressed the cell membrane for 0.5 s. Voltage-activated inward Ca super(2+) currents were measured by the whole cell patch clamp. Stimulation of neurons with 100 mu M NMDA in the presence, but not the absence, of co-agonist (10 mu M D-serine) caused transient [Ca super(2+)] sub(i) responses (101[plus-or-minus-sign]9 nM) and potentiated [Ca super(2+)] sub(i) peak responses to subsequent mechanical stimulation more than two-fold (P<0.001). NMDA-mediated potentiation of mechanically induced [Ca super(2+)] sub(i) responses was inhibited by the selective protein kinase C (PKC) inhibitor GF109203X (GFX 10 [mu]M), which had no independent effects on NMDA- or mechanically induced responses. Short-term treatment with the PKC activator phorbol dibutyrate (1 [mu]M PDBu for 1-2 min) also potentiated mechanically induced [Ca super(2+)] sub(i) responses nearly two-fold (P<0.001), while longer exposure (>10 min) inhibited the [Ca super(2+)] sub(i) transients by 44% (P<0.001). Both effects of PDBu were prevented by prior treatment with GFX. Inhibition of voltage-dependent Ca super(2+) channels with 25 [mu]M La super(3+) had no effect on mechanically induced [Ca super(2+)] sub(i) transients prior to NMDA, but prevented enhancement of the transients by NMDA and PDBu. NMDA pretreatment transiently enhanced nifedipine-sensitive, voltage-activated Ca super(2+) currents by a process that was sensitive to GFX. In conclusion, activation of NMDARs on cultured DRG neurons sensitize voltage-dependent L-type Ca super(2+) channels which contribute to mechanically induced [Ca super(2+)] sub(i) transients through a PKC-mediated process.