Effect of protein kinase C activation on the glycine evoked Cl- current inspinal cord neurons

We investigated whether the effect of phorbol-12-myristate-13-acetate (PMA) was altered by a kinase inhibitor and by down-regulation of protein kinase C (PKC) in order to determine if glycine receptors in mouse spinal neurons , unlike those in hippocampal and trigeminal neurons, can be inhibited by P KC. To examine the above, electrophysiological and immunoflorescence studie s were carried out in mouse spinal neurons kept in culture for up to 3 week s. The inhibition of the glycine activated current by PMA (1 muM) increased from 12 +/-3% during week 1 to 27 +/-6% during week 3. The effect of PMA w as completely blocked by the PKC selective inhibitor RO 31-8220 (1 muM). Af ter culturing the cells with 1 muM PMA for 24 h, the inhibitory effect of a cute application of PMA disappeared altogether. suggesting that the effect of PMA was via PKC. Immunofluorescence studies showed that a short stimulat ion with PMA translocated the enzyme to the periphery whereas longer term s timulation (24 h) down regulated the PKC signal. These results indicate tha t activation of PKC by PMA inhibits the glycine receptor in cultured spinal neurons and that its sensitivity changes during neuronal development. (C) 2001 Elsevier Science B.V. All rights, reserved.