Alpha 1 adrenoceptor activation potentiates taurine response mediated by protein kinase C in substantia nigra neurons.

1. The potentiation of glycine receptor-mediated taurine response (Itau) by alpha 1 adrenoceptor activation was investigated in neurons freshly dissociated from the rat substantia nigra (SN) using a nystatin perforated-patch recording. 2. Norepinephrine (NE) at a concentration of 10(-4) M in the presence of 10(-5) M yohimbine and 10(-5) M propranolol potentiated the peak amplitude of Itau (10(-3) M) at a holding potential of -40 mV under voltage clamp conditions. NE could be substituted by phenylephrine at this potentiation. 3. This potentiation of the taurine response persisted in the treatment with pertussis toxin (500 ng/ml) for 18 h. The intracellular application of GDP-beta S (100 microM) with a conventional whole cell patch recording mode abolished the effect of alpha 1 adrenoceptor activation on the Itau. 4. Staurosporine (10(-7) M) blocked the enhancement of Itau by 10(-4) M NE with 10(-5) M yohimbine and 10(-5) M propranolol. In additional phorbol-12-myristate 13-acetate (10(-5) M) potentiated Itau. 5. The intracellular application of 0.275 U/ml protein kinase C (PKC) with a conventional whole cell configuration gradually increased the peak amplitude of Itau. On the other hand, intracellular perfusion either without PKC or with PKC plus 4 microM PKC (19-36), a PKC inhibitor, did not potentiate Itau. 6. A single channel recording in a cell attached configuration revealed that NE (10(-4) M) with 10(-5) M yohimbine and 10(-5) M propranolol increased the total open time of the taurine-activated channel. This increase of the channel opening was antagonized by staurosporine (10(-7) M). 7. Neither tapsigargin (10(-6) M), LiCl (10(-4) M), trifluoperazine (10(-5) M) nor (S)-5-isoquinolinesulfonic acid, 4-[2-[(5-isoquinolinylsulfonyl) methylamino]-3-oxo-(4-phenyl-1-piperazinyl)-propyl]phenyl ester (10(-4) M) applied in the perfusate were found to affect the potentiation of Itau by alpha 1 adrenoceptor. The intracellular application of inositol triphosphates (10(-4) M) in a conventional whole cell recording also had no effect on Itau. 8. These findings thus indicate that alpha 1 adrenoceptor coupled with pertussis-insensitive G protein increases the intracellular PKC activity, thus leading to an increase in the channel opening activated by taurine and an enhancement of the peak amplitude of Itau in the SN neurons.