Involvement of protein kinase C in the presynaptic nicotinic modulation of [3H]‐dopamine release from rat striatal synaptosomes

Article date: February 2001

By: Lev Soliakov, Susan Wonnacott in Volume 132, Issue 3, pages 785-791

Presynaptic nicotinic ACh receptors modulate transmitter release in the brain. Here we report their interactions with protein kinase C (PKC) with respect to [3H]‐dopamine release from rat striatal synaptosomes, monitored by superfusion.

Two specific PKC inhibitors, Ro 31‐8220 (1 μM) and D‐erythro‐sphingosine (10 μM) significantly reduced (by 51 and 26% respectively) [3H]‐dopamine release stimulated by anatoxin‐a (AnTx), a potent and selective agonist of nicotinic ACh receptors. The inactive structural analogue of Ro 31‐8220, bisindolylmaleimide V (1 μM) had no effect.

Two phorbol esters, PDBu (1 μM) and PMA (1 μM) potentiated AnTx‐evoked [3H]‐dopamine release by 50 – 80%. This was Ca2+‐dependent and prevented by PKC inhibitors. In the absence of nicotinic agonist, phorbol esters enhanced basal release through a PKC‐independent mechanism.

A 86Rb+ efflux assay of nicotinic ACh receptor function confirmed that Ro 31‐8220 has no nonspecific effect on presynaptic nicotinic ACh receptors.

These results suggest that PKC is activated by nicotinic ACh receptor stimulation and mediates a component of AnTx‐evoked [3H]‐dopamine release. In addition, independent activation of PKC can further amplify the response, offering a potential mechanism for receptor crosstalk.

Presynaptic nicotinic ACh receptors modulate transmitter release in the brain. Here we report their interactions with protein kinase C (PKC) with respect to [3H]‐dopamine release from rat striatal synaptosomes, monitored by superfusion.

Two specific PKC inhibitors, Ro 31‐8220 (1 μM) and D‐erythro‐sphingosine (10 μM) significantly reduced (by 51 and 26% respectively) [3H]‐dopamine release stimulated by anatoxin‐a (AnTx), a potent and selective agonist of nicotinic ACh receptors. The inactive structural analogue of Ro 31‐8220, bisindolylmaleimide V (1 μM) had no effect.

Two phorbol esters, PDBu (1 μM) and PMA (1 μM) potentiated AnTx‐evoked [3H]‐dopamine release by 50 – 80%. This was Ca2+‐dependent and prevented by PKC inhibitors. In the absence of nicotinic agonist, phorbol esters enhanced basal release through a PKC‐independent mechanism.

A 86Rb+ efflux assay of nicotinic ACh receptor function confirmed that Ro 31‐8220 has no nonspecific effect on presynaptic nicotinic ACh receptors.

These results suggest that PKC is activated by nicotinic ACh receptor stimulation and mediates a component of AnTx‐evoked [3H]‐dopamine release. In addition, independent activation of PKC can further amplify the response, offering a potential mechanism for receptor crosstalk.

British Journal of Pharmacology (2001) 132, 785–791; doi:10.1038/sj.bjp.0703873

DOI: 10.1038/sj.bjp.0703873

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