While magnocellular neurons in the supraoptic nucleus (SON) possess rich Gi/o-mediated mechanisms, molecular and cellular properties of G-protein-activated inwardly rectifying K(+) (GIRK) channels have been controversial. Here, properties of GIRK channels are examined by RT-PCR and whole-cell patch-clamp techniques in @entity35 SON neurons. Patch clamp experiments showed that the selective GABAB agonist, @entity1772 , enhanced currents in a high K(+) condition. The @entity1772 -enhanced currents exhibited evident inward rectification and were blocked by the selective GABAB antagonist, @entity7234 , the IRK channel blocker, @entity8594 , and the selective GIRK channel blocker, tertiapin, indicating that @entity1772 activates GIRK channels via GABAB receptors. The GIRK currents were abolished by @entity8816 pretreatment, and prolonged by GTPyS inclusion in the patch pipette, suggesting that Gi/o proteins are involved. RT-PCR analysis revealed mRNAs for all four @entity50633 -4 channels and for both @entity68406 and @entity24415 receptors in @entity35 SON. However, the concentration-dependency of the @entity1772 -induced activation of GIRK currents had an EC50 of 110  M, which is about 100 times higher than that of @entity1772 -induced inhibition of voltage-dependent @entity141 channels. Moreover, @entity1772 caused no significant changes in the membrane potential and the firing rate. These results suggest that although GIRK channels can be activated by GABAB receptors via the Gi/o pathway, this occurs at high agonist concentrations, and thus may not be a physiological mechanism regulating the function of SON neurons. This property that the membrane potential receives little influence from GIRK currents seems to be uncommon for CNS neurons possessing rich Gi/o-coupled receptors, and could be a special feature of @entity35 SON neurons.

Analysis of G-protein-activated inward rectifying K(+) (GIRK) channel currents upon GABAB receptor activation in XXXX supraoptic neurons.

@entity7234 :: ('MESH:C085075', 'Chemical') :: ['CGP55845A'] @entity68406 :: ('81657(Tax:10116)', 'Gene') :: ['GABABR1'] @entity24415 :: ('83633(Tax:10116)', 'Gene') :: ['GABABR2'] @entity141 :: ('CHEBI:29108', 'Chemical') :: ['Ca(2+)'] @entity8816 :: ('MESH:D005033', 'Chemical') :: ['N-ethylmaleimide'] @entity8594 :: ('MESH:C080430', 'Chemical') :: ['Ba(2+)'] @entity35 :: ('10116', 'Species') :: ['rat'] @entity50633 :: ('50599(Tax:10116)', 'Gene') :: ['GIRK 1'] @entity1772 :: ('MESH:D001418', 'Chemical') :: ['baclofen']
@entity35 :: (10116,Species) :: ['rat']
