MODULATION OF THE DELAYED RECTIFIER K-II TYPE-2 RECEPTOR FRAGMENT( CURRENT IN NEURONS BY AN ANGIOTENSIN)

Angiotensin IT (ANG II) stimulates the delayed rectifier K+ current (I -K) in neurons cultured from rat hypothalamus and brain stem via AT(2) receptors, and this effect involves activation of a G(i) protein and protein phosphatase 2A (PP2A). However, there was no evidence that the AT(2) receptor involved in this response was the same as the recently cloned AT(2) receptor. In the present study, intracellular injection of a 22-amino acid peptide (PEP-22) corresponding to the putative thir d intracellular loop of the cloned AT(2) receptor elicited an increase in I-K in cultured neurons that was similar to the effect produced by ANG II. Furthermore, this effect of PEP-22 was abolished by pertussis toxin (200 ng/ml, 24 h) pretreatment and also by superfusion of the P P2A inhibitor okadaic acid (10 nM), suggesting the involvement of G(i) protein and PP2A, respectively. Intracellular injection of a random p eptide or normal pipette solution did not affect neuronal I-K. This is direct evidence to link the cloned AT(2) receptor to a defined respon se elicited by ANG II.