Brain region-specific and time-dependent decreases of Gαi2 in amygdala-kindled rats

Immunoreactivity levels of G protein α‐subunits, Gαs (45 and 52 kDa), Gαi1, and Gαi2, were determined in plasma membranes prepared from ipsilateral amygdala‐pyriform cortex (AM/PC), contralateral AM/PC, dorsal hippocampus (DH), and ventral hippocampus (VH) in amygdala‐kindled rats 24 h, 1 month, and 3 months after the last seizure. Relative to sham controls, immunoreactivity levels of Gαi2 were significantly reduced in ipsilateral AM/PC and DH, with maximal decreases observed, respectively, at 24 h (26% form control levels) and 1 month (18% from control levels) postseizure. No significant alterations in the levels of Gαi1 or either of the Gαs isoforms were observed. The reduction in Gαi2 levels was, however, not accompanied by measurable changes in Gαi‐mediated inhibition of adenylyl cyclase, as estimated by GppNHp modulation of forskolin‐activated adenylyl cyclase activity. The present findings add support to the hypothesis that long‐term changes in brain functioning following kindling may involve altered expression and/or function of components of the transmembrane signalling cascade, including G proteins. © 1996 Wiley‐Liss, Inc.