Effects of chronic nicotine treatment on the expression of phospholipase C isozymes and the alpha subunit of Gq/11 protein in the rat brain.

The effect of chronic nicotine treatment on postreceptor sites of the phosphoinositide (PI) signaling system (i.e. phospholipase C (PLC) isozymes, Gq/11 protein) in the rat cortex was investigated. The expression of PLC isozymes (beta 1, gamma 1, and delta 1) and the alpha subunit of Gq/11 protein in the cortices of rats treated with saline or nicotine was determined by the Western blot technique using specific monoclonal antibodies. It was observed that chronic nicotine treatment (10 days) significantly increased the immunolabeling of the total PLC-beta 1, which was due to an increase in the immunolabeling of both the membranal and the cytosolic PLC-beta 1 isozyme in the rat cortex. On the other hand, the immunolabeling of total, membranal, and cytosolic PLC-delta 1 and -gamma 1 isozymes in the rat cortex was not significantly altered by chronic nicotine treatment. In addition, Western blot analysis also demonstrated that chronic nicotine treatment has no significant effect on the immunolabeling of the alpha subunit of Gq/11 protein in the rat cortex. Thus, these findings suggest that an increase in the expression of the PLC-beta 1 isozyme may be involved in the neuroadaptational mechanisms associated with tobacco addiction.