[AUCTeX] Indenting a region is problematic in LaTeX mode

[Rodolfo Medina]

Normally, in Emacs, in text mode, to indent a region, say, by 8 columns, after
marking the region I do: `C-u 8 C-x TAB' to indent every single line, then
`M-q' to fill the paragraph with the new indentation.

In LaTeX, mode, `M-q' does not do the job.

Is there any setting to make that possible, or do I have to switch every time
to text mode to do the job and then to LaTeX mode again?

Thanks for any help
Rodolfo