In a plugin I don't have access to database?

[eluser]xcristi[/eluser]
Hello,

My problem is giving me headaches:
I have a plugin placed in application/plugins, called menu_pi.php. From this plugin I need to access my postgresql database. From a model I have no problem. But inside the plugin the code

$this->db->get('meniu'); doesn't work. So I think so, because my site get a blank screen.

My question: plugins cannot access database?

Thanks.
Cristian