Need to check disabled constraints

Can anyone please let me know how I can check disabled constraints in postgresql 9.1 database. 

I know that ALTER TABLE tablename DISABLE TRIGGER ALL; can disable foriegn constraints, but how I can check if it is really disabled. Similarly I need to check if constraint is enable. 

In oracle we have option to check status of constraint in user_constraints table but do we have same in postgresql as well? 

Appreciate your response. 

Thanks.