creating a trigger to access another postgres database?

I have a question regarding postgres Trigger.

We have two applications which connect to two different databases (Both are postgres).

Is it possible to create a trigger (row based) in one database say A, which can access another database say B and updates a table there.

 

In brief, Is it possible to create Trigger in one database, which can connect to another database for making an update in the other database table.

 

thanks,