postgres connects to server every 5 minutes

[outsider <outs1der@list.ru>]

Hi!
After an upgrade from postgres 7.3 to postgres 7.4 I see every 5 minutes 
in the /var/syslog messages like
---
connection: Host=[local] Port=
user=postgres
---
postgres connects every 5 minutes to each database I have. What is the 
reason for this behaviour?
I'm using Debian SID.
Thank you in advance!
--
outsider