How to re-lock ssh private key?

[Robert Nichols]

After I've used ssh on a connection with RSA authorization and given
my keyring's passphrase to gnome-ssh-askpass, that keyring is now
unlocked and future connections can be made without the passphrase.
Is there a way, short of logging out and back in, to make the
passphrase required again for a connection?  I'd rather not have to
uninstall or disable openssh-askpass since it's nice not to have
to supply a lengthy passphrase repeatedly when needed in a short
period, but I really don't like leaving that key open indefinitely.

In searching for info I keep getting references to ssh-agent being
responsible for remembering the key, but I find that ssh-agent is
never executed on my system.

I'm running currently updated Fedora 10 with Gnome.

-- 
Bob Nichols     "NOSPAM" is really part of my email address.
                 Do NOT delete it.