Paired Ace vs. PFR OOP

[rjamesdunn]

Just read the "Typical Situation" post from this week's digest (thanks a ton for that service!), and here's an actual hand. I checked intending to c/r the PFR. In retrospect, I probably should have bet, hoping for a raise to clear the field, but here we are. Now what? What if I had bet and he raised?

Villain was 18/4/1.38 over 50 hands. Does your answer change if he's completely unknown?

Party Poker 2/4 Hold'em (9 handed) converter

Preflop: Hero is UTG+1 with J[img]/images/graemlins/club.gif[/img], A[img]/images/graemlins/heart.gif[/img].
UTG calls, Hero calls, MP1 calls, <font color="#666666">1 fold</font>, <font color="#CC3333">MP3 raises</font>, <font color="#666666">3 folds</font>, BB calls, UTG calls, Hero calls, MP1 calls.

Flop: (10.50 SB) A[img]/images/graemlins/spade.gif[/img], 5[img]/images/graemlins/spade.gif[/img], Q[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(5 players)</font>
BB checks, UTG checks, Hero checks, <font color="#CC3333">MP1 bets</font>, <font color="#CC3333">MP3 raises</font>, BB folds, UTG calls, Hero ?