I agree with Kelvinsmom. I had a breast reduction several years ago, then gained a lot of weight. I had my LapBand done in October 2007 and, after having lost 61 pounds, I may need a breast augmentation! Isn't that crazy?!?
When you have your plastic surgery consultation, ask the surgeon if he does a pedicle flap or a free nipple graft technique. The pedicle flap should not reduce any nipple sensation since the nipple is not removed from the breast during the reduction. My reduction was this type and I have had no problems with lack of sensation. The free nipple graft technique actually removes the nipple for a short time before suturing it back on: I understand there is a chance for varying degrees of sensation afterwards.
As with all surgeries, don't hesitate to ask your surgeon anything and everything!