Additionally, the presence of caffeine in the thawing solution stimulated both capacitation and
the spontaneous acrosome reactions of frozen-thawed boar sperm .
Although we believe that the presence of another substance (e.g. adenosine) inhibits the spontaneous
acrosome reaction of capacitated boar sperm
we still do not know why frozen-thawed sperm maintain
their capability for fertilization in the presence of
caffeine.