Hi Sonja. This sounds like playing to me, although aggressive playing! Isabella is VERY aggressive with her toys at this time of year, almost violent with a few of them! But, it keeps her busy, and like you said, a busy, happy 'Too is a beautiful thing
! I, too, have noticed some panting, but NOT the hormonal, "over-sexed" type of panting, more the out-of-breath-from-exertion" panting.
I think you can safely chalk it up to "the season," sigh...
Hang in there!