In 1850 there was a large snowshoe rabbit

True, because the species wouldn't have evolved in such a short amount of time.

Second messenger systems: The amino acid-derived hormones epinephrine and norepinephrine bind to beta-adrenergic receptors on the plasma membrane of cells. Hormone binding to receptor activates a G protein, which in turn activates adenylyl cyclase, converting ATP to cAMP.