Effects of acute and chronic corticosterone treatments in the American Bullfrog wound healing

Glucocorticoid (GC) release is triggered by adverse stimuli that activate
hypothalamus-pituitary-adrenal/interrenal (HPA/I) axis. Glucocorticoids
may enhance or suppress immune functions depending on the level of
elevation. In this study, we investigated the effects of transient and
chronic increases of CORT on the wound healing of the American bullfrog.
Frogs were submitted to a daily transdermal hormonal application that
acutely elevated CORT plasma levels, or vehicle as a control. Other frogs
were surgically implanted with a silastic tube filled with CORT that
resulted in chronic elevation of CORT plasma levels or received empty
implants as a control. A dermal biopsy was performed to create a wound and
was photographed every 3 days. Individuals treated with transdermal CORT
started healing faster than their control 32 days after the biopsy. Frogs
that received CORT implants tended to heal slower than control subjects.
Plasma bacterial killing ability (BKA) was not affected by treatment,
which reinforces the constitutive nature of this innate immune
trait.  By the end of the experiment, frogs from the acute CORT
treatment had smaller wounds compared to those receiving the CORT-filled
implants, highlighting the differential effects of acute (immunoenhancing)
and chronic (immunosuppressive) elevation of CORT plasma levels.