After 40 minutes, ZENK expression was increased in several cases in
both lens-treated and contralateral control eyes, compared with
untreated control chicks (
P = 0.01 for positive
lens-wearing eyes,
P = 0.23 for negative lens-wearing
eyes,
P = 0.06 for fellow eyes of chicks with positive
lenses and
P = 0.008 for fellow eyes of chicks with
negative lenses; unpaired two-tailed
t-test). After 40
minutes, there was only a tendency for ZENK expression to be higher in
eyes wearing positive lenses and lower in eyes wearing negative lenses
(+12 D, −12 D:
P = 0.15, 0.19, respectively). After 80
minutes, the defocus-induced differences in the number of
ZENK-expressing glucagon amacrine cells reached significance, higher in
eyes wearing positive lenses (compared with the contralateral control
eyes:
P = 0.04) and lower in eyes wearing negative
lenses (
P = 0.003). It is striking that the interocular
differences were almost entirely produced by the changes in ZENK
expression in the contralateral control eyes, as opposed to the
lens-treated eyes
(Fig. 3B) . After 120 minutes, there was no longer a
difference in ZENK expression between treated and contralateral control
eyes in the same animals (
P = 0.34 for +12 D and
P = 0.1 for −12 D lenses). ZENK expression declined
even beyond baseline levels (positive and negative lenses,
respectively,
P = 0.0001 and
P = 0.02
for contralateral control eyes,
P = 0.0004 and
P = 0.02 for treated eyes, compared with untreated
control chicks, unpaired two-tailed
t-test).