Intranasal administration
Atosiban is a competitive OT receptor antagonist24. Both OT and
atosiban have been shown to be bioavailable when administered
intranasally25,26.
The intranasal dose of normal saline was 20μl/day. The intranasal dose
of OT was 1mg/kg/day, diluted in 20μl saline. The intranasal dose of
atosiban was 10mg/kg/day, diluted in 20μl saline.
Mice were handled daily one week
before the start of intranasal treatments to reduce the stress
associated with the procedure. Two
days before DSS-induced colitis, mice had been received an intranasal
saline, OT or OT with atosiban. Mice were picked up by the scruff of the
neck and exposed in a supine position to immobilize them for the
intranasal administration. This position of head was maintained
throughout procedure preventing drainage of drug solution to trachea and
esophagus. The total volume of 20μl solutions was administered by
pipette in 5μl drops in alternating naris every 30 seconds. The drop was
placed at the naris opening while occluding the opposite naris allowing
the animal to snort the drop into the nasal cavity.
Study design
Behavior and biochemical test comprised four groups: NC, DSS, DSS+IN OT,
DSS+IN OT+IN atosiban. NC group was treated with plain drinking water
for seven days; untreated DSS group was treated with 2% DSS powder in
plain drinking water for 7days; DSS+IN OT group was treated with 2% DSS
powder in plain drinking water and intranasal administration of OT for
seven days. DSS+IN OT+IN atosiban group was treated with 2% DSS powder,
intranasal administration of OT and atosiban forseven days.
At seventh day, half of each group
were submitted to a water avoidance stress test for 10 minutes. The
other half were sacrificed to perform a biochemical test.
In the second series of experiments, chemical colitis was induced in
mice 15 days after splenectomy. Splenectomy mice were assigned to the
following experimental groups: splenectomy, DSS +splenectomy and DSS+IN
OT +splenectomy. With NC, DSS and DSS+IN OT groups together, these three
groups were performed the same experiments as the first series. The
design can be seen in Supplementary figure.