2.8. Experimental overview
Experiment 1 investigated the impact of stressor controllability
on the extinction of drug-seeking behavior. Following cocaine selfadministration,
rats were randomly assigned to either ES or yoked
IS or HC treatment (n ¼ 9e12/group). One week following stress
treatment animals underwent extinction training.
Experiment 2 determined the role of the IL in mediating the
facilitated extinction produced by prior ES. Prior to catheter implantation,
AAV-NpHR-eYFP or AAV-eYFP was delivered bilaterally
to the IL. Following cocaine self-administration, NpHR-eYFP and
eYFP rats were assigned to either ES or HC (n ¼ 8e10/group). On the
day of stress treatment, optical fiber implants were connected to a
patch cable that interfaced with a FC/PC fiber-optic rotary joint
(Doric Lenses) which then interfaced with a 532 nm solid-state
green laser located outside the wheel-turn box. Continuous light
delivery coincided with the onset of tailshock and terminated 2 s
following the offset of tailshock. An additional ES group (n ¼ 5)
received NpHR-mediated IL silencing distributed at random during
the intertrial interval (ITI) with no specific relationship to shock
onset or offset. This group was included to determine whether the
observed effects of IL inhibition on ES extinction behavior required
silencing to be “tied” to tailshock (when the controlling response
occurs). Animals then underwent extinction one week later as
described above.