Suppo
rting ou
r hypothesis of common biological bases fo
r post-t
raumatic st
ress diso
rde
r (PTSD) and addiction, we
recently
repo
rted that
rats exposed to a single p
rolonged st
ress (SPS), a PTSD model, develop a delayed behavio
ral sensitization of the no
rad
rene
rgic system, simila
r to that obse
rved in mice afte
r fou
r repeated d
rug administ
rations. Howeve
r, sensitization afte
r t
rauma was modulated by
reactivity to novelty, and this aspect that had not been explo
red in the addiction model. The fi
rst aim of the pape
r was thus to investigate the influence of
reactivity to novelty on delayed behavio
ral sensitization in
rats afte
r fou
r repeated amphetamine injections. Injections we
re eithe
r dist
ributed ove
r 4 days, as conducted in mouse models of addiction, o
r massed du
ring a single session,
rep
roducing SPS conditions. The second aim was to investigate whethe
r repeated amphetamine injections have simila
r behavio
ral consequences to those induced by PTSD.
Our results showed that massed amphetamine injections induced more anxiety than distributed injections, and led to avoidance of drug-associated cues avoidance, while distributed injections somewhat reduced the startle response, such as is seen in SPS. In addition, massed amphetamine injections induced a delayed behavioral sensitization clearly affected by the reactivity to novelty, reproducing results observed following exposure to traumatic events. Finally, all rats receiving repeated amphetamine injections exhibited a behavioral sensitization in response to exposure to drug-associated cues. Taken together, these data strengthen the position that drug addiction and PTSD share some common mechanisms that we tried to clarify in this paper.