P. Olausson et al., Behavioral sensitization to nicotine is associated with behavioral disinhibition; counteraction by citalopram, PSYCHOPHAR, 142(2), 1999, pp. 111-119
This study investigated the effects of repeated nicotine treatment on locom
otor activity and behavioral inhibition, and the influence of citalopram on
the behavioral effects obtained. Male rats received daily subcutaneous inj
ections of vehicle +vehicle (veh + veh); citalopram (5.0 mg/kg) + vehicle (
cit + veh), vehicle + nicotine (1.0 mg/kg; veh + nic) or citalopram+nicotin
e (cit + nic). Acutely, nicotine stimulated locomotor activity, and repeate
d daily nicotine injections sensitized veh+nic rats to the nicotine-induced
locomotor stimulation after 5, 10 and 15 treatment days, whereas in cit+ni
c rats, the enhancement of nicotine-induced locomotion was suppressed. Howe
ver, when challenged with nicotine after citalopram withdrawal (-36 h), the
cit + nic treated animals were also observed to be sensitized. In the elev
ated plus-maze, repeated nicotine treatment produced behavioral disinhibiti
on, measured as an increase of time spent in and entries made into open arm
s (%), and chronic citalopram treatment attenuated the expression of behavi
oral disinhibition. Moreover the degree of nicotine sensitization correlate
d to the behavioral disinhibition observed. In summary, these findings sugg
est that behavioral sensitization to nicotine is associated with behavioral
disinhibition and that chronic citalopram treatment counteracts the expres
sion of both phenomena. Since citalopram is a highly selective serotonin re
uptake inhibitor, the effects of citalopram may be due to a facilitation of
serotonin neurotransmission caused by the chronic citalopram treatment.