Behavioral sensitization to nicotine is associated with behavioral disinhibition; counteraction by citalopram

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.