[Effects of intraseptal microinjection of 6-hydroxydopamine upon the time discrimination behavior in rats]

An intraseptal 6-hydroxydopamine (6-OHDA) injection technique was used in order to examine the specific functions of the catecholamine (CA) neurons in the septal area upon the time discrimination behavior. After some preliminary CRF trainings of 5 days, 21 rats of Wistar strain were divided into 3 homogeneous groups according to their performance on the last session. 6-OHDA group (n = 6) was stereotaxically injected into the medial septal area with 8 micrograms of 6-OHDA in 0.9% saline solution containing 0.1% ascorbic acid. Ascorbic acid group (n = 5) was injected with only ascorbic acid solution and the remaining group (n = 10) received no treatments. Following the 6 recovery days and the next CRF trainings of 5 days, all subjects were exposed to a DRLL 20/LH 36 training for 30 min per day and consecutively for 30 days. As the results of these trainings, 6-OHDA group showed significantly better performance and less acceleration of operant responding just after incorrect (non-rewarded) responses as compared with other control groups in the early 10 sessions of the trainings. These findings suggested that the acquisition of time discrimination behavior was facilitated in the 6-OHDA group which was hardly affected by the emotional disturbance just after non-rewards. Therefore the authors consider that the emotional disturbance caused by non-rewards impairs the inhibition of operant responding by mediating the CA neurons in the septal area.