Aims:

6-OHDA lesion of dorsal noradrenergic bundle, causing depletion in noradrenaline (NA) content of the prefrontal cortex (PFC) impairs attention. Selective depletion of cortical NA by anti-dopamin-beta-hydroxylase-saporin injected into the medial PFC caused a reduced discriminative accuracy in 5 choice serial reaction time tests. Effects of selective NA lesion of prelimbic subdivision of PFC in attention are not known and comparable data are not available for cued discrimination task condition.

Methods: 

Therefore, water deprived rats were trained to cued discrimination task. The press the lever under one of two possible illuminated panel lights was reinforced and recorded as a correct response. Incorrect and missed responses were recorded, too. Following the animals were achieving accuracy of 75%, 6-OHDA lesions were carried out with potent DA re-uptake inhibitor GBR12935 to make selective lesion of NA terminals in the prelimbic cortex. 6-OHDA injection without GBR 12935 pretreatment was also applied to study the involvement of dopamine terminals. Postoperatively, the animals were observed in tests with different ITIs to manipulate the level of attention demands. Immunohistology was used to detect tyrosin-hydroxylase-positive fiber loss in the PFC.

Results: 

Our results showed that postoperatively no significant differences were found in the omission errors between groups in the case of 10 sec and variable (5-11 sec) ITIs throughout 160 trials/session. Both lesioned groups had significantly less incorrect responses (related to all responses) compared to controls. The 6-OHDA lesion caused a decrease in correct responses and enhanced omission errors with decreasing the incorrect responses if the ITI was 5 sec.

Conclusion: 

In conclusion, the catecholamine inputs of the prelimbic PFC play a role, though in different manner in attention: DA may be involved in initiation of responses; NA may be involved in signal control on sustained attention demand.

Support: 

NKTH-OTKA K68431 and HAS