Spontaneous and Amphetamine‐Evoked Release of Cerebellar Noradrenaline After Sensorimotor Cortex Contusion: An In Vivo Microdialysis Study in the Awake Rat

: Microdialysis sampling combined with HPLC was used to assess spontaneous and d‐amphetamine (AMPH)‐evoked release of noradrenaline (NA) in the cerebellum 1 day after probe implantation and 1 day after contusion of the right sensorimotor cortex (SMCX) in rats. In normal controls the mean β SEM basal NA release was 10.08 β 0.97 pg in the left cerebellar hemisphere and 8.21 β 1.17 pg in the right hemisphere 22–24 h after probe implantation. The average β SEM NA release in a 3‐h period after administration of AMPH (2 mg/kg, i.p.) increased to 453 β 47.35 pg in the left and to 402 β 49.95 pg in the right cerebellar hemisphere. NA release (range of 413–951% increase over baseline) was maximal 20–40 min postdrug, returned to basal levels within 5 h, and remained unchanged for the 22–24‐h postdrug measurement period. Animals with a focal SMCX contusion had a marked depression of both spontaneous and AMPH‐evoked NA release. Mean β SEM basal NA release was 4.84 β 1.09 pg in the left and 4.95 β 0.43 pg in the right cerebellar hemisphere from 22 to 24 h postinjury, with NA levels increasing to 259 β 75.44 and 219 β 23.45 pg in the respective hemispheres over a 3‐h period after AMPH. The maximal AMPH‐induced increase in NA release ranged from 522 to 1,088% of basal levels in contused rats, with NA release returning to predrug levels within 5 h and remaining depressed for at least 48 h postinjury. These data indicate that although neocortical injury results in a bilateral reduction of extracellular levels of NA in cerebellum, AMPH‐releasable NA stores are present in the cerebellum. These effects may be related to locomotor impairments and AMPH‐facilitated behavioral” recovery after cortical injury.