In an earlier study it was found that partial neonatal lesions of the medial prefrontal cortex (mPFC) resulted in an increased dopaminergic innervation in the remaining part of mPFC along with functional sparing. The present study assessed whether this response is restricted to this part of the cortex or whether also other structures of the mesolimbocortical system are involved. Furthermore, it was investigated whether the other monoaminergic systems were affected by neonatal mPFC lesions. In 6-day-old rats, the mPFC was partially ablated or a sham operation was made. The concentrations of dopamine (DA) and its metabolites increased to 250-350% in the remaining part of the mPFC compared to the sham-operated controls. The response was most prominent in this part of the cortex; no other mesolimbocortical structure showed such major changes of DA and its metabolites. In addition, a small increase in the concentrations of noradrenaline, serotonin and their metabolites was also spotted in the remaining mPFC and some other mesolimbocortical structures of the lesioned animals. The present data support the suggested involvement of DA in the neural mechanism of sparing of function, and this DA response seems to be most prominent in the remaining mPFC. However, the responses of the noradrenergic and serotonergic systems may also be important for sparing of function to occur.