Synaptic plasticity in rat medial prefrontal cortex under chronic haloperidol treatment produced behavioral sensitization.

Morphometric analysis of the population of synapses in medial prefrontal cortex (layer VI) of rat treated daily with haloperidol in a dose of 1.0 mg/kg during 3 weeks was performed on the electronmicroscopic level. The density of synapses on dendritic shafts increased on 29% and on the head of spine it increased on 20%. Nearly all the parameters measured in axo-spinous synapses were significantly decreased (area of presynaptic terminal, summarized area of mitochondriae per terminal, number of synaptic vesicles near the active zone, area of postsynaptic spine). There were no differences between the parameters of axo-dendritic synapses in control and haloperidol-treated rats. The data suggest that haloperidol might have induced the formation of the new synapses and may have changed the efficacy of the synaptic transmission in axo-spinous synapses on the head of spine.