INCREASED INTERACTION OF DOPAMINE-IMMUNOREACTIVE VARICOSITIES WITH GABA NEURONS OF RAT MEDIAL PREFRONTAL CORTEX OCCURS DURING THE POSTWEANLING PERIOD

A double immunofluorescence technique has been used to assess postnata l maturational changes in the extent to which dopamine-immunoreactive (DA-IR) varicose fibers form contacts with gamma-aminobutyric acid (GA BA)-immunoreactive (IR) neuronal cell bodies in rat medial prefrontal cortex (mPFCx). Two separate measures of interaction, the percentage o f GABA-IR cell bodies having DA-IR varicosities in apposition and the number of such profiles in contact with any given GABA-IR cell, were a ssessed. Between birth and adulthood, there was a progressive linear i ncrease (r = 0.75, P less than or equal to 0.0005) in the percentage o f GABA-IR cell bodies having at least one DA-IR varicosity in appositi on. While the number of varicosities in contact with any given GABA ce ll body showed very little change during the preweanling period, later during the postweanling interval, this parameter increased in a curvi linear fashion toward adult levels (r = 0.81, P less than or equal to 0.0005). Taking together these latter two measures, an index of intera ction was found to be 1.8 times higher when adult animals were compare d to postweanling rats, and 2.5 times higher when compared to preweanl ing rats. Overall, these results are consistent with the view that the re are late postnatal changes in the extent to which midbrain DA affer ents interact specifically with GABAergic interneurons in rat mPFCx. ( C) 1996 Wiley-Liss, Inc.