AN ELECTRON-MICROSCOPIC MORPHOMETRIC COMPARISON OF TYROSINE-HYDROXYLASE IMMUNOREACTIVE INNERVATION IN THE NEOSTRIATUM AND THE NUCLEUS-ACCUMBENS CORE AND SHELL

The synaptic targets and size distributions of the sectioned profiles of tyrosine hydroxylase immunoreactive fibers and boutons in the neostriatum and shell and core of the nucleus accumbens were evaluated. Significantly more synaptic contacts where dendrite shafts are the postsynaptic element were observed in the shell than in the core of the nucleus accumbens or neostriatum. Relative to the core and neostriatum, a significantly greater proportion of the tyrosine hydroxylase immunoreactive innervation of the accumbal shell consisted of thin fiber and small bouton profiles. Thus, with regard to the morphometric parameters evaluated, the core of the nucleus accumbens is aligned with neostriatum and the shell is different from the core and neostriatum. In the light of these data, it is probable that the effects of the dopaminergic innervation in the core resemble the effects in neostriatum more than do those in the shell.