Dopamine metabolism, spiperone binding and adenylate cyclase activity in the adult rat hippocampus after ingrowth of dopaminergic neurones from embryonic implants.

The growth of dopamine (DA) neurones of rat embryonic mesencephalic brain tissue implanted close to the anterior part of the hippocampus of adult rats was studied by measuring the levels of DA and 3,4-dihydroxyphenylacetic acid (DOPAC) in the host hippocampus. The hippocampal levels of DA and DOPAC reached maximal values 6 months after transplantation. The neuroleptic drug haloperidol evoked an increase in the levels of DOPAC. No evidence was found for the induction of DA-sensitive adenylate cyclase activity or of binding sites of [3H]spiperone. These results indicate that there is a substantial ingrowth of transplanted DA neurones into the host hippocampus, but no evidence was found for the development of functional contacts between the embryonic DA neurons and the host tissue.