Striatal acetylcholinesterase-containing interneurons innervate hippocampal tissue in co-cultured slices

Co-cultures of hippocampal and striatal slices were prepared from 7-day-old rats. After a month in vitro they were examined by histochemical and electrophysiological techniques. Acetylcholinesterase-positive fibers, originating in presumed cholinergic local circuit neurons of the striatum, invaded the adjacent hippocampus, resulting in a functional innervation displaying the characteristics of muscarinic inputs. These observations demonstrate that interneurons, when offered an appropriate target, are capable of mimicking projection neurons. Such a target-induced change in growth characteristics can take place even during relatively advanced phases of their development.