Fig. 1. Cerebellar `stop' versus hippocampal `go' signals. (A) Characteristics of hippocampal and cerebellar neuronal cultures under basal conditions, showing expression of the neuronal markers TuJ1, MASH1 and MATH1, and levels of apoptosis (TUNEL, dark brown) and proliferation (BrdU incorporation, blue-black). (B,C) Exposure of hippocampal cells to CM_Cerebellum reduces BrdU incorporation (B); exposure of cerebellar cultures to CM_Hippocampus stimulates BrdU uptake (C). (D) In hippocampal-cerebellar slice co-cultures, hippocampal cell proliferation is reduced in the presence of cerebellar slices, whereas cerebellar cell proliferation is slightly increased in the presence of hippocampal tissue. Dose dependency of CM_Cerebellum anti-mitotic effects in hippocampal cultures are shown in E; the peptidergic nature of the anti-proliferative activity present in CM_Cerebellum is indicated by the fact that anti-proliferative activity is lost after boiling CM_Cerebellum. CM_Cerebellum also exerts anti-proliferative effects on hippocampus-derived HiB5 cells (F). Scale bar: 50 µm. Numerical data refer to mean±s.d. (n=4-6) *P<0.05, **P<0.01, ***P<0.001 (versus appropriate controls).