Leukaemia inhibitory factor prevents loss of p75-nerve growth factor receptor immunoreactivity in medial septal neurons following fimbria–fornix lesions

Abstract

Transection of the fimbria–fornix leads to retrograde degeneration of axotomized septal cholinergic neurons as manifested by loss of choline acetyltransferase and low-affinity nerve growth factor receptor (p75 NGFR) immunoreactivity. Nerve growth factor administered into cerebral ventricles at the time of axotomy can prevent these changes, while ciliary neurotrophic factor can prevent the loss of p75 NGFR immunostaining. Leukaemia inhibitory factor shares structural homologies with ciliary neurotrophic factor and has similar actions in the nervous system. Both proteins share the same signalling pathways, which involve the interleukin-6 transducing receptor components leukaemia inhibitory factor receptor β and gp130. In this study, we compared the effects of leukaemia inhibitory factor, ciliary neurotrophic factor and nerve growth factor, administered into cerebral ventricles, on p75 NGFR and choline acetyltransferase immunoreactivity in septal neurons after fimbria–fornix transection. We found that leukaemia inhibitory factor, like ciliary neurotrophic factor, prevents the loss of p75 NGFR-stained medial septal neurons after fimbria–fornix axotomy, without maintaining choline acetyltransferase expression in these neurons. In addition, p75 NGFR-immunostained neurons had significantly smaller mean diameter after axotomy in leukaemia inhibitory factor- and ciliary neurotrophic factor-treated animals as compared with either nerve growth factor-treated or unlesioned animals. These findings suggest that both leukaemia inhibitory factor and ciliary neurotrophic factor can prevent the axotomy-induced cell death of septal cholinergic neurons, but that, in contrast to nerve growth factor, these growth factors do not maintain the expression of choline acetyltransferase or the normal neuronal size of these injured neurons.