Ciliary neurotrophic factor is expressed in the magnocellular neurosecretory system of the rat in vivo: evidence for injury- and activity-induced upregulation.

Although ciliary neurotrophic factor (CNTF) has been shown to promote the survival of magnocellular neurons when applied exogenously to explants of the paraventricular and supraoptic nuclei (SON) in vitro, little is known regarding its expression or regulation in the adult magnocellular neurosecretory system (MNS) following injury in vivo. Therefore, we utilized in situ hybridization and immunocytochemical analysis in conjunction with quantitative optical densitometric analysis to identify the cellular source of CNTF and examine the temporal pattern of its expression, following unilateral transection of the hypothalamo-neurohypophysial tract in the adult rat. In intact rats, CNTF immunoreactivity (CNTF-ir) was predominantly localized within identified astrocytes within the ventral glial limitans subjacent to the SON. Quantitative optical densitometric analysis of CNTF-ir levels in the axotomized SON demonstrated that the proportional area of CNTF-ir was significantly elevated between 3 and 30 days following injury. A significant but more limited increase was also observed in the non-injured contralateral SON. In situ hybridization confirmed the expression and upregulation of CNTF in the axotomized SON. These results demonstrate the expression of CNTF in the adult rodent MNS in vivo and provide evidence that levels of CNTF are upregulated in response to both direct injury, and heightened metabolic activity, within the lesioned and sprouting SON, respectively.

Watt JA ，Bone S ，Pressler M ，Cranston HJ ，Paden CM ... -  《EXPERIMENTAL NEUROLOGY》

CNTF receptor alpha is expressed by magnocellular neurons and expression is upregulated in the rat supraoptic nucleus during axonal sprouting.

Ciliary neurotrophic factor (CNTF) is expressed by glial cells at multiple levels of the magnocellular neurosecretory system (MNS). CNTF is present in astrocytes in the hypothalamic supraoptic nucleus (SON) as well as in perivascular cells in the neurohypophysis, and a several fold increase in CNTF immunoreactivity occurs in the SON following either axotomy of magnocellular neurons or during axonal sprouting by intact magnocellular neurons. CNTF also promotes survival and stimulates process outgrowth from magnocellular neurons in vitro. While these findings suggest that CNTF may act as a growth factor in support of neuronal plasticity in the MNS, little is known regarding possible expression of receptors for CNTF in the MNS. We have therefore used immunocytochemistry and in situ hybridization to examine the expression of CNTF receptor alpha (CNTFRalpha) in the rat MNS. Robust immunoreactivity for CNTFRalpha was observed associated with oxytocinergic and vasopressinergic neurons distributed throughout the SON. Astrocytes located within the ventral glial lamina (VGL) of the SON were also immunoreactive for CNTFRalpha. Robust hybridization of an anti-sense [(35)S]-cRNA probe to CNTFRalpha mRNA was observed throughout the SON, while binding of a control sense probe was much lower. Grains were found clustered predominantly over neuronal somata, indicative of expression by magnocellular neurons within the SON. We next examined changes in expression of CNTFRalpha mRNA by magnocellular neurons 7 days following unilateral transection of the hypothalamo-neurohypophysial tract. The level of CNTFRalpha mRNA was increased 32% (compared to age-matched intact controls; p<0.05) in magnocellular neurons in the SON contralateral to the lesion, which are undergoing extensive collateral axonal sprouting, but was unchanged in axotomized magnocellular neurons in the SON ipsilateral to the lesion. These findings suggest that CNTF produced by MNS glia and acting via CNTFRalpha may exert neurotrophic effects on magnocellular neurons.

Watt JA ，Lo D ，Cranston HJ ，Paden CM ... -  《-》

Ciliary neurotrophic factor increases the survival of magnocellular vasopressin and oxytocin neurons in rat supraoptic nucleus in organotypic cultures.

Organotypic cultures of the rat hypothalamus are very useful models for the long-term study of parvocellular vasopressin (VP) neurons in the paraventricular (PVN) and suprachiasmatic (SCN) nuclei. However, they do not preserve significant numbers of VP magnocellular neurons (VP-MCNs) in either the PVN or the supraoptic nucleus (SON). Vutskits et al. [(1998) Neuroscience 87:571-582] reported that ciliary neurotrophic factor (CNTF) was a selective survival factor for rat VP-MCNs in organotypic cultures of the rat hypothalamic paraventricular nucleus (PVN). We examined the effects of CNTF on the survival of these neurons in rat and mouse SONs. CNTF (10 ng/ml) in the culture media increased the survival of VP-MCNs by 6-fold and OT-MCNs by 3-fold. In the mouse, both OT- and VP-MCNs survive very well in organotypic cultures under standard culture conditions and the addition of CNTF had no further effect. Consistent with these results, in situ hybridization showed substantially higher levels of VP- and OT-mRNA in rat PVNs and SONs in the presence of CNTF, but produced no changes in these nuclei in the mouse. The optimum period for the survival effect of CNTF on MCNs in the rat hypothalamic cultures was in the first 7-10 days of culture and this effect is maintained for at least 5 additional days if CNTF is then removed from the medium. Therefore, using CNTF in the culture media can provide an opportunity for long-term studies of rat VP- and OT-MCNs in SONs in organotypic cultures.

Rusnak M ，House SB ，Arima H ，Gainer H ... -  《MICROSCOPY RESEARCH AND TECHNIQUE》

Neuronal activity and axonal sprouting differentially regulate CNTF and CNTF receptor complex in the rat supraoptic nucleus.

We demonstrated previously that the hypothalamic supraoptic nucleus (SON) undergoes a robust axonal sprouting response following unilateral transection of the hypothalamo-neurohypophysial tract. Concomitant with this response is an increase in ciliary neurotrophic factor (CNTF) and CNTF receptor alpha (CNTFRα) expression in the contralateral non-uninjured SON from which the axonal outgrowth occurs. While these findings suggest that CNTF may act as a growth factor in support of neuronal plasticity in the SON, it remained to be determined if the observed increase in neurotrophin expression was related to the sprouting response per se or more generally to the increased neurosecretory activity associated with the post-lesion response. Therefore we used immunocytochemistry and Western blot analysis to examine the expression of CNTF and the components of the CNTF receptor complex in sprouting versus osmotically-stimulated SON. Western blot analysis revealed a significant increase in CNTF, CNTFRα, and gp130, but not LIFRß, protein levels in the sprouting SON at 10days post lesion in the absence of neuronal loss. In contrast, osmotic stimulation of neurosecretory activity in the absence of injury resulted in a significant decrease in CNTF protein levels with no change in CNTFRα, gp130, or LIFRß protein levels. Immunocytochemical analysis further demonstrated gp130 localization on magnocellular neurons and astrocytes while the LIFRß receptor was found only on astrocytes in the SON. These results are consistent with the hypothesis that increased CNTF and CNTFR complex in the sprouting, metabolically active SON are related directly to the sprouting response and not the increase in neurosecretory activity.

Askvig JM ，Leiphon LJ ，Watt JA 《-》

Altered neuronal responses and regulation of neurotrophic proteins in the medial septum following fimbria-fornix transection in CNTF- and leukaemia inhibitory factor-deficient mice.

Naumann T ，Steup A ，Schnell O ，Schubert KO ，Zhi Q ，Guijarro C ，Kirsch M ，Hofmann HD ... -  《EUROPEAN JOURNAL OF NEUROSCIENCE》