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CNTF inhibits high voltage activated Ca2+ currents in fetal mouse cortical neurones
Ninna R Holm1, Palle Christophersen, Jørn Hounsgaard
1NeuroSearch, Pederstrupvej, Ballerup, Denmark.
Abstract:
Neurotrophic factors yield neuroprotection by mechanisms that may be related to their effects as inhibitors of apoptosis as well as their effects on ion channels. The effect of ciliary neurotrophic factor (CNTF) on high-threshold voltage-activated Ca channels in cultured fetal mouse brain cortical neurones was investigated. Addition of CNTF into serum-free growth medium resulted in delayed reduction of the Ca2+ currents. The currents decreased to 50% after 4 h and stabilized at this level during incubation with CNTF for 48 h. Following removal of CNTF the inhibition was completely reversed after 18 h. CNTF reduced the current of all pharmacological subtypes of Ca channels as shown by use of selective blockers of L, N, and P/Q type Ca channels (nifedipine, omega-conotoxin MVIIA, omega-agatoxin IVA). The Ca channel depression was mediated via the CNTF receptor, because enzymatic cleavage of the alpha-subunit glycerophosphatidylinositol anchor of the receptor eliminated the response. The CNTF effect was not elicited through pertussis toxin-sensitive G proteins. Other neurotrophic factors like neurotrophin-3 and insulin-like growth factor-I had no effect on the Ca2+ currents. These results may have important implications for the possible functions of CNTF in the nervous system, such as altered synaptic activity, neuronal excitability and susceptibility to brain ischaemia.
Insights
Ciliary neurotrophic factor (CNTF) reduces calcium channel activity in developing neurons, impacting synaptic function and brain ischemia susceptibility. This neuroprotective effect is reversible and mediated through the CNTF receptor.
Area of Science:
- Neuroscience
- Molecular Biology
- Cell Biology
Background:
- Neurotrophic factors are crucial for neuronal survival and function.
- Mechanisms of neuroprotection involve apoptosis inhibition and modulation of ion channels.
- Ciliary neurotrophic factor (CNTF) is a key neurotrophic factor with potential roles in neuronal plasticity.
Purpose of the Study:
- To investigate the effect of CNTF on high-threshold voltage-activated calcium (Ca2+) channels in cultured fetal mouse brain cortical neurons.
- To elucidate the signaling pathways involved in CNTF-mediated modulation of Ca2+ currents.
- To explore the potential implications of CNTF's actions on neuronal excitability and brain ischemia.
Main Methods:
- Primary neuronal cultures from fetal mouse brains were utilized.
- Calcium (Ca2+) currents were measured using electrophysiological techniques.
- Selective pharmacological blockers were employed to identify affected Ca2+ channel subtypes (L, N, P/Q).
- Enzymatic cleavage of the CNTF receptor's GPI anchor and pertussis toxin treatment were used to investigate signaling pathways.
Main Results:
- CNTF addition caused a delayed, reversible reduction in Ca2+ currents, reaching 50% inhibition after 4 hours and fully reversing within 18 hours of removal.
- CNTF affected all pharmacologically identified subtypes of Ca2+ channels (L, N, and P/Q types).
- The observed Ca2+ channel depression was mediated via the CNTF receptor, as receptor cleavage abolished the response.
- The effect was independent of pertussis toxin-sensitive G proteins.
- Other neurotrophic factors (NT-3, IGF-I) did not affect Ca2+ currents.
Conclusions:
- CNTF significantly modulates high-threshold voltage-activated Ca2+ channels in developing cortical neurons.
- The mechanism involves the CNTF receptor but not pertussis toxin-sensitive G proteins.
- These findings suggest CNTF plays a role in regulating neuronal excitability, synaptic activity, and potentially offers neuroprotection against ischemia.