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Real-time detection of mitochondrial inhibition at frog motor nerve terminals using increases in the spatial variance
1Department of Pharmacology, James H. Quillen College of Medicine, East Tennessee State University, Johnson City 37614-0577, USA.
Abstract:
The effects of Hg2+, methyl mercury, and flufenamic acid, all of which inhibit mitochondria, were examined at frog motor nerve terminals. Unbiased estimates of m (no. of transmitter quanta released), n (no. of functional release sites), p (probability of release), and vars p (spatial variance in p) were obtained using K(+)-induced asynchronous neurosecretion (m, n and p not having the same definitions as with nerve-evoked release). Transient but significant increases in m, n, p and vars p were found with all three agents. These findings indicate that mitochondrial inhibition and release of sequestered Ca2+ can be detected as a real-time increase in vars p. The results also suggest that changes in vars p might be used to differentiate between cellular (membrane) and subcellular (organellar) actions of drugs at the nerve terminal.
Insights
Mitochondrial inhibitors like Hg2+ increase neurotransmitter release and release sites at frog nerve terminals. Changes in release site variance (vars p) can signal mitochondrial dysfunction and drug actions.
Area of Science:
- Neuroscience
- Cell Biology
- Pharmacology
Background:
- Mitochondria play a crucial role in cellular energy production and calcium homeostasis.
- Inhibition of mitochondrial function can disrupt neuronal signaling.
- Understanding drug effects at the nerve terminal is vital for neuroscience and pharmacology.
Purpose of the Study:
- To investigate the impact of mitochondrial inhibitors on neurotransmitter release at frog motor nerve terminals.
- To assess whether changes in release site variance (vars p) can indicate mitochondrial inhibition and drug actions.
Main Methods:
- Utilized K(+)-induced asynchronous neurosecretion to estimate neurotransmitter release parameters (m, n, p, vars p).
- Examined the effects of mercury (Hg2+), methyl mercury, and flufenamic acid, known mitochondrial inhibitors.
Main Results:
- All three tested agents caused transient increases in neurotransmitter release (m), release sites (n), release probability (p), and spatial variance in release probability (vars p).
- Observed that mitochondrial inhibition and calcium release correlate with increased vars p in real-time.
- Demonstrated that vars p changes can distinguish between membrane and organellar drug effects.
Conclusions:
- Mitochondrial inhibition at nerve terminals leads to measurable changes in neurotransmitter release dynamics.
- Spatial variance in release probability (vars p) serves as a sensitive indicator of mitochondrial function and drug-induced cellular events.
- Vars p offers a novel metric for dissecting drug mechanisms of action at the cellular and subcellular levels.