Gases as neurotransmitters.

Area of Science:

• Neuroscience
• Molecular Biology
• Physiology

Background:

• Nitric oxide (NO) and carbon monoxide (CO) are gaseous signaling molecules synthesized in neurons.
• Both molecules can readily diffuse across cell membranes.
• Long-term potentiation (LTP) is a key cellular mechanism for learning and memory.

Purpose of the Study:

• To investigate the roles of NO and CO in the induction and stabilization of LTP in the hippocampus.
• To explore the involvement of NO in spinal cord sensitization and chronic pain.

Main Methods:

• Utilized nitric oxide synthase (NOS) inhibitors and knockout mice to study NO production.
• Examined the effects of CO production inhibitors on LTP.
• Investigated the role of heme oxygenase-2 (HO-2) in CO production and LTP.
• Assessed the impact of NOS inhibitors on spinal hyperalgesia models.

Main Results:

• NOS inhibitors block hippocampal LTP induction; endothelial NOS is likely involved.
• CO inhibitors affect LTP, but this effect doesn't correlate with CO production.
• LTP is normal in HO-2 knockout mice, suggesting limited CO involvement.
• NO diffuses postsynaptically to modulate neighboring neurons and presynaptic terminals, potentially via guanylate cyclase (GC) activation.
• Both NO-dependent and NO-independent forms of LTP exist, allowing for synaptic input discrimination.
• NOS inhibitors prevent spinal hyperalgesia, indicating NO's role in chronic pain.

Conclusions:

• NO is a significant modulator of hippocampal LTP and spinal cord sensitization.
• NO's role in LTP involves diffusion and interaction with GC, contributing to synaptic plasticity.
• NO contributes to chronic pain states by influencing spinal sensitization.
• CO's role in LTP is less clear and may not be directly mediated by HO-2.