Healthy cardiac myocytes can decrease sympathetic hyperexcitability in the early stages of hypertension.

Area of Science:

• Cardiovascular Physiology
• Neuroscience
• Hypertension Research

Background:

• Sympathetic neurons significantly influence cardiac excitability.
• Hypertension involves sympathetic hyperactivity, characterized by reduced M current and increased Cav2.2 activity, leading to elevated intracellular calcium and enhanced neurotransmission.
• Retrograde signaling from myocytes may modulate neuronal synaptic plasticity.

Purpose of the Study:

• To investigate if cross-culturing healthy myocytes with diseased stellate neurons impacts sympathetic excitability.
• To explore the role of paracrine signaling from myocytes in modulating sympathetic neuron function.

Main Methods:

• Neuronal mono-cultures, co-cultures of neonatal ventricular myocytes and sympathetic stellate neurons, and conditioned media experiments were used.
• Neuronal firing properties were measured using current-clamp recordings as an indicator of excitability.
• Comparisons were made between neurons from normal (Wistar) and pre-hypertensive (SHR) rats.

Main Results:

• SHR neurons exhibited higher maximum firing rates and reduced rheobase compared to Wistar neurons.
• Co-culturing Wistar neurons with healthy myocytes did not alter their firing rate or biophysical properties.
• Cross-culturing SHR neurons with healthy myocytes or myocyte-conditioned media decreased their firing rate, mimicking Wistar neuron responses.

Conclusions:

• Healthy myocytes exert a modulatory effect on hyperactive sympathetic neurons.
• A paracrine signaling pathway exists from healthy myocytes to diseased neurons, capable of reducing sympathetic excitability.
• This myocyte-to-neuron signaling pathway presents a potential therapeutic avenue for hypertension-related sympathetic overactivity.