Serotonin- and proton-induced and modified ionic currents in frog sensory neurons

Area of Science:

• Neuroscience
• Cellular Physiology
• Pharmacology

Background:

• Dorsal root ganglion (DRG) cells play a crucial role in sensory signal transmission.
• Serotonin (5-HT) and changes in pH are known modulators of neuronal activity.
• Understanding these modulations is key to deciphering sensory processing.

Purpose of the Study:

• To investigate the effects of serotonin (5-HT) and extracellular acidity on membrane currents in frog DRG neurons.
• To determine if these effects are dependent on DRG cell morphology.
• To examine the impact of 5-HT and acidity on high-threshold calcium currents.

Main Methods:

• Whole-cell patch-clamp technique applied to isolated frog DRG cells in short-term culture.
• Classification of DRG cells based on granular content (granule-containing vs. clear neurons).
• Application of serotonin (5-HT) and sudden decreases in pH to assess membrane current changes.

Main Results:

• 5-HT induced a rapidly desensitizing inward current in 76% of granule-containing neurons, blocked by (+)-tubocurarine.
• A fast-inactivating inward current was induced by decreased pH in 74% of clear neurons.
• Both 5-HT and increased H+ significantly reduced high-threshold calcium currents in all tested DRG neurons.

Conclusions:

• 5-HT receptors are likely expressed on a morphologically distinct population of DRG neurons (granule-containing).
• The cells responsible for the fast inactivating proton-induced current are not clearly linked to a specific morphology.
• Both 5-HT and acidity act as negative modulators of high-threshold calcium currents in frog DRG neurons.