Exogenously induced brain activation regulates neuronal activity by top-down modulation: conceptualized model for...

Area of Science:

• Neuroscience
• Pain Research
• Neurostimulation

Background:

• Sensory processing is modulated by physiological and exogenous factors at various nervous system levels.
• Transcranial direct current stimulation (tDCS) may employ top-down mechanisms to regulate information flow.
• Chronic stress can significantly alter nervous system function and pain perception.

Purpose of the Study:

• To investigate if tDCS-induced brain activation initiates top-down modulation of sensory processing.
• To determine if chronic stress disrupts the top-down modulatory effects of tDCS.
• To examine the role of brain-derived neurotrophic factor (BDNF) in stress and tDCS effects on pain.

Main Methods:

• Adult male Wistar rats underwent chronic restraint stress for 11 weeks.
• tDCS or sham-tDCS was applied over 8 days.
• BDNF levels were measured in the spinal cord, brainstem, and hippocampus.
• Mechanical pain threshold was assessed using the von Frey test.

Main Results:

• tDCS reduced spinal cord and brainstem BDNF levels only in unstressed animals.
• tDCS reversed stress-induced allodynia and increased pain thresholds in unstressed rats.
• An inverse relationship was observed between pain sensitivity and spinal cord BDNF levels.

Conclusions:

• tDCS can modulate pain pathways, but its efficacy is impaired by chronic stress.
• Stress disrupts the neurotrophic and analgesic effects of tDCS.
• Descending pain modulation pathways should be incorporated into brain electrical stimulation models.