Diffuse noxious inhibitory controls (DNIC) in animals and in man

Area of Science:

• Neuroscience
• Pain Research
• Spinal Cord Physiology

Background:

• Diffuse Noxious Inhibitory Controls (DNIC) are a descending pain modulation system.
• DNIC selectively inhibit convergent neurons in the dorsal horn.
• These inhibitions are triggered by nociceptive stimuli and involve supraspinal structures.

Purpose of the Study:

• To investigate the neural structures involved in Diffuse Noxious Inhibitory Controls (DNIC).
• To identify the specific brainstem nuclei mediating the descending inhibitory pathway.
• To elucidate the role of the Subnucleus Reticularis Dorsalis (SRD) in DNIC.

Main Methods:

• Electrophysiological recordings in the spinal cord dorsal horn.
• Lesion studies targeting various brainstem structures (PAG, Cuneiform nucleus, Parabrachial area, RVM, SRD).
• Psychophysical measurements and nociceptive reflex recordings (RIII reflex) in humans.

Main Results:

• Lesions in the Periaqueductal grey (PAG), Cuneiform nucleus, Parabrachial area, and Rostral Ventromedial Medulla (RVM) did not affect DNIC.
• Lesions of the Subnucleus Reticularis Dorsalis (SRD) significantly reduced DNIC.
• SRD neurons are activated by nociceptive stimuli with a whole-body receptive field and project to the dorsal horn via the dorsolateral funiculus.
• Human studies confirmed DNIC's effect on both nociceptive reflexes and pain perception.

Conclusions:

• The Subnucleus Reticularis Dorsalis (SRD) plays a crucial role in mediating Diffuse Noxious Inhibitory Controls (DNIC).
• DNIC involves a spinobulbospinal loop with the SRD as a key component.
• These findings highlight the SRD's importance in descending pain modulation and offer insights into pain management strategies.