Gate control in dorsal horn
Gate control / dorsal horn
Transmission of the pain signal in the dorsal horn is supposed to be subject to various modulatory influences (the gate control theory (Melzack and Wall, 1965)).
The transmission neuron receives input from nociceptive neurons (Aδ and C) and inhibitory interneurons.The nociceptive neurons connect both directly and indirectly via the (inhibitory) interneuron to the transmission neuron.To transmit the pain signal to the transmission neuron in the dorsal horn, the nociceptive pathways use mostly substance P and glutamate as neurotransmitters.
The direct signal is always stimulatory and results in transmission of the pain signal to the spinal cord and higher. The indirect signal to the interneuron can be stimulatory (the interneuron inhibits the transmission neuron: + and - = -, and thus the pain signal is inhibited) or inhibitory (the interneuron stimulates the transmission neuron: - and - = + and thus enhances the pain signal). To transmit the signal to the transmission neuron, the interneuron uses enkephalins and GABA (gamma amino butyric acid) as neurotransmitters.
Rubbing a painful area is really useful, because the Aδ-neurons, which inhibit the transmission cell, are then stimulated.
Gray matter is composed of myelinated axons.