How does the primary afferent synapse or interact with dorsal horn neurons

How does the primary afferent synapse or interact with dorsal horn neurons? 

There are interneurons that have intervening synapses between some of the primary afferents and neurons at deeper layers in the dorsal horn such as lamina V.

Some of these lamina V neurons have long dendrites extending into lamina II and synapse directly with primary afferents.

The dorsal horn is a very fertile territory for modulatory influences from descending nerves arising from higher centers as well as local interneurons. The interneurons are typically inhibitory.

The preponderant influence from descending neural input is also inhibitory.

Here is the table with a summary of dorsal horn neurotransmitters or ligands.

Ligand Receptor Interaction

ReceptorDrug or NeurotransmitterChannel and DirectionEffect
GABA-AGABAChloride influxInhibitory
GABA-BGABAPotassium influxInhibitory
GlycineGlycineChloride influxInhibitory
OpioidOpioidsPotassium influxInhibitory
μ, κ, σOpioidsPotassium influxInhibitory
α1, α2NorepinephrinePotassium influxInhibitory
SHTSerotoninPotassium influxInhibitory
AMPAGlutamateSodium influxExcitatory
NMDAGlutamateSodium and calcium influxExcitatory
NK-1Substance-PSodium and calcium influxExcitatory
NK-1,2NK-1Sodium and calcium influxExcitatory
CCGPCGRPSodium and calcium influxExcitatory
GABA-BBaclofenPotassium influxInhibitory
GABA-ABenzodiazepineChloride influxInhibitory
Gabapentinoid receptorGabapentin/PregabalinBlocks calcium, L-typeInhibitory
α1, α2SNRIPotassium influxInhibitory
5-HTSNRIPotassium influxInhibitory
NMDAKetamineSodium and calcium influxExcitatory
Conopeptide receptorω-ConopeptideBlocks calcium, N-typeInhibitory

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