Pain
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Diffuse noxious inhibitory controls (DNIC) are very powerful long-lasting descending inhibitory controls, which are pivotal in modulating the activity of spinal and trigeminal nociceptive neurons. The principal feature of DNIC is that they are subserved by a loop that involves supraspinal structures that have not yet been identified. Using behavioral, in vivo extracellular electrophysiological and anatomical approaches, we studied the neuronal network underlying DNIC. ⋯ We show that inactivating the lateral parabrachial area - by microinjecting the GABA(A) agonist, muscimol - strongly attenuates DNIC-induced inhibition of C-fiber-evoked responses. Finally, our neuroanatomical tracing study demonstrates that the descending pathway for DNIC does not involve direct descending projections from the PB area. We conclude that (1) lamina I/III spinoparabrachial neurons that express the NK1 receptor and (2) parabrachial neurons are involved in the ascending part of the loop underlying DNIC and that the descending pathway for DNIC might include indirect projections to the spinal or medullary dorsal horn.