Chapter 5 Spinal dorsal horn circuitry involved in the brain stem control of nociception

Abstract

Publisher Summary This chapter discusses the spinal dorsal horn circuitry involved in the brain stem control of nociception. The role of several neurochemicals in the brain stem projections to dorsal horn sensory systems has been examined. The double immunofluorescence method provides information on the colocalization of neurochemicals within single neurons or axon terminals. The descending 5-hydroxytryptamine (5HT) modulation of dorsal horn neuronal activity exhibits a predominantly postsynaptic mechanism that occurs at a variety of sites. 5HT contacts are found on several different populations of long distance projection neurons and interneurons. There is no strong morphological support for 5HT presynaptic effects on primary afferent axons. The spinomesencephalic, spinothalamic and dorsal column postsynaptic (DCPS) neurons receive 5HT contacts, thus, 5HT innervation of projection pathways is a common feature of monoaminergic modulation of dorsal horn neural circuits. The different classes of projection neurons receiving 5HT inputs suggest that 5HT plays a role in modulating output systems having a diversity of function.