Immunohistochemical localization of adenosine deaminase in primary afferent neurons of the rat.

Adenosine deaminase (ADA) was detected immunohistochemically in neuronal cell bodies of dorsal root ganglia (DRG) of the rat. ADA-immunoreactivity was confined exclusively to small type B ganglion neurons in cervical, thoracic and lumbar sensory ganglia; large type A neurons in sensory ganglia were devoid of immunostaining for ADA. It was consistently found that only a small proportion of type B neurons in DRG contain immunohistochemically detectable ADA. It is suggested that the expression of high ADA levels is a distinguishing feature of a subpopulation of type B DRG neurons and, further, that ADA in these neurons may reflect their utilization of purines (adenosine or adenine nucleotides) as transmitters or cotransmitters.