XXXX immunocytochemistry of primary afferent terminals in the rat dorsal horn.

@entity2227 @entity1246 @entity535 @entity492 @entity143 @entity3698 @entity3505
We combined transganglionic tracing methods with postembedding electron microscopic immunocytochemistry to determine whether identified primary afferent fibers terminating in spinal laminae I-IV may use @entity2227 and @entity492 as neurotransmitters. Sciatic injections of @entity3505 -germ agglutinin conjugated to horseradish @entity3698 labeled fine afferent fibers with terminals in laminae I-II of the lumbar spinal cord, whereas injections of the B subunit of cholera toxin conjugated to horseradish @entity3698 labeled primary afferent terminals in deeper laminae. Many labeled primary afferent terminals in superficial laminae were involved in glomerular synaptic arrangements; others established nonglomerular contacts. Most glomerular arrangements were clearly immunopositive for @entity2227 , compared with dendrites, astrocytes, or terminals immunopositive for @entity1246 ( @entity1246 ). The degree of enrichment varied in labeled terminals of different morphological types. @entity492 was enriched, though to a lesser degree than @entity2227 , in labeled central terminals of glomeruli in superficial laminae. Labeled primary afferent terminals in laminae III-IV were immunopositive for @entity2227 , though at lower levels than glomerular terminals in superficial laminae. @entity492 was not enriched in these terminals compared with dendrites, glia, and @entity1246 -positive terminals. These results support a neurotransmitter role for @entity2227 in primary afferents to the dorsal horn. Quantitative differences in the content of @entity2227 in identified primary afferent terminals may be related to functional differences. Enrichment of @entity492 in terminals in superficial but not deep laminae is compatible with a role for this @entity535 in sustained, @entity143 -mediated phenomena characteristic of activity in fine caliber afferents.
