GABA-like immunoreactivity in type I glomeruli of rat substantia gelatinosa

A postembedding immunogold study of type I synaptic glomeruli in lamina II of rat dorsal horn was carried out using antiserum to gamma-aminobutyric acid (GABA). Gold particles were concentrated over some peripheral axons and vesicle-containing dendrites within these glomeruli and both types of profile were presynaptic to central axons. These results suggest that GABA is involved in presynaptic inhibition of unmyelinated primary afferents and is released by some presynaptic dendrites within lamina II.