EVIDENCE FOR COLOCALIZATION OF GABA AND GLYCINE IN AFFERENTS TO RETROGRADELY LABELED RAT ABDUCENS MOTONEURONS

The coexistence of gamma-aminobutyric acid (GABA) and glycine in axon terminals impinging on rat abducens motoneurones was investigated usin g a double staining procedure combining retrograde labelling of the mo toneurones with HRP and post-embedding immunocytochemical staining of axon terminals. Adjacent ultrathin sections of cell bodies of identifi ed motoneurones were individually treated with GABA or glycine antibod ies. The terminals single labelled for GABA represented 11.4% of the t erminals analyzed, while 8% of them were glycine immunoreactive and 9% were both GABA and glycine immunoreactive. All the labelled terminals contained pleomorphic vesicles. The mean length of apposition of the double labelled terminals was statistically larger (2.20 +/- 0.97 mu m ) than the GABA (1.65 +/- 0.57 mu m) or glycine immunoreactive ones (1 .37 +/- 0.35 mu m).