Variable varicosity sizes in GABAergic input axons. Representative axon varicosities labeled by BDA injections in structures known to innervate the thalamus with GABAergic axons: anterior pretectal nucleus (APT; a), zona incerta (ZI; b), and thalamic reticular nucleus (TRN; c, d). Scale bar: 10 µm. e, Size distribution of axonal varicosities grouped into discrete intervals according to their maximal cross-sectional area. f, Box-plot diagram showing axonal varicosity sizes.