Figure 3. Local action of noradrenaline modulates song-induced gene expression in NCM.

a) Camera lucida drawing of a parasagittal section containing NCM, field L2a and CMM (about 500 µm from the midline), indicating the site of injections (pipette and dashed circle). b) Schematic representation of the experimental design depicting the timing of stereotaxic injection into NCM of awake restrained birds in relation to silence and song stimulation periods. c) Autoradiograms of adjacent parasagittal sections from a representative bird that received an injection of phentolamine or vehicle (opposite hemispheres) into NCM, hybridized with zenk, c-fos or hat2 riboprobes. d) Fold-induction values for zenk, c-fos and hat2 in the NCM of vehicle- (white bars) or phentolamine-injected (gray bars) hemispheres in birds stimulated for 10 min with conspecific song normalized to the corresponding injected hemispheres in unstimulated controls. For abbreviations, see Figs 1 and 2. Scale bar in a: 2 mm.