CRH-positive neuronal populations are abundant in the amygdala (a) and hippocampus (b, c) of the developing (10-day old) rat. Within the amygdala complex, CRH-immunoreactive cell bodies and fibers populate preferentially the central nucleus of the amygdala (ACe), which is involved in ‘processing’ of stress signals [29,35]. In the hippocampus, corticotropin-releasing hormone (CRH)-producing interneurons reside throughout CA1 and CA3 pyramidal-cell layers [stratum pyramidale (SP); b; arrowheads]. (c) A high magnification of the CA1 subfield demonstrates that CRH-immunoreactive interneurons and axon terminals (arrows) richly innervate pyramidal cell somata, presumably influencing the activity of these neurons. Scale bar, 150 μm for (a,b), 25 μm for (c).