α2-chimaerin mRNA distribution changes during postnatal development of the cortex and it is selectively expressed in adult brain regions. A, The laminar pattern of α2-chimaerin mRNA in the cortex is established postnatally. At postnatal day 7 (7d), it is evenly distributed throughout all layers of cerebral cortex, by day 12 there is a distinct laminar pattern (12d), and at day 17 deep cortical layers (arrow) show increased expression (17d). B, α2-chimaerin mRNA expression in adult rat brain was analyzed by in situ hybridization in a series of coronal sections from an anterior section (a) showing anterior olfactory nucleus (aon) through to (h) showing dorsal motor nucleus of the vagus nerve (dmv), area postrema (ap), and inferior olivary nucleus (ion). The laminar pattern found in the cortex of young rats is still evident in adult, although slightly less prominent (c, d). The highest level of signal is detected in the entorhinal cortex (ent) (f); expression was restricted to specific neuronal nuclei.cb, Cerebellum; cx, cerebral cortex;cl, claustrum; drn, dorsal raphe nucleus;hpc, hippocampus; lc, locus coeruleus;mh, medial habenula; pir, piriform cortex; ph, paraventricular hypothalamic nucleus;pi, pineal gland; pn, pontine nucleus;pt, paraventricular thalamic nucleus;rhα rhomboid nucleus of the thalamus;s, striatum; sn, substantia nigra. Scale bar, 2 mm.