Expression of Fos-like immunoreactivity by yohimbine and clonidine in the rat brain

Abstract To elucidate the role of α 2 -adrenoceptors in transcriptional control in the rat brain, we localized the Fos-like immunoreactivity (Fos-LI) induced by α 2 -adrenoceptor agonists and by an antagonist. Injections of yohimbine (5 mg/kg, i.p.) into rats led to the induction of Fos-LI in areas with a dense α 2 -adrenoceptor binding such as the locus coeruleus, the bed nucleus of stria terminalis, the central nucleus of amygdaloid complex, the paraventricular nucleus, the nucleus tractus solitarius, and ventrolateral medulla oblongata. Clonidine (500 μg/kg, i.p.) suppressed the Fos expression by yohimbine in these nuclei, and clonidine (100 μg/kg, i.p.) or guanabenz (4 mg/kg, i.p.) induced Fos-LI in oxytocin neurons in the paraventricular and supraoptic nuclei in the hypothalamus. Thus, the α 2 -adrenoceptor is involved in transcriptional control via Fos expression in neurons related to autonomic and other functions.