Differential activation of Fos-like immunoreactivity in the arcuate nucleus and amygdala after intracerebroventricular injection of sodium nitroprusside and N-omega nitro-L-arginine in conscious and urethane-anesthetized lactating rats

The effect of intracerebroventricular injection of a nitric oxide (NO) dono r (sodium nitroprusside, SNP) or NO synthase inhibitor (N-omega nitro-L-arg inine, L-NA) on Fos-like immunoreactivity (FLI) in the arcuate nucleus (ARC ) and the medial, cortical and central amygdaloid nuclei was examined in co nscious and urethane-anesthetized lactating rats. In conscious darns, the n umber of FLI-cells in the medial and cortical amygdaloid nuclei were signif icantly larger after the injection of L-NA than after SNP injection. In ane sthetized darns, the number of FLI-cells was decreased in the medial and co rtical amygdaloid nuclei by L-NA injection, whereas the numbers were increa sed in the ARC and the medial amygdaloid nuclei after the injection of SNP. The nucleus-specific response to SNP or L-NA suggested possible involvemen t of NO in modulation of dynamics of neuronal activity within these nuclei. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.