NON RADIOACTIVE IN SITU HYBRIDIZATION OF CRFR1 mRNA IN AN ANIMAL MODEL OF DEPRESSION.

FERNÁNDEZ MACEDO GV., SIFONIOS L., CLADOUCHOS ML., WIKINSKI S

Tandil, provincia de Bs. As.

Congreso; Reunión Anual de la Sociedad Argentina de Investigación en Farmacología Experimental; 2008

Corticotrophin releasing factor (CRF) has been shown altered in depressive patients as well as in animal models of depression. In this pathological condition, it exerts its action mainly through activation of type one CRF receptor (CRFR1). We developed a non radioactive in situ hybridization method to measure CRFR1 mRNA. We used a cRNA digoxigenin-labeled probe synthesized by the in vitro transcription of a rat CRFR1 cDNA subcloned in a vector. Hybridization was performed on rat brain sections and the probe specifically hybridized with the CRFR1 mRNA was detected by a commercial kit. Specificity to CRFR1 mRNA was confirmed in sections hybridized with sense probes, the specificity to RNA was tested digesting the tissue with RNAses prior to hybridization and the specificity of the detection procedure was study without using the label probe. We measured the expression of CRFR1 in two hippocampal areas (CA3 and dentate gyrus) of animals after 21 days of exposure to the learned helplessness (LH) paradigm. We compared: a control group (C, rats not exposed to stress), LH+ (rats that develop the behavioural despair after exposure to stress) and LH- (rats that fail to develop the behavioural despair after exposure to stress). LH+ showed a decrease in the mRNA CRFR1 expression versus LH- or C, both in CA3 and in dentate gyrus (p<0.01). We conclude that 3 weeks after exposure to the LH paradigm the expression of CRFR 1 is downregulated. Supported by: PICT 31953, PIP 5870, UBACYT M013 and M073.