Simultaneous visualization of two cellular mRNA species in individual neurons by use of a new double in Situ hybridization method.

We present a new method for the simultaneous detection of two mRNA species within individual neurons. The technique involves the use of radio-labeled and digoxigenin-labeled cRNA probes, the application of which confers a high specificity and sensitivity to the in situ hybridization analysis. We demonstrate the use of this method by illustrating the coexpression of preprogonadotropin-releasing hormone (GnRH) mRNA and preprogalanin mRNA in neurons in the rat forebrain and report a distinct sexual dimorphism in galanin gene expression by GnRH neurons. Coupling this technology with semi-quantitative analysis of the mRNA species hybridized with the isotopically labeled mRNA would permit studies of gene regulation in individual cells among the heterogeneous populations of the brain.