Distribution of somatostatin mRNA in the rat nervous system as visualized by a novel non-radioactive in situ hybridization histochemistry procedure.

The cellular localization of preprosomatostatin mRNA in the rat brain and sensory ganglia has been examined in detail using a newly developed highly sensitive non-radioactive in situ hybridization histochemistry procedure. An alkaline phosphatase labelled anti-sense 30mer oligodeoxynucleotide probe was used for detection of somatostatin mRNA. This probe readily demonstrated somatostatin gene expression throughout the rat CNS with very high contrast and good cellular localization. As a result, we visualized numerous somatostatin mRNA-positive cells in many CNS areas which had previously not been shown to contain a mRNA signal. This method detected a number of somatostatin mRNA-positive cells, in the mitral cell layer of accessory olfactory bulb, the glomerular layer of the main olfactory bulb, the dorsal part of the lateral septum, superficial gray layer of superior colliculus, inferior colliculus, anterior ventral cochlear nucleus, granular layer and Purkinje cell layer of cerebellum, and substantia gelatinosa of medulla and spinal cord, all areas where signal detection using radiolabelled in situ probes has previously been rather difficult. The principle advantages of the present method include the very precise cellular resolution of signal, the rapid reaction time and low background. The sensitivity of the present method seems to be at least equivalent to most immunocytochemical procedures and more sensitive than most isotopic in situ hybridization methods.