Distribution and cellular localization of preproenkephalin mRNA in the ovine brain and pituitary.

In this study in situ hybridization histochemistry was used to determine the regional and cellular localization of preproenkephalin (PPE) mRNA in the sheep brain and pituitary. Coronal brain sections were hybridized with an 35S-labelled synthetic 45-mer deoxyribonucleotide probe complementary to a portion of the bovine PPE gene. The specificity of the probe was confirmed by Northern blot analysis. The highest density of labelled cell bodies was found in the nucleus accumbens, caudate-putamen, olfactory tubercle, the central nucleus of the amygdala, the paraventricular nucleus of the hypothalamus, the suprachiasmatic nucleus and in the gigantocellular division of the medullary reticular formation. Labelled cells were also found in the olfactory bulb, prefrontal cortex, piriform cortex and cerebral cortex and in the vicinity of the locus coeruleus, parabrachial nucleus and the nucleus of the solitary tract. In the pituitary a dense PPE mRNA signal was observed in the intermediate lobe; cells in the anterior or neural lobe did not express PPE mRNA. The widespread distribution of cells containing PPE mRNA transcripts within the ovine brain agrees with a similar distribution in the rat. The data suggest that PPE neurons may be involved in diverse physiological functions including the processing of sensory and nociceptive information and in the regulation of endocrine and motor responses.