CIRCANNUAL SOMATOSTATIN GENE AND SOMATOSTATIN RECEPTOR GENE-EXPRESSION IN THE EARLY POSTNATAL RAT PINEAL-GLAND

The origin of somatostatin in the pineal gland is controversial as a d ouble origin - neural in pinealopetal nerve fibers and parenchymal cor responding to locally synthesized peptide - is suggested. We have inve stigated the ontogeny and possible circadian and circannual variations of somatostatin and somatostatin receptor gene expression in the rat pineal gland using RT-PCR. Somatostatin gene expression was observed i n the pineal of animals up to 15 days of postnatal life in autumn and winter, but not in prepubertal or adult rats; no transcript was detect ed during spring and summer at any age and a circadian rhythm was only detected in 15-day-old rats, In situ hybridization confirmed these re sults. The transcript of the somatostatin receptor gene (SSTR2) was de tected at all ages studied with no seasonal variations in its expressi on, indicating separate regulatory mechanisms. In conclusion, somatost atin and somatostatin receptor mRNAs are expressed in the neonatal rat pineal with circadian and seasonal variations.