Different developmental profiles of the expression of preprosomatostatin and preprotachykinin-A mRNAs in rat SCN neurons

The suprachiasmatic nucleus (SCN), a central circadian oscillator of mammal s, contains various peptides arranged in the compartment specific manner. L n the present study, we examined a distinct population of neurons in the ce ntral part of the SCN. In situ hybridization histochemistry has demonstrate d that these neurons coexpressed both preprosomatostatin (PPSS) and preprot achykinin A (PPT-A) mRNAs, but the developmental expression profiles were d ifferent among two. PPSS mRNA first appeared in the SCN at postnatal day 1( P1). The intensity and number of PPSS mRNA signals increased and peaked at P7-P14 and gradually decreased as to adult age (P56). However, PPT-A mRNA-p ositive appeared late at P7, and gradually increased up to P56. These findi ngs suggest that neurons encoding both the PPSS and PPTA genes first expres s PPSS and then express PPT-A at a later stage of maturation. (C) 2001 Else vier Science B.V. All rights reserved.