Scientists looked at where a peptide called DSIP is found in the brains of young guinea pigs. They saw it in many important brain areas, and the amount and brightness of the signal grew as the animals got older. The peptide’s fibers were often close to blood vessels and brain fluid spaces.

The distribution and development of delta sleep-inducing peptide (DSIP) in the guinea-pig brain were studied in 2- to 60-day-old animals by using the indirect immunofluorescence method. DSIP-immunoreactive perikarya were observed in the olfactory bulb and tubercle, diagonal band of Broca, septum, preoptic area, anterior and lateral hypothalamus, arcuate nucleus and hippocampus. In addition to the densest innervation of the median eminence, DSIP-immunoreactive fibres were widely localized from forebrain to mesencephalon. The field of immunoreactive fibre endings appeared to be in close association with either the blood vessels of brain, ventricles, subarachnoid space or immunolabelled perikarya. Furthermore, throughout development the topographic distribution pattern of immunolabelled neuronal elements seemed to be similar. However, a generalized increase in number, immunofluorescence intensity and varicosities of DSIP fibres was displayed with the growth. The present results provide an anatomical basis for understanding multiple actions of DSIP in the central nervous system and future research for DSIP on development.