Effects of microinjections of substance P into the suprachiasmatic nucleus region on hamster wheel-running rhythms

Hugh D. Piggins, Benjamin Rusak

    Research output: Contribution to journalArticlepeer-review

    Abstract

    The suprachiasmatic nucleus (SCN) receives a direct retinal projection, which in rats includes substance P (SP)-immunoreactive retinal ganglion cells. While SP has been shown to have neurophysiological effects on SCN cells in Syrian hamsters and rats, it is not known what effects SP in the SCN has on circadian rhythms in hamsters. We examined this question using male Syrian hamsters that were implanted with cannulas aimed at the SCN region and maintained in constant dim red lighting conditions. Hamsters received 0.5 μl microinjections of saline or SP (500 pmol in saline) at a variety of circadian times (CT). Saline injections had little or no phase-shifting effects at any phase tested. SP had no significant effects st CT4-8, 16-20, or 20-24, but did cause small phase delays of -23.7 ± 7 min (mean ± sem) at CT12-16. In order to examine the dose-response relations of this effect, hamsters were also microinjected with 50 and 2500 pmol of SP at CT12-16. Both the 50 and 2500 pmol doses induced very small phase delays (-14.2 ± 7 min and -18.2 ± 5 min, respectively), indicating no obvious dose dependence within this range. These results do not suggest that SP alone in the SCN mimics light effects on circadian rhythms or is a key neurotransmitter involved in photic entrainment. It remains to be determined whether SP interacts with other transmitters in the SCN to modulate their effects on rhythm phase.
    Original languageEnglish
    Pages (from-to)451-455
    Number of pages4
    JournalBrain Research Bulletin
    Volume42
    Issue number6
    DOIs
    Publication statusPublished - 1997

    Keywords

    • Circadian rhythm
    • Hypothalamus
    • Neuropeptide
    • Tachykinin
    • Wheel-running

    Fingerprint

    Dive into the research topics of 'Effects of microinjections of substance P into the suprachiasmatic nucleus region on hamster wheel-running rhythms'. Together they form a unique fingerprint.

    Cite this