A Blog Around The Clock

Phase-Response Curves to Melatonin

NBM found an excellent online article (which I have seen before but I forgot) depicting Phase-Response Curves (PRC) to injections of melatonin in humans, rodents and lizards.

i-9a75d14c85618ecff2f8964bb2ca0bf6-melatonin PRCs.gif

Note how the shape is roughly opposite to that of a PRC to light pulses, i.e., at phases at which light elicits phase-delays, melatonin produces advances and vice versa:

i-ffb38d9dcbdd11cc953e2fea7150ff18-melatonin-light-PRC small.jpg

The lizard PRC was actually constructed in our lab, about ten years before I joined. The article, though, gives the wrong reference to this:

Underwood, H. and M. Harless (1985). “Entrainment of the circadian activity rhythm of a lizard to melatonin injections.” Physiology & Behavior 35(2): 267-70.

In that paper, lizards were entrained by daily melatonin injections. The PRC was reported in a different paper the following year:

H Underwood (1986) Circadian Rhythms in Lizards: Phase Response Curve for Melatonin, Journal of Pineal Research 3 (2), 187-196.

Update: an alert reader sends a better figure, taken from this freely available recent paper:

i-a43ada0288d40b8998e1b71e1e56ad5c-human PRC light and melatonin.jpg


  1. #1 nbm
    August 13, 2007

    Thanks! Finally that superimposed version which I’ve only read about, not seen before.
    Now wouldn’t it be nice if all studies were online in full text, not just those tantalizing abstracts??

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