Positive allosteric modulators at GABAB receptors exert intrinsic actions and enhance the influence of baclofen on light-induced phase shifts of hamster circadian activity rhythms

► Baclofen inhibits light-induced phase shifts of hamster circadian activity rhythms. ► GABAB receptor positive allosteric modulators were tested for similar activity. ► GS 39783 and RacBHFF enhanced inhibitory effects of baclofen GS 39783 and RacBHFF also display agonist-allosteric activity on phase delays.