Lack of the PAC1 receptor alters the circadian expression of VIP mRNA in the suprachiasmatic nucleus of mice

PACAP in the retinohypothalamic tract mediates photic information to the suprachiasmatic nucleus via the PAC1 receptor. The diurnal and circadian VIP mRNA expressions in the suprachiasmatic nucleus of PAC1−/− and wild type mice were quantified. During light/dark cycles identical VIP mRNA rhythms were found while the oscillation pattern differed between the two types of animals during constant darkness. The results show that the circadian VIP mRNA expression is influenced by the absence of PAC1 signalling.