Both genotypes become arrhythmic when placed in constant darkness and both genotypes display an almost inverted TP profile being more like a diurnal animal. and low light intensity. Furthermore, we examined the manifestation of PAC1- and VPAC2 receptors in the SCN of the different genotypes in combination with visualization of PACAP and VIP and identified whether compensatory changes in peptide and/or receptor manifestation in the reciprocal knockouts (KO) (PAC1 and VPAC2) experienced occurred. Our data demonstrate that in although becoming closely related at both ligand and receptor structure/sequence, Rabbit Polyclonal to PFKFB1/4 PACAP/PAC1 receptor signaling are self-employed of VIP/VPAC2 receptor signaling and vice versa. Furthermore, lack of either of the receptors does not result in compensatory changes at neither the physiological or anatomical level. PACAP/PAC1 signaling is definitely important for light controlled behavior, VIP/VPAC2signaling for stable clock PhiKan 083 function and both signaling pathways may play a role in shaping diurnality versus nocturnality. Intro In mammals, the brains biological clock located in the suprachiasmatic nucleus (SCN) [1] produces circadian rhythms in physiology and behavior of approximately 24 h. 10C20.000 neurons constitute the neuronal network of the SCN, and the individual neurons express a molecular clockwork based on positiveCand negative feedback loops of so-called clock proteins and their respective genes [2]. To keep up a rhythmic clock function, the individual neurons in the SCN need to be synchronized. Important signals are mediated from the neuropeptide VIP and its receptor, the VPAC2 receptor [3C5]. VIP is definitely indicated in neurons of the ventral SCN while the VPAC2 receptors happen throughout the SCN although with higher manifestation corresponding to the dorsomedial shell region of the SCN [6, 7]. Mice lacking either VIP or VPAC2 receptors have related phenotype. Both strains of mice become arrhythmic in constant darkness but display stable nocturnal activity during normal light-dark photoperiods. The nocturnal behavior is definitely strongly dependent on the light conditions [4, 5, 8] as are additional rhythmic behaviors and physiology such as heat, metabolism, food intake, heart rate and hormone secretion. However, in VIP/VPAC2 receptor deficient PhiKan 083 mice these rhythms are significantly advanced by 5C6 h compared to activity onset [5, 9C11]. The ventral SCN receives retinal input via the retinohypothalamic tract (RHT) which daily entrains the clock to light [12, 13], and VIPergic neurons located in this part of the SCN project both within and outside the nucleus [6]. The VIPergic neurons are hypothesized to be important for relaying photic info in light controlled behavior [14]. The neuropeptide PACAP is definitely structurally related to VIP. Three seven transmembrane G-protein coupled receptors PhiKan 083 (GPCR) for PACAP have been identifiedCPAC1, VPAC1 and VPAC2; however, only the PAC1 receptor is definitely selective for PACAP, while VPAC1 and VPAC2 receptors display equivalent affinities for PACAP, and VIP [15]. PACAP has been attributed a role as neurotransmitter in the RHT involved in masking control [16C18]. PACAP signaling is definitely mediated by PAC1 receptors located in SCN neurons [17] and mice lacking either PACAP or PAC1 receptors display impaired photoentrainment and masking at low light intensities [16C18]. Behavior and physiology in VPAC2 deficient mice are strongly controlled by light most likely as a result of masking [3]. As a result, we decided to use VPAC2 and PAC1/VPAC2 double mutant mice in comparison with PAC1 receptor deficient mice to further elucidate the part of PACAP in the light mediated rules of behavior and physiology of the circadian system. We compared circadian rhythms in mice equipped with operating wheels or implanted radiotransmitter recording core body temperature, which were kept inside a FPP and SPP at high and low light intensity. Furthermore, we examined the manifestation of PAC1- and VPAC2 receptors in the SCN of the different genotypes in combination with visualization of PACAP and VIP and identified whether compensatory changes in peptide and/or receptor manifestation in the reciprocal knockouts (KO) (PAC1 and VPAC2) experienced occurred. Material and methods Animals From our colony of PAC1 receptor deficient [16] and VPAC2 deficient mice [5] we generated a strain of PAC1/VPAC2 deficient double mutant mice. Male and female mice of each genotype were included in the study. Mice were 10C12 weeks aged when included in the experiments and were managed in 12:12 h LD cycles in individual cages with water and food (Altromin 1324; Altromin Spezialfutter, Germany) unless normally stated. Animals were treated according to the.