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PACAP-deficient mice exhibit light parameter-dependent abnormalities on nonvisual photoreception and early activity onset.

Kawaguchi C, Isojima Y, Shintani N, Hatanaka M, Guo X, Okumura N, Nagai K, Hashimoto H, Baba A - PLoS ONE (2010)

Bottom Line: The photopigment melanopsin has been suggested to act as a dominant photoreceptor in nonvisual photoreception including resetting of the circadian clock (entrainment), direct tuning or masking of vital status (activity, sleep/wake cycles, etc.), and the pupillary light reflex (PLR).These data suggest that the dysfunctions of entrainment and masking were caused by the loss of PACAP, not by the loss of light input itself.These results indicate that PACAP regulates particular nonvisual light responses by conveying parametric light information--that is, intensity and duration.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan.

ABSTRACT

Background: The photopigment melanopsin has been suggested to act as a dominant photoreceptor in nonvisual photoreception including resetting of the circadian clock (entrainment), direct tuning or masking of vital status (activity, sleep/wake cycles, etc.), and the pupillary light reflex (PLR). Pituitary adenylate cyclase-activating polypeptide (PACAP) is exclusively coexpressed with melanopsin in a small subset of retinal ganglion cells and is predicted to be involved extensively in these responses; however, there were inconsistencies in the previous reports, and its functional role has not been well understood.

Methodology/principal findings: Here we show that PACAP-deficient mice exhibited severe dysfunctions of entrainment in a time-dependent manner. The abnormalities in the mutant mice were intensity-dependent in phase delay and duration-dependent in phase advance. The knockout mice also displayed blunted masking, which was dependent on lighting conditions, but not completely lost. The dysfunctions of masking in the mutant mice were recovered by infusion of PACAP-38. By contrast, these mutant mice show a normal PLR. We examined the retinal morphology and innervations in the mutant mice, and no apparent changes were observed in melanopsin-immunoreactive cells. These data suggest that the dysfunctions of entrainment and masking were caused by the loss of PACAP, not by the loss of light input itself. Moreover, PACAP-deficient mice express an unusually early onset of activities, from approximately four hours before the dark period, without influencing the phase of the endogenous circadian clock.

Conclusions/significance: Although some groups including us reported the abnormalities in photic entrainments in PACAP- and PAC(1)-knockout mice, there were inconsistencies in their results. The time-dependent dysfunctions of photic entrainment in the PACAP-knockout mice described in this paper can integrate the incompatible data in previous reports. The recovery of impaired masking by infusion of PACAP-38 in the mutant mice is the first direct evidence of the relationship between PACAP and masking. These results indicate that PACAP regulates particular nonvisual light responses by conveying parametric light information--that is, intensity and duration. The "early-bird" phenotype in the mutant mice originally reported in this paper supposed that PACAP also has a critical role in daily behavioral patterns, especially during the light-to-dark transition period.

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Early onset of activities in Adcyap1−/− mice.(A) Representative double-plotted actogram in LD cycles (light phase 20lx) and subsequent DD conditions. Dark phases are shaded. (B–C) Quantification of wheel-running activities in the LD cycles with a 20lx (B) or 100lx (C) light phase (n = 12). (D) Quantification of wheel-running activities in subsequent DD conditions (after 20lx LD cycle; n = 12). Values denote means ± SEM **p<0.01 versus Adcyap1+/+ during ZT/CT 8–11, two–way repeated-measures ANOVA.
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pone-0009286-g005: Early onset of activities in Adcyap1−/− mice.(A) Representative double-plotted actogram in LD cycles (light phase 20lx) and subsequent DD conditions. Dark phases are shaded. (B–C) Quantification of wheel-running activities in the LD cycles with a 20lx (B) or 100lx (C) light phase (n = 12). (D) Quantification of wheel-running activities in subsequent DD conditions (after 20lx LD cycle; n = 12). Values denote means ± SEM **p<0.01 versus Adcyap1+/+ during ZT/CT 8–11, two–way repeated-measures ANOVA.

Mentions: Adaptation of daily activity rhythms to environmental LD cycles is reported to be attained by harmonization with entrainment and masking [7]. We tested the effects of the deficits in entrainment and masking found in Adcyap1−/− mice on their behavioral adaptation. Under LD cycles with a 20 or 100lx light phase, Adcyap1−/− mice showed robust behavioral rhythms nearly identical to those in Adcyap1+/+ mice (Fig. 5A, B); however the mutants unexpectedly exhibited an earlier onset of activities, about four hours before the dark phase, but showed a normal offset latencies after the dark phase (Fig. 5A, B). These aberrant activities were still observed in subsequent DD conditions (Fig. 5A, C). We hypothesized that this early onset of activity was ascribable to molecular clock disturbances with a positive phase angle; therefore, we examined the circadian fluctuation of Period1 (Per1: a major clock gene that determines the free-running period) [25] and Prokineticin2 (Prok2: a clock-controlled gene that suppresses day-time activity) [26] transcripts in the SCN. Adcyap1+/+ mice showed remarkable circadian fluctuations in both genes with the same peak times (Fig. 6), as reported previously [25], [26]. Inconsistent with our hypothesis, Adcyap1−/− mice showed an almost all identical phase angle and waveform to those of Adcyap1+/+ mice. Additionally, the free-running period in DD conditions was not altered in Adcyap1−/− mice (Adcyap1−/−, 23.7±0.09 hours, n = 12; Adcyap1+/+, 23.8±0.08 hours, n = 12).


PACAP-deficient mice exhibit light parameter-dependent abnormalities on nonvisual photoreception and early activity onset.

Kawaguchi C, Isojima Y, Shintani N, Hatanaka M, Guo X, Okumura N, Nagai K, Hashimoto H, Baba A - PLoS ONE (2010)

Early onset of activities in Adcyap1−/− mice.(A) Representative double-plotted actogram in LD cycles (light phase 20lx) and subsequent DD conditions. Dark phases are shaded. (B–C) Quantification of wheel-running activities in the LD cycles with a 20lx (B) or 100lx (C) light phase (n = 12). (D) Quantification of wheel-running activities in subsequent DD conditions (after 20lx LD cycle; n = 12). Values denote means ± SEM **p<0.01 versus Adcyap1+/+ during ZT/CT 8–11, two–way repeated-measures ANOVA.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2823792&req=5

pone-0009286-g005: Early onset of activities in Adcyap1−/− mice.(A) Representative double-plotted actogram in LD cycles (light phase 20lx) and subsequent DD conditions. Dark phases are shaded. (B–C) Quantification of wheel-running activities in the LD cycles with a 20lx (B) or 100lx (C) light phase (n = 12). (D) Quantification of wheel-running activities in subsequent DD conditions (after 20lx LD cycle; n = 12). Values denote means ± SEM **p<0.01 versus Adcyap1+/+ during ZT/CT 8–11, two–way repeated-measures ANOVA.
Mentions: Adaptation of daily activity rhythms to environmental LD cycles is reported to be attained by harmonization with entrainment and masking [7]. We tested the effects of the deficits in entrainment and masking found in Adcyap1−/− mice on their behavioral adaptation. Under LD cycles with a 20 or 100lx light phase, Adcyap1−/− mice showed robust behavioral rhythms nearly identical to those in Adcyap1+/+ mice (Fig. 5A, B); however the mutants unexpectedly exhibited an earlier onset of activities, about four hours before the dark phase, but showed a normal offset latencies after the dark phase (Fig. 5A, B). These aberrant activities were still observed in subsequent DD conditions (Fig. 5A, C). We hypothesized that this early onset of activity was ascribable to molecular clock disturbances with a positive phase angle; therefore, we examined the circadian fluctuation of Period1 (Per1: a major clock gene that determines the free-running period) [25] and Prokineticin2 (Prok2: a clock-controlled gene that suppresses day-time activity) [26] transcripts in the SCN. Adcyap1+/+ mice showed remarkable circadian fluctuations in both genes with the same peak times (Fig. 6), as reported previously [25], [26]. Inconsistent with our hypothesis, Adcyap1−/− mice showed an almost all identical phase angle and waveform to those of Adcyap1+/+ mice. Additionally, the free-running period in DD conditions was not altered in Adcyap1−/− mice (Adcyap1−/−, 23.7±0.09 hours, n = 12; Adcyap1+/+, 23.8±0.08 hours, n = 12).

Bottom Line: The photopigment melanopsin has been suggested to act as a dominant photoreceptor in nonvisual photoreception including resetting of the circadian clock (entrainment), direct tuning or masking of vital status (activity, sleep/wake cycles, etc.), and the pupillary light reflex (PLR).These data suggest that the dysfunctions of entrainment and masking were caused by the loss of PACAP, not by the loss of light input itself.These results indicate that PACAP regulates particular nonvisual light responses by conveying parametric light information--that is, intensity and duration.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan.

ABSTRACT

Background: The photopigment melanopsin has been suggested to act as a dominant photoreceptor in nonvisual photoreception including resetting of the circadian clock (entrainment), direct tuning or masking of vital status (activity, sleep/wake cycles, etc.), and the pupillary light reflex (PLR). Pituitary adenylate cyclase-activating polypeptide (PACAP) is exclusively coexpressed with melanopsin in a small subset of retinal ganglion cells and is predicted to be involved extensively in these responses; however, there were inconsistencies in the previous reports, and its functional role has not been well understood.

Methodology/principal findings: Here we show that PACAP-deficient mice exhibited severe dysfunctions of entrainment in a time-dependent manner. The abnormalities in the mutant mice were intensity-dependent in phase delay and duration-dependent in phase advance. The knockout mice also displayed blunted masking, which was dependent on lighting conditions, but not completely lost. The dysfunctions of masking in the mutant mice were recovered by infusion of PACAP-38. By contrast, these mutant mice show a normal PLR. We examined the retinal morphology and innervations in the mutant mice, and no apparent changes were observed in melanopsin-immunoreactive cells. These data suggest that the dysfunctions of entrainment and masking were caused by the loss of PACAP, not by the loss of light input itself. Moreover, PACAP-deficient mice express an unusually early onset of activities, from approximately four hours before the dark period, without influencing the phase of the endogenous circadian clock.

Conclusions/significance: Although some groups including us reported the abnormalities in photic entrainments in PACAP- and PAC(1)-knockout mice, there were inconsistencies in their results. The time-dependent dysfunctions of photic entrainment in the PACAP-knockout mice described in this paper can integrate the incompatible data in previous reports. The recovery of impaired masking by infusion of PACAP-38 in the mutant mice is the first direct evidence of the relationship between PACAP and masking. These results indicate that PACAP regulates particular nonvisual light responses by conveying parametric light information--that is, intensity and duration. The "early-bird" phenotype in the mutant mice originally reported in this paper supposed that PACAP also has a critical role in daily behavioral patterns, especially during the light-to-dark transition period.

Show MeSH
Related in: MedlinePlus