4623 Exam 2 Study Guide
4623 Exam 2 Study Guide Psych 4623
Popular in Biological Clocks and Behavior
Popular in Neuroscience
NEUROSC 3000 - 020
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This 14 page Study Guide was uploaded by Laura Hogan on Monday March 7, 2016. The Study Guide belongs to Psych 4623 at Ohio State University taught by Dr. Randy Nelson in Spring 2016. Since its upload, it has received 101 views. For similar materials see Biological Clocks and Behavior in Neuroscience at Ohio State University.
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Date Created: 03/07/16
4623 Exam 2 Study Guide SCN contain master circadian oscillator z10000 neurons same size as mouse SCN GABAergic GABA is the primary neurotransmitter o inhibitory NT 0 ventralmost portion of the thalamus Studies leading to the discovery of the SCN as the master oscillator o 2 DG deoxyglucose injections gt showed metabolic activity in the SCN at different points throughout the day 0 brain slicing kill animal preserve brain slice thinly and raise temperature back to body temp so that neurons begin to fire again SCN neurons have the highest rates of activity during subjective day 8H2 compared to night 12 Hz 0 lesion studies lesion put in SCN but animal is kept alive and functioning no consolidation of rhythms sporadic activity patterns This is proof that the SCN is a biological clock but further research is needed to prove that it is the Master 0 tissue was then isolated outside of the brain gt individual neuron oscillations can be monitored all individual cells still oscillate even without synaptic connections 0 cell dispersion 2030 hours 0 the individual cells have an inherent capacity to keep time Generation of Rhythms at the Cellular Level Possible Ideas 0 membrane excitability oscillations 0 feedback mechanisms driven by Ca2 K and Na channels 0 redox oscillation 0 reaction electron transfer to generate ATP 0 transcriptionaltranslational oscillation 0 genes expressed at different times through the day interactions creation of oscillation patterns Bulla Gouldiana bubbleshell gastropod 0 cut off eye stalks and measure firing properties fired at 24 hour periods 0 central dogma DNA gt mRNA gt protein was used to try to find the basis of the oscillator o disrupted mRNA at the protein stage by poisoning the eye stalks with cycloheximide and anisomycin measured period effects 0 more protein production inhibition gt more period effects period was lengthened 0 Protein production plays a key role in setting clock for circadian oscillator Gene expression is a central component of circadian timing mechanism reduce the rate of protein synthesis longer tau z48 hour periods At this point the Circadian Clock Model in theory is based on a transcriptional feedback loop where clock genes give rise to negative elements proteins that negatively regulate their own expression Forward Genetics o seeking a genetic basis for an observed phenotype or behavior 0 ENU screening is an example 0 ENU is an alkylating agent that triggers A gt T base transversions 1 mutation per1000ocD o ENU generated point mutations can trigger a gainoffunction or lossoffunction in a gene Mutations can be reflected in the behavior of the animals using gene mapping approaches 0 ENU changes the structure of the protein gt changed function of the protein gt behavioral change 0 mutagenize animal gt arrhythmic phenotype detected cross animals that show this gene lt24 hour tau offspring gt 2 copies of mutant gene gt all activity consoHda onislost 0 first piece of evidence that the circadian oscillator has at least 1 gene based on its functionality Clock Gene 0 basic helixloophelix bHLH transcription factor 0 DNA binding domain 0 Protein interaction domains PAS which allows CLOCK to bind to other proteins transcription factors such as BMAL1 bHLH transcription factors dimerize and bind to DNA changes on amino acid side chains allow binding to specific frequencies 0 EBOX sequence CACGTG Clock will bind to EBOX BMAL1 0 Yeast 2hybrid screen identified BMAL1 as Clock s binding partner 0 similar structure to Clock bHLH PAS domain allows binding to Clock binds to Ebox Transcardial Perfusion Studies 0 probe thinly sliced pieces of brain tissue at both the mRNA and the protein level 0 found that both Clock and BMAL1 are expressed in the SCN and therefore play a key role in the generation of oscillations Reverse Genetics 0 seeks to find what phenotypes arise as a result of a particular gene 0 Knockout technology is an example 0 BMAL1 knockout mice 0 pups with double mutation very small gained weight very slowly higher mortality 0 1020 weeks start dying 0 2050 weeks rapid sink in survival rate 0 premature aging osteoporosis low muscle weight low heart rate low muscle weight 0 eye vision and respiratory problems 0 circadian timing disruption seems to disrupt all other bodily processes and aspects of physiology and health Clock and BMAL1 two positive elements that drive gene expression required for circadian timing Period Gene 0 Drosophila period mutation identified 0 genetic mechanism that underlies rhythmicity o transcardial perfusion is PER expressed in the SCN 0 Yes gene sequencing revealed the presence of 3EBOXs on the PER 1 regulatory region provided a molecular mechanism by which clock and BMAL1 could bind and generate rhythm Firefly Luciferase Testing 0 test to see if Clock and BMAL stimulate PER1 expression firefly luciferase amount of light generated amount of transcription of PER1 Clock alone low luciferase BMAL1 alone low luciferase neither very low both high luciferase 0 indicates that Clock and BMAL1 drive the expression of the PER1 gene PER1 luciferase reporter gene assay 0 increasing the concentration of PER1 reduces the capacity of Clock and BMAL1 to stimulate luciferase expression via the PER1 promoter 0 therefore PER1 is a NEGATIVE element PER1 regulates its own expression 0 closure of the circadian loop negative feedback Testing Period Gene Function 0 for the noted molecular model to work the Period genes 1 and 2 must translocate into the nucleus 0 in simple expression assays the majority of Per 1 and 2 does not enter the nucleus 0 thus there must be a binding partner that allows the PER genes to translocate Cryptochromes c class of flavoproteins that are light sensitive particularly to blue light in plants their function is photoreception that cues developmental programs interest in the human homolog of these cryptochromes in mice the functional component of CRYs different from those in plants but CRYs seemed to play a role in circadian timing 0 CRY1 shorter tau CRY2 longer tau cross the two arrhythmic indication that there is a high degree of redundancy between CRY1 and 2 similar to PERs CRYs as the Missing Binding Partners of PERS 0 rhythmic CRY expression in the SCN o combine CRYs and PERs CRYs stimulate robust PER1 and 2 nuclear translocation o luciferase reporter gene assay increasing the concentration of CRYs and PERs reduces the capacity of Clock and BMAL1 to stimulate luciferase expression via the PER1 promoter OOO Tau Mutant Hamster o tau z20 hour period c the tau phenotype results from a point mutation in the Casein Kinase 1 Epsilon Gene CK1 c this is a gain of function mutation which is why there is an increased rate of circadian oscillation more rapid tau period z20h Casein Kinase 1 Epsilon o A kinase is an enzymatic protein that drives the transfer of a terminal phosphate from ATP gt target protein In doing so the functionality of the target protein is altered Phosohorylation can trigger protein degradation CK1 triggers phosphorylation of PER genes in 3 locations Phosphorylation regulates PER and CRY stability and in turn the period of the Circadian m o All phosphorylation processes lead to degradation of PER and CRY genes eventually by CK1 many rounds of phos 0 PER and CRY gt drop to baseline levels gt relief of negative pressure of Clock and BMAL gt another round of transcription If you block phosphorylation ability of CK1 tau becomes very long Enhance CK1 tau becomes much more rapid shorter Monitoring Clock Gene Oscillations in the SCN in vivo 0 in vivo refers to studying the gene in the body of a living animal 0 animals can be injected with firefly luciferase c an optical fiber can be used to see light oscillations Genome Regulation by Circadian Clock 0 BMAL1 has been shown to bind to over 2049 sites in the genome 0 among the top 200 sites more than 90 are significantly rhythmic which suggests that a large number of genes not just core clock genes are under the control of the circadian clock 0 perhaps 10 of the entire genome could be regulated by the circadian clock direct and indirect 0 direct via Clock and BMAL1 o indirect ancillary pathways ie CREB gt VIP Key Question How the output of the coreclock transcriptional circuit creates phasecoherence of oscillations within the SCN 0 key finding from dispersed SCN neuronal cell culture experiments 0 isolated cellular oscillators exhibit a wide range of rhythms o if you average these rhythms across a 24 hour period you would end up with a noncircadian output pattern 0 obviously this is the opposite of what you would find in the SCN 0 so how do cells communicate time to each other in vivo Modulatory Neuropeptides 0 VP 88 VIP our focus all are rhythmic show clockgated expression andor release 0 they oscillate at the mRNA level and in their release properties o Neuropeptides large dense core vesicles used by neurons to communicate with each other neuronal signaling 0 work both pre and postsynaptically 0 function through slowacting metabotropic signaling channels Gprotein passages I much slower than GABA and glutamate Vasoactive Intestinal Peptide VIP 0 28 amino acid residues 0 produces in a numerous tissues 0 gut o pancreas 0 brain including SCN o Func ons o vasodHa on o lowers BP 0 relaxes smooth muscles 0 regulates pituitary hormone release 0 SCN physiology 0 the VIP gene consists of 7 exons and is translated into a 170 amino acid prepropeptide that produces at least two biologically active peptides o sidenote a proprotein or propeptide is an inactive protein or peptide that can be turned into its active form by post translational modification VIP binds to a metabotropic receptor 7 on the membrane it can regulate activity by regulating calcium release levels and cyclic AMP cAMP production SCN Functional Neuroanatomy o the SCN is not a homogeneous cell population very heterogeneous o immunofluorescent labelling o AVP is expressed in the lateral SCN and dorsal region 0 VIP is expressed in the ventral regions above the optic chiasm 0 Core and Shell Reoions 0 Core GABA and VIP are expressed they are weakly rhythmic 0 Shell GABA and AVP are expressed robustly rhythmic main pacemaker cell populations 0 These two regions communicate the Core regulates the Shell VIP Knockout and VIP Receptor Knockout 0 VIP plays an essential role in the generation of SCN circadian rhythms 0 VIP K0 and VIP Receptor KO rhythms are compromised fragmented hardly consolidated ARRHYTHMIC o if there is any tau at all it is very long but arrhythmia is the main finding 0 looks similar to ClockBMAL1 KO study results So far Intercellular VIP circuit that o regulates amplitude of the core clock 0 wires together the cell autonomous oscillators 0 creates a coherent output signal How does VIP regulate this circuit 0 VIP activates calcium and cAMP levels 0 Helios Gene Gun 0 allows injection of different reporter genes right into the cells 0 biolistic transfer of the chameleon gene into an SCN slice I chameleon gene changes the presence of Ca2 two arms binds to Ca2 called FRET I low red fluorescence low Ca2 I high red fluorescence high Ca2 0 changes in calcium gt changes in excitability of cells 0 Results intracellular calcium levels oscillate in the SCN Thus intracellular Ca2 levels are gated by the circadian clock Role of cAMP in this Circuit 0 luciferase studies 0 add a drug called MDL which inhibits cAMP gt profound effects on oscillatory capacity 0 wash out inhibitor MDL gt rhythms return 0 cAMP and Ca2 regulate the amplitude of SCN rhythms similar pattern in VIP KO studies 0 this is an inhibition of the downstream pathways of VIP 0 so VIP is a clock output gene that regulates the clock Phosphorylation 0 causes conformational changes in proteins that either activate top or inactivate bottom protein function 0 Phosphorylation is a reversible PTM Posttranslational Modification that regulates protein function Core Transcriptional Oscillator and Cytoplasmic Signaling Oscillator Communication 0 Cyclic AMP and Calcium Kinase regulate protein kinase A o a temporal activation can occur at the kinase level 0 Targets of Ca2 and cAMP 0 often kinases o a kinase is an enzymatic protein that drives the transfer of a terminal phosphate from ATP gt target protein In doing so the functionality of the target protein is altered Ca2 stimulates Ca2 kinases cAMP stimulates protein kinase A CREB CREB 0 can be rapidly phosphorylated phosphorylation can drive gene expression 0 CREB binds to a transcriptional complex o CREB sits on CRE instead of EBOX CRE TGACGTCA 0 similar oscillation to Clock and BMAL1 o CRE site is found in the period 5 regulatory region o If PER and CRY genes bind to CREB CREB might regulate Clock as well 0 5 CREs were found on PER1 as well as the 3 EBOXs o hypothesis ability of CREB ClockBMAL1 to drive robust rhythms through PER1 o stimulation CAMP and Ca2 big increase in Per1 and Per2 o stimulation of VIP 78 fold increase in expression o If CREB is blocked Per1 expression is disrupted o CREB is a key regulator of clock amplitude I CREB and Clock BMAL1 drive cycle rhythmicity these two synch through cytoplasmic and transcriptional feedback to create robust rhythm Without CREB cells have weak oscillations and no synchrony I increased cAMP and Ca2 sensed by CREB gt increased PER and CRY expression Photic Input Pathways and Clock Entrainment o timing of the endogenous clock can be effectively regulated by changes in the environmental light cycle so that animal can sync its internal clock with the everchanging light cycle encountered over the seasonalyearly basis 0 Phase Resbonse Curve Shows the phase shifting effects of photic stimuli 0 early night pulse of light gt activity onset moves back phase delay 0 late night pulse gt activity onset shifts fonNard phase advance 0 light in the middle of the day gt no effect I clock is only sensitive to light in the middle of the night 0 rhythmicity is adjusted to match changing solar cycles Visual System Circuits 0 classic image forming visual circuit 0 retinal ganglion cells form the optic nerve I retina gt optic nerve gt visual area of the thalamus gt visual cortex 0 RHT retinohypothalamic tract delivers light info to the SCN I SCN perceives time rather than seeing light I bilateral innervation from retina gt RHT I RHT is glutamatergic drives depolarizationexcitation of GABAergic neurons in the SCN I RHT glutamatergic innervates the SCN GABAergic o clock entrainment does not require rods and cones I KO mice lacking green cones are still able to phase shift How does SCN detect light 0 retrograde transport experiment to find out how SCN receives light input 0 findings small subset of retinal ganglion cells gt SCN o morphology of cells is unique 0 these retinal ganglion cells are photosensitive I redgreen light does not entrain I blue light does entrain 0 Visual system of the unconscious mind Blind Sight 0 lightsensitive ganglion cells express melanopsin o melanopsin lightsensitive photopigment Melanopsin is only expressed in RGCs exclusively sensitive to bluish light genetic elimination of melanopsin gt completely blocks clock entrainment 0 Areas where brain shows melanopsin SCN optic nerves IGL 0 genetic lesion using diphtheria toxin to disrupt melanopsin protein synthesis genetic deletion of melanopsin in RGCs gt no more light entrainment MelanopsinPositive IPRGCs Circuits to Functions 0 Low acuity visual function 0 hippocampus moodlearning and memory 0 pupil reflexes o circadian timing Light Evoked Phase Shifting 0 cut off RHT terminal light evoked phase shifting is blocked 0 block postsynaptic NT receptors light evoked phase shifting is blocked 0 block kinase activity light evoked phase shifting is blocked 0 add protein synthesis inhibitors light evoked phase shifting is blocked MAPK Signaling Cascade o pathway for coupling changes in cytosolic calcium to transcriptional activation 0 RAF gt MEK gt ERK 0 once ERK is activated it can translocate into the nucleus 0 ERK activation gt dimerization gt translocation into the nucleus 0 thus regulation of gene expression is possible 0 Light can trigger ERK activation in the SCN 0 One of the most highly regulated targets of MAPK pathway is CREB MAPK Targets o MAPK can regulate Per1 expression 0 block CREB gt block the ability of MAPK to regulate Per1 expression 0 block glutamate gt same results 0 CREB is a key regulator of glutamatephotic induced Per1 expression MAPK and Neuronal Plasticity o Hippocampal LTP o Associative olfactory learning 0 conditioned taste aversion o associative and cued fear conditioning U0126 Pharmacological KO Study 0 small compound that interacts with MEK does not allow MEK to activate ERK o ERK cannot translocate into the nucleus and thus cannot regulate gene expression 0 because of the importance of the MAPK signaling pathway traditional KO studies cannot be used in a living animal 0 Methodology 0 inject U0126 using stereotaxic microinjection tiny steel tube gt brain 0 inject into the lateral ventricle which will flow into the 3rd ventricle which is right next to the SCN 0 Results Disruption of this pathway uncouples light from clock entrainment phase shifting effect of light is blocked Photic Input Resetting the Clock 0 light triggers the expression of a large number of genes in the SCN 0 light gt rapid induction of Per1 oscillating homolog 0 light can penetrate the core clock mechanism photic entrainment can disrupt the core clock 0 lightevoked expression of a core clock gene is important because light triggers an outofphase induction of Per1 expression in the night when Per1 should be low 0 light entrainment of the clock results from a resetting of the phasing of the core clock transcriptional loop 0 nonphotic resetting of clock triggers a rapid decrease in period expression 0 activity triggers degradation of clock gene rather than activation activity as entrainment stimuli o nonphotic input resets the clock by degrading period expression Light evoked phaseshifting requires Per1 expression Entraining Effects of Dim Light 0 tau can be slightly lengthened z2414 hours Effects of Constant HighIntensity Light on Rhythms c three different types of rhythms depending on light intensity 0 arrhythmia o tau can be lengthened z25 hours 0 splitting showing 2 different bouts of activity I long tau for about 40 days then split into 2 6hour long activity bouts I 2 nuclei become split 2 oscillators are not communicating with each other humans can also exhibit split rhythms o constant light disrupts cellular communication from shell gt core Why is synchrony of mother rabbits clocks with pups clocks adaptive o avoidance of predation 0 conservation of energy 0 optimize feeding o efficiency for mom all eating at once Development of SCN 0 period length largely genetically determined 0 rhythms detected in SCN during the last 23 days of fetal life 0 exposure to environmental light cycles not necessary for oscillator development c SCN becomes rhythmic before the retinas receive photic input o RHY synapses are not developed until about 4 days after birth Deguchi 1978 o NAT Nacetyltransferase rhythms of pups in sync with mom 0 regulation by internal biological clock independent of environmental cues o NAT controls pineal melatonin secretion so it is expected to peak in darkness 0 experiment with keeping mom in DD during pregnancy and pups after birth in DD versus mothers from original LD cycles who were 180 degrees outof phase with each other determined that mom has both a prenatal and a postnatal influence on circadian phase of rat pups rhythm Prenataly o mom s innate rhythm retinal info light input gt coordinates rhythms of pups SCN Postnataly 0 early on 1st z6 days mom can still impact pups rhythms after that their RHTs are developed and they can have their own independent rhythms o RHT innervation 4 days photic entrainment 6 days Rodent Development Timeline prenatal days 1316 SCN neurogenesis a few days before birth metabolic SCN activity a few days after birth RHT innervation of SCN 4 days6 days light gt SCN entrainment is possible mom gt overridden 23 weeks after birth most behavioralhormonal rhythms begin FC Davis 0 syrian hamsters pacemaker likely becomes rhythmic before overs rhythms can be detected 0 in a litter of hamsters raised in dim light dim LL after pregnant mother is also in dim LL their activity rhythms are approximately coincident with mom s and with each others 0 pups crossfostered at birth rhythms are closely related to phase of their biological mother rather than foster mother 0 suggests that mom entrains pups rhythms before they are born 0 study also suggests that entrainment by mother is done at some point before weaning o pups of SCNx SCN lesioned mothers do not show synchronous rhythms I SCN of mom is required for phase setting I sync occurs at some point before day 14 Melatonin Involvement 0 daily melatonin injections in SCNx mothers gt mother s melatonin rhythms could be involved in synchronizing the rhythms of pups o melatonin is a sufficient but not necessary entraining signal 0 timed daily melatonin injections prenatally gt sufficient to entrain pups rhythms Dopamine o timed daily SKF38393 DA agonist gt also a sufficient to entrain pups postnatal rhythms 0 similar to light DA agonists include cfos expression in the SCN o theory that DA may be the NT that mediates the ability of light to set the phase of fetal circadian rhythms 0 pregnant rats injected with DA agonist or saline Resulted gt those receiving the DA agonist and NOT saline were able to set the phase of pups circadian locomotor activity rhythm postnatally in DD Primates vs Rodents o Primates o SCN function mid gestation 0 light entrainment prenatal o melatonin early postnatal 0 other outputs varied o Rodents o SCN function late gestation 0 light entrainment postnatal 715 0 melatonin postnatal 1020 0 other outputs varied o Rodents birth comparable to 3rd trimester in primates they are born very altricial Premature Babies 0 baby is preterm if it is born lt37 weeks 0 cycled light improved growth rates 0 DD gt simulates the womb babies used to be kept in near DD this was a development 15 years ago 0 LL is a very stressful environment for these babies causes irregular heart rhythms and decreased amounts of sleep 0 cycled light established a daynight rhythm mimicking the circadian cues that are established for fullterm babies in utero Ultradian Rhythms o rhythms with a period 7 of substantially lt24 hours 0 usually lt8 hours often z90 minutes 0 examples 0 basic restactivity cycle 0 REM sleep 0 swallowing o attention and cognitive performance motivation can maskoverride URs not as robust as Circadian rhythms do NOT map onto geophysical cycles tau gives no info about the functional significance of a UR generally appear in development before Circadian rhythms more pronounced during different phases of the year c 10x more variable than circadian rhythms Pulsatile Release of Various Hormones 0 functional relationship between LH luteinizing hormone and GnRH gonadotropin releasing hormone circhoral pattern of LH release in primates driven by pattern of GnRH release Circhoral about once per hour 0 this can be used in treatment of infertility I GnRH is a smaller molecule that is easier to synthesize commercially than LH I most infertility cases are related to hypothalamic disorder rather than pituitary failure I frequency of pulses may increase ration of LHFSH follicle stimulating hormone o sidebar Lupon is a GnRH agonist that causes sterilization le punishment for child molesters by continual administration of GnRH the system turns off Pulses are crucial steady activation gt opposite effect chemical castration 0 GH growth hormone in rats 0 33 hour frequency 0 synchronized with LD cycle 0 pulsatile release continues after SCNX but does not sync to LD cycle 0 sex difference in frequency of pulses o HPA Axis o cortisol Released in a circadian fashion highest early morning lowest night m ultradian fashion pulses throughout the day Feeding Rhythms o feeding rhythm is ultradian o timing of meals may actually be more important than feedback mechanism of eating hunger gt eating 0 common vole foraging behavior wheel running only at night feeding about every 2 hours during day and less regular at night I field behavior assessed by setting traps and checking every 20 mins 0 bout of activity every 2 hours after sunrise less synchronous towards end of day I outof sync voles more likely to be eaten o URs are more apparent in cold months because days are shorter less time to forage 0 longer night activity is more spread out shorter night more compressed o URs can override CRs in this circumstance Are URs independent of CR5 0 Deuterium heavy water D20 alters Circadian but NOT Ultradian rhythms o evidence that they are independent 0 25 solution of D20 significantly lengthens period of CR without affecting UR o Voles with brain lesions that eliminate CRs SCNx or PVNx do NOT eliminate UR Possible Relationship Between URs and CR5 0 evidence so far CR is not required to regulate the frequency of URs O 0 eg SCNx did not prevent UR of GH in rats 0 CRs and URs are connected but not with event timing ultradian behaviors appear to oscillate in circadian time o D Melanogaster study Mutants of per gene I these mutants ultradian behaviors ie activity and courtship song cycles are exactly proportional to their CRs 0 WT 60 second songs 0 Per Mutants 40 80 or no rhythm at all I BUT various per mutant females despite their genotype prefer 55 second songs 0 Males use CRs to determine the length of their songs BUT females do not use their CRs to determine their song preference 0 fundamental difference between ultradian transmitter and receiver mechanisms 0 also suggests that timer in drosophila is not part of an ultradian oscma on Relationship between CRs and URs profound and uncertain Daylight Savings Time DST 0 spring traffic accidents rise immediately after timeshift 0 fall traffic accidents reduce immediately after shift 0 construction accidents follow a similar pattern Tide Sets Phase 0 timing of tides vary across a coast Animal rhythms depend on particular beach and level 0 translocation from one tidal situation gt another causes a rapid adoption of new tidal pedod o tidal animals that live in a nontidal habitat gt show daily rhythms in lab but they can also adopt tidal rhythms intertidal zone flooded by the sea twice in a lunar day 248 hours animals that live across zones must be flexible to optimize feeding nt fixedinvariant like Circadian Rhythms Circadian and Circatidal Rhythms o Fiddler Crab 02 consumption rhythm gt same as activity metabolism is also circatidal o penultimatehour crab activity is influenced by both CR and CT rhythms 0 peak activity Circadian 11pm and Circatidal high tide midpoints circadian clock overlies circatidal rhythms LD cycle changes 0 constant conditions bimodal rhythm will free run with a period greater than 248h 0 LD cycle bimodal rhythm gt period of exactly 248h 0 LL free run because LL suppressed CRs but still there is activity splitting Tidal Rhythms Entrainment LD Cycle 0 penultimate crab 62h62h LD cycle 0 no phase change of circatidal activity Chemical Interruption 0 D20 and EtOH lengthen period of tidal rhythm and activity 0 If both tidal and light cycles affect rhythm these chemicals will alter rhythms identically 0 Evidence for a single master clock Aspects of the Tide that Produce Entrainment o lnundation o expose arrhythmic crabs to 10 sessions of 124 cycle 62h in water 62h in air I aftenNards activity rhythm NOT entrained 0 Temperature Variation 0 exposed crabs to same sessions but now WATERCOLD and AlRWARM I aftenNards activity peaks same as times of cold inundation ENTRAINMENT o no inundation expose crabs to 10 sessions of 62h warm air62h cold air I ENTRAINMENT I TEMPERATURE ENTRAINS TlDAL RHYTHMS o Atmosbheric Pressure also resulted in entrainment 0 Mechanical agitation can also entrain rhythms in some cases synodic month interval between successive new moons o menstrual cycle NO LINK with lunar cycle PredatorPrey Circalunar Rhythm 0 nocturnal predators increase activities during evenings around full moon decrease as full moon wanes o nocturnal prey avoid nighttime activity around full bright moon 0 these rhythms DO NOT free run in DD gt WEAK o OVERALL evidence for lunar rhythms is weak most likely just relates to mood brightness and subsequent visibility
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