The Pineal Gland and ________

The ______ gland or _______ synthesizes and secretes _______, a structurally simple hormone that

communicates information about environmental _________to various parts of the body.

Ultimately, melatonin has the ability to entrain biological rhythms and has important effects on reproductive

function of many animals. The light-transducing ability of the pineal gland has led some to call the pineal the

“_______".

Anatomy of the Pineal GlandThe pineal gland is a small organ shaped like a ______ (hence its

name). It is located on the midline, attached to the posterior end of the roof of the third ventricle in the brain. The pineal varies in size among species; in humans it is roughly 1 cm in length, whereas in

dogs it is only 1 mm long. To observe the pineal, reflect the cerebral hemispheres laterally and look for a small grayish bump in front of the cerebellum. The images below shows the pineal gland of a horse in relation to the brain.

Histologically, the pineal is composed of “__________" and glial cells. In older animals, the pineal often contains calcium deposits

(“________").

How does the retina transmit information about light-dark exposure to the pineal gland?

________ to the retina is first relayed to the suprachiasmatic nucleus of the hypothalamus, an area of

the brain well known to coordinate ________clock signals. Fibers from the hypothalamus descend to the

spinal cord and ultimately project to the superior cervical ganglia, from which post-ganglionic neurons ascend back to the pineal gland. Thus, the pineal is similar to the adrenal medulla in the sense that it

transduces signals from the SNS into a hormonal signal.

Melatonin: Synthesis, Secretion and Receptors

The precursor to melatonin is _______, a neurotransmitter that itself is derived from the amino acid _______. Within the pineal gland, serotonin is acetylated and then methylated to yield ___.

_______ is the only hormone secreted by the pineal gland. Melatonin was discovered in 1958 by Aaron B. Lerner and other researchers at Yale University. Melatonin is

produced in humans, other mammals, birds, reptiles, and amphibians.

It is present in very ____amounts in the human body.

Synthesis and secretion of melatonin is dramatically affected by______ exposure to the _______.

The fundamental pattern observed is that serum concentrations of melatonin are ____during the daylight hours, and increase to a peak

during the ____.

Examples of the circadian rhythm in

melatonin secretion in humans is depicted in the figure to the right (adapted from Vaughn, et al, J Clin

Endo Metab 42:752, 1976). dark gray bars

represent night, and serum melatonin levels

are shown for 2 individuals (yellow versus light blue). Note that blood levels of melatonin are

essentially undetectable during _______, but rise sharply during the dark. Very similar

patterns are seen in other species. The duration of melatonin secretion each day is

directly proportional to the length of the night.

The mechanism behind this pattern of secretion during the dark cycle is that activity of the rate-

limiting enzyme in melatonin synthesis - ______________________ (NAT) - is low

during daylight and peaks during the dark phase. In some species, circadian changes in NAT

activity are tightly correlated with transcription of the NAT messenger RNA, while in other

species, post-transcriptional regulation of NAT activity is responsible.

Activity of the other enzyme involved in synthesis of melatonin from serotonin - the

methyltransferase - does not show regulation by pattern of light exposure.

2 __________receptors have been identified from

mammals (designated Mel1A and Mel1B) that are differentially expressed in different tissues

and probably participate in implementing differing biologic effects.

These are _________ cell surface receptors. The highest density of receptors has been found

in the suprachiasmatic nucleus of the ________________, the anterior pituitary

(predominantly pars tuberalis) and the retina. Receptors are also found in several other areas of

the ______.

Biological Effects of Melatonin

______ has important effects in integrating photoperiod and affecting

circadian rhythms. Consequently, it has been reported to

have significant effects on reproduction, _____________ cycles

and other phenomena showing circadian rhythm.

Effects on Reproductive Function

Seasonal changes in day length have profound effects on _______ in many species. Melatonin is a key player in controlling such events. In temperate climates, animals like hamsters, horses and sheep have distinct breeding season. During the non-breeding season, the gonads become inactive (males fail to produce sperm in any number), but as the breeding season approaches-gonads must be rejuvenated. _____ (length of day vs. night) is the most important cue allowing animals to determine which season it is. The pineal gland is able to measure day length and adjust secretion of melatonin accordingly. A hamster without a pineal gland or with a lesion that prevents the pineal from receiving photo information is not able to prepare for the _______.

The effect of melatonin on reproductive systems can be

summarized by saying that it is ____________. In other words, melatonin inhibits the secretion of the

gonadotropic hormones LH and FSH from the anterior pituitary. Much of this inhibitory effect seems due to inhibition of ______ from the hypothalamus, which is

necessary for secretion of the anterior pituitary hormones.

One practical application of melatonin's role in controlling seasonal reproduction is found in its use to artificially manipulate cycles in seasonal breeders. For example, sheep that normally breed only once per year

can be induced to have two breeding seasons by treatment with melatonin.

Effects on ____ and Activity

Melatonin is probably not a major regulator of normal ____ patterns, but undoubtedly has some

effect. One topic that has garnered a large amount of

interest is using melatonin alone, or in combination with phototherapy, to treat sleep

disorders. There is some indication that _______levels are

lower in elderly insomniacs relative to age matched non-insomniacs, and melatonin therapy

in such cases appears modestly beneficial in correcting the problem.

Another sleep disorder is seen in _______, who often find it difficult to adjust to working at night and sleeping

during the day. The utility of melatonin therapy to alleviate this problem

is equivocal and appears not to be as effective as phototherapy.

Still another condition involving disruption of circadian rhythms is jet lag.

In this case, it has repeatedly been demonstrated that taking _______ close to the target bedtime of the

destination can alleviate symptoms; it has the greatest beneficial effect when jet lag is predicted to be worst (e.g.

crossing many time zones).

In various species including humans, administration of ______ has been shown to

decrease motor activity, induce fatigue and lower body temperature, particularly at high doses. The effect on body temperature may play a significant role in melatonin's ability to entrain sleep-wake

cycles, as in patients with _______.

Other Effects of Melatonin

One of the first experiments conducted to elucidate the function of the pineal, extracts of pineal glands from cattle were added to water

containing tadpoles. Interestingly, the tadpoles responded by becoming very light in color or almost

transparent due to alterations in melanin pigment distribution.

Although such cutaneous effects of melatonin are seen in a variety of "lower species", the hormone does not have such effects in mammals or birds.

______ tumors

______ tumors are rare, occurring most often in children and young adults. The most common of these are germ cell tumors (germinomas and teratomas), which arise from embryonic remnants of germ cells. These tumors

are malignant and invasive and may be life-threatening. Tumors of pinealocytes also occur and vary in their

potential for malignant change.

_____tumors may cause headache, vomiting, and seizures due to the increase in pressure within the head

that results from the enlarging tumor mass.

Pineal tumors

Endocrinologic effects may also be observed. Some patients may become hypogonadal with regression

of secondary sex characteristics, while others may undergo precocious puberty because of secretion of

___________. ___________ is frequently associated and is usually due

to tumor invasion of the hypothalamus and posterior pituitary. Invasion of the pituitary stalk may interfere with the ongoing inhibition of prolactin secretion by

dopamine from the hypothalamus, resulting in elevated serum prolactin levels, a finding that may lead to a

mistaken diagnosis of prolactinoma. Treatment consists of surgical relief of the increased intracranial pressure

and X-ray therapy.

Calcification of pineal begins in second decade of life

By Age 60, 70% is calcifiedNo evidence of change in gland activity

Descartes called “seat of the soul”

Continuous light, onset of sexual development

Remove pineal gland, prevent gonadal regression

Melatonin-Metabolized in liver for excretion

Eyes Wide Open

The United States Army Aeromedical Research Laboratory is housed in a low orange brick building in Fort Rucker, Alabama,

Fort Rucker is the largest training base for helicopter pilots in the United States.

Also where, for more than a decade, the sleep researchers John and Lynn Caldwell have been conducting pioneering work on

sleep deprivation. Their laboratory contains an elaborate flight simulator with wraparound projected images mimic the visual experience of flight. “It’s not like sitting at a video monitor or a computer

screen,” John Caldwell said recently. “It’s as close to the real thing as you can get.”

Eyes Wide Open

Kept 6 helicopter pilots, in full combat garb were kept awake continuously for two 40h periods-separated by

one night of recovery sleep. Detailed performance evaluations were conducted at regular intervals. The pilots were ordered to execute precision maneuvers: Caldwells assessed how sleep

deprivation affected the pilots performance.

Eyes Wide Open

The military has a practical interest in such matters. In last several year, bombing mission in Afghanistan and Iraq that

require the 2-man crew of a B-2 stealth plane to fly there from Missouri without stopping -- a trip halfway around the world. In ordinary circumstances- sleep-deprived pilots make more errors and respond more slowly. Yet some of the pilots in the Caldwells’ study were little affected by the loss of sleep. These

were pilots who had been given the compound 2-(diphenylmethyl)-sulfinylacetamide, also known as modafinil. “Drugs are a tactical

necessity for sleep deprivation,” John Caldwell says.

_____, approved by the FDA for the treatment of ______,

is not a conventional stimulant, and has almost no detectable effect on people who are already fully alert.

Yet the drug is at the center of a burgeoning new area of research into the neurochemistry of sleep and wakefulness,

which promises to transform the treatment of sleep disorders.

At the same time, scientists are exploring the prospect that people may be able to sustain a state of poised and

productive alertness for days on end. Some have even raised the question of whether advances in

biopharmacology will ultimately make regular sleep unnecessary.

Several years ago, scientists in Texas identified a new family of neurotransmitters called ________.

_____ are proteins produced by a remarkably small

number of nerve cells -- a few thousand, at most -- in a single area of the hypothalamus.

scientists created “knockout” mice, which lacked the orexin gene The genetically engineered mice seemed

normal in all respects but one: they had trouble staying awake.

The scientists got in touch with scientists in Boston who confirmed that orexin regulated the sleep-wake cycle.

“If you think about a normal day, 98% of the time is spent either awake or asleep,” Saper says. “There is a

very short transition period between the two. The brain seems to have a flip-flop switch that changes the state

from wakefulness to sleep, and orexin acts like the thumb that keeps this switch in the ‘on’ position.”

A deficiency of orexin causes narcolepsy.

A research team dissected the hypothalamus of a________. The hypothalamus appeared normal: it was the size of a plum, and had

the color and consistency of tofu. They performed immunohistochemistry

No orexin was foundWhat had happened to the orexin neurons?

Unlike the knockout mice, the majority of human narcoleptics have normal genes for producing orexin proteins and receptors.

Researchers believe that the orexin neurons are destroyed as part of an autoimmune reaction.

Until recently, the only “countermeasures” to sleepiness

have been conventional stimulants, most notably amphetamines like Dexedrine. Dexedrine has been the

standard treatment for narcolepsy, and it has had military applications as well: the US Air Force supplied it to most

air crews during the Persian Gulf War. More than 60% of the pilots who used the drug said it was “essential” to

accomplishing their mission. Unfortunately, amphetamines, in addition to a high

potential for addiction, cause jitteriness, hypertension, rapid and irregular heartbeat, overconfidence, and a

negative “rebound” effect -- nonrestorative sleep -- when they wear off.

What scientists have sought instead is something that would boost wakefulness by replicating the brain

chemistry of healthy, well-rested people.

Like many drugs, ________ was discovered before its

mode of action was understood. In the early 1980s-, a French pharmaceutical company,

was exploring new treatments for somnolence by injecting hundreds of compounds into lab animals and

observing the results. In rats and then in humans, modafinil was found to

cause wakefulness, yet, unlike stimulants, it did not give rise to hyperactivity.

In clinical trials conducted by Cephalon, a Pennsylvania-based company that licensed the drug, modafinil was demonstrated to be a safe and effective treatment for

narcolepsy. Somehow, it made up for the missing orexin.

“Modafinil is a key to understanding biologically what it

means for us to be awake,” Miller believes that through evolution we have developed

2 different systems in the brain which previously were lumped together under the broad term of wakefulness.

The first system is associated with vigilance, where one is tensely alert to potential threats in the environment.

The physiology of vigilance seems to involve the dopamine, NE and serotonin pathways: stimulating

these pathways results in hyperactivity and a reduction of reaction time.

The second system is the “calm” type of wakefulness, where one is attentive and engaged in so-called

“executive functions” -- able to focus on cognitive tasks. Such wakefulness may involve the histamine pathways.

“the trouble with conventional stimulants -- caffeine and cocaine, as well as amphetamines -- is that they indiscriminately activate

all the wakefulness-promoting neurons throughout the brain. Modafinil, by contrast, promotes the more selective firing of

neuronal circuits in the cerebrum, particularly in the prefrontal cortex, where many of the higher executive functions of cognition

and emotion seem to lie.

For narcoleptics, the results can be dramatic.

Modafinil preserves normal “sleep architecture.” Unlike stimulants, modafinil

seems to have no potential for addiction; nor have users been known to develop tolerance. Indeed, because of modafinil’s effectiveness

and safety, many physicians are experimenting with it for patients with other disorders;

modafinil has been shown, for instance, to alleviate drowsiness and fatigue associated with multiple sclerosis, Parkinson’s, and

depression.

Of course, one of the reasons so many Americans have trouble staying awake is that they have trouble falling asleep.

Estimated that 30% of the population has significant insomnia on occasion

10-15%, it is a regular condition. Some researchers believe that the orexin pathway may point toward a new-generation sleeping pill that would not have the disadvantages of conventional sleeping pills, which almost always degrade the quality

of the sleep they induce. A drug that blocked orexin might replicate the sort of rapid transition to sleep that narcoleptics experience. “But there is still a lot we don’t know about the kind of sleep that might result,” Thomas Scammell,

the Boston sleep researcher, warns. “If it meant prolonging REM sleep, you might have 8h of intense dreams with an erection.”

Paradoxically, some investigators speculate that modafinil itself could be helpful for insomniacs, since they report low energy during the day. A more  alert, fruitful day could usher in a night of restorative sleep.

Even as sleep disorders increase, firms are pushing their

employees to disrupt their normal sleep patterns in order to provide services around the clock.

A fitness center that is open twenty-four hours a day, or a restaurant that can deliver in the early morning. Etc.

Are at least 237 Home Depots and nearly 1300 Wal-Marts that never close.

A health-club chain called 24 Hour Fitness has more than 430 places; - spends an extra 5 million dollars a year to stay

open all the timeextended hours generate an estimated 50 million

In the corporate world, of course, to be able to get by on 5 hours of sleep or less is a badge of honor, .

The military’s sleep research is going far beyond shift-worker experiments and flight-simulator studies.

Department of Defense Advanced Research Projects Agency, or DARPA, does studies on“innovative research and development

proposals in the prevention of degradation of cognitive performance due to sleep deprivation.”

The capability to resist the mental and physiological effects of sleep deprivation will fundamentally change current military concepts of

“operational tempo” and contemporary orders of battle for the military services.

In short, the capability to operate effectively, without sleep, is no less than a 21st Century revolution in military affairs.... As combat

systems become more and more sophisticated and reliable, the major limiting factor for operational dominance in a conflict is the

warfighter. Eliminating the need for sleep while maintaining the high level of both cognitive and physical performance of the individual will

create a fundamental change in warfighting and force employment.

One study, at Sea World, focuses on dolphins, which never

go fully to sleep. “If these dolphins fell asleep, they could die in the water,”

“As mammals, they have to surface regularly for oxygen, so

they’ve had to adapt.” In dolphins, only one cerebral hemisphere sleeps at a time: when the left hemisphere is asleep, the right one is awake,

and vice versa.

Carney believes that working out how the dolphin hemispheres shift between wakefulness and sleep while the

animal maintains a basic level of alertness may lead to methods by which cognitive performance might be

sustained in human beings.

The Pentagon wants soldiers who can be

awake and high-functioning for up to a full week, even in circumstances where a single

error can have disastrous consequences. And for civilian society, too, the prospect of gaining control over the cycles of sleep and

wakefulness has great appeal; lost productivity caused by sleep disorders costs an estimated

18 billion dollars every year. But will biology permit it?

But will biology permit it? The widespread assumption that sleep is necessary was supported by early studies of sleep-deprived

rats: they suffered deterioration not only in behavior but in body metabolism and immune defenses. As repeated experiments have verified, when

rodents are prevented from sleeping they often die of sepsis, with some succumbing after only 5d, the

hardiest lasting a full month. surprisingly, there is very little hard data showing

that prolonged sleep deprivation truly has deleterious effects on humans

.

A record for documented continuous wakefulness was set in 1964,-a high-school student kept himself awake for 12 days.

rate of thinking and response slowed- no dramatic physiological problems.

More systematic work on the effects of prolonged wakefulness 28 people kept continuously awake for 4 days, and found that the major consequence was the expected decline in cognitive functioning. Other studies of chronic sleep deprivation, where subjects are allowed to sleep for 4h and are kept awake for 20,

found temporary changes in glucose metabolism, with an increase in insulin resistance, a condition seen in early

diabetes. Some of the sleep-deprived subjects also had about a 25%

increase in the number of circulating WBC. clinical significance of such changes is unclear.

Many researchers believe that sleep is necessary for the brain to replenish its energy stores, the hypothesis remains

unproved.

In the absence of such basic medical knowledge, sleep experts caution about the use of drugs like modafinil as a substitute for sleep. They worry that high-achieving types may be

tempted to take them in order to stay awake 2-3 days a week throughout the year.

And they worry about abuse among students cramming for exams.

In fact, the medical consequences of such regular on-off sleep behavior are simply not known, and probably

will not be known for a long time.

Modafinil is the most tempting drug for our society to come along in decades,” “It promises to satisfy our relentless desire to control time.”

Is caffeine a mirror of society’s craving, and its view of sleep as a dispensable commodity.

“For years, coffee was taken in small doses, but the growth of Starbucks says it all,” he says. “A venti” -20 ounces of coffee -- “is loaded with the

drug. It’s the beverage of choice in America. In middle school, it’s Mountain Dew, which is also packed with caffeine.”

But research has shown how limited caffeine’s effects are. When his team studied people kept awake for 88 hours, caffeine turned out to be

effective for only some 20 hours. “Modafinil looks much better than caffeine,”

“Wakefulness becomes effortless.”

It’s a prospect that is both exciting and disturbing.

The hypocretins (orexins) are a newly identified

peptide family comprised of two peptides, hypocretin-1 and hypocretin-2.

These peptides play a role in the regulation of behavioral state.

-when infused into the lateral ventricles in awake animals, hypocretin-1 elicits increased duration of waking beyond that observed in

vehicle-treated animals. Same true for Hypocretin-2, but less potent

-rapidly emerging as functionally important neurotransmitters.

(Hcrt-1/OXA, Hcrt-2/OXB) encoded by the same precursor gene and 2 G-protein coupled receptors

(Hcrtr1/OXR1, Hcrtr2/OXR2) are currently known. Alterations in hypocretin neurotransmission causes the sleep disorder narcolepsy in mice, dogs and humans.

Effects on appetite, neuroendocrine and energy metabolism regulation are also suggested by other

studies. Hypocretins are uniquely positioned to link sleep, appetite and neuroendocrine control, three

behaviors of major importance in psychiatry.

Orexin-A and B were identified as endogenous ligands for the orexin-1 (HCRT1) and orexin-2 (HCRT2) G-protein coupled receptors

These peptides are identical to 2 hypothalamic peptides that share a high

degree of homology with secretin, designated hypocretin-1 and hypocretin-2.

ICV administration of orexin-A and B stimulated food intake in rats. reports suggest a role in the sleep-wake cycle.

FINAL EXAM

20 points cumulative

Dec 15 at 3 PM