Pineal indoles: significance and measurement

Pinealectomy in Rats

The pinealectomy technique consists of the surgical removal of the superficial pineal gland. This procedure allows the ablation of circulating indoles produced by this gland. Withdrawal of systemic melatonin, a pineal hormone, affects animal circadian rhythms and induces several physiological changes that are the subject of many investigations. In this chapter, we describe the pinealectomy protocol adapted to rats. We describe the animal placement on the stereotaxic fixation system, and the procedure for the pineal gland removal and animal recovery from surgery.

Alternative methods for feline fertility control: Use of melatonin to suppress reproduction

PRACTICAL RELEVANCE

Reversible contraceptives are highly desired by purebred cat breeders for managing estrous cycles and by scientists managing assisted reproduction programs. A variety of alternative medicine approaches have been explored as methods to control feline fertility.

SCOPE

In the field of veterinary homeopathy, wild carrot seed and papaya have been used for centuries. Both appear to be safe, but their efficacy as feline contraceptives remains anecdotal. In contrast, the use of melatonin in cats has been investigated in a number of studies, findings from which are reviewed in this article.

RATIONALE

Cats are seasonally polyestrous (they cycle several times during their breeding season) and are described as long-day breeders because endogenous melatonin negatively regulates estrous cyclicity. Exogenous melatonin administered parenterally also suppresses ovarian activity in cats, and long-term oral or subcutaneous melatonin administration is safe.

CHALLENGES

The therapeutic use of melatonin is limited by its short biological half-life (15-20 mins), its poor oral bioavailability and its central effects in reducing wakefulness. Research is required to determine whether higher doses, longer-release formulations, repeated administration or combination implants might overcome these limitations.

A potential multiple resonance mechanism by which weak magnetic fields affect molecules and medical problems: The example of melatonin and experimental “multiple sclerosis”

A biophysical hypothesis to explain the powerful ameliorating effects of weak (nanoTesla range) magnetic fields on melatonin-related diseases is presented. The effects are dependent upon the molarity of the melatonin within specific organ spaces. The optimal ameliorating effects upon experimental allergic encephalomyelitis for both the derived intensities (about 35 and 70 nT) and the frequency (7 Hz) were congruent with the empirical observations from previously published and unpublished experiments with rats involving about 1-5000 nT strengths of either 0.5, 7, 40, or 60 Hz magnetic fields. The hypothesis predicts that weaker magnetic fields within the nanoTesla to picoTesla range would optimally affect concentrations of melatonin (in this situation) within the micromolar range and that neurological states (epilepsy) or conditions (ethanol, antidepressants, sleep deprivation) that affect nocturnal melatonin levels in human beings would determine the optimal effective intensity within the 7 Hz range. The resonance solution also suggests that mitochondrial proton gradients may be critical to the process. The model offers an alternative explanation to the variations of Faraday's Law and the Boltzmann constant that have been employed to explain and to dismiss biological effects from weak magnetic fields.

Thermoregulation as a sleep signalling system

Temperature and sleep are interrelated processes. Under normal environmental conditions, the rhythms of core body temperature Tc and sleep propensity vary inversely across the day and night in healthy young adults. Although this relationship has drawn considerable interest, particularly in recent years, it is still not known whether this relationship is causative or merely coincidental. As somnogenic brain areas contain thermosensitive cells, it is possible that the sleep/wake cycle may be directly affected by thermoregulatory changes themselves. That is, that changes in temperature may trigger, either directly or indirectly, somnogenic brain areas to initiate sleep. There is now an emerging body of evidence from both physiological and neuroanatomical studies to indicate that this may indeed be the case. This paper will examine the literature relating to this relationship and propose a model where thermoregulatory changes provide an additional signal to the brain regions that regulate sleep and wakefulness. The model attempts to explain how temperature changes before and after sleep onset act in a positive feedback loop to maintain a consolidated sleep bout.

Separation and assay methods for melatonin and its precursors

Melatonin is an indoleamine hormone that is synthesized from tryptophan via 5-hydroxytryptophan, serotonin and N-acetylserotonin in the vertebrate pineal gland. Many chromatographic and non-chromatographic techniques have been developed and improved for the determination and measurement of melatonin and its related indoleamines. At present, gas chromatography with mass spectrometry and reversed-phase high-performance liquid chromatography with fluorescence or electrochemical detection are widely used for indoleamine determinations in the pineal gland. This review will deal with methods for the separation and determination of the melatonin and its related indoleamines.

Symphony of rhythms in the Xenopus laevis retina

The photoreceptor layer in the retina of Xenopus laevis harbors a circadian clock. Many molecular components known to drive the molecular clock in other organisms have been identified in Xenopus, such as XClock, Xper2, and Xcrys, demonstrating phylogenetic conservation. This model system displays a wide array of rhythms, including melatonin release, ERG rhythms, and retinomotor movements, suggesting that the ocular clock is important for proper retinal function. A flow-through culture system allows measurements of retinal rhythms such as melatonin release in vitro over time from a single eyecup. This system is suited for pharmacological perturbations of the clock, and has led to important observations regarding the circadian control of melatonin release, the roles of light and dopamine as entraining agents, and the circadian mechanisms regulating retinomotor movements. The development of a transgenic technique in Xenopus allows precise and reliable molecular perturbations. Since it is possible to follow rhythms in eyecups obtained from adults or tadpoles, the combination of the flow-through culture system and the transgenic technique leads to the fast generation of transgenic tadpoles to monitor the effects of molecular perturbations on the clock.

Sudden unexpected deaths in epileptics--a literature review

In summary, SUDEP accounts for death in approximately 8% of the young epileptic population. It is commoner in young male epileptics with a long history of generalised seizures, who have a history of head trauma and alcohol excess, and who are taking more than one antiepileptic drug. Most deaths are unwitnessed and occur at home, usually in bed and presumably overnight. Subtherapeutic AED levels do not necessarily imply non compliance, and may simply reflect drug degradation in the plasma after death. Many victims have pulmonary oedema on postmortem examination, and some show ischaemic damage of the heart despite normal coronary arteries. This possibly arises as a result of repeated episodes of vasoconstriction from seizure related catecholamine bursts. Animal studies have demonstrated the occurrence of central apnoea and also support the theory of acute fatal cardiac failure. Possible association with the daily level of geomagnetic activity is reported. The precise reason for a particular seizure being fatal in an otherwise healthy individual is as yet undetermined.

I. Role of the pineal gland in multiple sclerosis: a hypothesis

Despite intensive research over the past several decades, the etiology and pathogenesis of multiple sclerosis (MS) remain elusive. The last 20 years have seen only meager advances in the treatment of the disease in part because too much attention has been devoted to the process of demyelination and its relationship to the neurologic symptoms and recovery of the disease. A host of biological phenomena associated with the disease involving interactions among genetic, environmental, immunologic, and hormonal factors, cannot be explained on the basis of demyelination and, therefore, require refocusing attention on alternative explanations, one of which implicates the pineal gland as the pivotal mover of the disease. This review summarizes the evidence linking dysfunction of the pineal gland with the epidemiology, pathogenesis, clinical manifestations, and course of the disease. The pineal hypothesis of MS also provided the impetus for the development of a novel and highly effective therapeutic modality, one that involves the transcranial application of AC pulsed electromagnetic fields in the picotesla flux density.

Dysregulation of melatonin metabolism in chronic renal insufficiency: role of erythropoietin-deficiency anemia

Chronic renal failure (CRF) is associated with a variety of neurological and endocrine disorders. In this study, we examined the effect of CRF and the associated anemia on circadian variation of pineal hormone, melatonin. Animals were studied six weeks after 5/6 nephrectomy (CRF group, N = 26) or sham operation (control group, N = 28). A group of erythropoietin-treated CRF animals (CRF/EPO, N = 6) was included to discern the possible role of EPO-deficiency anemia. Compared with the normal control group, the CRF group showed a marked attenuation of the nocturnal surge in serum melatonin concentration. In addition, pineal gland melatonin content measured after a 12-hour dark cycle (< or = 2 lux) was significantly depressed in the CRF group when compared to that obtained in the control group. However, the CRF animals exhibited appropriate suppression of serum concentration and pineal tissue melatonin content in response to bright light (> or = 2500 lux). Administration of EPO led to correction of the CRF anemia and a marked improvement of the defective nocturnal rhythm of serum melatonin. Based on our results, experimental CRF is associated with a marked attenuation of the normal nocturnal surge of serum melatonin concentration. Regular EPO administration results in the correction of anemia and substantial reversal of this abnormality suggesting the partial role of EPO deficiency. The possible role of melatonin dysregulation in the pathophysiology of CRF and the potential value of melatonin supplementation in this condition is uncertain and awaits future investigations.

Melatonin and light induce phase shifts of circadian activity rhythms in the C3H/HeN mouse

This study examines the effect of light pulses and administration of the pineal hormone melatonin on the circadian activity rhythm of C3H/HeN mice. Mice were housed in constant dark in cages equipped with running wheels. Phase shifts in the circadian rhythm of wheel-running activity were measured following treatment with a 15-min pulse of light (300 lux) or administration of vehicle (ethanol/saline) or melatonin (90 micrograms, sc). Light treatment induced phase changes in circadian activity rhythms; specifically, delays during early subjective night (circadian time [CT] 12.5 to CT 18.5) and advances during late subjective night (CT 0.5). A single dose of melatonin administered at various CTs had no consistent effect on free-running circadian activity rhythms. By contrast, melatonin administration for 3 consecutive days at the same clock time induced advances in circadian activity rhythms by more than 1 h when the first dose was administered at CT 10 and induced delays in circadian activity rhythms by up to 1 h when the first dose was administered between CT 24 and CT 2. With the caveat that multi- ple melatonin treatments are required to induce phase shifts, the results suggest that the circadian timing system controlling the rhythm of wheel-running activity in the C3H/HeN mouse is responsive to both light and melatonin.

The pineal gland, cataplexy, and multiple sclerosis

Since the discovery of melatonin as the principal hormone of the pineal gland in 1963, scientists have come to recognize that melatonin is a "master hormone" involved in the control of circadian rhythms and other biological functions. Although little is known about the influence of the pineal gland on motor control, important clues may be obtained by considering the pattern of melatonin secretion during the sleep cycles and particularly during rapid eye movement (REM) sleep when melatonin plasma levels are at their lowest. Since REM sleep is characterized by the occurrence of profound atonia which results in an almost complete paralysis of striated muscles, it is suggested that there might be a causal relationship between inhibition of melatonin secretion during REM sleep and the development of REM sleep atonia. This relationship is supported by the findings that melatonin regulates the activity of brainstem serotonin (5-HT) neurons which characteristically cease to fire during REM sleep and which faciliate the development of REM sleep atonia. Moreover, as the muscular atonia of REM sleep is physiologically and pharmacologically indistinguishable from cataplexy, it is possible that the pineal gland also influences to the development of cataplexy. Cataplexy is an ancillary symptom of narcolepsy and also occurs in multiple sclerosis (MS). In fact, it is believed that several of the neurological symptoms experienced by patients with MS such as weakness in the legs, feeling of collapsing knees, paroxysmal sudden falling, weakness in the neck, extreme fatigue, intermittent paresthesias, slurring of speech and intermittent blurring of vision, which often are exacerbated by stress and other emotional influences, may reflect the manifestations of cataplexy. Thus, several of the clinical features of MS may reflect a dissociated state of wakefulness and sleep and may improve by the administration of anticataplectic drugs.

Sudden unexpected death in epileptics following sudden, intense, increases in geomagnetic activity: prevalence of effect and potential mechanisms

Abrupt, intense increases in global geomagnetic activity during the local night may precipitate a significant proportion of sudden unexpected (or unexplained) deaths (SUD) in epileptics. Over a 2-year period SUD in healthy chronic epileptic rats occurred when the average daily geomagnetic activity exceeded 50 nT (nanoTesla) and suddenly began during local night. Other experiments demonstrated that epileptic rats displayed more spontaneous seizures per night if there had been sudden increases in geomagnetic activity. Analyses of previously published data indicated that the number of SUDs/month in a population of human epileptics was positively associated with the number of days/month when the average geomagnetic activity exceeded 50 nT. The results support the hypothesis that suppression of the nocturnal concentrations of the endogenous anticonvulsant melatonin by sudden increases in geomagnetic activity may encourage fatal cardiac arrhythmias by uncoupling the insular/amygdaloid-paraventricular hypothalamic-solitary nucleus pathways.

A comparative study of melatonin production in the retina, pineal gland and harderian gland of Bufo viridis and Rana esculenta

1. The circadian patterns of melatonin and of its synthesizing enzyme N-acetyltransferase (NAT) were investigated in the serum, retina, pineal gland and Harderian gland (HG) of two amphibian species, Bufo viridis and Rana esculenta. 2. Serum melatonin levels showed no diurnal fluctuations in Bufo viridis, whereas, in Rana esculenta, they exhibited a circadian rhythm, with the highest values occurring during the night. Retina melatonin exhibited characteristic circadian patterns in both species, with the highest values occurring during the day, in Bufo, and the highest concentrations occurring at night in Rana. 3. In the retina, NAT activity peaked at night in both amphibians, but in Bufo the levels were up to 30 times higher than in Rana. In the HG and in the pineal gland, NAT activity showed different patterns in the two species with no diurnal variations in Bufo, and characteristic circadian rhythms in Rana. 4. In the HG and pineal gland of both species, melatonin was only occasionally detectable over the 24-hr period. 5. This is the first report exploring melatonin production in Bufo viridis and Rana esculenta. In our experimental conditions, marked differences emerged between the two species.

The influence of the pineal gland on migraine and cluster headaches and effects of treatment with picoTesla magnetic fields

For over half a century the generally accepted views on the pathogenesis of migraine were based on the theories of Harold Wolff implicating changes in cerebral vascular tone in the development of migraine. Recent studies, which are based on Leao's concept of spreading depression, favor primary neuronal injury with secondary involvement of the cerebral circulation. In contrast to migraine, the pathogenesis of cluster headache (CH) remains entirely elusive. Both migraine and CH are cyclical disorders which are characterised by spontaneous exacerbations and remissions, seasonal variability of symptoms, and a relationship to a variety of environmental trigger factors. CH in particular has a strong circadian and seasonal regularity. It is now well established that the pineal gland is an adaptive organ which maintains and regulates cerebral homeostasis by "fine tuning" biological rhythms through the mediation of melatonin. Since migraine and CH reflect abnormal adaptive responses to environmental influences resulting in heightened neurovascular reactivity, I propose that the pineal gland is a critical mediator in their pathogenesis. This novel hypothesis provides a framework for future research and development of new therapeutic modalities for these chronic headache syndromes. The successful treatment of a patient with an acute migraine attack with external magnetic fields, which acutely inhibit melatonin secretion in animals and humans, attests to the importance of the pineal gland in the pathogenesis of migraine headache.

Rhythmic regulation of retinal melatonin: metabolic pathways, neurochemical mechanisms, and the ocular circadian clock

1. Current knowledge of the mechanisms of circadian and photic regulation of retinal melatonin in vertebrates is reviewed, with a focus on recent progress and unanswered questions. 2. Retinal melatonin synthesis is elevated at night, as a result of acute suppression by light and rhythmic regulation by a circadian oscillator, or clock, which has been localized to the eye in some species. 3. The development of suitable in vitro retinal preparations, particularly the eyecup from the African clawed frog, Xenopus laevis, has enabled identification of neural, cellular, and molecular mechanisms of retinal melatonin regulation. 4. Recent findings indicate that retinal melatonin levels can be regulated at multiple points in indoleamine metabolic pathways, including synthesis and availability of the precursor serotonin, activity of the enzyme serotonin N-acetyltransferase, and a novel pathway for degradation of melatonin within the retina. 5. Retinal dopamine appears to act through D2 receptors as a signal for light in this system, both in the acute suppression of melatonin synthesis and in the entrainment of the ocular circadian oscillator. 6. A recently developed in vitro system that enables high-resolution measurement of retinal circadian rhythmicity for mechanistic analysis of the circadian oscillator is described, along with preliminary results that suggest its potential for elucidating general circadian mechanisms. 7. A model describing hypothesized interactions among circadian, neurochemical, and cellular mechanisms in regulation of retinal melatonin is presented.

Determination of 5-methoxyindoles in pineal gland and plasma samples by high-performance liquid chromatography with electrochemical detection

A liquid chromatographic analysis with electrochemical detection of 5-methoxytryptamine, 5-methoxytryptophol, 5-methoxyindoleacetic acid and melatonin is described. Optimal elution conditions were determined by studying several variables: pH, buffer salt, counter ion and organic modifier. Measurement of 5-methoxyindoles in the pineal gland and plasma of hamsters has been performed after extraction. This method is specific and sensitive, and enables detection of 5-methoxyindoles in a pool of two hamster pineal glands. This is also the first time that these three 5-methoxyindoles have been measured simultaneously in plasma.

Regulatory sites in the melatonin system of mammals

The hormone melatonin was first identified about 30 years ago as a secretory product of the pineal gland. In mammals, the daily rhythm of pineal melatonin synthesis is controlled by neural inputs. The CNS is thought to be a primary target organ involved in mediating the influence of melatonin on a variety of physiological and behavioral processes, including biological rhythms, neuroendocrine function, activity levels and sleep. It now appears that melatonin is also produced in the retina and affects various aspects of retinal physiology. The purpose of this article is to provide a brief overview of potential regulatory sites involved in the production and action of melatonin. In particular, this review focuses on the rapid advances being made in the characterization and localization of melatonin receptors in the CNS, retina and pituitary and on recent findings pertaining to the regulation of melatonin synthesis in the mammalian pineal gland and retina.

Differential effects of indolepyruvic acid and 5-hydroxytryptophan on indole metabolism in the pineal gland of the rat during the light-dark cycle

The effect of two serotonin precursors, 5-hydroxytryptophan (5-OH-TRP) and indolepyruvic acid (IPA), a tryptophan ketoanalogue, on rat pineal indole metabolism during the light-dark cycle was investigated. 5-OH-TRP drastically increased the production of 5-hydroxyindoleacetic acid at a dose of only 10 mg/kg, whereas 50-100 mg/kg was needed to reach higher serotonin levels. It had no effect on the pathway leading to the production of N-acetylserotonin and melatonin. IPA, on the other hand, led to a marked dose-related increase in tryptophan, 5-OH-TRP, serotonin and 5-OH-indoleacetic acid, and was also active on N-acetylserotonin and melatonin synthesis in both phases. The different behaviour of these two substances with regard to melatonin synthesis was also confirmed by their effects on N-acetyltransferase, since IPA increased, whereas 5-OH-TRP decreased its activity. These data suggest that an increase in serotonin does not necessarily lead to an increase in melatonin, and that IPA may in fact induce this effect by altering the activity on N-acetyltransferase, which is regarded as a key enzyme in pineal hormone synthesis.

The relationship between ECT responsiveness and subtypes of tardive dyskinesia in bipolar patients

Despite intensive research, the mechanisms of action of electroconvulsive therapy (ECT) remain elusive. In addition, there are no known biological factors predicting ECT responsiveness in bipolar patients. A study was conducted to investigate the relationship between ECT responsiveness and tardive dyskinesia (TD), a common side effect of neuroleptic therapy, and its subtypes (i.e., orofacial and limb-axial dyskinesias) in a group of 18 bipolar patients. There was a significant difference in orofacial dyskinesia scores between ECT responders and non-responders (p less than 0.005), while there was no significant association in scores of limb-axial dyskinesia between ECT responders and non-responders. These findings suggest an association between ECT responsiveness and the presence of orofacial dyskinesias in bipolar patients with TD and add further support to the notion that TD is a heterogeneous disorder comprising at least two subtypes with distinct underlying pathophysiological mechanisms.

Possible role of pineal melatonin in the mechanisms of aging

The pineal gland has captured man's attention as early in recorded history as the Greeks when philosophers considered it the "seat of the soul". Descartes, in the Middle Ages, furthered this concept naming it "esprits animaux" or, in current language, the psychic and somatic activating principle. These notions about the pineal gland were initially purely speculative and unsupported by scientific facts. However, with the development of a sound knowledge base concerning the pineal gland over the past twenty years, evidence has accumulated to suggest a pivotal role for the pineal in the 'fine tuning' and integrating of various neural and endocrine functions. The secretion of pineal melatonin has been shown to decline progressively with age. Recent hypotheses of aging have suggested that cumulative neuronal insults associated with free radical production may be associated with the process of aging. There is evidence to suggest that melatonin may protect against the age processes in part by attenuating the effects of free radical-induced neuronal damage. Other studies derived mainly from observations on pinealectomized rats also suggest that diminished melatonin secretion may be associated with acceleration of the aging process. Thus, pineal melatonin may be a natural anti-aging hormone.

Tardive dyskinesia associated with depression in a bipolar patient: possible role of melatonin

Several clinical studies have suggested that patients with affective disorder are at high risk for developing tardive dyskinesia (TD). An intriguing aspect of the relationship between TD and affective disorders involves mood dependent alterations in the severity of TD in bipolar patients. In most reported cases, depressive episodes have been reported to be associated with exacerbation of TD, while manic episodes were accompanied by attenuation of TD. Current neurochemical hypotheses of TD do not explain adequately the relationship of TD to depression or mania in bipolar patients. A patient with bipolar illness is presented in whom TD emerged concurrently with the onset of depression that developed during management of an acute manic episode. It is suggested that decline in melatonin secretion with onset of the depression was associated with the emergence of TD. Thus, the increased incidence and risk of TD in bipolar patients may in part be related to decreased melatonin secretion, while increased melatonin secretion during manic episodes may have protective effect against the development of TD.

Circadian variations of adrenergic receptors in the mammalian pineal gland: a review

Pineal adrenergic receptor numbers show circadian variations in both rat and Syrian hamster. In the rat pineal beta-adrenergic receptor density reaches peak values either late in the light phase or at middark; the differences in the circadian phase seem related to the light:dark cycle to which the animals are exposed. No circadian rhythm of pineal alpha-adrenergic receptors is documented in intact rats. In the Syrian hamster pineal beta-adrenergic receptor density is high throughout the light phase and drops to minimal values at the time of the nocturnal peak of melatonin production. The circadian rhythm of pineal alpha-adrenergic receptor numbers runs parallel to the beta-adrenergic receptor variation, but is less pronounced. In the rat, pineal melatonin production is rapidly induced by beta-adrenergic agonists at any time during a 24-hour period, even when the pinealocyte beta-adrenergic receptor number is lowest (early in the light phase). In contrast, the Syrian hamster pineal seems most responsive to beta-adrenergic agonists in the late night while being less responsive during the day when beta-adrenergic receptor density is high. Interestingly, the human pineal gland is also not especially responsive to adrenergic stimulation during the light phase, possibly making the Syrian hamster pineal a better model than the rat pineal for determining neural/pineal interactions in humans. Comparison of the circadian variations in pineal adrenergic receptors leads to the conclusion that the functional differences between rat and hamster pineal are probably not explicable in terms of the adrenergic receptors, but are caused most likely by (a) intracellular mechanism(s) beyond the adrenergic receptors.

Determination of pineal melatonin by high-performance liquid chromatography with electrochemical detection: application for rhythm studies and tissue explants

High-pressure liquid chromatography with electrochemical detection has been used for the determination of melatonin in rat pineal glands and tissue explants. Rat pineal melatonin content was measured at 2-hr intervals during a 24-hr period by direct injection of supernatants from centrifuged pineal homogenates into a reversed-phase C18 column. The lower limit of sensitivity was 32 pg per gland for a 2:1 signal-to-noise ratio, which allows melatonin measurements during daytime. Both absolute values and circadian rhythmicity obtained with the present method are in agreement with previously validated radioimmunoassays. In addition, isoproterenol-induced release of melatonin from individual rat pineal explants was measured after chloroform extraction of the incubation medium.

Pineal gland free amino acids and indoles during postnatal development of the rat: correlations in individual glands

Free amino acids and indoles were measured by HPLC in single pineal glands of 5-, 10- and 20-day-old rats sacrificed during mid-light and mid-dark at each age. Melatonin was detectable in neonates (5-day-old), but day vs night differences in indole constituents did not occur until 10 days of age. Free amino acid steady state levels were high in neonates and there was a tendency for reversal of day vs night differences coinciding with the onset of circadian rhythmicity in indole biosynthesis. High correlations (r greater than 0.85) existed for taurine vs. glutamate in individual glands regardless of age and time of sacrifice. These findings suggest that taurine and glutamate are biochemically interrelated and that developmental changes in amino acid metabolic pools reflect functional innervation of the gland.

Pineal melatonin functions: possible relevance to Parkinson's disease

Barbeau hypothesized that Parkinson's disease is associated with hypothalamic deficiency of the specialized neuroendocrine cell system (A.P.U.D.) and that the degeneration of brainstem monoaminergic neurons is secondary to progressive functional loss of this cell system in the disease. The pineal gland meets criteria of the A.P.U.D. cell system and it is possible that dysfunction of the pineal gland may be associated with the pathophysiology and clinical manifestations of Parkinson's disease. Since the role of pineal melatonin in humans remains enigamatic, it is currently unclear which of the symptoms of Parkinson's disease may be associated with deregulation of the secretory activity of pineal melatonin. This review summarizes evidence linking possible alterations of pineal melatonin functions with the clinical manifestations of Parkinson's disease.

The use of hypothermia in surgical pinealectomy of the neonate rat

A technique is described in which rat pups (5-7 days old) are induced into a state of suspended animation by placing them in the freezing compartment of a refrigerator at -20 degrees C for 8-10 minutes. This induces cessation of respiration and heart beat for 12-15 minutes. Surgical pinealectomy is undertaken during this period. Postoperation the animal is gradually warmed and restored to its dam. The effectiveness of pinealectomy was checked after some 400 days by measurement of plasma dark cycle melatonin levels using radioimmune assay. The method is reliable, robust and the results predictable, no melatonin being detectable 400 days after surgery.

Chronic exposure to ELF fields may induce depression

Exposure to extremely-low-frequency (ELF) electric or magnetic fields has been postulated as a potentially contributing factor in depression. Epidemiologic studies have yielded positive correlations between magnetic- and/or electric-field strengths in local environments and the incidence of depression-related suicide. Chronic exposure to ELF electric or magnetic fields can disrupt normal circadian rhythms in rat pineal serotonin-N-acetyltransferase activity as well as in serotonin and melatonin concentrations. Such disruptions in the circadian rhythmicity of pineal melatonin secretion have been associated with certain depressive disorders in human beings. In the rat, ELF fields may interfere with tonic aspects of neuronal input to the pineal gland, giving rise to what may be termed "functional pinealectomy." If long-term exposure to ELF fields causes pineal dysfunction in human beings as it does in the rat, such dysfunction may contribute to the onset of depression or may exacerbate existing depressive disorders.

Investigation of circadian rhythms for pineal 5-hydroxytryptophol and other indoles in the rat

5-hydroxytryptophol (5HTL) occurs in the pineal gland of the rat at levels comparable to those of melatonin, yet few studies have been conducted to investigate 5HTL as a potential alternative pineal hormone. In this study the pineals of 90-day-old male Sprague Dawley rats have been assayed by high performance liquid chromatography coupled with electrochemical detection. Significant (P less than .0001) circadian variation was measured in 5HTL levels, and a fivefold plateau elevation occurred during the middle of the light period. By comparison with the timing of the variations in N-acetyl serotonin and melatonin levels, it is suggested that 5HTL may not be regulated by simple competition with N-acetyl transferase for the common substrate 5HT but may, in fact, be regulated independently. Literature supporting such a suggestion, and a model incorporating it, are presented for discussion.