A Bit More about the Pineal
I have resumed my research into the pineal organ, which is more than just a gland. In birds it is known to e sensitive to the earth’s magnetic fields, and it also responds to light. It was theorised in the 1980s that pineal is sensitive to magnetic fields in humans too (by Robert Becker).
Birds use their pineals for navigation and it is involved in their migratory behaviour. In birds and reptiles the pineal is located at the surface of the brain but in mammals it is located deep within the brain, located at the roof of the third ventricle, the fluid-filled
chamber between the thalami.
The principal hormone secreted by the pineal is melatonin, which is synthesised at night (during sleep) from the indole amine serotonin. Serotonin and melatonin both have effects on mood and serotonin, mainly produced in the Raphe Nuclei of the brainstem, also acts as a neurotransmitter in other parts of the brain. Prozac and the other SSRI antidepressants are known to lower melatonin levels.
The synthesis of melatonin from serotonin is modulated by the autonomic nervous system, especially the sympathetic nervous system, whose neurotransmitter noradrenaline stimulates the activity of the relevant enzymes in the pineal. The sympathetic innervation of the pineal is not direct – it was discovered in the 1960s that the sympathetic information arrives at the pineal via the sympathetic chain in the neck and loops back up to the pineal. The circadian and diurnal rhythms that the pineal is known to be involved in are modulated by the suprachiasmatic nucleus (SCN) of the hypothalamus, which has been described as our “circadian clock” and receives input from the retinae of the eyes.
The pineal also has a parasympathetic (rest and digest) innervation involving the neurotransmitter acetyl choline. In addition to the autonomic innervation the pineal receives inputs from diverse parts of the brain through the pineal nerve. This part of its physiology is poorly understood and has not been researched much. Most of the research has been on its influence on the endocrine (hormonal) system, sleep cycles, circadian rhythms and the immune system.
Scientists have known about the pineal for a very long time. The ancient Greeks thought it functioned as a valve that controlled the flow of the “humours” in the 5th century BC. The ancient Indians thought it was the ‘third eye’, remarkable because Western science in the 20th century confirmed that it is phylogenically derived from the parietal eye of fish and amphibians and remains a light-sensitive organ in birds and mammals (including primates). In the Hindu tradition it is regarded as the Third Eye of Shiva; in the Buddhist tradition it has been called the third eye for seeing truth.
Descartes is famous for his seventeenth century statement that the pineal is the “seat of the soul”. However despite the discovery in the 1890s that tumours damaging the pineal cause precocious puberty (by the German physician Huebner), through most of the 20th century Western science declared that the pineal had no function in humans. They argued that the development of calcification in the gland (which they called ‘brain sand’) was proof that the pineal is a “primitive” vestige of no significance other than its function as an indicator of the midline on x-rays of the brain. A displaced pineal, called “midline shift” could indicate a tumour or haemorrhage displacing the brain.
In 1958 the vestigial theory was disproven with the discovery of melatonin by the dermatologist Aaron Lerner at Yale University. Lerner was looking for a skin-lightening compound, and it had been known since 1911 that frog skin lightened on exposure to pineal extracts. This is due to melatonin causing clumping of melanophores (pigment granules in amphibian skin). It was said that melatonin has no effect on human skin pigmentation though there reports in the 1970s that melanocyte stimulating hormone (MSH) is one of several pituitary hormones that are modulated by melatonin from the pineal.
The explanation for Huebner’s nineteenth century observation that pineal tumours in children cause precocious puberty is that melatonin inhibits the pituitary gonadotrophins FSH and LH (which regulate oestrogen and testosterone production). In fact in the nineteenth century pineal extracts were used a contraceptive in Germany. Studies in the 1960s indicated that the pineal also affects other pituitary hormones, including thyroid stimulating hormone (TSH) that regulates metabolic rate by modulating secretion of thyroxin by the thyroid gland in the neck.
Melatonin is an ancient molecule found in single-celled organisms as well as plants. It is found in both invertebrates and vertebrates. This may relate to its known role as a free radical scavenger and anti-oxidant. This activity has led to the ingestion of melatonin as an anti-ageing hormone. However, this may not be a good idea, since taking exogenous hormones can suppress endogenous production.
Though most of the melatonin in mammals is produced by the pineal, small amounts are also synthesised in the eyes, skin and gut. Many parts of the eye produce melatonin and also have melatonin receptors, including the retina, lens, iris, ciliary body and lacrimal gland. It is thought that the melatonin production in the eyes is related to circadian rhythmicity and the detection of day length, as well as the regulation of sleep cycles.
There is very little melatonin produced in the brain of neonates. Production increases during the first few months of life with peak concentrations at 1 to 3 years. Production of melatonin decreases with age and this correlates with calcification of the gland, though there have been studies indicating that the reduction of melatonin is unrelated to the degree of calcification. There is considerable variation between the degree of calcification between individuals and there are also geographical and racial differences. Studies in the 1970s and 1980s indicated that the incidence of calcification (detected on skull x-ray) is much lower in Africa than the USA and also lower in African-Americans in the USA. It has also been reported to be lower in India and Japan than in the West.
Since the 1990s melatonin has been promoted for jet lag and as a mild sleeping tablet. It is said to “reset the body clock”. Questions about the body clock, circadian and diurnal rhythms, chronobiology and the role of the pineal cross interdisciplinary boundaries as do questions about the pineal generally. Does the pineal also have a role in our sense of time, timing and musical rhythm? What is the function of the neurones in the organ and do they sense magnetic fields? What structures in the brain are connected to the pineal through the pineal nerve? Is there a connection with the auditory system as well as the visual system?
What is the truth about the “third eye for seeing truth”?