The pineal gland: its possible significance in schizophrenia

Abstract

Historically, the pineal gland has for at least two centuries been implicated in psychiatry. Since the time Descartes described the gland as the seat of the soul, the pineal body has held a mysterious relationship with mental functioning. Thus, in the early 1900s aqueous pineal extracts were used in the treatment of abnormal mental states with some success. But for a variety of reasons, one of which was the lack of control experiments, the results were viewed with suspicion. It was not until the late 1950s that pineal research began to progress and over the last two decades has mushroomed to the point where the gland is now considered in man as part of the endocrine system. It is a single and compact organ situated medially between the habenular and posterior commisures. If the brain is cut near the median sagittal plane the pineal gland is exposed. Although it is seated in the middle of the brain it is not connected to the rest of the brain neuronally. It receives its nervous supply from the sympathetic nervous system via the posterior fibres from the superior cervical ganglion. It is also situated in close proximity to the third ventricle and so any hormone secretion could pass directly into the ventricular fluid or alternatively drain into the great cerebral vein and thus into the peripheral blood system. There exists no portal blood system between the pineal gland and other parts of the brain such as the hypothalamus or the pituitary.