The Diencephalon

Brain structure below the thalamus and main portion of the ventral region of the diencephalon, controlling homeostatic and nonhomeostatic basic body and brain functions, including circadian and feeding rhythms, energy metabolism, thermogenesis, sympathoadrenal, and neuroendocrine outflow (secretion of hormones by the pituitary gland), behavioral state and memory functions. 

Muller F. and O Rahilly J. (1988). The development of the human brain, including the longitudinal zoning the diencephalon at stage 15. Anat Embryol 179, 55-72. 

Ascending Reticular Activating System (ARAS) A network of neurons running up (ascending) through the core of the brainstem to the diencephalon and descending to the spinal cord. Also known as the reticular formation. 

Median forebrain bundle A bundle of monoaminergic neuronal axons travelling from the brainstem through the diencephalon to various limbic structures. 

It is possible that this compound (and perhaps related compounds) acts by direct entry into the diencephalon. 

In order to test whether water-soluble fullerenes could be potential agents against the treatment of Parkinson s disease and other CNS degenerative diseases related to neuronal apoptosis, the protective effects of water-soluble fullerene derivatives 1 and 6-8 on 6-hydroxydopamine-induced apoptosis of CNS dopaminergic neurons (Silva et al., 2005) in developing zebrafish were investigated. It was demonstrated that 1,6 and 7 were able to protect 42%, 47% and 23%, respectively of total CNS neurons, whereas 1,6 and 8 blocked each with 60%, 100% and 60% of specific dopaminergic neuronal death in the diencephalon as it is exemplarily shown for 8 in Fig. 3.8. 

The diencephalon is composed of several nuclei that are grossly grouped into the thalamus, hypothalamus, epithalamus, and subthalamic nucleus. The thalamus serves as a sensory relay, receiving projections from all of... 

Figure 1.2 presents a coronal section through the human brain. In brief, the brain may be divided into the brainstem (consisting of the medulla, pons and midbrain) that is linked to the diencephalon which is composed of the thalamus and the hypothalamus. The two cerebral hemispheres are linked by the corpus callosum, a large tract of nerve fibres that enables the two... 

Hippocampus Region primarily concerned with learning and short-term memory. Hypothalamus Part of the diencephalon comprising several nuclei where hormones such as oxytocin and antidiuretic hormone are S5mthesized and pass to the pituitary gland. Involved in the regulation of the peripheral autonomic system and pituitary hormones such as prolactin, growth hormone and adrenocorticotrophic hormone. 

Figure 5.2 The Hypothalamic Pituitary Axis The hypothalamus is part of the diencephalon within the brain. The pituitary, although located within the skull, is more correctly a part of the endocrine system than the nervous system. Together, the hypothalamus and pituitary form the interface between the nervous system and endocrine system and exert control over the majority of other hormone secreting organs. Releasing and inhibiting factors permit the hypothalamus to control the pituitary. Pituitary hormones are released into the general circulation, affecting metabolic function throughout the thorax and abdomen.

Figure 4 Correlation between the duration of chronic convulsion and the histamine level in the diencephalon in mice.

The last subcortical synapse is located in the sensory relay nuclei of the thalamus, a part of the diencephalon located deep in the base of the brain. 

The area of the brain enclosing the third ventricle is the diencephalon. This area consists of several important structures, including the thalamus and hypothalamus. The thalamus contains distinct nuclei that are crucial in the integration of certain types of sensations and their relay to other areas of the brain (such as the somatosensory cortex). The hypothalamus is involved in the control of diverse body functions including temperature control, appetite, water balance, and certain emotional reactions. The hypothalamus is also... 

In the unanesthetized dog, reserpine selectively depresses the sympathetic centers and induces facilitation of the parasympathetic centers in the diencephalon. The latter effect accounts for the bradycardia, miosis, aggravation of bronchial asthma, renal and biliary colic, and ulcerative colitis observed in some patients receiving the drug. 

Jones BE. Influence of the brainstem reticular formation, including intrinsic monoaminergic and neurons, on forebrain mechanism of sleep and waking In Mancia M, Marini G, eds. The Diencephalons and Sleep. New York Raven Press, 1990 31 18. 

Aldrich MS, Naylor MW (1989) Narcolepsy associated with lesions of the diencephalon. 

In the diencephalon, besides the hypothalamus, dopaminergic fibers have also been detected in the thalamic nuclei and in the habenula. It is interesting to note that in the thalamus dopaminergic fibers are distributed to nuclei that are also recipient of inputs from the ventral pallidum. 

Fig. 1. Location of dopaminergic perikarya (Au-A15) are depicted schematically on frontal sections (B-F) through the diencephalon of the rat. Section A is a sagittal view of the rat brain depicting the rostrocaudal location of frontal sections B-F. Abbreviations AH, anterior hypothalamus ARC, arcuate nucleus BST, bed nucleus of the stria terminalis f, fornix ic, internal capsule inf, infundibulum me, median eminence mt, mamillothalamic tract OC, optic chiasm ot, optic tract PH, posterior hypothalamus PIT, pituitary gland PeV, periventricular nucleus PVN, paraventricular nucleus RCH, retrochiasmatic area SON, supraoptic nucleus VMN, ventromedial nucleus ZI, zona incerta.

---