Posterior pituitary gland

Ocytocin Pituitary gland, posterior lobe Contraction of uterus... 

Figure 50-2. The pituitary gland, and the hormones secreted by the anterior pituitary and the posterior putuitary.

There may be a decreased resistance and inability to The posterior pituitary gland produces two hormones localize infection. The nurse observes the skin daily for vasopressin (antidiuretic hormone) and oxytocin (see localized signs of infection, especially at injection sites Chap. 53). Posterior pituitary hormones are summarized or IV access sites. Visitors are monitored to protect the in the Summary Drag Table Anterior and Posterior patient against those witii infectious illness. Pituitary Hormones. 

Concerning other endocrine activities of the pituitary gland, including the posterior lobe, not enough data appear to be available to... 

ADH, a nonapeptide, released from the posterior pituitary gland promotes re-absorption of water in the kidney. This response is mediated by vasopressin receptors of the V2 subtype. ADH enhances the permeability of collecting duct epithelium for water (but not for electrolytes). As a result, water is drawn from urine into the hyperosmolar inter-stitium of the medulla. Nicotine augments (p. 110) and ethanol decreases ADH release. At concentrations above those required for antidiuresis, ADH stimulates smooth musculature, including that of blood vessels ( vasopressin ). The latter response is mediated by receptors of the Vi subtype. Blood pressure rises coronary vasoconstriction can precipitate angina pectoris. Lypres-sin (8-L-lysine vasopressin) acts like ADH. Other derivatives may display only one of the two actions. 

The correlation of the hypothalamus and its hormones with the hormones of the anterior pituitary gland is summarized in figure 5.2. There is no direct vascular connection between the hypothalamus and the posterior lobe of the pituitary that would correspond to the portal vein system for the anterior lobe of the gland. Not all hypothalamo-pituitary hormones will be discussed in the subsequent sections. Only those that are well-defined chemical entities or have a direct connection with drug action are considered. 

The antidiuretic hormone is an octapeptide released from the posterior lobe of pituitary gland. It is used in the treatment of diabetes insipidus. ADH reduces the total urine volume and absence of this hormone cause diabetes insipidus. ADH acts on collecting duct cells to increase their water permeability. It acts on V2 receptors in collecting duct and regulate their water permeability through cAMP production. 

The pituitary gland is situated in sella turcica or hypophyseal fossa of the sphenoid bone attached to the brain by a stalk which is continuous with the part of brain i.e. hypothalamus and there is a communication between the hypothalamus and the pituitary gland by means of nerve fibres and a complex of blood vessels. Pituitary gland consists of three parts - anterior lobe or adenohypophysis, posterior lobe or neurohypophysis and middle lobe or pars intermedia. 

A. General description Oxytocin is a nonapeptide (molecular weight 1.0 kDa) that differs by two amino acids from vasopressin it is stored and released from the posterior pituitary gland. Commercially available oxytocin is prepared synthetically. 

The control of metabolism, growth, and reproduction is mediated by a combination of neural and endocrine systems located in the hypothalamus and pituitary gland. The pituitary weighs about 0.6 g and rests at the base of the brain in the bony sella turcica near the optic chiasm and the cavernous sinuses. The pituitary consists of an anterior lobe (adenohypophysis) and a posterior lobe (neurohypophysis) (Figure 37-1). It is connected to the overlying hypothalamus... 

The pituitary gland is composed of anterior and posterior lobes that are attached to the hypothalamus via the infundibulum or hypophyseal stalk, which includes the portal vessels. Processes from GnRH cells in the hypothalamus terminate on or in the vicinity of the portal vessels that convey blood to the anterior lobe of the pituitary. The... 

Many small peptides exert their effects at very low concentrations. For example, a number of vertebrate hormones (Chapter 23) are small peptides. These include oxytocin (nine amino acid residues), which is secreted by the posterior pituitary and stimulates uterine contractions bradykinin (nine residues), which inhibits inflammation of tissues and thyrotropin-releasing factor (three residues), which is formed in the hypothalamus and stimulates the release of another hormone, thyrotropin, from the anterior pituitary gland. Some extremely toxic mushroom poisons, such as amanitin, are also small peptides, as are many antibiotics. 

Figure 30-1 (A) Median sagittal section of the human brain. From Maya Pines.15 (B) Drawing illustrating the synthesis of peptide hormones in the hypothalamus and transport via portal blood vessels into the anterior lobe of the pituitary gland or via nerve tracts into the posterior lobe.16...

Connected to the brain by a stalk (Fig. 30-1), the pituitary gland releases at least ten peptide or protein hormones that regulate the activity of other endocrine (hormone-producing) glands in distant parts of the body. The pituitary is composed of several distinct parts the anterior lobe (adenohypophysis), a thin intermediate portion (pars intermedia), and a posterior lobe (neurohypophysis). Each has its own characteristic endocrine functions. 

Pituitary Hormones. The hormones of the hypophysis (pituitary gland) are quite numerous, being secreted variously in three parts of the gland — the ncurohypophysis (posterior lobel. the adenohypophysis (anterior lithe), and the pars intermedia, which connects the other two. 

OXYTOCIN. A polypeptide hormone which is secreted by the posterior lobe of the pituitary gland of mammals and other vertebrates. Oxytocin exerts a stimulating effect upon the muscles of the breast (milk-ejection) and those of the uterus of mammals. It is sometimes used medically to stimulate labor in cases of difficult childbirth and to time the onset of labor. 

Water excretion is further controlled by the antidiuretic hormone from the posterior pituitary gland which acts to increase water resorption in the kidney through making the collecting tubule permeable to water for additional resorption beyond what took place in the tubule. The posterior pituitary gland secretes the hormone as a rapid and sensitive response... 

Vasopressin and oxytocin are peptide hormones secreted from the posterior lobe of the pituitary gland. They function primarily to raise blood pressure (vasopressin), as antidiuretic (vasopressin), and to promote contraction of uterus and lactation muscies (oxytocin). The isolation, identification, and synthesis of these hormones was accomplished by Vincent du Vigneaud, for which he was awarded the Nobel Prize in chemistry in 1955. 

The neurotransmitter histamine (HA) exerts several functions in the hypothalamus [1-2] including an involvement in the neuroendocrine regulation of pituitary hormone secretion [3]. HA has no effect directly at the level of the pituitary gland, but influences the secretion of anterior pituitary hormones either by an exerted e.g. in the paraventricular nucleus (PVN) on other central transmitters or hypothalamic regulating factors, which subsequently regulate the release of anterior pituitary hormones. In addition, HA acts on the supraoptic nucleus (SON) in the hypothalamus where the posterior pituitary hormones are synthesized and thereby exerts a direct effect on the release of the posterior pituitary hormones. Immunohistochemical studies have revealed that the histaminergic neurons, which originate in the tuberomammillary nuclei of the posterior hypothalamus, densely innervate most of the hypothalamic areas involved in the neuroendocrine control of pituitary hormone secretion [4-5]. Within the last two decades the effect of HA on pituitary hormone secretion have been explored in several studies and it has been... 

Autoradiographic studies have revealed that H3 receptors are located in most areas of the brain with the highest content in the basal ganglia and the cortex [9]. H3 receptors are distributed with moderate density in the hypothalamus, where the highest density of histaminergic nerve fibers are found [4-5], and were demonstrated in the anterior, medial and posterior hypothalamus [8]. However, their localization in hypothalamic areas primarily involved in the regulation of pituitary hormone secretion were not studied in detail. In the pituitary gland the H3 receptors were scarce. 

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