Pars Nervosa

The posterior lobe is composed of nerve fibres and endings of hypothalamic neurones (Fig. 250), capillaries (Figs. 251,254, and 255) and characteristic as-troghal cells, the pituicytes. In rapidly frozen, freeze-substituted neural lobes of male albino rats, pituicytes occupied close to 60% of the basal lamina at the neurohaemal contact zone, while axons occupied about 20% (Tian et al. 1991). Takei et al. (1980) classified the human pituicytes into five classes based on their ultrastructural features  

In tissue culture, the glial cells derived from posterior lobes of dog and rat had the same morphological characteristics as protoplasmic astrocytes derived from various parts of the brain (Hild 1954). Oligodendroglia cells were sometimes observed in cultures of posterior lobe macrophages, which according to the investigations of Costero (1930) are probably identical with microglial, are a very common observation. 

Oxidative enzymes (a-glycerophosphate dehydrogenase, succinic dehydrogenase, and reduced diphospho- and triphosphopyridine nucleotide dia-phorases) gave a very intense nitroblue tetrazolium (formula [18]) reaction in the matrix of the posterior lobe from mature female Sprague-Dawley rats (Fand and Wattenberg 1963). 

Nitric oxide synthase (EC 1.14.13.39) immuno-staining was positive, especially within dilated axon terminals (Herring bodies) of man (Lloyd et al. 1995). 

Activity increased in the posterior pituitary of salt-loaded rats (Kadowaki etal. 1994). N 0-Nitroarginine significantly inhibited NOS activity in the posterior pituitary in a dose-dependent manner, but did not influence NOS mRNA levels. Two percent salt loading for 3 or 4 days significantly depleted the contents of both arginine vasopressin and oxytocin in the posterior pituitary, and simultaneous treatment with daily injections of N -nitroarginine at a dose of 10 mg/kg significantly enhanced the depletion of both hormones. 

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Gayrard V, Thiery J-C, Thibault J, Tillet Y (1995) Efferent projections from the retrochiasmatic area to the median emience and to the pars nervosa of the hypophysis with special reference to the A15 dopaminergic cell group in the sheep. Cell Tiss Res 281 561-567. 

Fig. 251. Scantiness of neurosecretory granules in some neurones (bottom) in the pituitary pars nervosa (block 1330) of a rat (No. 11) treated for 8 consecutive days with intraperitoneal injection of 15 mg carbocromene per kg body weight x-day. On the last 5 days of experimentation the animal was exposed to an atmosphere containing only 5% oxygen for 30 min. On August 5, 1976, half an hour er the last exposure under pentobarbital anaesthesia (30 mg/kg), the animal was perfused from the abdominal aorta with 2.5 % glutaraldehyde in 0.1 M sodium cacodylate buffer (pH 7.4). Postfixation with 1 % osmium tetroxide in sodium cacodylate buffer. Embedded in Epon 812 and sectioned at 50 nm. Lead citrate and uranyl acetate. Plate 3462...

Fig. 255. Vacuoles (arrow) in the vascular endothelium in the intermittent hypoxic and reoxygenated pituitary pars nervosa (block 1451) of a rat (No. 15) treated for 8 consecutive days...

Ciliated cells are occasionally found in the junctional zone between pars intermedia and pars nervosa of the rat pituitary particularly in association with the ramifications of the pituitary cleft (Howe and Maxwell 1968). 

The pars nervosa is made of neuroglial cells and nervous fibers that are most abundant in the stalk of the pituitary. The pars nervosa contains three different types of cells that cannot be distinguished with ordinary staining techniques. The posterior lobe of... 

The pituitary body, or hypophysis, is double in origin and multiple in functions. From the stomodceal pouch of Rathke is developed the anterior lobe and the -pars intermedia from the floor of the third ventricle are formed the pars nervosa of the posterior lobe, the infundibulum and the tuber cinereum. The pituitary autacoids are of two types secretions acting directly on other tissues, and hormo-kinetic secretions acting indirectly by stimulating other endocrine glands. 

B. Posterior Lobe (pars intermedia and pars nervosa)... 

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