Pituitary Gland: Neuropeptides, Neurotransmitters and Growth Factors

Abstract

ABSTIZACXThe hypothalamus receives neuronal afferents from numerous sources including inputs from limbic structures, such as the amygdala and hippocampus, and from brainstem regions involved in the regulation of the cardiovascular system and other autonomic functions. These afferents using a vast array of neurotransmitters and neuropeptides influence the activity of the hypothalamic neurons which synthesize and secrete the hypothalamic releasing and release-inhibiting factors into the hypophyseal portal circulatory system. The afferents can modulate the activity of the hypothalamic neurons by forming synapses on the neuronal cell body, on the nerve terminals in the median eminence or both. The chemicals most frequently used as neurotransmitters are the biogenic amines, including the catecholamines (norepinephrine, dopamine and epinephrine), serotonin, acetylcholine and gamma-aminobutyric acid (GABA). The stirnulatory influence of norepinephrine, serotonin, and acetylcholine on the secretion of corticotropin (ACTH) in rodents and man will be discussed, whereas GABA exerts an inhibitory effect on the secretion of ACTH in both man and rodents. These effects appear to be mediated by changes in the secretion of the corticotropin-releasing hormone (CRH) and vasopressin into the hypophyseal portal circulation. Numerous neuropeptides appear to alter the secretion of ACTH in the rat. We will discuss the stirnulatory actions of neuropeptide Y (NPY), angiotensin 11, and peptides of immune cell origin on the secretion of ACTH and CRH. The opioid peptides inhibit the secretion of CRH into the portal blood, however, they exert a potent stirnulatory effect on prolactin secretion in the rat and man. We will discuss the receptor subtypes involved in mediating these effects and the interactions of the opioid peptides with the neurotransmitter-containing neurons which project to the hypothalamus. This discussion will focus on the factors which impinge on the releasing factor-containingneurons in the hypothalamus and how they can be studied under in viso and in vitro conditions.

Identification of Thyroid Hormone Receptor Binding Sites and Target Genes Using ChIP-on-Chip in Developing Mouse Cerebellum

“…It has long been recognized that active TREs can reside within introns of TH responsive genes. The TH-regulated expression of GH is mediated through both a TRE in the regulatory region upstream of the TSS [38] and a site with higher affinity for TR within the third intron of the gene [39]. Similarly, the expression of hepatic carnitine palmitoyltransferase-I alpha, an enzyme involved in fatty acid metabolism, is regulated by TR action at a TRE located in the first intron [40].…”

Opioid and cocaine combined effect on cocaine-induced changes in HPA and HPG axes hormones in men

“…Hypothalamic control of ACTH release is mediated by the secretion of corticotropin-releasing factor (CRH). CRH release is in turn influenced by several systems/peptides, such as NPY, angiotensin II, and opioids (Aguilera et al, 1995; Dimitrov et al, 2007; Koenig, 1989; Suda et al, 1993). Endogenous opioid peptides (EOPs) released as a stress defense (Amir et al, 1980) inhibit CRH release into the hypothalamo-hypophyseal portal system, resulting in downstream decrease in ACTH/cortisol release (Koenig, 1989; Kuhn and Saltiel, 1986; Morley, 1983).…”

Neuropeptides in anterior pituitary development

“…Regulatory peptides originally identified in the nervous system were called neuropeptides, although they were also found in most endocrine glands, where they are probably employed as modulators of the synthesis and/or paracrine or autocrine secretion of hormones (Hokfelt et al, 2000;Houben et al, 1990;Houben and Denef, 1994;Jones et al, 1990;Koenig, 1989).…”