Catecholamine mechanisms in medio-basal hypothalamus influence prolactin but not growth hormone secretion

Day, Trevor A.; Jervois, P.M.; Menadue, Margaret; Willoughby, John O.

doi:10.1016/0006-8993(82)90688-6

Cited by 22 publications

(15 citation statements)

References 32 publications

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“…INTRODUCTION It is well documented that dopamine is the main inhibitory regulator of pituitary prolactin secretion and that it exerts its effects directly at the level of the lactotroph (Birge, Jacobs, Hammer & Daughaday, 1970;MacLeod & Lehemeyer, 1974;Shaar & Clemens, 1974;Caron, Beaulieu, Raymond et al 1978;Gudelsky, Nansel & Porter, 1980). Noradrenaline is also involved in the control of prolactin secretion, act¬ ing at the level of the hypothalamus (Voogt & Carr, 1981;Day, Jervois, Menadue & Willoughby, 1982). The presence of both dopamine and noradrenaline in an anterior pituitary gland transplanted under the kidney capsule has been reported (Iturriza, Rubio, Gómez-Dumm & Zieher, 1983;Fernández-Ruiz, Ubeda, Tresguerres et al 1985).…”

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confidence: 99%

Possible role of dopamine and noradrenaline in the regulation of prolactin secretion from an ectopic anterior pituitary gland in female rats

Fernández‐Ruiz¹,

Cebeira²,

Agrasal³

et al. 1987

Journal of Endocrinology

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It was recently reported that anterior pituitary tissue transplanted to an ectopic site contains measurable amounts of dopamine and noradrenaline. To examine the possibility of local catecholaminergic control of prolactin secretion from ectopic pituitaries, pituitary grafted and sham-operated female rats were submitted to several pharmacological treatments modifying catecholamine synthesis. Administration of a single dose of alpha-methyl-p-tyrosine (alpha-MPT) significantly reduced dopamine content in the graft, while noradrenaline content was not modified. Similar changes in the contents of dopamine and noradrenaline after alpha-MPT administration were observed in the hypothalamus and in the in-situ pituitary in both grafted and sham-operated rats. Plasma concentrations of prolactin were increased in both grafted and sham-operated rats after administration of alpha-MPT. A single injection of L-3,4-dihydroxyphenylalanine (L-DOPA) increased dopamine content in the ectopic pituitary gland without altering the noradrenaline content, and produced similar effects in the hypothalamus and in-situ pituitary of grafted and control rats. Plasma prolactin concentrations were decreased by L-DOPA in both pituitary grafted and control rats. Administration of DL-treo-dihydroxyphenylserine (DOPS) increased noradrenaline content in the ectopic pituitary and reduced plasma prolactin concentrations in pituitary grafted rats. In contrast, injection of DOPS to control rats increased both hypothalamic noradrenaline content and plasma prolactin concentrations. These results suggest that dopamine and noradrenaline present in the ectopic pituitary tissue have a role in mediating prolactin release from pituitary transplants.

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confidence: 99%

Possible role of dopamine and noradrenaline in the regulation of prolactin secretion from an ectopic anterior pituitary gland in female rats

Fernández‐Ruiz¹,

Cebeira²,

Agrasal³

et al. 1987

Journal of Endocrinology

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“…a:-Adrenoceptor activation stimulated GH release both in the PO/AHA and MBH, enlarging the more lim ited conclusions of several reports [6][7][8][9][10], In the MBH there was a trend for all doses to increase GH levels (table 1) while the effect was less consistent in the PO/ AHA where an intermediate dose of 0.1 nmol of clonidine was effective but not higher doses. The loss of a GH stimulatory effect of high doses of PO/AHA clonidine might be due to inhibitory at-adrenoceptor effects of clonidine blocking the stimulatory a?…”

Section: Discussionmentioning

confidence: 75%

“…The experimental proce dure was chosen to provide an indication of the baseline secretory status of each animal and is an improved experimental design over our initial studies using only posttreatment samples [9,10]: blood samples were taken every 15 min, 3 before intracerebral injection and 3 or 4 after. In most of the experiments, unilateral hypotha lamic injections were made.…”

Section: Methodsmentioning

confidence: 99%

“…We use a chronically prepared model for these studies [9][10][11], Pentobarbitone-anesthetized animals were prepared with a silastic indwelling venous catheter and 23-gauge steel intracerebral guide cannulae directed towards the preoptic anterior hypothalamic area (PO/AHA), where somatostatin neurons are located [12] or the medial basal hypothalamus (MBH), where GRF neurons are located [ 13]. The guide tubes and catheter connector were fixed to the skull with steel screws and dental cement.…”

Section: Methodsmentioning

confidence: 99%

“…In the region of somatostatin neurons, «2-receptor activation increased GH secretion [8], while rxi-adrenoceptor activation was indirectly impli cated in the inhibitory effect of catecholamines on GH because gd-and |3-adrenoceptor agonists did not replicate the inhibitory effects of noradrenaline [9]. In the region of GRF neurons, catecholamines were without stimulatory effects on GH, but basal values were too low to demon strate inhibition [10], possibly due to stress because pro lactin levels were concurrently elevated.…”

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confidence: 99%

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Local Hypothalamic Adrenoceptor Activation in Rat: α<sub>1</sub> Inhibits and α<sub>2</sub> Stimulates Growth Hormone Secretion

1993

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We made stereotaxic microinjections of adrenoceptor agonists and the catecholamine-releasing agent, tyramine, into the preoptic anterior hypothalamic area (PO/AHA) or the medial basal hypothalamus (MBH) of unstressed rats. Growth hormone (GH) plasma concentrations were measured serially before and after intrahypothalamic injections. Noradrenaline and phenylephrine inhibited GH secretion wherever injected but were effective at lower doses in the PO/AHA. Clonidine stimulated GH secretion at both sites, at several doses in the MBH and only at one dose in the PO/AHA. Tyramine inhibited GH when injected in the PO/AHA, but not in the MBH. We conclude: (a) α₁ inhibition is predominant over α₂ stimulation of GH on or near somatostatin neurons; (b) α₁ stimulation predominates over α₁ inhibition of GH on or near GRF neurons, and (c) endogenous catecholamines in the PO/AHA have a predominantly inhibitory effect on GH secretion.

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The distribution of growth‐hormone‐releasing factor (GRF) immunoreactivity in the central nervous system of the rat: An immunohistochemical study using antisera directed against rat hypothalamic GRF

Sawchenko

Swanson

Rivier

et al. 1985

J of Comparative Neurology

239

117

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Immunohistochemical methods have been used to chart the distribution of rat hypothalamic growth-hormone-releasing factor (rhGRF) immunoreactivity in the brains of normal and colchicine-treated adult albino rats. The results suggest the existence of at least two distinct rhGRF-containing systems: one responsible for delivery of the peptide to portal vessels in the median eminence, and one whose relationship, if any, to hypophysiotropic function is less direct. A dense plexus of rhGRF-stained fibers was found throughout the external lamina of the median eminence that is the route by which the peptide is delivered to the anterior pituitary. This projection appears to arise primarily from a group of rhGRF-immunoreactive neurons centered in the arcuate nucleus. Some 1,000-1,500 rhGRF-positive neurons were counted on each side of the brain in rats pretreated with colchicine. Colocalization studies, using a sequential double staining technique, indicated that a subset of rhGRF-immunoreactive neurons in the arcuate region contain neurotensin immunoreactivity. No evidence was obtained for colocalization of rhGRF with either of two pro-opiomelanocortin-derived peptides (alpha-melanocyte-stimulating hormone, adrenocorticotropic hormone (1-24)) in individual neurons in the arcuate nucleus. Much smaller groups of neurons were localized in the parvicellular division of the paraventricular nucleus of the hypothalamus and in the dorsomedial nucleus, and it is unclear whether they contribute to the plexus of rhGRF-stained fibers in the median eminence. The only other region in the rat brain in which rhGRF-stained cells were found reliably was in the area that roughly encapsulates the caudal aspect of the ventromedial nucleus of the hypothalamus. Because cells in this region are not known to project to the median eminence, they may be assumed to contribute to the extrahypophysiotropic rhGRF-stained projections outlined below. From the level of the arcuate and ventromedial nuclei, rhGRF-immunoreactive fibers could be traced along the base of the brain and through the periventricular system to discrete terminal fields limited almost exclusively to the hypothalamus and adjoining parts of the basal telencephalon. All parts of the periventricular region of the hypothalamus receive an input, including the preoptic and anterior parts in which somatostatin-containing neurons that project to the median eminence are clustered. Other prominent terminal fields were localized in discrete parts of the dorsomedial, paraventricular, suprachiasmatic, and premammillary nuclei, and in the medial preoptic and lateral hypothalamic areas.(ABSTRACT TRUNCATED AT 400 WORDS)

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Catecholamine mechanisms in medio-basal hypothalamus influence prolactin but not growth hormone secretion

Cited by 22 publications

References 32 publications

Possible role of dopamine and noradrenaline in the regulation of prolactin secretion from an ectopic anterior pituitary gland in female rats

Possible role of dopamine and noradrenaline in the regulation of prolactin secretion from an ectopic anterior pituitary gland in female rats

Local Hypothalamic Adrenoceptor Activation in Rat: α<sub>1</sub> Inhibits and α<sub>2</sub> Stimulates Growth Hormone Secretion

The distribution of growth‐hormone‐releasing factor (GRF) immunoreactivity in the central nervous system of the rat: An immunohistochemical study using antisera directed against rat hypothalamic GRF

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