Galanin‐Induced Growth Hormone Secretion in Conscious Rats: Evidence for a Possible Involvement of Somatostatin

Tanoh, Tsutomu; Shimatsu, Akira; Ishikawa, Yasuhiro; Ihara, Chihiro; Yanaihara, Noboru; Imura, Hiroo

doi:10.1111/j.1365-2826.1993.tb00379.x

Cited by 19 publications

(7 citation statements)

References 35 publications

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“…In addition, it has been suggested that SRIF is not involved in ghrelin action [9,15,34], consistent with the present results. Although the inhibition of SRIF release by galanin was reported [42], we could not confirm it in this study.…”

Section: Discussioncontrasting

confidence: 78%

Relationship between Growth Hormone (GH) Pulses in the Peripheral Circulation and GH-Releasing Hormone and Somatostatin Profiles in the Cerebrospinal Fluid of Goats

Mogi

Yonezawa

Chen

et al. 2004

The Journal of Veterinary Medical Science

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ABSTRACT. Growth hormone (GH) is secreted in a pulsatile manner, but the underlying mechanisms of GH pulse generation remain to be resolved. In the present study, we investigated the relationship between GH pulses in the peripheral circulation and GH-releasing hormone (GHRH) and somatostatin (SRIF) profiles in the cerebrospinal fluid (CSF) of male goats. The effects of an intracerebrovent ricular (icv) injection of neuropeptide Y (NPY), galanin and ghrelin were also analyzed. Blood and CSF samples were collected every 15 min for 8 hr from the jugular vein and third ventricle, respectively. GH pulsatility in the goat was found to consist of distinct large pulses of 5 hr periodicity and small pulses of 1 hr periodicity. GHRH and SRIF in the CSF fluctuated in a pulsatile manner with 1 hr periodicity, and most of the descending phase of SRIF pulses were associated with the initiation of GH pulses. Icv injections of NPY, galanin and ghrelin stimulated GHRH release without affecting SRIF release. In addition, NPY suppressed, and galanin and ghrelin induced large GH pulses, although ghrelin was much more effective than galanin. These results suggest that an hourly fall in SRIF is involved in generating intrinsic circhoral rhythm of GH pulsatility. The mechanisms underlying the generation of large GH pulses of 5 hr periodicity remain unknown, while direct action of NPY and/or ghrelin on the pituitary might be involved. KEY WORDS: ghrelin, growth hormone, growth hormone-releasing hormone, NPY, somatostatin.J. Vet. Med. Sci. 66(9): 1071-1078, 2004 Growth hormone (GH) is secreted in a pulsatile manner in all mammalian species studied to date, and this pulsatility plays an important role in the regulation of somatic growth and metabolism [7,10,15,20]. Knowledge of the exact mechanisms underlying the generation of GH pulses is, therefore, of physiological and pathophysiological importance. It is generally accepted that GH pulses are governed by two hypothalamic peptides, GH-releasing hormone (GHRH) and somatostatin (SRIF), which are stimulatory and inhibitory for GH secretion, respectively [15,29,34,41]. Most studies on the neuroendocrine regulation of GH pulsatility have been performed in male rats, in which GH secretion is characterized by a strikingly regular ultradian rhythm with large secretory bursts of every 3-4 hr [15,41]. In the rat, indirect studies such as passive immunizations against GHRH and SRIF suggested that GH pulses depend on GHRH discharge in combination with a decrease in SRIF secretion [29,41]. However, the secretory profiles of GHRH and SRIF under physiological conditions in this species remain to be elucidated because of the technical difficulties involved in collecting pituitary portal blood from unanesthetized animals. On the other hand, direct measurement of GHRH and SRIF in the portal blood from conscious animals has been reported in the sheep [4,12,44]. According to these studies, GH pulsatility in the sheep seemed less regular and the secretory patterns of GHRH and SRIF seemed more complex than ...

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Section: Discussioncontrasting

confidence: 78%

Relationship between Growth Hormone (GH) Pulses in the Peripheral Circulation and GH-Releasing Hormone and Somatostatin Profiles in the Cerebrospinal Fluid of Goats

Mogi

Yonezawa

Chen

et al. 2004

The Journal of Veterinary Medical Science

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“…The expression of GAL in the ARC was similar in the ad lib and food-restricted animals. Evidence suggests that the effects of GAL on the secretion of GH involve SRIF-ergic inhibition (Loche et al 1990, Tanoh et al 1993 and GAL cells in the ARC project to the SRIF neurons in the PeVN (Liposits et al 1993). It is likely, therefore, that any effect on the GAL system may manifest as changes in the levels of SRIF in the PeVN and our results for the rPeVN are consistent with this.…”

Section: Rapid Communication R3supporting

confidence: 81%

Chronic food-restriction alters the expression of somatostatin and growth hormone-releasing hormone in the ovariectomised ewe

Henry¹,

Rao²,

Tilbrook³

et al. 2001

Journal of Endocrinology

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Changes in the secretion of GH induced by long-term alterations in nutritional status are thought to result from alterations in somatostatin (SRIF) and growth hormonereleasing hormone (GHRH) at the level of the hypothalamus. To date however, the effect of nutrition on the gene expression of SRIF and GHRH in a species where GH secretion is increased by food restriction, as is the case for the sheep and human, remains unknown. We determined the effect of under-nutrition on the expression of SRIF and GHRH in the hypothalamus of sheep. Ovariectomised ewes were randomly divided into two groups and either fed an ad lib diet (n=6) or a restricted diet of 500 g lucerne chaff per day (food-restricted; n=5) for 7 months. In situ hybridisation was used to study hypothalamic gene expression for GHRH, SRIF and galanin (GAL). The food-restricted animals had elevated plasma concentrations of GH; this was associated with an increase in GHRH mRNA levels in the arcuate nucleus (ARC) and reduced SRIF in the rostral periventricular nucleus and ventromedial hypothalamic nucleus. The level of gene expression of GAL in the ARC and SRIF in the caudal periventricular nucleus was similar in ad lib and food-restricted animals. In conclusion, the effect of chronic food-restriction on the secretion of GH reflects increased GHRH and reduced SRIF synthesis in the hypothalamus.

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“…In man, rat, porcine and human galanin stimulate basal GH secretion (3,4,29,30) as well as the somatotrope response to GHRH (5) and arginine (7). Based on animal (2,(31)(32)(33)(34)(35) and human (5,6,8,36) studies, the mechanisms underlying the GH-releasing effect of galanin seem to involve both GHRH-and somatostatin-mediated actions. However, a direct action of galanin on somatotrope cells cannot be ruled out (37,38).…”

Section: Discussionmentioning

confidence: 96%

Effect of galanin on basal and stimulated secretion of prolactin, gonadotropins, thyrotropin, adrenocorticotropin and cortisol in humans

Arvat

Gianotti

Ramunni

et al. 1995

European Journal of Endocrinology

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Galanin enhances both baseline and growth hormone-releasing hormone (GHRH)-induced GH secretion both in animals and in man. Although galanin has a clear influence on the secretion of other anterior pituitary hormones in animals, in man it increases prolactin (PRL) slightly but does not affect spontaneous thyrotropin (TSH), luteinizing hormone (LH), follicle-stimulating hormone (FSH) or adrenocorticotropin (ACTH) secretion. The aim of our study was to verify the effect of galanin on basal and releasing hormone-stimulated release of gonadotropins, PRL, TSH, ACTH and cortisol secretion. As GH release has been shown to be inhibited by corticotropin-releasing hormone (CRH), we also studied the effect of CRH on galanin-stimulated GH increase. The effect of porcine galanin (15 micrograms/kg iv infused in 60 min) alone and in combination with thyrotropin-releasing hormone (TRH, 200 micrograms iv bolus), CRH (100 micrograms iv bolus) and gonadotropin-releasing hormone (GnRH, 100 micrograms iv bolus) on GH, PRL, TSH, ACTH, cortisol, FSH and LH secretion in seven normal young women (aged 25-30 years) was studied. Galanin infusion caused an increase in serum GH levels (p < 0.02) but failed to modify significantly the spontaneous PRL, LH, FSH, TSH, ACTH and cortisol secretion. The combined administration of TRH, GnRH and CRH caused a significant increase in PRL (p < 0.02), LH (p < 0.02), FSH (p < 0.02), TSH (p < 0.02), ACTH (p < 0.02) and cortisol (p < 0.05), but not in GH levels.(ABSTRACT TRUNCATED AT 250 WORDS)

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Galanin‐Induced Growth Hormone Secretion in Conscious Rats: Evidence for a Possible Involvement of Somatostatin

Cited by 19 publications

References 35 publications

Relationship between Growth Hormone (GH) Pulses in the Peripheral Circulation and GH-Releasing Hormone and Somatostatin Profiles in the Cerebrospinal Fluid of Goats

Relationship between Growth Hormone (GH) Pulses in the Peripheral Circulation and GH-Releasing Hormone and Somatostatin Profiles in the Cerebrospinal Fluid of Goats

Chronic food-restriction alters the expression of somatostatin and growth hormone-releasing hormone in the ovariectomised ewe

Effect of galanin on basal and stimulated secretion of prolactin, gonadotropins, thyrotropin, adrenocorticotropin and cortisol in humans

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