Interactions Between Neuropeptide Y and Adrenergic Systems in the Stimulation of Luteinizing Hormone Release in Steroid-Primed Ovariectomized Rats*

Allen, L. G.; Crowley, William R.; Kalra, Satya P.

doi:10.1210/endo-121-6-1953

Cited by 65 publications

(25 citation statements)

References 37 publications

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“…The most plausible hypothesis in mammals is that NPY is a component of an excitatory neural circuit responsible for the induction of preovulatory LH release (Sahu et al, 1989) mainly interacting with the LHRH system, on which it could have a dual action. An initial stimulation of LHRH release from the median eminence (Khorram et al, 1987;Allen et al, 1987;Pau et al, 1989) is one about which no information is available in fish. A second action postulates a direct effect on pituitary gonadotrophs to activate and/or potentiate LH release induced by LHRH Sutton et al, 1987;Sahu et al, 1989).…”

Section: Discussionmentioning

confidence: 99%

Neuropeptide Y stimulates in vivo gonadotropin secretion in teleost fish

Breton¹,

Mikołajczyk²,

Popek³

et al. 1991

General and Comparative Endocrinology

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The effects of the neuropeptide Y (NPY), alone or in combination with a gonadotropinreleasing hormone analogue, D-Ala6+lesGly10-Pro9-Net LHRH (LHRHa), have been studied on the in vivo secretion of the maturational gonadotropin (GtH3 in the rainbow trout Oncorhynchus mykiss and the common carp Cyprinus carpio. Depending on the species, two routes of administration were used: in trout, intraperitoneal injection (20 p&g body wt); in carp, direct infusion (3 p&g body wt) into the third ventricle via a temporary brain cannula. In both cases NPY alone induced a twofold increase in GtH, secretion and peaked 2 to 4 hr after administration regardless of the route of injection. The plasma gonadotropin levels returned to basal within 8 hr. The relative increases (peaked secretion/basal secretion) did not differ with the route of injection. When the animals were first treated with NPY and then LHRHa (20 pg/kg) 1 hr later, the magnitude of the response to LHRHa was greater in the animals pretreated with NPY, indicating either a potentiation of LHRHa action by NPY or additive effects of the two peptides. The return to basal levels also took longer in fish receiving NPY tirst. NPY may act directly at tbe pituitary level or activate central neuromediatory systems. Q 195'1 Academic Press, Inc.

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Section: Discussionmentioning

confidence: 99%

Neuropeptide Y stimulates in vivo gonadotropin secretion in teleost fish

Breton¹,

Mikołajczyk²,

Popek³

et al. 1991

General and Comparative Endocrinology

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“…data]. In mammals, it has been shown that NPY influences GnRH release [32][33][34][35], colocalizes with GH-releasing factor in the arcuate nucleus [36] and interacts with monoamine neurotransmitters [13, 37,38], It is possible, therefore, that NPY actions on GH and GTH release in the goldfish may be also exerted via these hypothalamic regulators.…”

Section: Discussionmentioning

confidence: 99%

Neuropeptide Y Stimulates Growth Hormone and Gonadotropin Release from the Goldfish Pituitary in vitro

1990

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The effects of neuropeptide Y (NPY) on release of growth hormone (GH) and gonadotropin (GTH) from the goldfish pituitary in vitro were investigated. Exposure of perifused pituitary fragments, taken from female goldfish at late stages of gonadal recrudescence, to 5-min pulses of human NPY resulted in a rapid dose-dependent stimulation of GH and GTH release, with half-maximal effective dosages of 0.51 ± 0.24 and 2.37 ± 1.05 nM for GH and GTH, respectively. Repeated treatments with pulses of NPY (10 nM for GH, 5 nM for GTH) at 55-min intervals did not significantly alter the responsiveness of pituitary fragments to NPY; however, prior exposure of pituitary fragments to pulses of higher doses of NPY (50 nM GH, 10 nM for GTH) significantly reduced the subsequent hormone responses. When given at 85-min intervals repeated treatment with NPY did not blunt hormone responses to the second and third stimulations at these higher dosages. These results indicate that NPY acts at the pituitary level to stimulate GH and GTH secretion in female goldfish. The GTH response and, to a lesser extent, the GH response become desensitized to further stimulation by NPY in dose- and time-dependent manners. NPY should be considered as one element in the multifactorial systems regulating the GH and GTH secretion in goldfish.

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“…These neural events in sequential array are interrelated, as prior disruption of either the opioid or adrenergic modulatory influences block the antecedent accumulation and subsequent discharge of hypothalamic L H R H (16, 20, adrenergic transmitters in some of their projections from the brainstem to the preoptic-tuberal pathway (27,28,32), and because NPY acts in the same manner as norepinephrine in affecting LH and LHRH release (29), we hypothesized that NPY may play an important role in stimulation of LH release on proestrus (10,11). NPY has a dual site of action, one in the hypothalamus to excite LHRH release either on its own and/or in a co-action with adrenergic transmitters (30)(31)(32)(33)(34)(35), and the second, at the level of pituitary gonadotrophs to activate and/or potentiate LH release induced by LHRH (31). These observations were recently corroborated by two reports showing that NPY antiserum administered either intraventricularly or systemically blocked the progesterone-induced LH release in ovariectomized rats (36,37).…”

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confidence: 99%

Dynamic Changes in Neuropeptide Y Concentrations in the Median Eminence in Association with Preovulatory Luteinizing Hormone Release in the Rat

Sahu

Jacobson

Crowley

et al. 1989

J Neuroendocrinology

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Neuropeptide Y (NPY) stimulates luteinizing hormone (LH) release in the rat by a dual action, one in the hypothalamus to excite LHreleasing hormone (LHRH) release and the other at the level of pituitary gonadotrophs to activate and/or potentiate LH release induced by LHRH. Because NPY produces effects similar to norepinephrine with which it may comprise an excitatory hypothalamic circuit, it was hypothesized that NPY concentrations in the hypothalamus would change in a time-and site-specific manner in association with the preovulatory LH surge on proestrus. Concentrations of NPY in individual nuclei of the preoptic-tuberal pathway and serum LH levels were estimated by radioimmunoassays in rats during diestrus 2 and proestrus. On proestrus, serum LH levels were basal between 1000 and 1400 h, rose significantly at 1500 h and plateaued between 1600 and 1800 h. Of the five neural sites examined, only NPY in the median eminence displayed marked fluctuations in close association with the LH surge. NPY concentrations were low between 1000 and 1300 h, and rose abruptly at 1400 h (P< 0.05) preceding the onset of LH rise at 1500 h. These elevated levels were maintained until 1600 h, during which time serum LH rose to a plateau and then fell at 1800 h to the low range seen between 1000 and 1300 h. In contrast, the pattern of changes in NPY levels in the arcuate nucleus, suprachiasmatic nucleus and medial preoptic area, three additional sites in the preoptic-tuberal pathway known to participate in the preovulatory LH surge, were markedly different from that seen in the median eminence. In each of these three sites, NPY levels rose significantly at 1800 h from the values at 1000 to 1200 h with a slightly different time-course of increment. None of these areas exhibited changes in NPY concentrations on diestrus 2; NPY concentrations also were unaltered on diestrus 2 or proestrus in the ventromedial nucleus. The present observations of site-specific, dynamic changes in NPY levels on proestrus, in a manner previously documented for LHRH, support the hypothesis that a subset Of NPY neurons terminating in the median eminence may be a component of excitatory neural circuitry that either independently or in co-action with the adrenergic system is responsible for the induction of preovulatory LH release.The preovulatory release of luteinizing hormone (LH) during the critical period on the afternoon of proestrus occurs as a result of increased episodic discharge of LH-releasing hormone (LHRH) from the hypothalamus (1-7). The timing and duration of LHRH-induced pituitary activation on proestrus has been fully characterized (2,3,8). In addition, it is generally believed that neurogenic stimuli entrained to the daily photoperiod clock abruptly activate LHRH secretion into the hypophysial portal veins during the critical period (2, 9). The origin and route of transmission of these neural signals to LHRH neurons localized in the preoptic-tuberal pathway (2, 3), have not yet been delineated.A number of hypothalamic neural systems h...

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Interactions Between Neuropeptide Y and Adrenergic Systems in the Stimulation of Luteinizing Hormone Release in Steroid-Primed Ovariectomized Rats*

Cited by 65 publications

References 37 publications

Neuropeptide Y stimulates in vivo gonadotropin secretion in teleost fish

Neuropeptide Y stimulates in vivo gonadotropin secretion in teleost fish

Neuropeptide Y Stimulates Growth Hormone and Gonadotropin Release from the Goldfish Pituitary in vitro

Dynamic Changes in Neuropeptide Y Concentrations in the Median Eminence in Association with Preovulatory Luteinizing Hormone Release in the Rat

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