Subcellular Localization of LH Releasing Hormone in the Rat Hypothalamus&amp;rsquo;

Shin, S.H.; Morris, Alison; Snyder, Jeanne M.; Hymer, C.; Milligan, John V.

doi:10.1159/000122565

Cited by 14 publications

(2 citation statements)

References 4 publications

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“…Such an exclusively synaptosomal distribution is identical to that described for all other neurohormones tested so far (LHRH, Ramirez et al, 1975 ;Shin et al, 1974 ;Taber and Karavolas, 1975 ;TRH, Barnea et al, 1975 ;SRIF, Epelbaum et al, 1976). This similarity suggests that nondopaminergic PIF could be a peptide related to the other neurohormones.…”

supporting

confidence: 81%

Central neurotransmitters and control of prolactin secretion

Kordon¹,

Enjalbert²,

Carbonell³

1977

Ann. Biol. anim. Bioch. Biophys.

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Introduction.Despite extensive study during the last 10 years, several aspects of the neural control of prolactin secretion are still unelucidated. In mammals, the most important feature of this control is the existence of a predominant inhibitory regulation, as demonstrated by a number of older experiments involving hypothalamo-hypophyseal deconnexion, interruption of the portal circulation, ectopic grafts of the pituitary, as well as in vitro incubations of adenohypophyseal tissue (see review in Meites andNicoll, 1966 andPasteels, 1967). Under all these conditions, elimination of hypothalamic influences induces a remarkable stimulation of prolactin secretion. This powerful repressor effect of the hypothalamus often masked more limited stimulatory effects, which, nevertheless, can be expressed under certain physiological or experimental conditions. In other species like birds (Kragt and Meites, 1965 ; Gourdji and TixierVidal, 1966), such stimulatory effects even appear more important than the inhibitory component of the regulation.The complexity of mechanisms regulating prolactin release reflects the large variety of physiological situations in which changes in prolactin levels can be observed (stages of the estrous cycle, pregnancy, lactation, stress etc.). A variety of inputs may thus result in elevated prolactin production. In the present paper, we will attempt to describe some of the neural factors which modulate the release of prolactin, focussing our attention particularly on the role of neurotransmitters and neurohormones.General aspects of neurotransmitter-neurohormone interactions. Mena, 1972).The neural pathway involved in the suckling reflex has mainly been studied on the basis of oxytocic responses (Yokohama et al., 1967 ;Richard, 1970 ;Richard et al., 1970). One may infer that the same pathway is involved in the prolactin response. It can be concluded from lesion and deafferentation experiments that influxes generated by suckling first follow fibers from the posterior medullary roots (Richard, 1970) 1) The existence of a stimulatory effect of both NA and 5-HT on base-line secretion levels of the hormone is likely.2) The involvement of 5-HT appears better established in the suckling-induced prolactin secretion. Under these conditions, it has a facilitatory effect (positive modulation) on the hormonal response. It is as if an increase in hypothalamic 5-HT transmitted through the MFB sensitizes neurosecretory neurons towards the specific information transmitted by the bundle of Schutz.3) Under weaning conditions, an identical mammary stimulus is no longer able to affect hypothalamic 5-HT, or, parallely, to induce a massive release of prolactin. 4) Hypothalamic dopamine is also affected by the suckling reflex.Factors affecting the pituitary A. The problem of dopamine.It has been known for a long time that any drug interfering with the metabolism of DA or with the receptors of the amine has a spectacular effect on prolactin secretion (Meites, 1970 ;Lu et al.,1970 . In addition, PIF activity from the ...

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supporting

confidence: 81%

Central neurotransmitters and control of prolactin secretion

Kordon¹,

Enjalbert²,

Carbonell³

1977

Ann. Biol. anim. Bioch. Biophys.

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“…Also, we cannot disregard the possibility that this route of injection would avoid the pulmonary bed, which has the capacity to inactivate other biologic substances, such as bradykinin, angiotensin, prostaglandins [Ryan et al, 1972], In our experi ments the ovulation-facilitatory activity of the microsomal fraction may be explained by an increase in LH release, by LH potentiation at the ovary level, or by both possibilities. The first possibility must be considered in view of the presence of LH-RH associated to subcellular granules, as was shown by Ishii [1970], Clementi et al [1970], Shin et al [1974] and Taber et al [1975], The last authors reported that, after differential centrifugation, only the crude mitochondrial fraction increased LH release in vitro.…”

Section: Discussionmentioning

confidence: 99%

Subcellular Hypothalamic Fractions Active on Ovulation and Luteinizing Hormone Release in the Rat

Forcelledo¹,

Lastra²

1977

Neuroendocrinology

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Nuclear, microsomal and cytosol fractions were obtained from hypothalamic cells by differential centrifugation in sucrose solutions of different molarities. The nuclear fraction (NF) from immature female rats had an inhibitory effect on ovulation induced with pregnant mare’s serum (PMS) in immature rats and with luteinizing hormone (LH) in chlorpromazine (CPZ)-treated proestrous rats. The microsomal fraction from the same rats increased both types of ovulation. Nuclear and microsomal fractions obtained from immature male rats were inactive on ovulation. Cytosol fractions were inactive. NFs active to inhibit ovulation significantly reduced the release of LH induced with synthetic LH-RH in immature male rats and in chronically castrated male rats primed with testosterone (T).

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