Developmental Patterns of Tyrosine Hydroxylase Activity in Discrete Central Nervous System Regions and Serum LH and Prolactin in the Prepubertal Rat

Jimenez, Agnes E.; Meyer, Donald C.; Murphy, Peter J.

doi:10.1159/000123880

Cited by 10 publications

(4 citation statements)

References 16 publications

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“…In the prepubertal rat, postnatal changes in the hypothalamic content of LHRH (16,17), neurotransmitter synthesis (18,19), and morphology of LHRH neurons (20) may represent functional maturation of various regulatory mechanisms for LHRH and the ingrowth of synaptic contacts. These events appear to be largely independent of gonadal steroids (21,22).…”

Section: Discussionmentioning

confidence: 99%

N‐Methyl‐DL‐Aspartate Receptor Antagonism by D‐2‐Amino‐5‐Phosphonovaleric Acid Delays Onset of Puberty in the Female Rat

Howe

Naylor

1990

J Neuroendocrinology

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To investigate the possible role of N-methyl-DL-aspartate (NMDA) receptor activation in the initiation of puberty, we examined the effects of the selective competitive antagonist 2-amino-5-phosphonovaleric acid (AP5) on the timing of vaginal opening. Paired and weight-matched litter mates of immature female rats were implanted with osmotic minipumps for the intracerebroventricular infusion of DL-or D-AP5 or artificial cerebrospinal fluid from 27 to 30 days of age for 14 days. Each animal was weighed and examined daily for vaginal opening as the indicator of first oestrous. Infusion of 20 or 40 mM DL-AP5 beginning on Day 30 failed to delay vaginal opening. Administration 50mM of the single enantiomer D-AP5 beginning on Day 27 significantly delayed the age of vaginal opening to 40.6f 1.1 (mean kSEM) days compared to the cerebrospinal fluid-infused controls (36.5k0.6 days). Blockade of NMDA receptors in the D-AP5-treated animals was confirmed on Day 32 by the suppression of luteinizing hormone response to intravenous NMDA (20 mglkg) while the response to exogenous luteinizing hormone-releasing hormone (50 nglkg) remained intact. AP5-treated animals had a slower rate of growth (3.1 +0.2 glday) compared to controls (4.2k0.2 glday). However, a similar degree of growth retardation produced by a 75% restricted diet in untreated juvenile animals did not delay vaginal opening. This suggests that the slower growth rate in the D-AP5-treated animals could not account for the delayed onset of puberty. In conclusion, these data suggest that blockade of central NMDA receptors inhibits excitatory mechanisms which may be important in the control of pubertal onset in the female rat.Puberty in the female rat can be regarded as a series of maturational events in the CNS associated with the gradual emergence of a s) nchronized pattern of pulsatile luteinizing hormone-releasing hormone (LHRH) secretion culminating in first ovultion (1). Although a decline in opioid-mediated inhibitory control can be demonstrated prepubertally (2, 3), recent evidence suggests that the formation or activation of excitatory neurotransmitter pathwaqs may be important in the control of the onset of puberty. Thus, pulsatile administration of N-methyl-DL-aspartate (NMDA), an agonist at NMDA receptors, is able to advance Pubcrty in juvenile animals (4).There is good evidence that NMDA acts to stimulate LHRH release in hypothalamic neurons; NMDA is without effect on gonadotrophs in v i m (5, 6); NMDA excites release of LHRH from hypothalamic explants in vitro (7) and in vivo NMDAstimulated LH secretion can be blocked by LHRH antagonists (8). That the specific NMDA antagonist, D-2-amino-5-phosphonovaleric acid (D-AP5), suppresses pulsatile LH secretion in adult castrates, at least acutely, suggests a role for endogenous excitatory amino-acid neurotransmitters in the control of LHRH secretion (9). It is therefore important to ascertain whether the endogenous ligands (glutamate and aspartate) are implicated in the mechanisms underlying the onset of pubert...

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Section: Discussionmentioning

confidence: 99%

N‐Methyl‐DL‐Aspartate Receptor Antagonism by D‐2‐Amino‐5‐Phosphonovaleric Acid Delays Onset of Puberty in the Female Rat

Howe

Naylor

1990

J Neuroendocrinology

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“…Changes in hypothalamic TH activity during the estrous cycle [7], after gonadectomy, or in response to administration of gonadal steroids [4,25,26,28,29,33,36,37] have been found, and do not always correlate with changes in catecholamine turnover following similar treatments [25,26]. However, in regions where do paminergic terminals predominate, TH activity may be a relatively good indicator of dopamine turnover [3,23]. Per haps biochemical studies of the AVPv that compare TH ac tivity with dopamine turnover will aid in determining the relationship between adult testosterone levels, the density of TH-stained fibers, and dopamine turnover in the AVPv.…”

Section: Discussionmentioning

confidence: 99%

Influence of Perinatal Androgen on the Sexually Dimorphic Distribution of Tyrosine Hydroxylase-Immunoreactive Cells and Fibers in the Anteroventral Periventricular Nucleus of the Rat

Simerly¹,

Swanson

Handa³

et al. 1985

Neuroendocrinology

177

107

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Recently we reported that the anteroventral periventricular nucleus (AVPv) of the preoptic region contains a dramatic sexual dimorphism in the distribution of tyrosine hydroxylase- (TH-)immunoreactive cells and fibers in the rat. This sexual dimorphism appears to be due to a greater density of dopaminergic fibers, and a larger number of dopaminergic cell bodies, in the AVPv of the female. In the present study we used an indirect immunohistochemical method to evaluate the distribution of TH-immunoreactive cell bodies and fibers, and of dopamine-β-hydroxylase-(DBH-)stained fibers, in the AVPv of female rats that were treated with testosterone propionate (TP) perinatally or postnatally, or were left untreated. All of the postnatally TP-treated animals failed to show a phasic pattern of luteinizing hormone (LH) secretion in response to estrogen and progesterone injections. Both the perinatally and postnatally TP-treated females had polyfollicular ovaries that lacked corpora lutea at the time of gonadectomy. Perinatal TP exposure resulted in what appears to be a complete masculinization of both the number of TH-stained cells and the density of TH-stained fibers in the AVPv. The number of TH-stained cells in the postnatally TP-treated females was also completely masculinized, although the density of TH-stained fibers did not appear to be altered significantly. Gonadectomy resulted in a moderate increase in the density of TH-stained fibers in adult males, and did not significantly affect the fiber density in females, or the number of TH-stained cells in either sex. The distribution of DBH-stained fibers in the AVPv did not appear to be altered in any of the treatment groups. These results suggest that the distribution of dopaminergic fibers in the AVPv may be sensitive to testosterone levels in the adult male, and that although the critical period for the development of this fiber distribution may begin in the prenatal period, the number of dopaminergic cells in the AVPv can be completely sex reversed by a single postnatal dose of TP that appears to correlate with a permanent disruption of the normal pattern of gonadotropin secretion.

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“…The diffe rence between adult and immature rats may be due to the divergent methods of implantation employed and/or in sufficient maturation of the tuberoinfundibular DA system at 27 days of age. High circulating prolactin levels, de creasing only after day 30 and indicating low DA activity, have been recorded during the 4th postnatal week [9,15,20,34], After introduction into the VMAR, pimozide implants used in the present experiments induced a significant (p< 0.01) increase of prolactin secretion in adult, but not in 27-day-old females [W. Rohde and F. Docke, unpubl. data].…”

Section: Discussionmentioning

confidence: 86%

Influence of the Medial Preoptic Dopaminergic Activity on the Efficiency of the Negative Estrogen Feedback in Prepubertal and Cyclic Female Rats

et al. 1987

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Immature and adult female rats were bilaterally implanted in the medial preoptic area (MPOA) or hypothalamic ventromedial-arcuate region (VMAR) with the dopamine (DA) antagonist, pimozide, or the DA agonist, apomor-phine, and the sensitivity to the LH-inhibiting effect of a subcutaneous injection of estradiol benzoate (EB), the onset of puberty and ovarian cyclicity were investigated. Diminution of the inhibitory effect of EB on LH secretion was recorded in ovariectomized immature and adult females implanted in the MPOA with pimozide. This response was not obtained in rats implanted in the VMAR. In contrast, medial preoptic, but not intrahypothalamic, implantation of agar pellets containing apomorphine resulted in enhanced sensitivity to estrogen both prepubertally and during the ovarian cycle. The sensitizing effect of apomorphine was completely prevented in prepubertal rats by pretreatment with EB for 6 days. Bilateral implantation of pimozide-agar pellets in the MPOA of 28-day-old intact females induced significant advancement of the onset of puberty, whereas sexual maturation was not affected by daily subcutaneous injections of the DA antagonist from day 28 till the day of vaginal opening. In adult 4-day-cyclic rats fitted with guide cannulae, the forthcoming ovulation was delayed for about 7 days as compared to the controls implanted with agar if apomorphine was placed in the MPOA from the morning of metestrus to the morning of diestrus. Similar implants located in the VMAR were ineffective in this regard. The results suggest that: (1) low DA activity in the MPOA reduces and high activity enhances the sensitivity of the negative estrogen feedback in immature and adult female rats; (2) the medial preoptic DA activity seems to be involved in the control of female puberty and of the ovarian cycle, and (3) a relationship may exist between the estrogen-induced prepubertal and preovulatory desensitization of the negative estrogen feedback and the DA neurotransmission in the MPOA.

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Developmental Patterns of Tyrosine Hydroxylase Activity in Discrete Central Nervous System Regions and Serum LH and Prolactin in the Prepubertal Rat

Cited by 10 publications

References 16 publications

N‐Methyl‐DL‐Aspartate Receptor Antagonism by D‐2‐Amino‐5‐Phosphonovaleric Acid Delays Onset of Puberty in the Female Rat

N‐Methyl‐DL‐Aspartate Receptor Antagonism by D‐2‐Amino‐5‐Phosphonovaleric Acid Delays Onset of Puberty in the Female Rat

Influence of Perinatal Androgen on the Sexually Dimorphic Distribution of Tyrosine Hydroxylase-Immunoreactive Cells and Fibers in the Anteroventral Periventricular Nucleus of the Rat

Influence of the Medial Preoptic Dopaminergic Activity on the Efficiency of the Negative Estrogen Feedback in Prepubertal and Cyclic Female Rats

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