Effect of Lesions of the Corticomedial Amygdala on the Nocturnal Prolactin Surge

Clarke, William P.; Gala, Richard R.

doi:10.1159/000124193

Cited by 8 publications

(9 citation statements)

References 46 publications

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“…Necrotic responses to excitatory amino acid injections are well described, comprising an early phase lasting 1-14 d after infusion and a later stage that is characterized by an infiltration of astrocytic glia cells Marty et al, 1991). In the present experiment, glial coverage was observed in brains taken 16 d after NMDA infusion, and nocturnal PRL surges observed 6 -7 d after NMDA infusion were diminished in magnitude, as is characteristic for MEA-lesioned females (Clark and Gala, 1985;Polston and Erskine, 2001). Nevertheless, several lines of evidence suggest that it is the initial excitatory effect of NMDA on MEA neurons that is responsible for the present effects.…”

Section: Discussionsupporting

confidence: 58%

NMDA-Mediated Activation of the Medial Amygdala Initiates a Downstream Neuroendocrine Memory Responsible for Pseudopregnancy in the Female Rat

et al. 2001

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In female rats, genitosensory stimulation received during mating initiates twice-daily prolactin (PRL) surges, a neuroendocrine response that is the hallmark of early pregnancy or pseudopregnancy (P/PSP). Nocturnal and diurnal PRL surges are expressed repeatedly for up to 2 weeks after copulation, suggesting that a neuroendocrine memory for vaginocervical stimulation (VCS) is established at the time of mating. These studies investigated whether the processing and retention of VCS involves acute glutamatergic activation or de novo protein synthesis within the medial nucleus of the amygdala (MEA), a VCS-responsive brain site that is implicated in P/PSP initiation. Pharmacological activation of the MEA with the glutamate agonist, NMDA, initiated nocturnal PRL surges, causing a PSP state in females that had not received VCS. P/PSP initiation by mating was prevented by intra-amygdalar infusion of the NMDA receptor antagonist, 2-amino-5-phosphonopentanoic acid (AP-5), provided that it was administered before mating. AP-5 treatment also disrupted mating-induced c-fos expression in the principle bed nucleus of the stria terminalis and the ventrolateral division of the ventromedial hypothalamic nucleus, but not in the medial or anteroventral periventricular preoptic nuclei. Neither P/PSP nor downstream cellular activation was prevented when a protein synthesis inhibitor, anisomycin, was administered to the MEA. The results indicate that MEA cells are critical to the early processing of VCS through NMDA channel activation, rapidly conveying information to downstream hypothalamic cell groups that modulate neuroendocrine function.

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Section: Discussionsupporting

confidence: 58%

NMDA-Mediated Activation of the Medial Amygdala Initiates a Downstream Neuroendocrine Memory Responsible for Pseudopregnancy in the Female Rat

et al. 2001

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“…Prolactin release in P/PSP rats was also influenced by MePD integrity, as prolactin secretion was blunted across all times of day 6–7 days postmating in MePD‐lesioned females. A specific inhibition of the nocturnal prolactin surge after radiofrequency lesion of the corticomedial amygdala has been reported to occur 12 and 15 but not 8 days after VCS (30). In the present experiment, the suppression of prolactin secretion in BI females was marginally significant compared to sham females (P ≤ 0.06); however, when compared to IC females which showed slightly higher prolactin than did sham rats, the suppression of prolactin release in BI females was statistically significant (P ≤ 0.02).…”

Section: Discussionmentioning

confidence: 99%

Excitotoxic Lesions of the Medial Amygdala Differentially Disrupt Prolactin Secretory Responses in Cycling and Mated Female Rats

Polston¹,

Erskine²

2001

J Neuroendocrinology

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This study examined the role of the posterodorsal medial amygdala (MePD) in the control of prolactin secretion in gonadally intact female rats 20 min after mating, during the oestrous cycle, and during early pregnancy/pseudopregnancy (P/PSP). Cycling females received bilateral infusions of an excitotoxic dose of N-methyl-D-aspartate (NMDA) or vehicle into the MePD. Two to 4 weeks later, they were surgically implanted with intra-atrial catheters for repeated blood sampling and were mated on the evening of proestrus until receiving 5, 10, 15 or 20 intromissions or 15 mounts-withoutintromission (MO) from males. The percentages of rats becoming P/PSP increased as a function of numbers of intromissions received. All groups receiving intromissions showed similar approximately four-fold increases in plasma prolactin concentrations 20 min after mating, while MO rats showed no increase at this time. There was no effect of NMDA lesion on this acute secretory response. Among rats that continued cycling, bilateral MePD lesion completely abolished the diurnal preovulatory prolactin surge, while incomplete and sham lesions did not. In rats that subsequently became P/PSP, bilateral lesion of the MePD resulted in dampening of prolactin concentrations at all sampling times 6±7 days after mating, while incomplete or sham lesions did not alter prolactin secretion at these times. These results demonstrate that the MePD is selectively important for the secretion of prolactin on the afternoon of proestrus and that this structure may also modulate prolactin release in P/PSP rats. Activity within MePD neurones does not appear to be required for the acute prolactin response to vaginocervical stimulation which occurs within minutes after mating.

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“…In contrast, the VMH seems to have a uniformly stimulatory control over both nocturnal and diurnal surges [21, 22, 35]. The amygdala has been shown to alter the incidence of induction of pseudopregnancy [36, 37]and the termination of the nocturnal surge [38]. In addition, our previous work showed that Fos expression in the mPOA and VMH exhibited activated neuronal activity during the mating-induced nocturnal and diurnal PRL surges [23].…”

Section: Discussionmentioning

confidence: 99%

“…By using a double-label immunofluorescent technique, Tetel et al [30]found that high percentages of VCS-induced Fos-positive neurons in the mPOA, mAMYG and VMH also contained estrogen receptor-immunoreactivity. Given that these brain areas are important in the regulation of both hormone-induced afternoon PRL surge [12, 13]and VCS-induced twice daily PRL surges [21, 22, 34, 35, 38], the subset of neurons responding to estrogen and VCS may integrate the two forms of stimuli and directly or indirectly contribute to the PRL surge. However, the magnitude of the increase in Fos expression in these brain areas was considerably more subtle during the proestrous PRL surge than following mating.…”

Section: Discussionmentioning

confidence: 99%

Fos Expression in the Female Rat Brain during the Proestrous Prolactin Surge and following Mating

Yang

Lee²,

Voogt³

1999

Neuroendocrinology

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A prolactin (PRL) surge occurs in the female rat during proestrus in response to elevated estradiol levels. The elevated release of ovarian steroids on the day of proestrus is also associated with sexual receptivity. Mating triggers twice-daily PRL surges that supplant the proestrous PRL surge and are responsible for maintaining luteal function during the first half of pregnancy. In order to understand the neuronal mechanisms controlling the proestrous- and mating-induced PRL surges, we examined patterns of Fos expression by immunocytochemistry in specific brain regions as a measure of neuronal activity. Intact female rats were sacrificed at 09.00, 15.00, and 18.00 h on the day of proestrus and the day of diestrus. Brain tissues were also collected at 21.00 h on the day of proestrus from rats receiving intromissions or mounts from males or taken directly from their homecage. On the day of proestrus, the number of neurons expressing Fos in the medial preoptic area (mPOA), medial amygdaloid nucleus (mAMYG), and ventromedial nucleus of the hypothalamus (VMH) was few and was associated with low plasma PRL levels at 09.00 h; however, the number of Fos-positive cells in these brain regions significantly increased at 15.00 and 18.00 h when the proestrous PRL surge occurred. Mating during the evening of proestrus resulted in a dramatic increase in the number of Fos-positive cells in the mPOA, mAMYG, and VMH as well as in the arcuate nucleus (ARC). Nonmated animals in diestrus showed low and unchanged PRL levels and Fos expression in all the brain areas throughout the day. These results suggest that the mPOA, mAMYG, VMH and ARC may be important brain sites for the integration of stimuli associated with proestrous- and mating-induced PRL surges.

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Effect of Lesions of the Corticomedial Amygdala on the Nocturnal Prolactin Surge

Cited by 8 publications

References 46 publications

NMDA-Mediated Activation of the Medial Amygdala Initiates a Downstream Neuroendocrine Memory Responsible for Pseudopregnancy in the Female Rat

NMDA-Mediated Activation of the Medial Amygdala Initiates a Downstream Neuroendocrine Memory Responsible for Pseudopregnancy in the Female Rat

Excitotoxic Lesions of the Medial Amygdala Differentially Disrupt Prolactin Secretory Responses in Cycling and Mated Female Rats

Fos Expression in the Female Rat Brain during the Proestrous Prolactin Surge and following Mating

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