Seasonal variations of the beta-endorphin neuronal system in the mediobasal hypothalamus of the jerboa (Jaculus orientalis).
ABSTRACT The distribution of neurons expressing beta-endorphin immunoreactivity was explored in the brain of adult jerboa during two distinct periods characterizing its reproductive cycle. A large presence of cell bodies displaying beta-endorphin immunoreactivity occured within different parts of the mediobasal hypothalamus along its rostrocaudal extent, from the retrochiasmatic area to the posterior arcuate nucleus. Quantitatively, the highest density of immunoreactive beta-endorphin neurons was noted at the medial level of the arcuate nucleus. Furthermore, a seasonal study showed that the number of IR-beta-endorphin neurons was highest in the anterior portion of the arcuate nucleus of jerboas sacrificed in autumn as compared to those sacrificed during spring-summer. Quantitatively, the number of beta-endorphin containing neurons in autumn was 200% in comparison to that found in spring-summer. These results suggest that beta-endorphin containing neuronal population especially localized in the anterior part of arcuate nucleus, exerts an inhibitory influence on the GnRH neurosecretory system in the jerboa, notably in autumn, probably via an increasing expression of its products. The results provide morphofunctional arguments in favour of inhibitory opioid control of GnRH neurons activity and hence the neuroendocrine events regulating reproduction in jerboa.
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ABSTRACT: A combination of the glucose oxidase-diaminobenzidine (DAB) method and the DAB-nickel method can successfully bring out details of immunoreactive structures in immunostained preparations. It is especially beneficial for visualizing fibers and terminals.Neuroscience Letters 03/1988; 85(2):169-71. · 2.03 Impact Factor
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ABSTRACT: The neural components underlying the influence of photoperiod upon reproductive functioning are poorly understood. In this study, we have used immunocytochemistry to examine whether changes in photoperiod may influence specific neuronal cell populations impli- cated in mediating gonadal steroid feedback actions on GnRH neu- rons. Short day (SD) exposed ewes in the midluteal stage of the estrous cycle and long day (LD) anestrous ewes were perfused in pairs and hypothalamic brain sections immunostained for tyrosine hydrox- ylase (TH), neuropeptide Y (NPY), b-endorphin (bE), and the estrogen receptor (ER). The number of ER-immunoreactive cells detected within the preoptic area, but not the hypothalamus, was approxi- mately 20% higher (P , 0.05) in LD ewes compared with SD animals. The numbers of TH-immunoreactive neurons comprising the A12, A14, and A15 cell groups were not different between LD and SD ewes, and the percentage of A12 (;15%) and A14 (;25%) neurons express- ing ERs was similarly unaffected by photoperiod. The number of bE neurons detected in the arcuate nucleus was 50% lower (P , 0.05) in SD vs. LD ewes, whereas NPY-immunoreactive cell numbers in the median eminence were 300% higher (P , 0.05). Approximately 3% of NPY neurons in the median eminence, and 10% in the arcuate nu- cleus, expressed ER immunoreactivity in a photoperiod-independent manner. These studies indicate that changes in photoperiod may regulate ER expression within the preoptic area and suggest that hypothalamic NPY and bE neurons are involved in the seasonal regulation of reproductive activity in the ewe. (Endocrinology 138: 2585-2595, 1997)Endocrinology 01/1997; 138(6):2585-2595. · 4.72 Impact Factor
- Endocrinology 01/1979; 104(5):1286-1291. · 4.72 Impact Factor