Circadian and Cyclic LHRH Variations in the Organum vasculosum of the Lamina Terminalis of Female and Male Rats

Wenger, T.; Leonardelli, J

doi:10.1159/000123097

Cited by 17 publications

(7 citation statements)

References 23 publications

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“…A similar conclusion was reached by Samson & McCann (1979) who found that similar OVLT lesions significantly decrease the positive feedback effect of progesterone on LH secretion in oestradiol-primed ovariectomized rats. The present interpretation is also supported by the fact that the LH-RH content of the OVLT fluctuates during the different phases of the oestrous cycle (Kalra, 1976a;Wenger & Leonardelli, 1980), and by the observation that the electrical stimulation of the periventricular area (which includes the OVLT) induces gonadotrophin release and ovulation in female rats in which these processes had been blocked by pentobarbitone (Kawakami, Kimura & Konno, 1973;Kawakami & Kimura, 1975). Indirect support for the hypothesis may also be found in data in older papers.…”

Section: Discussionsupporting

confidence: 76%

Role of the organum vasculosum laminae terminalis in the control of gonadotrophin secretion in rats

Piva¹,

Limonta²,

Martini³

1982

Journal of Endocrinology

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The organum vasculosum laminae terminalis (OVLT) was destroyed by radiofrequency lesions in regularly cycling and in long-term ovariectomized adult rats. After OVLT lesion practically all cyclic females (16 out of 22) became dioestrous, as indicated by vaginal smears. At the time of killing these animals (8 days after the lesion) serum LH levels were undetectable, while serum FSH was as low as in cyclic animals in dioestrus. In the few OVLT-lesioned animals which exhibited some sort of oestrous cyclicity, serum LH showed a small subphysiological increase at pro-oestrus; this was not accompanied by a parallel increase in serum FSH and in these animals a delayed peak of FSH occurred on the day of oestrus. Ovariectomized rats bearing OVLT lesions had serum titres of Lh and FSH as high as those of ovariectomized control rats. It is suggested that the OVLT may play a role in the control of the cyclic release of gonadotrophins but is not involved in the tonic regulation of gonadotrophin secretion.

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Section: Discussionsupporting

confidence: 76%

Role of the organum vasculosum laminae terminalis in the control of gonadotrophin secretion in rats

Piva¹,

Limonta²,

Martini³

1982

Journal of Endocrinology

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“…Although circadian fluctuations in the concentration of LHRH corresponding to the reproductive cycle of the rat have been reported to occur in this area [21,40], no detecta ble changes were observed as a result of ovariectomy or suckling in the present study. These findings are in agree ment with earlier studies in which ovariectomy was found to have no effect on the concentration of immunoreactive LHRH in the preoptic area [9,17,23].…”

Section: Discussioncontrasting

confidence: 74%

Immunocytochemical Evidence that Suckling Inhibits the Postovariectomy Depletion of Median Eminence Luteinizing Hormone Releasing Hormone

Culler¹,

McArthur²,

Dees³

et al. 1982

Neuroendocrinology

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Suckling has been demonstrated to impair the release of pituitary luteinizing hormone (LH) and to prevent the dramatic increase in plasma LH observed following ovariectomy. In the present study, the effect of suckling (10 pups/animal) for either 1 or 3 weeks on the relative amount of luteinizing hormone releasing hormone (LHRH) present in the hypothalamus and preoptic area of ovariectomized and intact rats was examined using immunocytochemical methodology. Controls consisted of nonlactating animals which were either intact (diestrous) or ovariectomized for 1 or 3 weeks. Brains were removed following transcardial perfusion of phosphate-buffered formalin and Bouin’s fixative. After dehydration, clearing and paraffin embedding, the brains were sectioned and LHRH localized by an indirect immunoperoxidase technique. A positive reaction denoting the presence of immunoreactive LHRH was observed over axons and termini throughout the rostral to caudal extent of the median eminence (ME) and surrounding the organum vasculosum of the lamina terminalis (OVLT) in the preoptic area. Ovariectomy resulted in a progressive decline in the concentration of LHRH within the ME as evidenced by a reduction in the intensity of the staining reaction and in the number of axons over which the reaction was observed. In contrast, brains from ovariectomized rats which had been suckled appeared to have concentrations of LHRH in the ME equal to or greater than that of the diestrous controls. Similarly, the concentration of LHRH In the ME of intact, suckled rats did not differ significantly from that of the diestrous controls. Neither ovariectomy nor suckling produced any observable change in the relative concentration of LHRH located near the OVLT. These data demonstrate that suckling prevents the depletion of LHRH from the ME following ovariectomy and provide evidence for mechanism by which the suckling stimulus may suppress plasma LH.

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“…The OVLT lacks a blood-brain barrier [27], and a release of peptides into the bloodstream via the OVLT is possible. The OVLT has been considered to be invol ved in estrous cycle rhythmicity [24,40], osmoregulation and drinking behavior [25,34]. However, the role of substance P in these functions remains unknown.…”

Section: Discussionmentioning

confidence: 99%

Substance P in the Median Eminence and Pituitary of the Rat: Demonstration of Immunoreactive Fibers and Specific Binding Sites

Mikkelsen

Larsen²,

Møller³

et al. 1989

Neuroendocrinology

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The distribution of substance P was demonstrated by immunohistochemical methods, and receptor binding with ¹²⁵I-8-iodinated 8-tyrosine-substance P as an analog was used to describe possible specific binding sites in the hypothalamo-hypophysial system of the rat. The immunohistochemical experiments showed fibers exhibiting substance P-immunoreactivity in the external and internal layer of the median eminence. In the external layer some of the fibers were located in apposition to the portal capillaries. In the posterior pituitary substance P-immunoreactive fibers were identified. These terminals varied in size and were located near the capillaries as well as in the neuropil. The anterior lobe contained a number of substance P-immunoreactive fibers distributed around the pituitary cells. The kinetic analysis on crude membrane fractions from anterior and posterior pituitaries revealed the presence of a specific binding site for substance P in the anterior pituitary. These data indicate that substance P may be released from the median eminence and posterior pituitary to the vascular system and reach specific receptors in the anterior pituitary. However, a direct innervation of the anterior pituitary is possible. The lack of binding sites in the posterior pituitary indicates that fibers in this organ release substance P into the blood stream.

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Circadian and Cyclic LHRH Variations in the Organum vasculosum of the Lamina Terminalis of Female and Male Rats

Cited by 17 publications

References 23 publications

Role of the organum vasculosum laminae terminalis in the control of gonadotrophin secretion in rats

Role of the organum vasculosum laminae terminalis in the control of gonadotrophin secretion in rats

Immunocytochemical Evidence that Suckling Inhibits the Postovariectomy Depletion of Median Eminence Luteinizing Hormone Releasing Hormone

Substance P in the Median Eminence and Pituitary of the Rat: Demonstration of Immunoreactive Fibers and Specific Binding Sites

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