摘要:

Multiparous female Long-Evans rats, 20 months or older, were seen to progress from irregular estrous cycles to a constant-estrous syndrome to a series of irregular pseudopregnancies to an anestrous state. An animal in constant estrus was characterized by ovaries with well developed and sometimes cystic follicles, no corpora lutea, an estrogen-stimulated uterus, and an anterior pituitary that appeared normal. Repeatedly pseudopregnant rats had long diestrous periods of variable length, ovaries with many corpora lutea, uteri with numerous secretory glands, and anterior pituitaries that often showed hemorrhagic or small tumorous areas. Anestrous rats had small, atrophic ovaries with no obvious follicular or luteal elements, atrophic uteri, and large pituitary tumors. Twice-daily injections of L-dopa induced the resumption of regular or irregular estrous cycles in most constant-estrous but not in pseudopregnant or anestrous rats.

ISSN:0028-3835    

DOI:10.1159/000122367

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

Resting pituitary melanocyte-stimulating hormone (MSH) content was studied in adult rats kept under a controlled 14 h light-10 h dark regimen. A diurnal rhythm was found in pituitary MSH levels, showing peak values at 4.00–6.00 p.m., and low values during darkness and the beginning of the light period. The normally occurring fall in pituitary MSH content between 6.00 p.m. and midnight was also found in rats exposed to a prolonged photoperiod. Sympathetic denervation of the pineal gland by superior cervical ganglionectomy, as well as pinealectomy, did not block the rhythm in pituitary MSH, and had no effect on pituitary MSH content. In addition, melatonin administered i.v. did not affect pituitary MSH levels, either when MSH activity was tested on the Anolis skin in vitro, or when the in vivo assay with hypophysectomized frogs (Rana pipiens) was used. It was concluded that the diurnal rhythm in pituitary MSH content is not directly related to the light-dark cycle and is not controlled by pineal melatonin or any other pineal facto

ISSN:0028-3835    

DOI:10.1159/000122368

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

In order to evaluate the precise role of luteinizing hormone-releasing factor (LRF) in mediating the onset of sexual behavior, the specificity, time-course, and dose-response relationship of LRF-facilitated lordosis behavior were determined. Ovariectomized female rats, pretreated with estrone and LRF, displayed a pattern of lordosis behavior which differed little from that produced by estrone-progesterone. Little if any lordosis behavior was observed in response to LRF alone, estrone alone, or estrone in combination with luteinizing hormone (LH), follicle-stimulating hormone (FSH), or thyrotropin-releasing factor (TRF). Furthermore, LRF-induced lordosis behavior occurred in the absence of the adrenals, thus eliminating adrenal progesterone as a factor in facilitating the appearance of lordosis behavior. The LRF-facilitated lordosis behavior was seen 2 h after the injection of LRF and was maintained for a total of 8 h. A minimal dose of 150 ng LRF was required to initiate the first consistent appearance of lordosis behavior; the maximum response was obtained with 500 ng. It is thus suggested that LRF is not only responsible for the ovulatory discharge of LH and subsequent ovulation, but may also play a role in the initiation of the onset of mating behavior in the female rat.

ISSN:0028-3835    

DOI:10.1159/000122369

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

Precocious ovulation was induced in 26-day-old rats by means of 25 IU pregnant mare’s serum gonadotrophin (PMS). Rats were given injections at either 09.00 or 16.00 in order to determine whether the course of pubertal changes in corticosterone (B), progesterone (P) or time of ovulation would be dependent upon the time of injection. Blood samples were collected by decapitation at 4-h intervals on the day of expected ovulation (day 28). In saline-treated controls at 28 days of age there was a demonstrable daily variation in both serum B and P with maximum values at 16.00 and minimum values at 08.00. In rats given PMS at 09.00, there was a peak of P and B at 16.00 on day 28 but the values were higher than in controls. Ovulation took place at 24.00 on day 28–29. In rats given PMS at 16.00 the pattern of P and B was different, with continual high values from 16.00 to 04.00 at 28 days of age; ovulation took place later in this group (between 02.00–08.00 on day 28). It can be concluded that there is a daily rhythm of P a few days before puberty and that the induction of precocious ovulation with PMS is associated with a different pattern of B and P and a different time of ovulation depending upon when PMS is adminis

ISSN:0028-3835    

DOI:10.1159/000122370

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

A considerable number of small and medium-size neurons are described in the subependymal layer of the caudal part of the middle portion of the rat median eminence. They are arranged mainly in rostro-caudally oriented rows. Fine structure of these nerve cells is similar to that of the arcuate neurons. Small axon terminals establish synaptic contacts with these cells. The possible functional significance of these neurons is discussed.

ISSN:0028-3835    

DOI:10.1159/000122371

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

Serum prolactin was measured in lightly etherized rats between 4 and 5 a.m. and between 11 a.m. and 12 noon at various times after operation in intact rats and rats that had been operated on. Serum prolactin was elevated in the late nocturnal samples from intact rats and this elevation was prevented by pinealectomy. With time following the operation, daytime serum prolactin was also lowered in pinealectomized animals. In animals rendered anosmic by olfactory bulb removal, serum prolactin was also lowered. Superimposed pinealectomy only lowered late nocturnal serum prolactin in anosmic rats. Blinding the rats by ocular enucleation lowered nocturnal serum prolactin initially and dampened the daily rhythm in prolactin, but superimposed pinealectomy had no effect on the blinded animals. The combined sensory deprivation produced by both blinding and olfactory bulb removal resulted in low prolactin titers regardless of whether blood samples were taken during the day or late at night and, as in the case of blinded animals, there was no effect of pinealectomy. Superior cervical ganglionectomy also lowered serum prolactin. Serum prolactin declined following castration in intact animals and this decline was accentuated by pinealectomy. Either blinding or anosmia also lowered serum prolactin in the castrated animals but, as in intact animals, pinealectomy had little effect on the sensory-deprived rats. A further lowering of prolactin occurred in castrated animals which were both blinded and anosmic; in these animals, pinealectomy again had no additional effect. Measurement of the pituitary prolactin content in the castrated animals at sacrifice revealed a significant lowering of values in blinded animals, with restoration of the values to control levels by pinealectomy. Anosmia also lowered the pituitary prolactin content

ISSN:0028-3835    

DOI:10.1159/000122372

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

Arginine vasopressin (AVP) and vasotocin (AVT) were measured by radioimmunoassay in extracts of cerebral cortex, cerebellum, brain stem, pineal, hypothalamus, and neurohypophysis from normal Long-Evans rats. AVP was present in expected concentrations in pituitary and hypothalamus and there was no evidence of its accumulation elsewhere. AVT was not detectable in these tissues (within the limits imposed on our assay by the presence of excessive amounts of AVP) but was easily detectable in pineal tissue with a concentration of 22.4 ± 6.6 µU/gland. Extracts of neurohypophysis and pineal glands from homozygous Brattleboro rats (rats with hereditary hypothalamic diabetes insipidus) revealed the total absence of AVP and AVT. We conclude that the Brattleboro rat is incapable of synthesizing biologically active neurohypophyseal peptides which contain arginine in position

ISSN:0028-3835    

DOI:10.1159/000122373

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

25-day-old female rats were left intact, or rendered either blind-anosmic or blind-anosmic-pinealectomized. Five weeks later, blind-anosmic animals were found to possess significantly depressed body, anterior pituitary, uterine and ovarian weights. The pituitary levels of LH were elevated while pituitary prolactin was depressed in the dual sensory-deprived rats. Blind-anosmic animals also had significantly depressed plasma levels of LH and elevated plasma levels of prolactin. The effects of blinding and anosmia were effectively reversed by pinealectomy. Ovariectomized, estrogen and progesterone-treated (OVX, EP-treated) rats that received an intracarotid injection of a medial basal hypothalamic (MBH) extract from intact or from blind-anosmic-pinealectomized female rats exhibited a marked rise in plasma LH to a peak at 10 min after injection. This peak was followed by a steady decline in plasma LH concentration. Animals injected with MBH extract from blind-anosmic rats also demonstrated a rise in plasma LH with the levels remaining more or less constant for the 10 and 20-min samples. Rather than declining, the plasma LH levels in 3 out of 4 rats exhibited a further increase until the 40-min sample. The injection of either cortical extract or saline had no effect on plasma LH levels. OVX, EP-treated rats receiving either MBH extracts from intact or blind-anosmic rats or cortical extract exhibited a depression in plasma prolactin titers 5 min following injection. This response was followed by a slight increase in plasma prolactin at 10 and 20 min with a subsequent decrease. Each of the OVX, EP-treated recipients injected with MBH extract from blind-anosmic-pinealectomized rats responded with an obvious increase in plasma prolactin levels within 5 min after injection,

ISSN:0028-3835    

DOI:10.1159/000122374

出版商:S. Karger AG    

年代:1975

数据来源: Karger

ISSN:0028-3835    

DOI:10.1159/000122375

出版商:S. Karger AG    

年代:1975

数据来源: Karger

ISSN:0028-3835    

DOI:10.1159/000122376

出版商:S. Karger AG    

年代:1975

数据来源: Karger