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F Döcke

Publications and source records attributed to F Döcke.

At least 55 records · Page 3Linked to original sources
PubMed1980

Evidence for direct central nervous inhibition of LH secretion during sexual maturation of female rats.

Intact and ovariectomized female rats were bilaterally lesioned in the anterior part of the medial amygdaloid nucleus (AMN) at 15, 21 or 26 days of age. The onset of puberty and the LH concentration in the peripheral serum on the third day after lesioning, respectively, were recorded. Damage to the AMN on day 15 induced a significant delay of vaginal opening and the first puberal ovulation and suppressed completely the castration-induced increase of LH secretion. In contrast, females lesioned on day 21 showed true precocious puberty and a significant elevation of the LH level as compared to the ovariectomized controls. The LH-inhibiting effect of s.c. administered estradiol benzoate (0.05 micrograms/100 g/day) was not diminished by lesions produced at this age. Neither the onset of puberty nor the LH concentration were influenced by lesioning of the AMN on day 26. Estimation of the LH concentration in untreated female rats revealed a distinct decline between 19 and 23 days of age followed by a significant increase between days 24 and 26. The findings indicate a transient LH-inhibiting activity of the medial amygdala in three-week-old female rats that is not related to the negative estrogen feedback. In other species, too, a temporary inhibitory action of the central nervous system may play a significant role in the prepuberal control of gonadotropin secretion.

Aging↗
PubMed1980

Involvement of a cholinergic mechanism in the mediation of hippocampal influences on female sexual maturation and somatic development.

Female Wistar rats were bilaterally lesioned in the anterior part of the ventral hippocampus (VHPC) at 21, 26 or 32 days of age. Irrespective of the age at lesioning a significant delay of vaginal opening and of the first ovulation was recorded. This delay of the onset of puberty was consistently associated with a retardation of the body weight increase. Both the puberty-delaying and growth-retarding effects of VHPC lesions produced on day 21 could be prevented by daily s.c. injections of 50 micrograms/100 g b.w. pyridostigmine from day 21 till vaginal opening, but not by the administration of 2 mg/100 g/day pargyline. The findings suggest a cholinergic mediation of stimulatory effects exerted by the hippocampus on sexual maturation and somatic development.

Animals↗
PubMed1980

Failure of estradiol-17 beta implants located in the medial preoptic area to induce ovulation in cyclic rats.

Female rats exhibiting regular 4-day vaginal cycles were injected with progesterone on day 1 (estrus = day 0) and implanted bilaterally with estradiol-17 beta (E2) in the medial preoptic area (MPOA) or, for control, in the medial amygdaloid nucleus on day 2. The implants which contained different quantities of E2 were prepared by different methods and were either expelled immediately after introduction of the capillary tubes into the brain, or the tubes were left in place till autopsy. Evaluation of the ovulatory response at autopsy on day 4 revealed that E2 placed in the MPOA had not abolished the delay of ovulation produced by progesterone, whereas implants located in the medial amygdala were effective in this respect. The findings confirm former results obtained with estradiol benzoate and suggest that the MPOA may not be the primary site of action of estrogen in its ovulation-inducing effect in rats.

Amygdala↗
PubMed1979

[Neurohormonal regulation of male gonad function].

In a survey the neurohormonal regulatory mechanisms are discussed which control the incretory and spermiogenetic function of the testicles in adulthood. The central position of LH-RH and the factors influencing its secretion, the negative feedback between the testicular hormones including inhibin and the hypophyseal gonadotropins as well as the periodic changes superimposed to the basal secretion of the sexual hormones are explained. Finally, the present knowledge is summarized on the cooperation of the different hormones and mechanisms in the regulation of the incretory and excretory testicular functions.

Androgens↗
PubMed1979

Experimental studies on the neurohormonal control of female puberty.

Experiments were performed in rats to study the role played by ovarian estrogens, the hypothalamus, the medicortical amygdala, and the ventral hipopcampus in the neurohormonal control of female sexual maturation. The results obtained demonstrated that the ovulation-inducing effect of a single administration of estradiol benzoate (EB) to immature female rats is not tantamount to the induction of precocious puberty. Long-term treatment with very low doses of EB, however, can accelerate sexual maturation, although it was established that the endogenous ovarian estrogen secretion during prepuberal life is not essential for the maturation of the cyclic ovarian function. Implantation of very low quantities of EB into the mediobasal hypothalamus of ovariectomized immature and postpuberal female rats revealed that the hypothalamic sensitivity to the LH-inhibiting effect of estrogen exhibits a gradual decrease that begins some days prior to the onset of puberty. It may be responsible for a temporary elevation of the LH level in the blood triggering final maturation of the ovarian follicles and an increase of estrogen secretion. - Studies on the influence of the limbic system on female sexual maturation lead to the following conclusions: 1. The mediocortical amygdala has an essential function in the maturation of the positive estrogen feedback. 2. An LH-inhibiting activity not related to the negative estrogen feedback is exerted by this nuclear region during critical periods of sexual maturation. It may form an additional protective mechanism against precocious stimulation of the ovaries. 3. By means of its stimulatory action on growth hormone and FSH secretion, the ventral hippocampus may be involved, by cholinergic mechanisms, in the interrelationships between metabolism and the onset of female puberty. The results which suggest a significant role of the limbic system in the control of female sexual maturation will be discussed with regard to recent data obtained in girls and women.

Animals↗
PubMed1978

[Animal experiment studies on the neurohumoral control of female puberty].

To study the mode of action of oestrogen in female sexual maturation, prepubertal female rats were treated in different ways with oestradiol benzoate (OB). Using an improved implantation method, former findings on a hypophysial site of oestrogen action in the positive feedback (Hohlweg effect) were confirmed. A single s.c. injection or intrahypophysial implantation of OB at 25 or 26 days of age induced precocious vaginal opening (VO) and one ovulation, but the subsequent ovarian cycle was significantly prolonged, so that the first spontaneous ovulation occurred only at the normal time of the onset of puberty. Further studies demonstrated that the sensitivity to the ovulation-inducing effect of oestrogen increases as the rats approach the age of puberty, and that the first pubertal ovulation can be suppressed by intrahypophysial, but not by intrahypothalamic implantation of progestereone. The conclusion is drawn that the precocious induction of one ovulation via the Hohlweg effect is not tantamount to an advancement of puberty. The results furthermore suggest that the positive oestrogen feedback forms the basis for the first pubertal ovulation as it does with regard to later cyclic ovulations. True acceleration of sexual maturation was achieved by daily injections of 0,05 microgram OB/100 g b.w. from 5 days of age to VO. In contrast to findings obtained by other authors in Sprague-Dawley rats, a shortened OB treatment from 26 days of age to VO was not effective in advancing the onset of puberty unless the rats had additionally been injected with OB from 5 to 10 days of age. A final experiment demonstrated that the first ovarian cycle was not prolonged after neonatal ovariectomy and implantation of ovaries at 24, 28 or 32 days of age. Thus, maturation of the neurohormonal mechanisms that are responsible for the cyclic ovarian function continues during the prepubertal development in the absence of ovarian steroids.

Age Factors↗
PubMed1978

[Animal experiment studies on the neurohumoral control of female puberty. 2. Studies on the influence of amygdala and of the hippocampus on sex maturation].

Immature female rats were bilaterally lesioned in the rostral or caudal part of the mediocortical amygdala (MCA) or in the ventral hippocampus (VHPC) at 21 days of age. In a second experiment, simultaneous lesioning of the MCA or VHPC and the medial preoptic area or hypothalamic ventromedial-arcuate region was performed in 21-day-old rats. Finally, discrete lesions were placed into the anterior or posterior parts of the medial (MAN) or cortical amygdaloid nuclei ath 21, 26 or 32 days of age. The effects of the different treatments on the onset of puberty were evaluated by recording the age at vaginal opening and first ovulation, the body weight on the day of vaginal opening, and the subsequent ovarian or vaginal cyclicity. The following conclusions may be drawn from the findings obtained: 1. At three weeks of age, the MCA exerts a gonadotropininhibiting function that is localized in the anterior part of the MAN. This activity is not demonstrable in older females. 2. The MAN, particularly its posterior part, may play an important role in the prepuberal maturation of the maturation of the neurohormonal ovulatory mechanisms that takes place in female rats during the fourth week of life. 3. The VHPC may be involved in the control of female sexual development mainly by its growth-stimulating activity. The results suggest an essential role of the subcortical limbic system in female sexual maturation and offer an explanation of contradictory findings on the gonadotrophin-controlling function of the MCA before puberty.

Amygdala↗
PubMed1978

Studies on the time and localization of the puberal desensitization to oestrogen in female rats.

Immature and postpuberal female rats were ovariectomized at 20 or 27 days of age or on the day of the first vaginal oestrus and chronically implanted with oestradiol benzoate (OB) and cholesterol at the ratios of 1 : 60, 1 : 120 or 1 : 240 on the day following castration. Autopsy was performed on day 6 after implantation and the plasma LH concentration determined by radioimmunoassay. Whereas 1 : 60 and 1 : 120 implants of OB and cholesterol placed into the hypothalamic ventromedial-arcuate region depressed the castration-induced elevation of the LH level before and after puberty, the 1 : 240 mixture was effective only in immature rats, but not after vaginal opening and the first ovulation had occurred. A similar trend was recorded after implantation of OB into the cortical amygdaloid nucleus (CAN). However, the oestrogen dose had to be doubled to get comparable results. Bilateral lesioning of the CAN or deefferentation of the mediocortical amygdala by transection of the stria terminalis did not distinctively influence the LH-suppressing effect of daily s.c. injections of 0.1 or 0.05 microgram OB/100 g b. w. in prepuberal rats. The findings demonstrate a sudden change in the hypothalamic threshold to the gonadotrophin-inhibiting effect of oestrogen over a narrow range of time near the onset of puberty. They furthermore suggest that the mediocortical amygdala is not involved in possible extra-hypothalamic control of the puberal desensitization process.

Animals↗
PubMed1978

Morphological differentation of limbic nuclei during sexual maturation of female rats.

Cell nuclear volumes were measured in the central parts of the medial amygdaloid nucleus (MAN), cortical amygdaloid nucleus (CAN) and basolateral amygdaloid nucleus (BLAN), the anterior part of the ventral hippocampus (VHPC) and, for control, in the parietal cortex of immature female rats at 21, 26, 32, or 36 days of age, or at the onset of puberty. The cortical cell nuclei did not show any variation of their volumes during the period of development under investigation. In all limbic regions studied, a significant increase of cell nuclear size was found from day 21 to day 26 indicating that a general maturation process runs off in the limbic system during the fourth week of life. Cell nuclei were significantly smaller in 32-day-old rats as compared to 26-day-old females in the MAN, CAN and VHPC, but not in the BLAN. From day 32 to day 36, nuclear volumes had distinctively increased in the MAN and BLAN, not changed in the CAN, and further decreased in the VHPC. The first ovulatory oestrus was associated with diminution of nuclear sizes in the MAN and BLAN, and with enlargement of cell nuclei in the CAN and VHPC. The results which suggest a specific development of different limbic nuclei are discussed with regard to recent findings on the gonadotrophin-controlling function of the limbic system in immature and cyclic female rats.

Aging↗
PubMed1978

[Karyovolumetric studies of postnatal differentiation of the amygdaloid complex in ovarectomized rats].

The caryovolumetrically definable prepubertal morphokinesis of the medial, cortical and basolateral amygdaloid nuclei in intact female rats (DOCKE and SMOLLICH 1978), which is probably related to the maturation of the ovulatory meachnisms, could not be demonstrated in females ovariectomized on the first day after birth and autopsied at 21, 26, 32, 36 or 39 days of age. Simultaneously, postnatal castration induced a specific stimulation of the metabolic activity of amygdaloid neurons. A distinct increase of cell nuclear volumes as compared to intact rats was recorded in the medial and basolateral amygdaloid nuclei and, to a lower degree, in the cortical amygdaloid nucleus. Neurons located in the parietal cortex did not respond in this way. The findings support the assumption that the mediocortical and basolateral amygdaloid regions belong to the cerebro-hypophyseo-gonadal axis and are involved in the differentiation and/or maturation of this axis.

Aging↗
PubMed1977

[Regulation of the endocrine system].

The universal significance of the endocrine system for the regulation of the vital functions and the extra ordinarily high biological activity of the hormones require sensitive mechanisms of regulation within this system. The central nervous system is integrated into these regulatory processes and controls by neurotransmitters and hypothalamic releasing and inhibiting of the hormones the secretion of the hypophyseal and peripheral hormones. Central and peripheral feed-back mechanisms making possible the adaptation of the neuroendocrine system to changing external and internal conditions are operative between the peripheral endocrine glands and the hypothalamo-hypophyseal system as well as during synthesis, transport, action and metabolism of hormones. The knowledge of the fundamental regulatory mechanisms is a presupposition for the effective diagnosis and therapy of endocrine dysfunctions.

Endocrine Glands↗
PubMed1977

[Relationship between the limbic system and gonadal function. 2. Quantifiable prepuberal differentiation of medial cortical amygdaloid nuclei].

In juvenile female rats beteen the 21st and 26th days of age, the neurons of the medial and cortical amygdaloid nuclei undergo a highly significant karyovolumetrically measurable activation which, however, partially declines almost immediately. Such prepuberal variation of activity was found to be correlated with age-dependent effects of direct interventions with these nuclear regions upon the hypothalamy-pituitary-gonadal axis, e.g. implantation of oestradiol benzoate, stimulation or lesioning. This basically, is a quantitatibe-morphological confirmation of an assumption that had been derived earlier from experimental studies, according to which the mediocortical part of the amygdala undergoes in the prepuberal period a functional muteration or differentiation which is specific and related to puberty and gonadal functions (Döcke, 1976a, b; Döcke et al., 1976).

Aging↗
PubMed1977

Different effects of amygdaloid lesions on compensatory ovarian hypertrophy in cyclic and prepubertal female rats.

Cyclic and 28-day-old immature female rats were hemiovariectomized and partly bilaterally lesioned in the cortical amygdaloid nucleus (CAN). The compensatory ovarian hypertrophy (COH) recorded in the adult females on the 8th day after hemicastration was completely prevented by the amygdaloid lesions. In contrast, damage to the CAN did not alter the ovarian weight in prepubertal females, although COH was also induced in these animals by unilateral ovariectomy.

Amygdala↗
PubMed1977

[Karyovolumetric studies on possible central-nervous-system action sites of the positive estrogen feedback].

In adult, progesterone-pretreated female rats, the medial preoptic and ventral premamillary nuclei of the hypothalamus, and the medial amygdaloid nucleus of the limbic system exhibit a significant karyovolumetrically measurable activation of their neurons after the subcutaneous administration of an ovulation-inducing dose of oestradiol benzoate. The finding suggests that these nuclear regions are sites of action of the positive oestrogen feedback and are involved in the induction of ovulation. The infundibular and lateral septal nuclei, and the bed nucleus of the stria terminalis were also investigated karyovoumetrically but failed to reveal, at the time of testing, any quantifiable morphokinesis that might have been attributable to the administration of the hormone.

Animals↗
PubMed1977

A possible mechanism of the puberty-delaying effect of hippocampal lesions in female rats.

Untreated female Wister rats and females in which advancement of the onset of puberty was induced by bilateral lesioning of the medial preoptic area or the ventromedial-arcuate region, or by the daily s.c. injection of 0.05 microgram oestradiol benzoate/100 g b.w., were bilaterally lesioned in the anterior part of the ventral hippocampus at 21 days of age. Irrespective of the applied treatment, a significant delay of vaginal opening and of the first puberal ovulation resulted from the hippocampal lesions. This delay of the onset of puberty was consistently associated with a retardation of the body weight increase, so that the stage of body development necessary for the occurrence of spontaneous or precocious puberty was reached at later ages in these rats. The results suggest that a normal function of the hippocampus may be necessary for adequate somatic development during sexual maturation.

Animals↗