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Biomedical subjects

C Aron

Publications and source records attributed to C Aron.

At least 55 records · Page 3Linked to original sources
PubMed1987

Stress-related effects on the secretion of progesterone by the adrenals in castrated male rats presented to stimulus males. Involvement of oestrogen.

Rats were orchidectomized (ORCH) as adults and given successive doses of 0.5 microgram or 1.0 microgram of oestradiol benzoate (EB) combined or not with dexamethasone (DEXA) at the end of oestrogen treatment; successive doses of olive oil. They were presented to stimulus males on the day of the last EB injection and decapitated immediately after the behavioural test. Animals given EB or olive oil only served as controls. There was a significant rise in blood progesterone concentration in animals given 0.5 and 1.0 microgram EB as compared with oil-treated animals. A higher blood progesterone concentration was observed at the end of the behavioural session in oil-treated and 0.5 microgram EB-treated ORCH rats than in their isolated counterparts, an effect which appeared not to dependent on lordosis responses to mounting attempts of the males. DEXA completely suppressed the rise in blood progesterone concentration in oestrogenized ORCH rats presented to stimulus males. Presentation of ORCH rats to stimulus males was then concluded to constitute a stressful condition capable of inducing adrenocortical progesterone secretion in ORCH animals.

Adrenal Cortex↗
PubMed1986

Accessory olfactory bulb lesions and lordosis behavior in the male rat feminized with ovarian hormones.

Orchidectomized rats were given estrogen and progesterone and tested for feminine behavior in the presence of a mounting male after accessory olfactory bulb removal (AOBR). Complete AOBR caused a rise in the number of estrogen-progesterone-treated male rats responding by lordosis behavior to male mounts as compared to controls and sham-operated animals. By contrast, LQ scores did not appear to differ in these three groups of animals. The results are discussed in terms of involvement of the main and the accessory olfactory systems in the regulation of feminine behavior in the male rat.

Animals↗
PubMed1986

Endogenous progesterone and lordosis behavior in male rats given estrogen alone.

Male rats castrated as adults were given successive doses of estradiol benzoate (EB) combined or not, with dexamethasone (DEXA) at the end of estrogen treatment. Two experiments were done to determine if progesterone (P) of adrenocortical origin was involved in the display of lordosis behavior under these experimental circumstances. There was a significant rise in blood P concentration in animals given 0.5 and 1.0 microgram EB when compared with oil-control injected animals, an effect which was completely suppressed by DEXA treatment. An increase in the proportion of estrogen treated animals displaying lordosis responses to male mounts was found with increasing doses of EB and paralleled the effects of EB on P adrenocortical secretion. However, the number of feminized animals given 1 microgram EB + DEXA was reduced to the level corresponding to the effects of 0.5 microgram EB on lordosis behavior. These data show that the secretion of P by the adrenals is involved in the expression of lordosis behavior in castrated male rats primed with repeated doses of estrogen.

Animals↗
PubMed1986

Olfactory environment and early mating behavior in the cyclic female rat.

The objectives of this study were to examine the effects of olfactory cues from the male and of olfactory bulb removal on early mating behavior in sexually inexperienced diestrous female rats primed with estrogen. Four-day cyclic rats isolated from the male were given either 2.5 micrograms or 10 micrograms estradiol benzoate (EB) and presented to stimulated males in the late afternoon of diestrus 2 between 18:00 and 19:00 for a 10 min sexual behavioral session. Dose-dependent effects of estrogen were observed since 10 micrograms EB significantly increased the proportion of females displaying early mating as compared with those given 2.5 micrograms EB. Olfactory bulb removal prior to estrogen treatment caused a rise in the number of females which mated early with respect to the non bulbectomized controls. Exposing the females to bedding soiled with male urine on diestrus 2 at 10:00 did not affect early mating behavior. By contrast the olfactory stimuli became efficient when 2.5 micrograms EB treated females were given 10 micrograms progesterone (P) by the time of exposure to male urine. The results were discussed with respect to the role played by the olfactory system in the control of lordosis behavior throughout estrous cycle in female rats. P was concluded to be involved in the perception of the olfactory signals from the male which facilitate early mating behavior in diestrous female rats.

Animals↗
PubMed1986

Testosterone-induced oestrous cycle blockade in the rat: no evidence for prolactin involvement.

The relation between testosterone-induced oestrous cycle disruption and prolactin (Prl) secretion was studied in the female rat. Testosterone propionate (TP) injection on dioestrus 2 (day 0) of 4-day cycles induced cycle interruption for 12 days. A diurnal pattern of Prl secretion was observed from day 1 to day 6 with high levels in the afternoon and low levels in the morning. Cycle interruption also occurred in TP treated females given a dose of bromocriptine (BRC) known to completely block Prl secretion. Impairment of follicular growth resulted from TP treatment and from TP and BRC treatment as well. Until resumption of prooestrous, the follicular size did not exceed that noted during the dioestrous period of the cycle. Despite resumption of follicular growth from day 9 until day 14, ovulation only took place in a small number of animals. These results indicate that the antigonadotropic effects of Prl were not responsible for cycle disruption in our experimental model and that other mechanisms were in itself sufficient for the disruption. This was discussed in the light of previous findings in our laboratory.

Animals↗
PubMed1986

Olfactory environment and coitus-induced ovulation and/or luteinization in the cyclic female rat.

The role of pheromones in the process of ovulation and/or luteinization induced by coitus was studied in female rats primed with estradiol benzoate (EB) and early mated during 4-day cycles. The effects of coitus were evaluated by using 1) the proportion of females displaying postovulatory corpora lutea (POCL) and/or luteinized unruptured follicles (LUF), and 2) the ovulation coefficient (OC) computed in each female by dividing the number of POCL by the total number of POCL and LUF. A greater proportion of females displayed ovulation and/or luteinization following coitus than those given EB only. This proportion was slightly but significantly increased when females were exposed to bedding soiled with 5 ml of male urine prior to mating, an effect prevented by complete olfactory bulbectomy. However, in the females given EB only, the pheromonal stimulus remained inefficient. Weak ovulatory effects of coitus, as assessed by low OC values, were noted whether the females were exposed or not to male urine. An increase in the frequency of lordosis occurred after olfactory bulbectomy, but no significant changes in OC values were observed in this experimental group. It was concluded that pheromones, act as a primer on the neuroendocrine mechanisms governing ovulation in the cyclic female rat, as in other species of rodents.

Animals↗
PubMed1985

Hormonal control of the perception of the olfactory signals which facilitate lordosis behavior in the male rat.

This study was designed to evaluate in the male rat the hormonal requirements for the facilitation of feminine behavior by the odor of male urine. Wistar rats from the WI and WII strains in our colony were orchidectomized (ORCH) as adults. A first group was given a single dose of 75 micrograms estradiol benzoate (EB) and tested for lordosis behavior 48 hr later. Exposure to the odor of male urine by 9 +/- 1 hr before the behavioral session did not increase the number of animals showing lordosis behavior as compared to non exposed controls. A second group of WI rats was given 0.5 micrograms EB every day for 4 to 8 days. A similar number of animals displayed lordosis behavior irrespective of whether they were exposed to the odor of urine before testing. A third group of WI rats was injected with 75 micrograms EB and 1 mg progesterone (P) 39 hr apart. Exposure to the odor of urine during estrogen treatment remained ineffective but significantly increased the number of animals showing lordosis behavior when performed at the time of P injection. A last group of WII rats was given 25 micrograms EB and 100 micrograms or 150 micrograms P 39 hr apart. Although uncapable as such to facilitate lordosis behavior the dose of 100 micrograms P rendered the animals responsive to the odor of urine. It was concluded that (1) the perception by feminized males of olfactory signals from the male was dependent on P; (2) an interaction between hormonal and sensory mechanisms was involved in the facilitation of lordosis behavior in the male rat.

Animals↗
PubMed1985

Prostaglandins involvement in the formation of luteinized unruptured follicles in the cyclic female rat.

The purpose of this investigation was to study the role played by prostaglandins in advanced ovulation and in the formation of luteinized unruptured follicles (LUF) in cyclic female rats. Dose related effects on ovulation were observed in rats given LH on diestrus 2 at 16.30. A significant positive correlation was observed between the number of postovulatory corpora lutea (POCL) and the increasing doses of LH. By contrast the number of LUF was negatively correlated with LH. Indomethacin treatment by 6h30 after administration of an ovulatory LH dose significantly increased the occurrence of LUF at the expense of POCL. Conversely PGF2 alpha when administered by 6h30 after a subovulatory LH stimulation enhanced in a dose dependent manner the number of POCL with respect to the LH treated controls. Under a similar treatment with a subovulatory dose of LH, PGE2 remained without ovulatory effects. The mechanisms of the formation of LUF are discussed on the basis of these results.

Animals↗
PubMed1984

Does corpus luteum function autonomously during estrous cycle in the rat? A possible involvement of LH and prolactin.

This study examined the of LH and prolactin in the control of corpus luteum function during 4-day cycles in the rat. Bromocriptine (BRC) treatment was performed on proestrus or/and estrus morning that means before or after the preovulatory release of LH. This caused complete blood prolactin depression from the time of injection until diestrus 1 afternoon. This decrease in blood prolactin concentration was associated with a rise in the tonic level of LH secretion in those females which received BRC as soon as on proestrus. We first observed that injection on the morning of proestrus of doses of BRC capable of blunting prolactin secretion on proestrus afternoon did not significantly impair the preovulatory release of LH and did not prevent ovulation occurring during the following night. The life span of the corpora lutea edified from ovarian follicles rupturing before or under BRC administration did not exceed that of those formed under physiological circumstances since 4-day cycles culminating in ovulation constantly took place in all the treated animals whatever the time of BRC injection. To determine the pattern of luteal activity in the absence of prolactin secretion, we measured blood progesterone concentration from estrus until late diestrus in female rats injected with BRC on proestrus and/or estrus at 1100 h. The initiation of the function of corpus luteum on estrus and the achievement of its full activity on diestrus 1 did not appear to be affected by BRC. By contrast the level of blood progesterone declined more rapidly on the morning of diestrus 2 in BRC-treated than in control females. The capacity for autonomous progesterone secretion by corpus luteum of the cycle was discussed in the light of previous and present observations.

Animals↗
PubMed1984

Progesterone secretion by luteinized unruptured follicles in mature female rats.

The ability of luteinized unruptured follicles (LUF) to display luteal activity was investigated in mature female rats. Previous findings in our laboratory showed that increasing doses of LH, when injected on late diestrus in 4-day cyclic rats, were capable of inducing the formation of either LUF or postovulatory corpora lutea (POCL) in a dose dependent manner. Four-day cyclers were injected on diestrus 2 at 4.30 p.m. (day 0) with 2.7 micrograms or 5.4 micrograms/100 g of an ovine LH preparation (x 2.94 NIH LH S3) and were killed at different times during the three successive days following injection. Natural 4-day cyclers were killed at corresponding times following spontaneous LH release on proestrus afternoon (day 0). Both LUF and POCL were observed in LH-treated females. LUF appeared more numerous in females given 2.7 micrograms LH than in both natural cyclers and in females injected with 5.4 micrograms LH. On day 1 during the rising phase of luteal activity serum progesterone (P) level did not differ in the three groups despite the high number of LUF in females given 2.7 micrograms LH. On day 2 at 11 a.m. lower P values were observed in both groups of LH-treated females than in natural cyclers, this corresponding to a greater proportion of LUF in the former than in the latter. On day 2, at 5 p.m. by the time of full activity of POCL in natural cyclers, P did not differ in the three groups irrespective of the relative number of ruptured or unruptured follicles. On day 3, P sharply declined in LH-treated and natural cyclers. These results suggest that LUF are capable of secreting P during a period corresponding to the duration of corpus luteum's life span in cyclic female rats.

Animals↗
PubMed1984

Olfactory cues and accessory olfactory bulb lesion: effects on sexual behavior in the cyclic female rat.

The influence of olfactory cues and accessory olfactory bulb (AOB) lesion on female sexual behavior was studied in virgin female Wistar rats. In Experiment 1, it appeared that distance or contact exposure to male urine soiled bedding for 8 hours before testing increased sexual receptivity, i.e., the number of receptive females at 18:00-19:00 on proestrus. In Experiment 2, we observed that sexual receptivity at 18:00-19:00 on proestrus was not affected by AOB lesion as compared to sham-operated females. In Experiment 3 the effects of both AOB lesion and olfactory cues were analyzed. Sexual receptivity at 18:00-19:00 on proestrus did not significantly differ in sham-operated and accessory olfactory bulbectomized females both exposed to the odor of male urine. Regarding lordosis quotient in the three experiments, no significant difference was observed. Mechanisms whereby olfactory cues and/or AOB lesion modified female sexual behavior on proestrus in virgin female rats were discussed in the light of previous and present observations.

Animals↗
PubMed1984

Olfactory cues from the female can affect feminine behavior in the male rat.

The aim of this work was to study the influence of the hormonal milieu on the facilitory effects of olfactory stimuli originating from female urine on lordosis behavior in orchidectomized (ORCH) feminized rats. Urine from ovariectomized (OVX) rats was shown to increase the proportion of ORCH rats displaying lordosis behavior, an effect which was enhanced if the OVX rats had been given progesterone. Treatment of OVX rats with estradiol benzoate did not affect the pheromonal activity of their urine. Dexamethasone treatment of OVX rats completely suppressed the facilitory effects of their urine on the feminine behavior in males. A higher proportion of feminized rats displayed lordosis following exposure to urine collected from pseudopregnant rats than did their unexposed counterparts. Dexamethasone treatment of pseudopregnant rats did not abolish this effect. These results suggest that the adrenal cortex is capable, in the absence of the ovaries, of manufacturing some pheromonal substance which stimulates feminine behavior in the male rat. The nature of this substance remains unknown. Furthermore progesterone itself is involved in the emission of olfactory signals which control feminine behavior in the male rat.

Androstenedione↗
PubMed1984

Are the amygdaloid projections to the hypothalamic ventromedial nucleus involved in estrous rhythm regulation in the female rat?

The aim of this investigation was to determine whether the corticomedial amygdaloid nucleus (CMA) and its projections to the hypothalamic ventromedial nucleus (VMN) were involved in the regulation of estrous rhythm by the VMN in the rat. It is known (Carrer et al., 1973-1974) that partial VMN lesions caused the occurrence of either 5-day or alternate 4- or 5-day cycles in about 50% of 4-day cyclic female rats and that large lesions induced cycle prolongation in most of the operated animals while hypothalamic dorsomedial nucleus (DMN) lesions left estrous rhythm unmodified. CMA lesions in 4-day cyclic female rats caused the occurrence of either 5-day or alternate cycles with sequence of 4, 5, 4 days, more frequently than in their sham operated counterparts (15/20 vs 3/20). Stria terminalis (ST) lesions placed at its emergence from the CMA or at its horizontal course over the internal capsule induced a higher proportion (10/14 and 9/16, respectively) of females to display changes in cycle duration than did sham operated and unoperated controls as well (10/32 and 7/29, respectively). Combined partial VMN and ST lesions resulted in a 24 hours cycle prolongation or alternate 4- and 5-day cycles in a greater number of females than in those bearing small VMN lesions only (15/18 vs 22/40). A noticeable proportion of CMA, ST and ST + small VMN lesioned females offered more or less prolonged diestrous periods immediately following surgery before resuming estrous cyclicity. It was suggested that the CMA neurons which project fibers to the VMN via the ST are implicated in estrous rhythm regulation in the rat.

Afferent Pathways↗
PubMed1984

Prolactin and the control of cycle length in the female rat.

Bromocriptine (BRC) was injected on oestrus afternoon at 16.00 h into 5-day cyclic female rats thus causing reduced cycle length to 4-days. When injected on dioestrus 1 at 13.00 h the drug remained without effects. Blood progesterone concentration on dioestrus 1 afternoon and on dioestrus 2 morning was shown to be lower in 5-day cyclic rats given BRC than in their untreated counterparts. No changes in the rate of follicular growth were observed on dioestrus 2 afternoon in BRC injected 5-day cyclic rats. The pattern of prolactin secretion on oestrus afternoon was compared in 4- and 5-day cyclic female rats. High prolactin values were observed on early afternoon in the former and on late afternoon in the latter. The decline in progesterone secretion during the dioestrous period of the cycle was supposed to be responsible for cycle shortening in 5-day cyclic rats given BRC. It was concluded that prolactin might play a critical role in the establishment of a 5-day rhythm in the rat by controlling progesterone secretion during the dioestrous period of the cycle.

Animals↗
PubMed1982

How different procedures of blood removal affect blood progesterone concentration in the cyclic female rat.

The effects of different procedures of blood removal on blood progesterone level were studied in female rats throughout the diestrous period of estrous cycle. Unoperated, sham operated, adrenalectomized and ovariectomized females were used. The complete manipulation comprising ether anaesthesia and blood collection lasted 3-4 min. Blood removal in itself did not exceed one minute. Blood progesterone levels appeared to be higher in unoperated, sham operated and ovariectomized females bled by heart puncture or from the abdominal vena cava under ether anaesthesia than in their decapitated counterparts bled without ether anaesthesia. Adrenalectomy prevented this effect from occurring. No difference in blood progesterone concentration was noted between anaesthetized and unanesthetized decapitated unoperated females. It was concluded that some procedures of blood removal under ether anaesthesia might cause a stress-related rise in blood progesterone concentration and that ether anaesthesia was not involved.

Adrenal Glands↗