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Biomedical subjects

D Chateau

Publications and source records attributed to D Chateau.

At least 37 records · Page 2Linked to original sources
PubMed1989

Lordosis behavior in male rats after lesions in different regions of the corticomedial amygdaloid nucleus.

The aim of the experiment was to study the effects of stereotaxic lesions of the anterior and the posterior regions of the corticomedial amygdaloid nucleus (CMN) on the display of lordosis behavior by the male rat. Animals were orchidectomized as adults and given estradiol benzoate and progesterone (P) sequentially. Sexual behavior testing was performed by 9 +/- 1 hr after P injection. Lesions placed into the posterior region of the CMN significantly decreased the proportion of animals showing lordosis behavior as compared to sham-operated and control animals. By contrast lesions in the anterior region of the CMN did not cause any changes in the proportion of animals displaying lordosis but markedly increased the lordosis quotient (LQ) of responding animals. The CMN was then concluded to exert a dual control in the display of lordosis behavior in the male rat with a posterior region regulating the willingness of animals to display lordosis behavior and rostral region subserving inhibitory mechanisms related to the sexual performance (LQ values).

Afferent Pathways↗
PubMed1988

Heterotypic sexual behavior in male rats after lesions in different amygdaloid nuclei.

Previous studies showed that different amygdaloid nuclei are involved in the control of lordosis behavior in female rats. The objective of the present study was to determine whether these nuclei played a role in the control of lordosis behavior in the male rat. Lesions were placed into different amygdaloid nuclei in male rats castrated as adults and primed with ovarian hormones. Lesions in the corticomedial amygdaloid nucleus completely suppressed lordosis behavior as expressed by the number of animals displaying lordosis responses to male mounts. By contrast extended lesions placed into the lateral amygdaloid nucleus (LN) remained without effects. Lesions placed in the very posterior part of the LN produced "hypersexuality" with a rise in the number of animals displaying lordosis responses and high LQ values. Lesions in the anterior part of the LN induced a decrease in the number of animals showing lordosis responses. The amygdala was then concluded to represent a functionally heterogeneous structure with different regions exerting opposite effects on the display of lordosis behavior in the male rat.

Amygdala↗
PubMed1987

Effects of ventromedial nucleus lesions on the display of lordosis behavior in the male rat. Interactions with facilitory effects of male urine.

Previous observations showed that exposure to the odor of male urine prior to mating could enhance the display of lordosis behavior in male rats feminized with ovarian hormones. This study was performed to determine in feminized male rats whether the control of lordosis behavior by the olfactory system was mediated by the ventromedial nucleus (VMN) of the hypothalamus. Male rats were orchidectomized (ORCH) as adults and primed with 25 micrograms estradiol benzoate (EB) and 150 micrograms progesterone (P) 40 hr apart. Lordosis behavior was tested 9 +/- 1 hr after P injection. VMN lesions were shown to completely suppress the display of lordosis behavior as compared to sham VMN operated and dorsomedial nucleus (DMN) lesioned animals. Exposure of feminized rats to the odor of male urine by 9 +/- 1 hr before mating significantly increased the proportion of ORCH rats that displayed lordosis behavior in response to male mounts. This effect was abolished by VMN lesions but was maintained in the sham VMN operated and DMN lesioned animals. These results were discussed in the light of the present knowledge on the neuroendocrine and olfactory structures which mediate lordosis behavior in the male rat.

Animals↗
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↗
PubMed1981

Follicular growth, ovulatory phenomena and ventromedial nucleus lesions in the rat.

Small ventromedial nucleus lesions were placed in 4-day cyclic female rats in order to determine whether cycle lengthening - previously observed in some females following such lesions - could result from changes in follicular growth. A slowing up in follicle development was observed in lesioned females with a 24-hour cycle lengthening as compared to those with a maintained 4-day cyclicity. Similarly, natural 5-day cyclers displayed slower follicular growth than natural 4-day cyclers. A rebound effect in follicular growth was observed on proestrus in either natural or VMN lesioned 5-day cyclers compared to either natural or VMN lesioned 4-day cyclers. Concomitantly blood FSH level appeared to be higher on proestrus morning and afternoon in 5-day than in 4-day cyclers. The pattern of LH release differed between natural 4-day and natural 5-day cyclers on proestrus at 17:00-19:00 h. LH release appeared to be delayed by one hour in VMN lesioned rats with 24 hour cycle lengthening as compared to natural 5-day cyclers. The duration of LH release in VMN-lesioned rats with a maintained 4-day cyclicity was shorter than in natural 4-day cyclers.

Animals↗
PubMed1976

Progesterone action on estrous rhythm in the rat following ventromedial nucleus lesions.

Small bilateral lesions of the hypothalamic ventromedial nucleus (SVMN) were produced in 4 day cyclic female Wistar rats by passing a 2 mA cathodic current through stereotaxically oriented platinum unipolar electrodes for 7 sec. The 24 h lengthening of cycle which occurred in 111 our ot 208 females was shown to depend upon lesion placement. Early s.c. injection of 0.75 or 1.5 mg progesterone caused 24 h cycle prolongation more frequently in SVMN-lesioned females with maintained 4 day cycles than in 4 day cyclic unoperated, sham VMN-lesioned, or dorsomedial nucleus (DMN) lesioned females. This effect proved to be related to lesion placement. It was therefore concluded that the VMN is involved in the mechanisms whereby progesterone controls estrous cycle duration in the rat.

Animals↗
PubMed1976

Hormonal mechanisms involved in the control of oestrous cycle duration by the odour of urine in the rat.

The mechanisms involved in the reduced cycle duration following exposure to the odour of urine were studied in natural and experimental 5-day cyclic female Wistar rats. A decrease in the rate of ovarian progesterone secretion from the morning of dioestrus I to that of dioestrus II was observed in females whose cycle duration was reduced from 5 to 4 days following exposure to the odour of rat urine. No decrease in ovarian progesterone secretion occurred in females maintaining a 5-day cyclicity despite exposure to this odour. An increase in follicular growth was noted in females with cycle duration reduced from 5 to 4 days, when compared with those maintaining a 5-day rhythm. As a result of exposure to the odour of urine no reduced cycle duration occurred in females with cycles lengthened from 4 to 5 days as a result of progesterone injection on dioestrus I of 4-day cycles. Hence the decrease in ovarian progesterone secretion, induced by exposure to the odour of urine, is considered to cause a speeding up in follicular growth, thereby reducing oestrous cycle duration in 5-day cyclic rats.

Animals↗
PubMed1976

[Chronologic and quantitative modalities of luteinization and ovulation in the female rat exposed to FSH action at the beginning of 4-day cycles].

Female Wistar rats were injected with two successive doses of 150 mug FSH on dioestrus I (5 p. m.) and dioestrus II (9 a.m.) of 4-day cycles. Superovulation and formation of an increased number of corpora lutea with included oocytes occurred in these animals. Meprobamate or pentobarbitone injections at 11.30 a.m. et 1.30 p.m. respectively completely blocked ovulation and luteinization phenomena in FSH-treated females. Ovulation normally occurred in FSH-treated females injected with meprobamate at 5.30 p.m. It was concluded that no modification of timing of the 'critical period' resulted from FSH treatment.

Animals↗
PubMed1976

[The effect of urine from castrated male or female guinea pigs and rats on the estrous cycle of guinea pigs and rats, respectively].

A 24-hour reduced cycle duration was observed in 5-day cyclic female rats exposed to the odor of urine from male or female castrated rats. A decrease in the duration of the period of vaginal closure, ranging from 2 to 5 days, was observed in female guinea pigs exposed to the odor of urine from male or female castrated guinea pigs. The pheromonal activity of urine in both species was concluded to be no dependent upon the gonadal function.

Animals↗