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L G Clemens

Publications and source records attributed to L G Clemens.

At least 19 recordsLinked to original sources
PubMed2005

A cross-fostering analysis of the effects of PCB 77 on the maternal behavior of rats.

Polychlorinated biphenyls (PCBs) are environmental contaminants known to cause multiple behavioral and developmental problems in humans and animals. In rats, gestational exposure to the PCB congener 3, 4, 3', 4'-tetrachlorobiphenyl (PCB 77) affects the brain and behavior of the offspring as well as the maternal behavior of the dams. Whether the behavior of dams is affected by direct effects of the contaminant or indirectly by actions of the PCB on the developing offspring is not known. We investigated this question using a cross-fostering paradigm in which pregnant rats were exposed to either oil vehicle or 2 mg/kg of PCB 77 on gestational days 6 through 18, and then raised pups that had been exposed to either oil or PCB 77 during gestation. Maternal behavior was observed on postnatal days 1, 2, 4 and 6. Some of the effects on maternal behavior, including an increase in the frequency of nursing bouts and in the amount of maternal autogrooming, can be ascribed to prenatal exposure of the litters to the PCB. Other behavioral effects, including an increase in time on the nest and in the amount of pup grooming as well as a reduction in high-crouch nursing, appear to be due to both direct effects of the PCB on the dams and effects mediated by changes in the offspring. Our results show that exposure to PCB 77 can have complex effects on the behavioral interactions between the dams and their litters with a potential impact on the development of the offspring.

Analysis of Variance↗
PubMed2004

Exposure to PCB 77 affects the maternal behavior of rats.

Polychlorinated biphenyls are environmental contaminants known to affect neurobehavioral development in many laboratory studies using different animal models. Because of their bioaccumulation and long half-life they are a serious concern for our own species. The dioxin-like PCB congener 3,4,3',4'-tetrachlorobiphenyl (PCB 77) has estrogenic and anti-estrogenic properties, and has been shown to affect brain chemistry and behavior of developing rats when administered during gestation. Since many developmental outcomes in mammals depend upon the type of maternal care provided by the dams, we investigated the effects of two doses of PCB 77 (2 and 4 mg/kg administered during gestational days 6-18) on the maternal behavior of the treated dams. Both doses of PCB 77 reduced the amount of nursing time in which the dams displayed the high-crouch posture over postnatal days 1-6. In addition, the high dose increased the amount of maternal licking and grooming of the litters and the amount of time the dams spent on the nest. The high dose also increased pup mortality, and both doses reduced the weight gain of the litters during the first 6 days of life. These results document effects of PCB 77 on maternal behavior and serve to raise questions about the importance of maternal contributions to the developmental effects of this and similar contaminants.

Age Factors↗
PubMed2002

Developmental exposure to polychlorinated biphenyls affects sexual behavior of rats.

Polychlorinated biphenyls (PCBs) are persistent environmental contaminants that have the potential to disrupt reproduction through a variety of different pathways. In the present study, we investigated the effects of fetal and lactational PCB exposure on reproductive behavior in male and female laboratory rats. These pregnant rats were injected daily with either 2,4,2',4'-tetrachlorobiphenyl (PCB 47) at the dosage of 1 or 20 mg/kg body weight or 3,4,3',4'-tetrachlorobiphenyl (PCB 77) at the dosage of 0.25 or 1 mg/kg body weight or sesame oil (control group) from gestational days 7 to 18. Offspring were then tested for sexual behavior as adults. Exposure to both PCB 77 and PCB 47 reduced the level of sexual receptivity in the female offspring, but had no detectable effects on the sexual behavior of the male offspring. In addition to changes in adult sexual behavior in the females, both PCBs produced a significant increase in the females' anogenital distance, suggesting a modification of androgen responsiveness in females resulting from PCB exposure during development. Similar effects were not seen with the males.

Analysis of Variance↗
PubMed2001

Effects of neonatal polychlorinated biphenyl exposure on female sexual behavior.

The effects of polychlorinated biphenyls (PCBs) on development and reproduction are well documented. However, very little is known about the effects of PCBs on sexual behavior. In this study, we examined the effects of two commercial PCB mixtures, Aroclor 1221 (A1221) and Aroclor 1254 (A1254), on the development of female sexual behavior and of the incertohypothalamic dopaminergic cells (A11 and A13) in Long-Evans rats. Neonatal exposure to A1254 significantly reduced sexual receptivity and reduced the female's latency to approach a male after an intromission. Neonatal treatment with A1221 did not affect female sexual behavior nor did treatment of adult females with A1221 or A1254. Since sexual behavior is affected by dopamine and since PCBs have been reported to alter dopamine content in the brain, we examined the effects of A1221 or A1254 on dopaminergic cells in the incertohypothalamic region of neonatally exposed rats. None of the treatments significantly affected the number of A11 or A13 neurons that were immunoreactive for tyrosine hydroxylase (TH) or the expression of Fos (i.e., the product of the immediate early gene c-fos) in these dopaminergic neurons. Therefore, the disruption of behavior induced by neonatal treatment with A1254 does not appear to be mediated by toxic effects of the mixture on incertohypothalamic dopaminergic systems.

Animals↗
PubMed2001

Effects of bisphenol A on energy balance and accumulation in brown adipose tissue in rats.

Some environmental contaminants have the potential to affect humans or animals by mimicking the effects of hormones. Bisphenol A (BPA) is a weak estrogen agonist when tested using in vitro or in vivo bioassays. In addition to the well documented effects of estrogens on reproductive functions, ovarian hormones also have salient effects on mammalian energy balance and feeding behavior. In this study, we investigated the effects of BPA on body weight and food intake of ovariectomized adult female rats. Treatment with doses of 4 or 5 mg/day for 15 days resulted in a significant reduction of body weight gain with no reduction in food intake. A dose of 1 mg/day did not affect feeding or weight gain. BPA was detected in the blood, brain and adipose tissues of the BPA-treated animals but not in the vehicle control group. There was a preferential concentration of BPA in brown adipose tissue. These results indicate that BPA can affect energy balance and that brown adipose tissue may be a primary tissue into which BPA accumulates in mammals.

Adipose Tissue↗
PubMed2000

Relation of Fos-IR expression in the pelvic ganglion to sexual behavior in laboratory rats.

The pelvic ganglion (PG) provides both sympathetic and parasympathetic innervation to the genitalia and other pelvic structures. To determine whether neuronal activity; of the PG, as detected by Fos-like immunoreactivity (Fos-IR), is related to sexual stimulation, male and female rats were tested under a variety of conditions. In males, Fos-IR expression in the PG was positively correlated with the amount of both genital and noncontact stimulation. In females, only ejaculation preceded by multiple intromissions induced a significant increase in Fos-IR; multiple intromissions or ejaculation preceded by only 0-1 intromission did not affect Fos-IR. Additional experiments comparing Fos-IR expression, in which some females were allowed to pace their sexual contact and others were not, revealed that ejaculation duration was the key factor in the induction of Fos-IR in female rats. Because the conditions under which Fos-IR expression occurred in females are identical to those required for sperm transport, we suggest that, in the female, sperm transport is regulated in part by autonomic outflow from the PG after copulation. These relations between sexual behavior and measures of PG activity are consistent with the idea that the sexually dimorphic organization of the peripheral nervous system plays a major role in mediating the gender-specific outcome of copulation: ejaculation in the male and sperm transport in the female.

Animals↗
PubMed1999

Vaginocervical stimulation inhibits female-female mounting in laboratory rats.

The objective of this study was to examine how vaginocervical stimulation (VCS) affects female-female mounting in laboratory rats. After receiving sexual stimulation from the male, the latency for the female to mount another female was significantly longer than that of control females. In the absence of any copulatory stimulation, the latency to initiate mounting of another female was about 3 min. However, following three mounts or three intromissions by a male, the latency for the experimental female to initiate mounting increased to about 10 min, and ejaculation abolished mounting for almost 2 h. Once females began mounting, regardless of the copulatory stimulation they received prior to testing, their mounting rate (mounting frequency/2 h) did not differ from stimulus control females. Artificial VCS also inhibited female mounting and anesthetization of the vaginocervical area diminished the inhibiting effect of ejaculation. Taken together, the present results provide evidence that VCS can temporarily inhibit female mounting, and that the duration of the inhibition is related to the amount of VCS received. These data are interpreted within the perspective that female mounting behavior is not a sexual behavior and is consequently suppressed within the context of normal copulation.

Animals↗
PubMed1998

Influence of male-related stimuli on female postejaculatory refractory period in rats.

Female rats "pace" their sexual contacts with the male when tested in situations where they can escape from the male during copulation. The type and quality of vaginocervical stimulation that the females receive during copulation influences their pacing behavior. This study investigated the effect of several male-related stimuli on the female's postejaculatory refractory period (PER). Females were tested in a two-compartment test chamber from which they could escape the male through one of four openings along the bottom of the barrier separating the two compartments. Experiment 1 examined the influence of the seminal plug, the penile cup, and prostate secretions on the female's PER. Results showed that neither the seminal plug, the penile cup, nor prostate secretions contributed to the female's PER. Experiment 2 investigated the relation of pre-ejaculatory intromission frequency, ejaculation duration, and the number of pelvic thrusts during ejaculation to the female's PER. Results indicated that pre-ejaculatory intromission frequency and ejaculation duration but not the number of pelvic thrusts during ejaculation were significantly correlated with the female's PER. In addition, pre-ejaculatory intromission frequency was significantly correlated with ejaculation duration. Partial correlation analysis suggested that pre-ejaculatory intromission frequency affected ejaculation duration which, in turn, influenced the female's PER. This finding was further supported by the evidence that ejaculation duration and the female's PER were significantly shorter in tests in which the male ejaculated on the first or second intromission.

Animals↗
PubMed1997

Effects of paraventricular lesions on sex behavior and seminal emission in male rats.

Oxytocinergic neurons of the paraventricular nucleus (PVN) of the hypothalamus have been implicated in modulating male sexual responses in rats. Previous investigators have shown that cerebrospinal fluid concentrations of oxytocin (OT) increased after ejaculation and that intraventricular administration of OT and electrolytic lesions of the PVN increased temporal measures of male sexual behavior. Recently, we have demonstrated that OT-immunoreactive neurons in the parvocellular subnuclei of the PVN project to lower levels of spinal cord. In the present study, N-methyl-D-aspartic acid lesions, which have been shown to destroy parvocellular PVN neurons while leaving magnocellular neurons intact, were used to evaluate the role of parvocellular neurons on male copulatory behavior and seminal emissions. OT-immunoreactive fibers were reduced in the lower lumbar spinal cord (L5-L6) following N-methyl-D-aspartic acid lesions in the PVN. This reduction was associated with a significant decrease in seminal emission at the time of ejaculation, but mount, intromission and ejaculatory latencies were unaffected.

Aging↗
PubMed1997

Function of intromissions on intromission-return latency of female rats during paced sexual behavior.

The objectives of this study were to examine how multiple intromissions affect the temporal pattern of the female rat's copulatory behavior; in particular, her latency to return to the male following intromission (intromission-return latency, IRL) and if different hormone replacement regimens affect the temporal aspects of female copulatory behavior. Repeated intromissions alone, without ejaculation, often resulted in prolonged IRLs equal to the postej aculatory refractory period (PER). The first prolonged IRL occurred most frequently between the 24th and 44th intromission. The similar pattern of IRLs around the PER and the prolonged IRLs may indicate that the mechanisms mediating the occurrence of the prolonged IRL are similar to those for the PER. One possible function of the prolonged IRLs may be to facilitate the male's ejaculation after the female has received enough vaginocervical stimulation for the induction of the progestational state of pregnancy. Finally, females receiving a single dose of 50 microg estradiol benzoate (EB) followed by an injection of 0.5 mg progesterone (P) 48 h later showed a significantly longer PER than those receiving 3 daily injections of 0.5 microg EB followed by an injection of 0.5 mg P 24 h after the last EB injection.

Animals↗
PubMed1996

Relation of intromissions to the female's postejaculatory refractory period in rats.

The objectives of this study were to investigate the temporal aspects of female sexual behavior during single and multiple ejaculatory tests. Females were tested in a two-compartment chamber where they could escape from the male following sexual contacts. In Experiment 1, correlation analysis showed that the number of intromissions received by the female over 3 ejaculatory series was positively correlated with the female's postejaculatory refractory period (PER). In Experiment 2, females receiving 2-4 intromissions before ejaculation had a PER that did not differ from those receiving 5-15 (average 10) intromissions preceding ejaculation. However, if the male ejaculated on the first or second intromission, the female's PER was significantly shorter than the other groups and did not differ from her return latency after an intromission without ejaculation. Females receiving 24-31 intromissions preceding ejaculation exhibited the longest PER. Analysis revealed that the number of intromissions received by females before ejaculation was positively correlated with the female's PER. We concluded that the male's ejaculatory reflex, seminal emission, and postejaculatory behavior alone without at least 2 preceding intromissions were not sufficient to induce a female's PER comparable to that seen after an ejaculation during normal copulation. In addition, the number of intromissions received by the female preceding ejaculation was positively correlated with the female's PER if the range of intromission frequency was large enough.

Animals↗
PubMed1996

Levels of serum steroids, aromatase activity, and estrogen receptors in preoptic area, hypothalamus, and amygdala of B6D2F1 male house mice that differ in the display of copulatory behavior after castration.

Most male B6D2F1 hybrid house mice continue to copulate after castration (continuers), whereas others do not (noncontinuers). Copulation in continuers appears estrogen dependent. Serum testosterone (T), 17 beta-estradiol (E2), and dihydrotestosterone (DHT), as well as aromatase activity (AA) and estrogen receptor (ER) levels in preoptic area (POA), hypothalamus (HYP), and amygdala (AM) were measured to determine if continuers and noncontinuers differ in estrogen physiology. In general, continuers and noncontinuers did not differ in serum steroid levels, AA, or ER levels. Castration reduced AA in the POA, HYP, and AM. Castration did not affect nuclear ER levels in the POA and HYP but reduced nuclear ER in AM. The data demonstrate that castrated B6D2F1 male mice continue to be under the influence of circulating nongonadal E2 that is important for copulation.

Amygdala↗
PubMed1994

Calcitonin gene-related peptide-like immunoreactivity in spinal motoneurons of the male mouse is affected by castration and genotype.

Calcitonin gene-related peptide (CGRP) is found in motoneurons of the mammalian spinal cord, including motoneurons of the androgen-dependent spinal nucleus of the bulbocavernosus (SNB) of the mouse. Motoneurons of the SNB innervate the bulbocavernosus (BC), a striated muscle involved in penile reflexes. CGRP is though to be a trophic factor produced by motoneurons to regulate the expression of the acetylcholine receptor at the neuromuscular junction. In rats, the number of SNB motoneurons containing CGRP is increased by gonadal steroids. This regulation appears to rely on an activity-dependent factor produced by the BC muscle. The purpose of the present study was to examine, using immunohistochemistry, the steroid dependence of CGRP in the SNB of male house mice. Genotypic differences in the steroid regulation of CGRP immunoreactivity were examined in three strains of mice that differ in their behavioral sensitivity to castration. The results demonstrate that castration reduces the number of CGRP-positive SNB motoneurons in mice. The magnitude of the change in CGRP in response to castration and the length of time required following castration to alter CGRP were dependent on genotype. Interestingly, the effect of castration in mice, to reduce the number of CGRP-immunoreactive SNB motoneurons, is opposite in direction from the increase in CGRP SNB motoneurons observed in rats observed following castration. These experiments suggest that androgens may alter neuromuscular junction function of mouse SNB by regulating the production of CGRP in a species-specific, genotypically dependent fashion.

Animals↗
PubMed1993

Neurophysin-containing pathway from the paraventricular nucleus of the hypothalamus to a sexually dimorphic motor nucleus in lumbar spinal cord.

A model that has been widely used in the study of steroid sensitive neurons, the spinal nucleus of the bulbocavernosus (SNB) is a sexually dimorphic motor nucleus in the lower lumbar spinal cord that innervates the striated bulbocavernosus (BC) muscle. The BC is responsible for penile reflexes in the male rat, which are important in ensuring pregnancy in females. The characterization of afferents to the SNB aids in the understanding of the neural circuitry involved in reproductive behavior. We have recently identified the paraventricular nucleus (PVN) as a possible source of afferents to the SNB. Because the PVN is the major source of oxytocin/vasopressin within the central nervous system (CNS), the purpose of the present study was to examine and characterize a neurophysin (NP)-containing pathway from the PVN to the SNB. The results demonstrate that neurons of the lateral parvicellular subnucleus of PVN, which project to levels of spinal cord containing SNB motoneurons, contain NP, the coproduct of oxytocin and vasopressin. NP-containing fibers and putative terminals were found in the region of the SNB and appear to contact the soma and proximal dendrites of SNB motoneurons which were retrogradely identified as BC-innervating. Electrolytic lesions, which destroy the lateral parvicellular subnucleus of PVN, abolish NP-containing fibers in the region of the SNB, suggesting that the PVN is the source of these NP fibers. The results of this study indicate a NP-containing projection from the hypothalamus directly to SNB motoneurons. It is suggested that this pathway may play a role in the integration of penile reflexes with other aspects of male copulatory behavior that are under hypothalamic control.

Animals↗
PubMed1993

Neurons in the paraventricular nucleus of the hypothalamus that project to the sexually dimorphic lower lumbar spinal cord concentrate 3H-estradiol in the male rat.

The location and distribution of estradiol-concentrating neurons in the hypothalamus afferent to segments of lumbar spinal cord that contain the sexually dimorphic spinal nucleus of the bulbocavernosus (SNB) were determined by combining retrograde fluorescent tract tracing with steroid hormone autoradiography. Injections of Fluorogold were made into segments of L5-L6 of the spinal cord of adult male rats and 12 days later animals were castrated. One week following castration, males received injections of [3H]estradiol and were perfused. Their brains were then processed for steroid hormone autoradiography. Following exposure times of 11 to 12 months, autoradiograms were developed and the hypothalamus was analyzed for neurons that concentrate estradiol and project to the spinal cord. Numerous neurons in the hypothalamus projected to the spinal cord, specifically neurons in the paraventricular nucleus (PVN), the lateral hypothalamus and the dorsal area of the hypothalamus. Although many subnuclei of PVN, as well as lateral hypothalamus, contained Fluorogold labelled neurons and estradiol concentrating neurons, the majority of double labeled cells were found in the lateral parvocellular (LP) subnucleus of PVN. Approximately 30% of the neurons in the lp subnucleus that projected to spinal cord also concentrated estradiol. Up to one half of the estradiol-concentrating neurons in lp sent axons to the lower lumbar spinal cord. These results suggest that some of the effects of gonadal steroid hormones on SNB development, plasticity and function may in fact, be indirect, via steroid-sensitive afferents.

Afferent Pathways↗
PubMed1991

Projections of the paraventricular nucleus of the hypothalamus to the sexually dimorphic lumbosacral region of the spinal cord.

Lumbar regions L5-L6 of the spinal cord of the male rat contain the sexually dimorphic motor nuclei, the spinal nucleus of the bulbocavernosus (SNB) and the dorsolateral nucleus (DLN), which innervate perineal muscles, the bulbocavernosus and the ischiocavernosus, respectively. This neuromuscular system controls penile reflexes which are essential to male reproductive success. Oxytocin has been shown to induce penile reflexes and the site of action for these effects is the PVN. Since PVN is known to project to cervical and thoracic levels of spinal cord, the present study examined projections of the PVN to the L5-L6 region of the spinal cord. WGA-HRP was injected into the region of L5-L6, aimed at the SNB and DLN and their dendritic extents, in intact male, castrated male and female rats. WGA-HRP-labelled cells bodies were found in the parvocellular subnuclei of PVN, as well as regions of the lateral hypothalamus and the dorsal area of the hypothalamus. These results demonstrate that the PVN projects to lumbar levels of the spinal cord that are sexually dimorphic and androgen-dependent. This suggests that PVN may modulate the activity of these motoneurons.

Animals↗
PubMed1991

Noradrenergic innervation to the VMN or MPN is not necessary for lordosis.

The purpose of the present study was to determine the importance of noradrenergic neurons terminating in the ventromedial nucleus (VMN) and medial preoptic nucleus (MPN) of the hypothalamus for lordosis behavior in ovariectomized, estrogen/progesterone-treated female rats. Seven days following bilateral injections of the noradrenergic neurotoxin 5-amino-2,4-dihydroxy-alpha-methylphenylethylamine (5-ADMP) into the ventral noradrenergic bundle (VNAB), norepinephrine (NE) concentrations (ng/mg protein) were reduced to 30-35% of control in the VMN and MPN. 5-ADMP-induced lesions of the VNAB also reduced lordosis quotients in these animals, and this effect was reversed by intracerebral ventricular administration of the alpha 1-adrenergic receptor agonist phenylephrine. These results indicate that neurotoxin-induced disruption of noradrenergic neurons in the VNAB is associated with a deficit in sexual receptivity in female rats. To determine if the reduction in sexual receptivity following 5-ADMP-induced lesions of the VNAB resulted from loss of noradrenergic neuronal projections specifically to the VMN or MPN, lordosis quotients were determined in ovariectomized, estrogen/progesterone-treated rats in which noradrenergic terminals in these hypothalamic nuclei were selectively lesioned. Injection of 5-ADMP directly into either the VMN or MPN reduced NE concentrations to 17% of control in these hypothalamic nuclei, but failed to alter lordosis. Furthermore, injection of phenylephrine into either the VMN or MPN of VNAB-lesioned rats failed to reinstate lordosis to the levels comparable to sham-lesioned controls. Taken together, these results indicate that noradrenergic neurons terminating in either the VMN or MPN are not essential for gonadal steroid induction of sexual receptivity in ovariectomized female rats.

Animals↗