Copulatory behavior and reproductive capacity of the genetically obese female Zucker rat.
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Animals↗
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Mating behavior and reproduction of the lone star tick, Amblyomma americanum.
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Animals↗
[Sex behavior and reproduction of farm animals].
The sexual behaviour of farm animals was followed up both at loose-pasture raising and under industrial conditions. It was studied in estrus, in the search for a sexual partner, with regard to the tolerance of the female animals for the males in the sexual act, with regard to the herd hierarchy, the intraspecies relationships, and the condition of dominance, aggressiveness, and subordination. The role is stated of the presence of male animals in the herd for the regular course of the sexual cycle, and the shortening and synchronization of the estrus. Discussed is also the importance of the artificial visual, sound, olfactory, tactile and other stimuli of the behaviour of the male breeding animals in substantiating the coitus and the proper semen production. It was found that the reproductive process is largely dependent on on the sexual reactions of the animals, which requires a proper knowledge with regard to the substantiation of each sexual cycle. Thus, it is stated, higher conception and fertility rates are to be expected. It was also established that under the conditions of industrial technologies of raising the number of behavioural reactions in their use was strongly reduced because of the lowered contact between the individual groups, while the practice of artificial insemination thoroughly rules out the contact between the male and female animals.
Animals↗
The significance of the nest-building of the nine-spined stickleback, Pungitius pungitius.
The reproductive behavior of the stickleback is unique and odd, occurring inevitably with nesting. However, upon investigation, it has been found that nesting is an obstacle to hatching. The author conducted a survey in the necessity of nesting behavior in the nine-spined stickleback, Pungitius pungitius, and reached following conclusion: For Pungitius pungitius, nesting is the means of communicating to descendants settlement at a fixed area where cold water flowed bountifully and the water temperature was constant. Pungitius pungitius has evolved a behavior pattern that involves settling where water temperature is uniform, without evolving physiologically or morphologically, thereby enabling Pungitius pungitius to adapt to the changes in environment.
Animals↗
Pheromones elicit equivalent levels of Fos-immunoreactivity in prepubertal and adult male Syrian hamsters.
Male reproductive behavior in the Syrian hamster is dependent on both pheromones from the female and the presence of gonadal steroid hormones. The pheromones are contained within female hamster vaginal secretions (FHVS) and stimulate anogenital investigation and mounting by the male. Administration of testosterone to castrated male hamsters facilitates anogenital investigation, mounts, and intromissions in adults, but elicits only anogenital investigation in prepubertal males. One hypothesis for why the full complement of reproductive behaviors is not activated by testosterone in prepubertal males is that the neural processing of pheromonal cues encountered during anogenital investigation is different in juveniles and adults. In the present experiment, we investigated the influence of sexual maturity on Fos expression in response to FHVS in the male Syrian hamster. We predicted a greater increase in Fos-immunoreactivity after exposure to FHVS within the neural circuit mediating male reproductive behaviors in adult compared to prepubertal males. Intact adult and prepubertal males were exposed to either a clean cotton swab or a swab containing FHVS. We found that, compared to animals exposed to a clean cotton swab, both prepubertal and adult males exposed to FHVS have a greater amount of Fos-immunoreactivity within several brain nuclei comprising the neural circuit mediating male reproductive behavior. Furthermore, this Fos response was equivalent in the two age groups. These results suggest that the inability of the prepubertal male hamster to perform the full repertoire of male reproductive behaviors is not due to a lack of a neuronal activation in response to the pheromonal cues present in FHVS.
Age Factors↗
Organizational effects of estrogens on brain vasotocin and sexual behavior in quail.
Reproductive behavior is sexually differentiated in quail: The male-typical copulatory behavior is never observed in females even after treatment with high doses of testosterone (T). This sex difference in behavioral responsiveness to T is organized during the embryonic period by the exposure of female embryo to estrogens. We showed recently that the sexually dimorphic medial preoptic nucleus (POM), a structure that plays a key role in the activation of male copulatory behavior, is innervated by a dense steroid-sensitive network of vasotocin-immunoreactive (VT-ir) fibers in male quail This innervation is almost completely absent in the female POM and is not induced by a chronic treatment with T, suggesting that this neurochemical difference could be organizational in nature. This idea was tested by injecting fertilized quail eggs of both sexes on day 9 of incubation with either estradiol benzoate (EB) (25 microg, a treatment that suppresses the capacity to show copulatory behavior in adulthood) or the aromatase inhibitor R76713 (10 microg, a treatment that makes adult females behaviorally responsive to T), or with the solvents as a control (C). At 3 weeks posthatch, all subjects were gonadectomized and later implanted with Silastic capsules filled with T. Two weeks later, all birds were perfused and brain sections were processed for VT immunocytochemistry. Despite the similarity of the adult endocrine conditions of the subjects (all were gonadectomized and treated with T Silastic implants providing the same plasma level of steroid to all subjects), major qualitative differences were observed in the density of VT-ir structures in the POM of the different groups. Dense immunoreactive structures (fibers and a few cells) were observed in the POM of C males but not females; EB males had completely lost this immunoreactivity (and lost the capacity to display copulatory behavior); and, conversely, R76713 females displayed a male-typical VT-ir system in the nucleus (and also high levels of copulatory behavior). Similar changes in immunoreactivity were seen in the nucleus of the stria terminalis and in the lateral septum (VT-ir fibers only in this case) but not in the magnocellular vasotocinergic system. These neurochemical changes closely parallel the effects of the embryonic treatments on male copulatory behavior. The vasotocinergic system of the POM can therefore be considered an accurate marker of the sexual differentiation of brain circuits mediating this behavior.
Analysis of Variance↗
Comparison of lethality, reproduction, and behavior as toxicological endpoints in the nematode Caenorhabditis elegans.
This study describes a new approach for assessing behavioral changes following toxicant exposure and compares the method to other common endpoints used in environmental toxicology. The nematode Caenorhabditis elegans was exposed to a range of ethanol concentrations to determine its effect on survival, reproduction and behavior. Each endpoint was evaluated for its sensitivity by comparing LC50, RC50 (concentration at which there is a 50% reduction in number of offspring as compared to controls), and BC50 (concentration at which there is a 50% reduction in movement as compared to controls) values for ethanol exposure. Worms showed 24-h lethality at concentrations of ethanol in the range of 83 g/L to 99 g/L. Reproduction in C. elegans was estimated by counting the number of off-spring after 3 d of exposure, which decreased with the increase in ethanol concentration from 8 g/L to 71 g/L. Behavior was quantified by using a new computer tracking method, which can simultaneously assess hundreds of nematodes and provides several behavioral parameters in real time. Worms showed some hyperactivity (increased movement) at very low ethanol concentrations (0.8 g/L and 2.4 g/L) and a decrease in movement at higher ethanol concentrations (4 g/L to 40 g/L). A comparison for sensitivity between the three endpoints was performed. Behavior and reproduction responses were found to be similar and, as expected, both are much more sensitive indicators of toxicity than lethality. The advantages and disadvantages of the computer tracking system are discussed.
Animals↗
Annual cycle of plasma testosterone in male copperheads, Agkistrodon contortrix (Serpentes, Viperidae): relationship to timing of spermatogenesis, mating, and agonistic behavior.
Reproductive cycles of the majority of squamate reptiles remain undescribed. Few studies are available on seasonal patterns of circulating steroid hormones in snakes. The goal of this study was to document the annual cycle of plasma testosterone (T) in male copperheads Agkistrodon contortrix, a North American pitviper (Serpentes, Viperidae). Two experimental conditions were used in this laboratory study. One condition (repeat-test group) consisted of 10 adult males that were sampled once each month for 11 months. The other condition (single-test groups) consisted of 10 groups each with 5 males (N = 50), and each male was tested a single time. The single-test condition was used to evaluate whether or not repeated handling and sampling affected T levels. The study was conducted from February-December, 1992. A well-defined seasonal pattern of plasma T levels was detected; patterns were similar under both experimental conditions with the exception that the repeat-test group had slightly lower levels. Levels of T were lowest (baseline) in April-May, increased in early summer (June), and were highest in late summer (August). Thereafter, T levels declined up to the time of hibernation (early November) and changed little during hibernation (November-January). Upon emergence from hibernation in late winter (February), T levels increased sharply from February to March and then decreased from March to April. The results are discussed in the context of timing of spermatogenesis, mating, and male agonistic behavior.
Agkistrodon↗
Estrogen-behavior correlates in the reproductive physiology and behavior of the ruffed lemur (Lemur variegatus).
The animal subjects of this study consisted of seven male-female pairs, living an open-air, off-exhibit area of the San Diego Zoo. Daily urinary estrogen levels in each of five females were measured and daily behavioral observations of the seven pairs were made. Behavioral patterns aligned by objectively determined, discrete physiologic events were analyzed to determine their temporal correlation to changes in estrogen excretion. The data indicate that approximately one-sixth of the female behaviors and one-third of the male behaviors sampled were significantly correlated to urinary estrogen levels in the females (P less than 0.05-0.005). In addition, both attractivity and receptivity were distinguishable and their component behaviors in males and females were found to be related to the estrogen profile. Proceptivity, however, was only weakly identified and its description in this sample population was ambiguous. Mating was observed to occur exclusively on 1 day, presumably the day of ovulation.
Animals↗
Perinatal astemizole exposure in the rat throughout gestation: long-term behavioral and anatomic effects associated with reproduction.
Astemizole (ATZ), a non-sedative antihistamine, which antagonize histamine at the level of H1 receptor, was administered daily to female Wistar rats as a 10-mg/kg dose throughout pregnancy. ATZ exposure reduced offspring body weight and delayed the pinna detachment and startle reflex without any modification of dams body weight during gestation. Long-term disruption of male reproductive behavior was seen in experimental animals, whereas female sexual behavior was not modified. In addition, no motor alterations were observed in female or males in adulthood. Testis wet weight was reduced, but no modifications were detected in vasa deferentia or seminal vesicle. We proposed that ATZ administration during pregnancy causes several effects mainly of a sexual nature by interfering either with the hormonal mechanism involved in the central nervous system masculinization or by a direct action of the drug on pups during the development.
Animals↗
Interactive effects of behavior and reproductive hormones on sex differences in risk for coronary heart disease.
It is well known that women in the United States, as in most industrialized countries in the world, are protected from coronary heart disease (CHD), relative to men. It is thought that this protection is by and large due to the effects of female reproductive hormones (i.e., estrogens) on lipid and lipoprotein metabolism and blood pressure, although women's relatively low rates of cigarette smoking are also thought to play a role. However, epidemiological studies that statistically adjust for sex differences in lipids, blood pressure, and smoking status cannot explain sex differences in CHD morbidity and mortality. Also, inconsistent with a simple main-effect model of reproductive hormones are data showing elevated risk of myocardial infarction and stroke among women who use oral contraceptives. Men who are prescribed estrogens have elevated risk of CHD, and case-control studies show that male CHD patients have elevated estradiol, compared to controls. This article suggests that simple main-effect models of female protection from CHD are inadequate. It argues that reproductive hormones are important determinants of protection from CHD, in interaction with behavioral characteristics. It also demonstrates that reproductive hormones can influence behavioral characteristics and that behavioral characteristics can influence the effects of reproductive hormones on CHD risk factors.
Arousal↗
Methoxychlor induces estrogen-like alterations of behavior and the reproductive tract in the female rat and hamster: effects on sex behavior, running wheel activity, and uterine morphology.
The current investigation was designed to determine if the pesticide methoxychlor (M) mimicked the effects of estrogen in the brain and on behavior. Running wheel activity (RWA) and sex behaviors were evaluated in this study because the role of estrogen in the regulation of these behaviors has been thoroughly established. M exposure at 400 mg/kg/day (90% pure) induced high levels of acyclic RWA and persistent vaginal estrus in the female rats. Following ovariectomy (ovx), RWA declined precipitously in controls but remained at high levels in M-treated-ovx females. M also produced estrogen-like alterations of the uterine endometrial epithelium, the ovary, and growth after ovx. In another study, ovx female rats were dosed with M at 200 mg/kg/day and then with progesterone (P). P acts as an antiestrogen and specifically suppresses estrogen-induced RWA. P blocks the synthesis of estrogen receptors in the CNS and reproductive tract but does not lower RWA induced by nonestrogenic mechanisms. After 14 days of M administration RWA was increased fourfold over the ovx-oil-treated females. Subsequently, P injections reduced RWA levels far below those seen when the ovx-M-treated rats were injected with oil. The P-induced decline represents a 95% inhibition of the M-induced increase in RWA. Subsequently, M-treated-ovx rats and hamsters were injected with P and tested for their ability to display reproductive behaviors when paired with a stud male. Female sexual behaviors are induced by the administration of estrogen followed by progesterone. In this study the M-treated females displayed reproductive behaviors, in contrast to the oil-treated rats and hamsters. The observation that the high levels of RWA induced by methoxychlor treatment in ovx rats can be suppressed by concurrent progesterone injections demonstrates that the increase in RWA is due to the estrogenic effects of methoxychlor on the CNS. The fact that methoxychlor, followed by P injections, induces behavioral estrus in the rat and hamster extends this estrogenicity to other areas in the CNS.
Animals↗
[Experimental studies on various model material. 3. Dimensional behavior and reproductive fidelity as compared to those of elastomers].
Bandless impressions of tooth stumps obtained with the model materials Begolith, Dentaloc, Tewestone, Impredur and Keramid-Cement in combination with the elastic impression materials Silcoflex, Sanal/Silcoflex, Xirux/Xirux F and Impergum were studied in relation to dimensional behavior and reproduction fidelity. With reference to these parameters as well as to the hardness and abrasive behavior of the model materials after processing at various temperatures, recommendations are made for the optimum combination of these two groups of materials in practice.
Acrylic Resins↗
Evolutionary precedents for behavioral actions of oxytocin and vasopressin.
It is clear that the behavioral actions of oxytocin and vasopressin in mammals are not newly acquired, but have evolutionary antecedents. Injection studies with fish, amphibians, reptiles, and birds indicate that AVT can activate certain reproductive behaviors. The strongest evidence that AVT acts centrally to control reproductive behaviors comes from research on T. granulosa. In this amphibian, injections of AVT agonists activate courtship behaviors (amplectic clasping) in males and egg-laying behaviors in females, whereas injections of AVT antagonists inhibit the behaviors. Also, in Taricha males, AVT concentrations in specific brain areas are associated with the expression of courtship behaviors. Several conclusions about steroid-peptide interactions can be drawn, based on research with this amphibian. First, gonadal steroid hormones act to maintain the behavioral actions of AVT in both males and females. In Taricha, gonadectomy abolishes and steroid implants restore AVT-induced courtship in males and egg-laying in females. Second, gonadal steroids maintain the behavioral actions of AVT, in part, by modulating AVT receptor numbers on target neurons. In Taricha males and females, gonadectomy reduces AVT receptor concentrations (but not binding affinity) in certain brain areas (amygdala pars lateralis) and not others. Third, the type of gonadal steroid determines whether AVT elicits male-like or female-like reproductive behaviors. Ovariectomized Taricha females respond to AVT injections with egg-laying behaviors when implanted with estradiol and with male-like amplectic clasping when implanted with dihydrotestosterone. Fourth, the masculinization of AVT-induced behaviors in females most likely reflects site-specific actions of androgens on AVT-synthesizing neurons. In Taricha, AVTir concentrations in the optic tectum are sexually dimorphic (higher in males than females) and reach peak levels in males during the breeding season. Fifth, AVT content in specific brain areas increase as a function of performing the behaviors. In Taricha, AVTir concentrations in DPOA, CSF, and ventral infundibulum are higher in males that exhibit courtship behaviors than in males that do not. These conclusions illustrate how steroid-peptide interactions in the control of behaviors entail multiple neuroanatomical sites and neurochemical actions.
Animals↗
Gonadotropin-releasing hormone and its receptors in rat brain.
Since the chemical identification of gonadotropin-releasing hormone (GnRH) in 1971, significant progress has been made in understanding the mechanisms by which GnRH action is mediated in the anterior pituitary. In contrast, relatively little information is available which identifies the intracerebral sites and mechanisms of action of GnRH in the brain. Early immunohistochemical studies of GnRH distribution in the central nervous system, together with behavioral and electrophysiological experiments, suggested that GnRH functioned as a neurotransmitter and was, possibly, involved in the expression of reproductive behaviors. The subsequent identification and characterization of GnRH receptors in the brain further strengthened the view that GnRH caused specific effects in select regions of the brain known to be involved in the neuroendocrine regulation of the anterior pituitary and in the generation of reproductive behaviors. After the mouse pituitary GnRH receptor was cloned it became possible to identify brain neurons which contained the GnRH receptor mRNA. Comparison of the locations of the GnRH peptide, the GnRH receptor protein, and the neurons which contain the GnRH receptor mRNA suggests that the GnRH neuronal system itself can potentially provide a direct link between the neuroendocrine regulation of anterior pituitary function and the intracerebral regulation of reproductive behaviors; furthermore, it is possible that the GnRH neuronal system takes an active part in intracerebral feedback loop systems between the mediobasal hypothalamus and the septum-diagonal band which regulate GnRH release from the median eminence.
Amino Acid Sequence↗
Effects of opioid peptides on the electrical activity of preoptic and hypothalamic neurons in the quail brain.
We have recently isolated three opioid peptides, i.e., Met- and Leu-enkephalins and Met-enkephalin-Arg6-Phe7, from the avian brain. In the present study, therefore, effects of these endogenous opioid peptides on the electrical activity of preoptic and hypothalamic neurons of the adult male Japanese quail were examined using a brain slice preparation. All of the three opioid peptides inhibited the spontaneous firing activities of subsets of neurons in the preoptic area and the paraventricular nucleus in the hypothalamus. Threshold concentrations for the inhibitory action were between 10(-7) and 10(-6) M in Met- and Leu-enkephalins and approximately 10(-6) M in Met-enkephalin-Arg6-Phe7, respectively. In a few cells in these brain areas, however, Leu-enkephalin rather potentiated the spontaneous activities, resulting in an increase of firing rates or a decrease of interburst intervals. The inhibitory effect of Met-enkephalin was completely blocked by naloxone, an opioid receptor antagonist, but not affected by bicuculline, a gamma-aminobutyric acid A (GABAA) receptor antagonist. These results suggest that there are functional opiate receptors in subsets of preoptic/hypothalamic neurons and that one of their main physiological functions in these areas is an inhibition of neuronal activities. Because these brain regions are considered to be involved with the regulation of a variety of male reproductive behaviors, opioid peptides may regulate some reproductive behavior through the mechanism that provokes such an inhibition.
Action Potentials↗
Inhibitory role of opioid peptides in the regulation of aggressive and sexual behaviors in male Japanese quails.
We have recently isolated three opioid peptides, i.e., Met- and Leu-enkephalins and Met-enkephalin-Arg6-Phe7, from the avian brain. Furthermore, electrophysiological studies have shown that the dominant effect of these enkephalins on preoptic and hypothalamic neurons is an inhibition of neuronal activities in the male Japanese quail. The hypothalamus and preoptic area are known to be involved in the control of male reproductive behaviors, such as aggressive and sexual behaviors. To determine the functional role of opioid peptides in these reproductive behaviors, therefore, the present study was undertaken using adult males of the Japanese quail. We examined behavioral changes following an injection of naloxone (0.2, 2.0, and 20.0 nmol), a nonselective opioid receptor antagonist, or D-Ala2-Met5-enkephalinamide (DALA; 0.2, 2.0, and 20.0 nmol), a selective delta opioid receptor agonist, into the preoptic and anterior hypothalamic regions. Naloxone treatment showed a significant increase in the frequency of several aggressive actions and the effect was dose dependent. In contrast, DALA treatment significantly decreased the frequency of aggressive actions in a dose-dependent manner. Similar significant effects of these two drugs were observed in the sexual behavior. These findings provide the first evidence for the role of opioid peptides in the reproductive behaviors in the bird and suggest an inhibitory action of opioid to evoke the behaviors.
Aggression↗
Low-sexually performing rams but not male-oriented rams can be discriminated by cell size in the amygdala and preoptic area: a morphometric study.
Brain regions of male sheep behaviorally classified as high-sexually performing (n=10), low-sexually performing (n=8) or male-oriented (n=9) were examined to determine if differences in reproductive behavior were associated with differences in density or sizes of neurons. High-sexually performing rams actively mounted estrous ewes, low-sexually performing rams failed to mount or had long latencies to mounting estrous ewes, and male-oriented rams mounted other rams in preference to ewes in estrus. Cell densities and sizes were quantified in Nissl stained sections through the medial amygdala (meAMY), preoptic area (POA), bed nucleus of the stria terminalis (BNST), ventromedial hypothalamic nucleus (VMH), lateral geniculate nucleus (LG) and medial geniculate nucleus (MG). Multivariate discriminant analysis based on soma sizes within nuclei of known importance for reproductive behavior and/or gonadotropin release (meAMY, POA, BNST and VMH) discriminated (Wilks Lambda P<0.05) low-performing rams from high-performing and male-oriented rams, but did not discriminate (Wilks Lambda P=0.14) between high-performing and male-oriented rams. Cell size in the parvocellular and magnocellular layers of the LG along with cells of the MG, structures without a specific role in reproduction, did not discriminate any of the three behaviorally defined groups of rams (Wilks Lambda P=0.57). Density of cells present in structures important for the display of reproductive behavior (POA, meAMY, BNST) and/or gonadotropin release (POA, VMH) had no discriminating power nor did density of cells in structures important for the processing of visual (LG) or auditory (MG) stimuli. In conclusion, significant differences in sizes of cells located within nuclei that are specifically important for the display of male reproductive behavior were found in low-sexually performing rams compared to high-sexually performing and male-oriented rams. These differences may result from neuron development in utero or occur later as a consequence of endocrine factors or behavioral experience. Neuronal cell size is a critical variable that determines excitability to synaptic inputs because cell surface area varies exponentially with cell diameter. Relatively small differences in neuron diameter could relate to functionally important differences in neuronal excitability.
Amygdala↗