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PubMed1996

Race, genetics, and human reproductive strategies.

The international literature on racial differences is reviewed, novel data are reported, and a distinct pattern is found. People of east Asian ancestry and people of African ancestry average at opposite ends of a continuum, with people of European ancestry averaging intermediately, albeit with much variability within each major race. The racial matrix emerges from measures taken of reproductive behavior, sex hormones, twinning rate, speed of physical maturation, personality, family stability, brain size, intelligence, law abidingness, and social organization. An evolutionary theory of human reproduction is proposed, familiar to biologists as the r-K scale of reproductive strategies. At one end of this scale are r-strategies, which emphasize high reproductive rates; at the other end are K-strategies, which emphasize high levels of parental investment. This scale is generally used to compare the life histories of widely disparate species, but here it is used to describe the immensely smaller variations among human races. It is hypothesized that, again on average, Mongoloid people are more K-selected than Caucasoids, who are more K-selected than Negroids. The r-K scale of reproductive strategies is also mapped on to human evolution. Genetic distances indicate that Africans emerged from the ancestral hominid line about 200,000 years ago, with an African/non-African split about 110,000 years ago, and a Caucasoid/Mongoloid split about 41,000 years ago. Such an ordering fits with and explains how and why the variables cluster.

Biological Evolution↗
PubMed1994

The role of central oxytocin in obsessive compulsive disorder and related normal behavior.

Oxytocin (OT) is a neurosecretory nonapeptide synthesized in hypothalamic cells, which project to widely distributed sites in the CNS as well as the neurohypophysis. Central OT affects a variety of cognitive, grooming, affiliative, sexual, and reproductive behaviors in animals. Obsessive Compulsive Disorder (OCD) includes a range of cognitive and behavioral symptoms that bear some relationship to dimensions of behavior associated with OT. Anecdotal data and a recently completed cerebrospinal fluid (CSF) study provide evidence that some forms of OCD are related to OT dysfunction. Based on these findings, we hypothesize: 1) that some forms of OCD are at the extreme end of a range of normal behaviors that are mediated by OT and related systems; and that 2) some normal cognitive, affiliative, and sexual behaviors contain elements that are similar to features of OCD. Alternative hypotheses are considered, and a series of predictions are presented concerning the relationship between central OT and the onset, course, treatment response, and response to challenge procedures seen in this form of OCD.

Animals↗
PubMed1999

Social cues attenuate photoresponsiveness of the male reproductive system in Siberian hamsters (Phodopus sungorus).

Transfer of adult Siberian hamsters (Phodopus sungorus) from long (16 h light and 8 h dark, 16L:8D) to short (8L:16D) daily photoperiods induces an involution of the gonads and a cessation of reproductive behavior 8 to 10 weeks later. However, when male and female long-day hamsters were paired on transfer to short photoperiods, the males' gonads did not undergo the typical short-day response. Similarly, when male long-day hamsters were paired with refractory females (i.e., females housed in short photoperiods for at least 28 weeks so that they became unresponsive to short photoperiods), the response of the males' reproductive system to short photoperiods also was attenuated. Thus, social cues can override or delay the effects of photoperiod on the testes of this species. These results suggest that the inhibitory effects of long durations of melatonin secretion (in response to short photoperiods) on the male hypothalamic-pituitary-gonadal axis may be attenuated by social cues such as contact with the opposite sex.

Animals↗
PubMed1992

Correlations between catecholamine levels and sexual behavior in male zebra finches.

In zebra finches, the combined actions of estrogens and androgens activate male courtship, including singing, and also strongly modulate norepinephrine (NE) levels and turnover in brain areas known to be involved in controlling courtship behavior. To determine whether changes in NE levels mediate changes in courtship, we administered DSP-4 to males and measured its effects on monoamine levels and reproductive behavior. DSP-4 treatment did not affect serotonin (5-HT), had small, variable effects on dopamine (DA), and caused moderate, nonsignificant reductions in NE. However, in DSP-4-treated males, NE levels in specific vocal-control nuclei showed high positive correlations with courtship singing. There were no significant correlations between NE levels in hypothalamic nuclei and any behavior or DA or 5-HT levels in any nuclei and any behavior. DSP-4-treated males took longer to begin singing and performed fewer song bouts and courtship displays, but their songs could not be differentiated from those of control males. This suggests that their behavioral deficits resulted from deficits in attention rather than an inability to sing.

Animals↗
PubMed1986

Effects of endocrine state on sociosexual behavior of female rats tested in a complex environment.

The influence of both natural and artificially induced endocrine states on sociosexual behavior of the female rat was examined during 15-min behavioral observations in a complex testing apparatus that allowed the test females to control their contacts with sexually active and passive males and ovariectomized (OVX) females. Factor analysis of the behavioral measures for all test females indicated separate loadings on a lordotic behavior factor; a factor for the test females' preference for proximity to OVX females or passive males; and a factor for the test females' locomotion between portions of the testing apparatus. Behavioral variables loading on these factors were influenced by endocrine state, but the nature of the relation between behaviors and endocrine state varied between factors. The utility of the present testing situation in investigations of the neuroendocrine substrates underlying the motivational aspects of feminine reproductive behavior is examined.

Animals↗
PubMed1991

A case-control study of nutrient status and invasive cervical cancer. I. Dietary indicators.

A study of 748 cases and 1,411 hospital and community controls in four Latin American countries evaluated the association between certain elements of diet and invasive cervical cancer. Subjects were interviewed about their adult consumption of 58 food items, including the major sources of putative protective agents (vitamin A, carotenoids, vitamin C, and folacin) as well as other behavioral and medical characteristics related to cervical cancer. Participation rates were above 95% for both cases and controls. After adjustment for age, study site, sexual and reproductive behavior, socioeconomic status, screening practices, and detection of human papillomavirus 16/18 by filter in situ hybridization, a slightly lower risk was observed for the highest quartiles of consumption of fruit and fruit juices, while no reductions in risk were associated with vegetables, foods of animal origin, complex carbohydrates, legumes, or folacin-rich foods. When nutrient indices were derived, significant trends of decreasing risk were observed for vitamin C (adjusted odds ratio (OR) = 0.69 for the highest vs. the lowest quartile; p for trend = 0.003), beta-carotene (OR = 0.68; p = 0.02), and other carotenoids (OR = 0.61; p = 0.003). Inclusion of vitamin C and beta-carotene in the same model attenuated the association with beta-carotene, while the association with vitamin C remained unchanged. The results are consistent with those of other investigations and provide support for a protective effect of vitamin C, carotenoids, and other substances found in the same fruits and vegetables against the development of invasive cervical cancer. However, the fact that the associations were driven by relation in two of the study sites and among women of higher socioeconomic status leaves open the possibility of selection bias or effects of unidentified aspects of dietary patterns.

Ascorbic Acid↗
PubMed1994

Contraceptive risk-taking in a medically-underserved, low-income population.

This study examines the phenomenon of contraceptive risk-taking, which is the non-use of contraception by women who are sexually active, fertile and not pregnant or trying to become pregnant. Based on a survey sample of low-income women in their childbearing years who had not received family planning care or advice from a doctor or clinic for at least three years, the study analyzed demographic predictors of contraceptive risk-taking, and also compared levels of contraceptive knowledge and pregnancy histories of non-contraceptors versus barrier method contraceptors. Contraceptive risk-taking was found to be higher for minority women, for parous women, for those age 30 and younger and for those whose knowledge of the fertility cycle is incorrect, but was found to be only weakly related to the women's marital status. Non-contraceptors were less knowledgeable concerning contraceptive methods and substantially more likely to have had previous unwanted pregnancies due to non-use of contraception, suggesting that current contraceptive risk-taking probably represents a relatively enduring feature of reproductive behavior for a sub-group of the medically-underserved low-income population.

Adolescent↗
PubMed1985

Laboratory management of the ferret for biomedical research.

Ferrets have become an increasingly important animal in biological research. This paper discusses unique aspects of the ferret's anatomy, reproductive behavior, husbandry, and diseases as they relate to the research use of this animal.

Anesthesia↗
PubMed1991

Medial nucleus of the amygdala in the adult Syrian hamster: a quantitative Golgi analysis of gonadal hormonal regulation of neuronal morphology.

The medial nucleus of the amygdala (Me) processes both chemosensory and hormonal input. In the male Syrian hamster the integrity of this nucleus is essential for normal reproductive behavior. To determine if gonadal steroids modulate neuronal structure in this nucleus, the morphology of Golgi-stained neurons in the anterior and posterior regions of Me were compared in castrated and reproductively intact adult hamsters. In castrated males, neurons in the posterior, but not the anterior, region of Me undergo structural changes, as indicated by a decrease in the mean highest dendritic branch level and mean somal area compared to intact males. To further elucidate the importance of testosterone and its metabolites in maintenance of neuronal structure in the adult, seven groups of male Syrian hamsters were studied. Animals were castrated and received a blank silastic capsule or a capsule filled with either testosterone, dihydrotestosterone, or estradiol, or two capsules containing both metabolites, dihydrotestosterone and estradiol. Two groups of reproductively intact animals were included: brains from one group were processed simultaneously with the castrated and hormone-treated groups (control intact group), and the other group was processed at the beginning of the experiment. Animals were tested for mating behavior and flank glands were measured to test whether the capsules were effective in releasing the hormones into circulation. After a 12-week survival period, the brains were processed with Golgi stain and well-impregnated neurons from the posterior Me were quantitatively analyzed for somal area, highest dendritic branch, total dendritic length, and density of spines. All the measures analyzed revealed a consistent pattern of response to the different gonadal steroids. Castration resulted in a decrease in the mean somal area, the mean highest dendritic branch, and the percentage of neurons with tertiary branch segments. Dihydrotestosterone treatment also resulted in a significant decrease in somal area, mean highest dendritic branch, and percentage of neurons with tertiary dendritic branches. In addition, the total dendritic length and spine density on terminal dendrites were reduced in these brains. The remaining hormone treatment groups were not significantly different from the control group. These results suggest that in orchidectomized male Syrian hamsters, testosterone or its aromatized form, estradiol, but not dihydrotestosterone, is sufficient to maintain the normal morphology of the neurons in the posterior part of the medial nucleus of the amygdala.

Amygdala↗
PubMed1990

Multisensory regulation of maternal behavior and masculine sexual behavior: a revised view.

Frank Beach's view of the multisensory regulation in Norway rats of copulation in males (12) and of pup retrieval in females (23) is critically analyzed and revised in terms of Lashley's influence, Beach's other work, and current neurobiological knowledge. Beach's view was that no single sensory stimulus is essential to elicit these behaviors, but that all relevant stimuli available summate in the neocortex; consequently, (a) sexual "arousal" is increased in males, leading to copulation, and (b) the "efficiency," or likelihood, of retrieval is increased in postpartum mothers. The revised view is based on a component analysis in which each of these behaviors consists of a chain of motoric responses elicited by somatosensory stimulation. Distal stimuli emanating from the female or pups induce proximity by provoking orientation, attention and arousal; the meaning of these stimuli is largely learned by conditioned associations during the initial executions of the behavior, although odors may have a prepotent influence for some individuals. Stimuli are integrated in a multisensory manner by both subcortical and neocortical mechanisms. Generalizations concerning the reproductive behavior of other mammalian species are suggested.

Animals↗
PubMed1999

Hormones, genes and the structure of sexual arousal.

Despite the inherent difficulty of connecting individual genes with integrated mammalian behaviors, it has been determined that a series of genes are turned on by estrogenic hormones acting in forebrain. Their products are, in turn, facilitatory for female reproductive behaviors such as lordosis. The causal routes by which two genes contribute to the control of lordosis behavior, the classical estrogen receptor gene (ER-alpha) and a thyroid hormone (TH) receptor gene (TR-beta), have been delineated. Beyond the mechanisms underlying the expression of concrete, specific natural behaviors, lies the question of sexual motivation. Required as an intervening variable to explain fluctuations in natural behaviors in the face of constant stimuli, motivational states have both general and specific features. Most theoretical and experimental approaches toward the general aspects of motivation have depended heavily on concepts of 'arousal.' Sexual arousal is likely to depend both on very general, broadly distributed neuronal influences and on specific affiliative and sexual tendencies. Is 'general arousal' a monolithic, undifferentiated process? In no way can a review at this time settle such issues, but the reasons behind six new experimental approaches to these questions are described.

Animals↗
PubMed2005

Gender distinction in neural discrimination of sex pheromones in the olfactory bulb of crucian carp, Carassius carassius.

Studies on projection of the sensory neurons onto the olfactory bulb in fish have revealed a clear subdivision into spatially different areas that each responded specifically to different classes of odorants. Amino acids induce activity in the lateral part, bile salts induce activity in the medial part, and alarm substances induce activity in the posterior part of the medial olfactory bulb. In the present study, we demonstrate a new feature of the bulbar chemotopy showing that neurons specifically sensitive to sex pheromones are located in a central part of the ventral olfactory bulb in crucian carp. Extensive single-unit recordings were made from these neurons, stimulating with four sex pheromones, 17,20beta-dihydroxy-4-pregnen-3-one, 17,20beta-dihydroxy-4-pregnen-3-one-20-sulfate, androstenedione, and prostaglandin F(2alpha), known to induce specific reproductive behaviors in males of carp fish. All substances were applied separately to the sensory epithelium at a concentration of 10(-9) M. Of the 297 neurons recorded in males, the majority (236 or 79.5%) responded exclusively to one of the four sex pheromones and thus showed a high specificity. Of the 96 neurons recorded from the olfactory bulb in females, only 1 unit showed such a specific activation. These findings reflect remarkable differences between males and females in the discriminatory power of the olfactory neurons toward these sex pheromones. The gender differences are discussed in relation to behavior studies, expression of olfactory receptors, and the convergence of sensory neurons onto the secondary neurons in the olfactory bulb.

Androstenedione↗
PubMed2001

The influence of testosterone on territorial defence and parental behavior in male free-living rufous whistlers, Pachycephala rufiventris.

We studied a population of rufous whistlers, Pachycephala rufiventris, throughout a single breeding season in central New South Wales, Australia. We evaluated the relation between plasma testosterone (T) and reproductive behaviors using both simulated territorial intrusions (STIs) and subcutaneous T implants. We compared circulating T values to aggression levels of males (using STI) during pair bond and territory establishment and again during incubation. Although plasma T levels were significantly lower in the latter period, male responsiveness to STI, in terms of proximity to decoy, call rate, and number of attacks on the decoy, was indistinguishable between the two breeding stages. T levels of males exposed to STI were not different from the levels of unexposed free-living males at the same breeding stage. The effect of exogenous T on parental behavior was examined by comparing duration of incubation bouts of males and their mates prior to and after T treatment. T males significantly reduced the amount of time they incubated following implantation, whereas Control males maintained their incubation effort. After cessation of breeding activities, T males displayed significantly higher call rates due to increased use of the primary intersexual advertisement call in this species. The reduction of incubation behavior following T implantation emphasises the functional significance of the rapid decline in T in free-living males during incubation. The results from both experiments suggest that intersexual advertisement, rather than territorial aggression, may be dependent on high T levels in this species.

Aggression↗
PubMed1997

Abnormal estrous cyclicity and behavioral hyporesponsiveness to ovarian hormones in genetically obese Zucker female rats.

Obese Zucker female rats are infertile. The present study was designed to assess estrous cyclicity in adult, ovary-intact, lean and obese Zucker rats and to compare reproductive behaviors induced by exogenous steroid hormones in ovariectomized (ovx) lean and obese Zucker rats. The majority (90%) of obese rats had incomplete cycles in comparison with the normal, 4-day cycles displayed by lean Zucker rats. After ovariectomy, all rats were treated with estradiol benzoate (EB, 15-100 micrograms/kg) or EB plus progesterone (P, 2-20 mg/kg), and tested for sexual receptivity and proceptivity (PRO). At the highest EB dose, obese Zucker females displayed lordosis less frequently than lean rats (lordosis quotient, LQ, 8 +/- 6% vs. 32 +/- 13%, respectively). At the lowest doses of EB plus P, lean females were extremely receptive and proceptive (LQ = 93 +/- 4%, PRO = 6.2 +/- 2 bouts/min). Zucker obese females, in contrast, were only slightly receptive (LQ = 26 +/- 11%) and showed less PRO than lean rats (PRO = 2.4 +/- 0.6 bouts/min). Increasing the dose of either EB or P, administered in combination with the lowest dose of the other hormone, produced receptivity and PRO in obese Zucker females that were comparable with those observed in lean rats. Serum estradiol and P levels in ovx obese rats were either equivalent to or higher than those in the ovx lean rats when both were given the same doses of hormones. These data suggest that considerably higher doses and serum concentrations of EB and/or P are required to elicit robust lordosis and PRO in ovx obese Zucker than in lean rats. This behavioral hyporesponsiveness to sex steroid hormones may contribute to infertility in the obese Zucker female rat.

Animals↗
PubMed1997

Effects of androgens on male sexual behavior and secondary sex characters in the explosively breeding spadefoot toad, Scaphiopus couchii.

In male Scaphiopus couchii, plasma elevations in androgens are associated with the seasonal expression of sexual behavior. To test the hypothesis that androgens are necessary for the expression of one aspect of sexual behavior, amplexus, and for the development of secondary sex characteristics in male S. couchii, the effects of testosterone (T) and dihydrotestosterone (DHT) on clasping behavior and thumb pad growth were investigated. Forty toads were divided into five treatment groups as follows: (1) intact, with no hormonal or surgical treatment; (2) sham-castrated, with silastic implants of cholesterol; (3) sham-castrated, with implants of T and DHT; (4) castrated, with implants of cholesterol; and (5) castrated, with implants of T and DHT. Displays of sexual behavior (amplexus) for each individual were counted during a 3-hr observation period at 2, 4, and 7 weeks after the surgical procedure. For each observation trial, there was no significant difference in the amount of clasping among treatment groups: virtually all individuals from each group displayed vigorous clasping. No calling was noted at any time. Thumb pad darkness of each individual was assessed at the 4- and 7-week time intervals. At both time periods, the thumb pads of androgen-treated males were significantly darker than those of cholesterol-treated males, while intact males remained intermediate. Measurement of plasma steroid levels from the treatment groups indicated that androgens were basal in the castrate group and higher in the implant treatment. These results suggest that in S. couchii, although androgens are associated temporally with the onset of reproductive behavior, they are not necessary for its expression. The elevation in androgens during the reproductive period may be instead important in the development and maintanence of secondary sex characteristics and possibly other reproductive functions.

Androgens↗
PubMed1994

Membrane receptors for corticosterone: a mechanism for rapid behavioral responses in an amphibian.

This paper reviews evidence that, in some cases, steroid hormones rapidly modulate behaviors by binding to specific cell-surface receptors on neurons. The evidence comes from research with an amphibian model, Taricha granulosa. In Taricha, stress and corticosterone inhibit reproductive behaviors with a rapidity that is inconsistent with traditional models for steroid action (models in which intracellular steroid receptors function as transcription factors). A series of radioligand binding assay studies identified a corticosteroid receptor in neuronal membranes that appears to mediate the rapid behavioral responses in Taricha. Studies with various steroids showed a strong correlation between their potencies to inhibit the behavior and their potencies to inhibit corticosterone binding. Neurophysiological studies of caudal brainstem neurons found that corticosterone administration rapidly modulates neuronal activity and selectively suppresses sensory processing. Another series of studies provided evidence that this corticosterone receptor interacts with G proteins in neuronal membranes. The studies suggest that there are G protein-coupled receptors for corticosteroids that provide an alternative mechanism by which this hormone regulates brain functions and behaviors.

Animals↗
PubMed2004

Organization of single components of defensive behaviors within distinct columns of periaqueductal gray matter of the rat: role of N-methyl-D-aspartic acid glutamate receptors.

The periaqueductal gray matter (PAG) is functionally organized in longitudinal columns arranged along the aqueduct. Stimulation of lateral and dorsal columns produces a complex set of unconditioned behaviors named the 'defense reaction.' Overt responses in rats comprise a tense immobile display, fully opened eyes (herein named exophthalmus), trotting, galloping, jumping, micturition and defecation. Besides, the PAG is rich in glutamate and respective receptors, including the N-methyl-d-aspartic acid (NMDA) type. Therefore, the present study employed regression analysis to map out electrically and NMDA-induced single components of defensive behaviors produced by stepwise increasing stimulation of PAG. Data confirmed the defensive nature of PAG-evoked responses. Neither the appetitive, nor offensive, mouse-killing or male reproductive behaviors were produced by stimulation of PAG in presence of appropriate targets. Threshold and dose-response logistic analyses largely corroborated the columnar organization of PAG-evoked responses. Thus, whereas the defecation was restricted to PAG lateral column, exophthalmus, micturition and somatic defensive responses were similarly organized in dorsolateral and lateral, but not in the ventrolateral column. Moreover, thresholds of dorsolateral and lateral repertoires were strictly hierarchical, with exophthalmus, immobility, trotting, galloping and jumping appearing in this very order. However, the defensive responses of PAG dorsolateral column required NMDA doses significantly lower than those of lateral PAG. Accordingly, NMDA receptors within the dorsolateral PAG are likely to play a major role in the initiation of PAG-evoked defensive responses. In contrast, the present data do not support the organization of unconditioned defensive behaviors in ventrolateral PAG. The neuroanatomical substrate of each response and the role of PAG and NMDA receptors are discussed in relation to the present data. Further, this is the first report on PAG columnar organization of single components of defensive behaviors.

Animals↗
PubMed1982

Testosterone acts as a prohormone to stimulate male copulatory behavior in male deer mice (peromyscus maniculatus bairdi).

In order to determine the importance of reduced and aromatized metabolites of testosterone for male sexual behavior in Peromyscus maniculatus bairdi, castrated males were treated with 5 alpha-reductase and aromatase inhibitors. In the first experiment, testosterone propionate (TP) activation of male copulatory behavior was blocked by the administration of the 5 alpha-reductase inhibitor 4-androsten-3-one-17-beta carboxylic acid (17 beta C). These treatments also prevented TP stimulation of seminal vesicles and ventral prostate gland weight. The inhibitory effects of 17 beta C were specific to testosterone, since 17 beta C did not prevent dihydrotestosterone propionate (DHTP) induction of male sexual behavior or seminal vesicles and ventral prostate gland weight increases. In the second experiment, TP activation of male copulatory behavior was prevented by the administration of the aromatase inhibitor 1,4,6-androstatriene-3,17-dione (ATD). The ATD did not interfere with DHTP activation of male reproductive behavior. Also, TP and DHTP stimulation of accessory sex organ weight was not blocked by ATD. On the basis of these data, it is suggested that metabolism of testosterone to both 5 alpha-reduced androgens and estrogens is obligatory for testosterone to reliably stimulate male sexual behavior in castrated male deer mice.

Androstatrienes↗