User:Charlene.est.33/My sandbox/Final

Endocrinology of Parenting Proposed Edits

The following are personal edits/comments I have noted in reviewing the wiki page (as well as the word docs) as it currently is.. (I have made these revisions at this point- 4/25/19):

Nonhuman females[edit]

Many nonhuman studies can be used as both potential models for humans and to show the phylogenetic conservation of some endocrine signals.[1] Estrogen and progesterone released by ovaries during pregnancy make oxytocin receptors more sensitive in female rats[7] and is associated with the onset of maternal behaviors in other species as well.[3][8][9] Maestripieri found a very similar relationship, whereas estrogen and progesterone are increased during pregnancy and oxytocin was increased postpartum (slightly confusing wording.. Reword to: “Maestripieri found a very similar relationship in which estrogen and progesterone are increased during pregnancy whereas oxytocin was increased postpartum” ) .[10] Estrogen, progesterone, and estradiol in pregnant mammals, in some species, but not all, correlate with maternal behavior before the birth of their offspring, with other infants, and after with their own infants.(appear to be awkward wording: The presence of estrogen, progesterone, and estradiol in pregnant mammals in some species appears to exhibit a correlation to maternal behavior in the mammals before and after the birth of their offspring as well as in interactions with other offspring/infants.) [3] However, an increase in hormones influences maternal behavior, but it is not always the cause of the onset of maternal behavior in females. Some studies on primates in which increased estrogen and progesterone have a negative or no (“absent” instead of “no”?) correlation with maternal responsivity are in black tufted-ear marmosets,[11] common marmosets,[12] lowland gorillas,[13] and baboons.[14] However an experimental study on nulliparous rats, who tend to avoid pups, found that when they were transfused with postpartum rat's blood, which is high in estrogen and progesterone approached the pups in response to their cues. (reword to say: Alternatively, however, one experimental study showed that nulliparous rats, which tend to avoid pups, were transfused with postpartum rat blood that is high in estrogen and progesterone, resulting in their responsiveness to the pups’ cues) [15] Because (Due to) of (omit) this variation between species, the effects of the hormones listed does not give much weight to the phylogenetic conservation of these neuroendocrine mechanisms; although Saltzman points out that the social structure of some species may be significant.[3] Previous exposure to infants, in social species, rely (relies) less on these hormones to activate mechanisms and more on modulating maternal behavior because parenting behaviors are not always dependent on hormones.[3] On the other hand, in non-human primates specifically, lactating females of multiple species exhibit an alarming correlation with increased estrogen, and (omit this) progesterone, and prolactin.[3] These species include black tufted-ear marmosets,[11] baboons,[14] rhesus macaques,[16] and gorillas.[13] Endogenous signals, like increasing estrogen compared to progesterone, increases the amount of prolactin, the “lactation hormone,” in the bloodstream, as well as exogenous cues from infants, like suckling. (reword: Endogenous signals such as an increase in estrogen compared to a decrease in progesterone, causes an increase in the levels of prolactin, the “lactating hormone,” in the bloodstream. Furthermore, exogenous cues from infants such as suckling induces this mechanism.) [17] Oxytocin, has been found to play a key factor in breastfeeding and increase similarly to prolactin, with increases in estrogen and infant cues. (reword: The hormone oxytocin, similarly to prolactin, has been found to increase with an increase in estrogen and the presence of infant cues such as suckling/breastfeeding.) Suckling also increases oxytocin levels in rhesus macaques (this fact appears to be misplaced) ,[10] and oxytocin has also been found in other non-human species to inhibit the rejection of offspring;[3] oxytocin is essential for responsive and sensitive caregiving.[19][20][3][21] Some specific examples include Francis' study on female rats which linked a high amount of oxytocin receptors to increased (omit this) an increase in acts grooming,[22] and another study by Maestripieri which linked (an increase in) oxytocin levels in free-ranging macaques to increased nursing and grooming. (to an increased tendency to nurse and groom.) [10] However, experimental results are less conclusive. (As aforementioned,) (omit) N(n)ulliparous mice do not respond to pup calls, but when administered with oxytocin they do.[23] A similar study conducted by Holmon and Goy tested nulliparous rhesus females, where (their behavior) post injection did not elicit a drastic response to infants, however there was a notable change in the adult's behavior, including increased proximity and touching. (however, a notable change within the adults presented an increase in proximity and touching). [24] Oxytocin is more often described as a hormone that facilitates bonding and not one that directly increases care.[25][24][26][10] Also, the mice were responding to pup calls and the rhesus macaque infants weren't necessarily providing cues. (clarify.. which cues (cues for maternal care and support?) Similar to the explanation provided for the variation in estrogen and progesterone, rhesus macaques live in drastically different environments. (expand upon the explanation and how it affects the variation in behavior?- it just sounds confusing) Saltzman proposes that this is due to primates living socially and having a slower developmental trajectory, in which learning is more important. (this appears to be out of place) [3]

Human females[edit]

Like in many nonhumnan (nonhuman) animals, human mothers go through a period of high progesterone during pregnancy that is followed by a decrease in progesterone and a subsequent increase in estrogen, prolactin, and oxytocin (near the end of their pregnancy). During pregnancy and postpartum, a high estradiol to progesterone ratio is associated with mother(s) reported (reporting) higher feelings of attachment.[27] High levels of progesterone, which is (are) associated with pregnancy, inhibits prolactin and therefore lactation.[28] Prolactin increases during the initial stages of lactation and can be stimulated by infant cues and estrogen, but not progesterone and infant cues (omit). [28] Research (,however,) focuses on the role of prolactin for breastfeeding and less on other behaviors.[28] Prolactin increases with infant suckling but not other forms of infant contact.[29] Oxytocin, on the other hand, increases with both suckling, and physical contact in human females.[28] Oxytocin in human females is associated with the level of physical affection and bonding. (Oxytocin levels in human females are associated with the presence of physical affection and bonding) Feldman (2010) found that mothers who displayed “high affectionate contact” had increased oxytocin levels post interaction, but not mothers who displayed “low affectionate contact.”[21] Oxytocin is believed to provide a feedback loop, meaning that maternal-infant contact increases oxytocin and oxytocin increases maternal behavior and facilitates bonding.[30] In one study oxytocin also played a role on mother reported attachment to her fetus.[31]

Nonhuman males[edit]

Wynne-Edwards and Timonin recognize that paternal care is not primed in the same way as females (maternal care) simply because they do not go through pregnancy. Therefore, males do not go through the same hormonal changes as women.[32] The simplest way, through natural selection, for paternal care to evolve or be maintained is to use the same or similar pathways as females.[33] Wynne and Reburn (2001) suggest that fathers who are pair bonded and spend time with the soon to be mother may activate paternal pathways through various cues.[33] Estradiol increases just before their offspring's birth in black-tufted-ear marmosets and dwarf hamsters and possibly activates certain pathways involved in paternal behavior.[34][35] This is similar to estrogen and progesterone in pregnant females. However, the manipulation of estradiol does not increase or decrease paternal behaviors.[32] This may be similar to the finding that women who do not breastfeed or do not have vaginal births still respond to their infants.[19] Like expecting and new mothers, fathers in multiple mammals have elevated prolactin levels compared to non-fathers. These species include California mice,[36] Mongolian gerbils,[37] dwarf hamsters[disambiguation needed],[38] meerkats,[39] marmosets,[40] and cotton-top tamarins.[41] However, the previously listed studies have different cues and are associated with different paternal behaviors and (this)- omit) may be due to species specific mechanisms or simply different contexts. The above species are biparental and the elevated prolactin levels in males were not exclusive to fathers. There are variable results between males of different species as to the effects of oxytocin on paternal care. (…between the effects of oxytocin on paternal care between males of different species). Oxytocin (levels are) is unchanged in California mice before and after becoming fathers,[42] but the amount of paternal exposure to rats is associated with (an increase in) oxytocin and increased care.[41] However, multiple studies on biparental species show an association between paternal care and oxytocin.[42][43][33][44] Since the species in these studies are biparental, excluding rats, it is unclear as to why California mice do not have a change in oxytocin postpartum.

Human males[edit]

In human mothers, oxytocin is associated with high physical contact and affection. However, studies on fathers show that oxytocin is related to high stimulatory contact and exploratory play.[21][45] This supports three hypotheses: 1. Mothers and fathers play different roles.[6] 2. Mothers and fathers have similar pathways.[32] 3. That there are parallels to animal models,[21] assuming that a high amount of OT receptors in nonhuman animals is associated with a high amount of oxytocin

Comparison of estrogen, progesterone, prolactin, and oxytocin between species and sex[edit]

Across multiple species and in some cases across sexes, there is evidence for the phylogenetic conservation of parental hormones. These include the relationships between the hormones estrogen, progesterone, prolactin, and oxytocin. In both non-human primates and humans, the increase in estrogen and progesterone during pregnancy is often followed by a decrease in progesterone and an increase in prolactin, postpartum.[11][14][13][24][28] In males across species, including humans, increased prolactin levels are associated with fatherhood.[36][37][38][39][40][41][46][47] In some studies on females across species, estrogen and progesterone prepartum is also related to oxytocin.[7][3][8][9][10] Although, the relationships between these hormones is similar across species, there is variation in the degree to how oxytocin effects behavior. For example, in some species, like rats, an increase in oxytocin greatly increases interactions with infants,[23] but an increase in oxytocin in macaques only mildly increased interactions.[24] However, the importance here is that oxytocin increased interactions in all of the relevant cited studies for females,[7][3][8][9][24] as well as the majority of studies cited for males.[42][43][33][44] In fathers across species the effects of oxytocin are more variable, however in general oxytocin is associated with increased paternal care.[42][43][33][44] In human fathers increased oxytocin is linked to increased involvement, however the type of involvement is different between fathers and mothers, where fathers focus more on stimulatory contact and exploratory play.[21][45] In human mothers oxytocin is associated with general care and affection.[21]

Cortisol and prolactin[edit source]

Nonhuman females[edit source]

Contrary to the positive effects of oxytocin on maternal behavior, heightened levels of cortisol postpartum has been linked to a decrease in maternal care in nonhuman species, including the Western lowland gorilla,[48] baboons,[49] Japanese macaques,[50] and rhesus macaques.[10] However, there has been some evidence to support that the increase in cortisol levels during pregnancy results in an increased maternal care in two baboon species.[51][14] This variation possibly shows an ontogenetic difference in the role of cortisol. (there is no mention of prolactin in most of this section)

Testosterone[edit source] (Re-adjust the order of the subtitles with human females first since there is not a section for nonhuman females!)

Nonhuman males[edit source]

The most commonly associated hormone with males is testosterone. It is believed to be the “anti-parental hormone”; it inhibits the activation of paternal mechanisms.[1] In many cases testosterone levels decrease when fathers have or actively care for their infants in non-humans.[49][64][50][34] However, testosterone can be converted into estradiol, which supports paternal behavior.[34][65] Testosterone is converted into estradiol through the process of aromatization.[65] Stated previously, with the repeated presence of pups to non-parental rats, caregiving mechanisms can inhibit other mechanism, like the avoidance mechanism;[15] similar inhibitions occur in male marmosets.[66] When male marmosets hold their infants, they did not have an increased testosterone response to novel females when they otherwise would. In other words, holding the infant inhibited the mating mechanisms. This could mean that caregiving supersedes mating in some situations. For example, it may be adaptive to continue to invest in your current offspring rather than potentially create another.

Human males[edit source] Multiple studies on fathers have shown that a reduction in testosterone results in increased responsiveness to infant cues[67][68][69] and that fathers in general have lower testosterone than non-fathers.[69][70][71] Testosterone in human males decreases with the number of offspring human males have.[69] However, human males with higher level testosterone had greater activation of neural mechanisms when interacting with their own infants,[72][73] this may be due to the activation of a paternal protection mechanism.[74]

Human females[edit source] Not many studies analyze the effects of testosterone and maternal behaviors in humans. However, Fleming found that lower testosterone was associated with more affectionate contact in human mothers.[28] (exclude this once I add my own info)

Comparison of testosterone between species and sexes[edit source] Between species variation in behaviors associated with testosterone in biparental species was not noted. Across species father experience was negatively correlated with testosterone[66][69] and lower levels of testosterone was associate with an increase in care.[67][49][69] Testosterone is more commonly studied in males than females. However, one study on human females found that lower testosterone is associated with increased maternal care.[28]

The following is data I have gathered from articles that I would like to add to this wiki page to improve it by including relevant and necessary info which was absent from it

Estrogen, progesterone, prolactin, and oxytocin

Nonhuman females

Bridges S. Robert, “Neuroendocrine regulation of maternal behavior.” Frontiers in neuroendocrinology, vol. 36, 2015, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4342279/pdf/nihms653698.pdf. Accessed 4 March 2019.

The function of oxytocin may lead to an increase in maternal behavior by subsequently reducing anxiety as it has been found to regulate anxiety, social recognition, and coping with stress. Early studies have found that oxytocin influenced maternal behavior of mother rats depending on the environment in which they were placed. Oxytocin seemed to have an opposing effect on anxiety so that when placed in a novel environment as opposed to a familiar one, mother rats were better able to cope with their higher levels of stress due to their increased oxytocin levels.

Human females

Bridges S. Robert, “Neuroendocrine regulation of maternal behavior.” Frontiers in neuroendocrinology, vol. 36, 2015, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4342279/pdf/nihms653698.pdf. Accessed 4 March 2019.

Studies have shown that plasma oxytocin in pregnant women is higher compared to non-pregnant women. The increased levels of oxytocin found in pregnant women predicted the duration of maternal care they would exhibit towards their infant postpartum which indicates that increased exposure to oxytocin may facilitate maternal behaviors. (exclude because this information is already mentioned).

Human males

Jaeggi, V. Adrian, et al. “Salivary oxytocin increases concurrently with testosterone and time away from home among returning Tsimane' hunters.” Biol. Lett., vol 11., no. 3, 2015, https://royalsocietypublishing.org/doi/pdf/10.1098/rsbl.2015.0058. Accessed 4 March 2019.

One study exhibited the proposed effects that oxytocin had on Tsimane men who had been hunting for varying periods of time. Once the men returned home, it was found that oxytocin levels were higher in those men who had hunted for longer periods of time. As a result of the longer time period spent hunting, the increased levels of oxytocin were thought to be interconnected with familial social contact dating back to humans’ evolutionary past.

Comparison of estrogen, progesterone, prolactin, and oxytocin between species and sex

Bridges S. Robert, “Neuroendocrine regulation of maternal behavior.” Frontiers in neuroendocrinology, vol. 36, 2015, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4342279/pdf/nihms653698.pdf. Accessed 4 March 2019.

One study utilized Silastic implants containing estradiol and progesterone which were implanted in nulliparous rats that either maintained the function of their pituitary glands or underwent a hypophysectomy to determine the length of time for maternal care to ensue. The rats with hypophysectomies exposed to these conditions for 5-6 days were not affected by the treatment and consequently did not induce any maternal behavior. However, it was found that those rats with functioning pituitary glands exhibited maternal behavior within about 3-4 days. It has been similarly shown in various studies dealing with oxytocin that adult virgin female rats that are estrogen-primed exhibit a decreased latency to interact with foster pups. (exclude this last sentence)

Madelon, Reim, et al. “Oxytocin effects on complex brain networks are moderated by experiences of maternal love withdrawal.” European Neuropsychopharmacology vol. 23, no.10, 2013, https://ac.els-cdn.com/S0924977X13000503/1-s2.0-S0924977X13000503-main.pdf?_tid=45f71592-7ac2-469c-be8362b26a9cdb77&acdnat=1551836373_8c17746d2720a1c1ee33e4cf4266aa08. Accessed 4 March 2019.

One study examined the effects that intranasal oxytocin spray administration has in relation to individuals’ childhood experiences of punishment by maternal love withdrawal. It was found that oxytocin effects were absent in individuals who experienced high maternal love withdrawal indicating that the parental behavior associated with withdrawal causes alterations in the genetic expression of endogenous oxytocin levels which affects their children into adulthood.

Cortisol and prolactin

Nonhuman females

Bridges S. Robert, “Neuroendocrine regulation of maternal behavior.” Frontiers in neuroendocrinology, vol. 36, 2015, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4342279/pdf/nihms653698.pdf. Accessed 4 March 2019.

The functions of prolactin have been extensively studied on rats which has revealed its effects and profound role in maternal care. The role of prolactin has been found to induce the maternal behavior in nulliparous rats exposed to a hypophysectomized steroid treatment as noted in which prolactin secreting pituitary implants were placed under the kidney capsule which caused a shortened latency to participate in maternal behavior towards foster pups. A different study used non-hypophysectomized, steroid-treated nulliparous rats were exposed to a dopamine D2 agonist, called bromocriptine, used to decrease the release of prolactin. Bromocriptine, in turn, consequently lowered the maternal behavioral tendency to foster the young pups. Conversely, when bromocriptine was used in conjunction with prolactin, the maternal behavior returned.

Melo, Angel I. et al. “Effects of prolactin deficiency during the early postnatal period on the development of maternal behavior in female rats: Mother's milk makes the difference.” Hormones and Behavior, vol. 56, no. 3, 2009, https://www.ncbi.nlm.nih.gov/pubmed/19538963. Accessed 16 March 2019.

Another experiment also utilized bromocriptine to inhibit the release of prolactin in mother rats who were lactating to their pups during a 2-5-day period. The inhibition of prolactin release appears to indicate a critical period of the development of prolactin mechanisms within the pups. One study demonstrated that a deficiency in prolactin during the postnatal period in rats has the potential to affect their maternal behavior. In this study bromocriptine-treated juvenile rats exhibited hyperactivity and distractibility from the pups during the maternal behavior test suggesting the importance of prolactin to promote maternal behavior. Adult rats also treated with bromocriptine showed similar differences when exposed to pups as opposed to control rats that exhibited maternal tendencies towards the pups. It was determined that prolactin deficiency may lead to disruptions in maternal behavior in adulthood, affect the neural substrates that promote maternal behavior, and that behavioral deficits are not only caused by a developmental delay in the systems regulating maternal behavior.

Testosterone

Human Females

Swain J.E, et al. “Research Report: Approaching the biology of human parental attachment: Brain imaging, oxytocin and coordinated assessments of mothers and fathers.” Oxytocin in Human Social Behavior and Psychopathology, Brain Research, vol. 1580, 2014, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4157077/pdf/nihms592483.pdf. Accessed 4 March 2019.

Additionally, these mothers exhibited positive maternal behavior such as alterations in their vocalization and gaze towards their infants which is correlated to the high oxytocin levels. ( <- exclude) Studies have been conducted that show an interaction between brain circuits that respond to baby-stimuli, such as infant cries, and testosterone and oxytocin pathways. It has been found that when acute amounts of testosterone and oxytocin are administered to nulliparous women exposed to infant cries, they cause decreased responses in the amygdala and increased insula and inferior frontal gyrus responses. The alterations in responses within those brain regions have been seen to induce maternal behaviors. As such, there is speculation that increasing the availability of testosterone and oxytocin alters the maternal brain to induce a non-aversive response to infant cries.