Maternal Behavior/Hormone and Behavior
Offspring are very vulnerable and inexperienced at birth and during the early stages of infancy therefore, maternal behavior is an integral part of an infant’s survival. They promote and assure an infant’s growth and development with out that death of the infant is almost always seen (Pryce et al., 1994). Maternal behavior as defined in Nelson (2000) is “any behavior that contributes directly to the survival of fertilized eggs or offspring that have left the body of the female.” Maternal investment is “the extent to which parents compromise their ability to produce additional offspring in order to assist current offspring.” Maternal behavior and investment can differ both within and among species. It can differ in the time spent providing care as well as the quality of care. The differences are due to the animal’s habitat as well as the developmental status of their young at birth (Kendrick et al., 1997). In a way it is the quality of the care given to the infant that is most important. Quality of care varies with the amount of direct mother-infant contact and the extent to which the mother provides the infant with carriage, warmth, security, stimulation, and protection (Pryce et al., 1994). I
When oxytocin is injected into the lateral cerebral ventricle it produces an immediate effect on maternal behavior in virgin females, within 30s in non-pregnant estrogen-primed female sheep and 30min in rats (this effect is only seen when circulating levels of estrogen are high) (Pederson et al., 1982, as seen in Reite et al., 1985). The difference in response time suggests that oxytocin is more potent in precocial mammals than altrical mammals. Oxytocin plasma levels should be higher in animals that give birth to small numbers of large animals (precocial mammals) than those that given birth to a large number of small animals due to the increased severity of uterine contractions (Carter, 1974). It is the act of parturition or VCS that triggers the onset of maternal behavior. An immediate maternal response is seen in hormonally primed rats as well as ewes (Kendrick et al., 1997; Pryce et al., 1994). This is due to the feedback to the brain via the spinal cord because this effect can be blocked by epidural anesthesia (Kendrick et al., 1997). Parity has also been seen to increase maternal proficiency (Pryce et al., 1994; Kinsley et al., 1999). b-endorphins have a high density of receptors in the limbic system. Experiments show there is a change in b-endorphin concentration during pregnancy probably to alter pain thresholds prior to parturition. Plasma concentrations increase during labor and birth while brain concentrations are low. In an experiment (Pryce et al., 1994) morphine was seen to disrupt pup-oriented behavior in multiparous rats when applied to the MPOA but not the ventral medial nucleus of the hypothalamus. An opioid receptor blocker, naltrexone, caused mothers to behave aggressively towards their infants as well as exhibit withdrawal behaviors. Naltrexone also decreased the ability of VCS to stimulate maternal behaviors. In certain areas of the brain, oxytocin is strongly regulated by b-endorphin (Kendrick et al., 1997). Therefore, opiate concentration may also effect the maternal behaviors exhibited by oxytocin. The limbic system is involved with the emotional and motivational aspects of maternal response and deficits are expressed as disorganized behaviors.
Some topics in this essay:
INTRODUCTION Offspring,
Hormones Behavior,
Olfactory Influences,
Changes Fifty,
EXPERIENTAL INFLUENCES,
Influences Suckling,
Estrogen Steroid,
INFLUENCES Hormones,
Experience Preparturition,
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maternal behavior,
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kendrick et al,
kendrick et,
reite et al,
reite et,
al 1985,
et al 1985,
pryce et,
al 1994,
pryce et al,
seen reite,
maternal behaviors,
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Approximate Word count = 4564
Approximate Pages = 18 (250 words per page double spaced)
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