Oxytocin

Cross references:   Pituitary Gland     Posterior Pituitary    Neuropeptides    Nonapeptides  Arginine Vasopressin   

Oxytocin (Wiki)   
http://en.wikipedia.org/wiki/Oxytocin   
    "Oxytocin is a mammalian hormone that acts primarily as a neuromodulator in the brain."   
    "Oxytocin is best known for its roles in female reproduction. It is released in large amounts
    1) after distension of the cervix and uterus during labor, and
    2) after stimulation of the nipples, facilitating birth and breastfeeding. Recent studies have begun to investigate oxytocin's role in various behaviors, including orgasm, social recognition, pair bonding, anxiety, and maternal behaviors.[2] For this reason, it is sometimes referred to as the "love hormone".[3]
"  
    "
Oxytocin has peripheral (hormonal) actions, and also has actions in the brain. The actions of oxytocin are mediated by specific, high-affinity oxytocin receptors. The oxytocin receptor is a G-protein-coupled receptor that requires Mg2+ and cholesterol. It belongs to the rhodopsin-type (class I) group of G-protein-coupled receptors.
"  
    "
Oxytocin evokes feelings of contentment, reductions in anxiety, and feelings of calmness and security around the mate.[18] Many studies have already shown a correlation of oxytocin with human bonding, increases in trust, and decreases in fear.
"  
    "
Modulation of hypothalamic-pituitary-adrenal axis activity. Oxytocin, under certain circumstances, indirectly inhibits release of adrenocorticotropic hormone and cortisol and, in those situations, may be considered and antagonist of vasopressin.[22]
"    
    "
Autism. Oxytocin may play a role in autism and may be an effective treatment for autism's repetitive and affiliative behaviors.[23]
"  
    "
Increasing trust and reducing fear. In a risky investment game, experimental subjects given nasally administered oxytocin displayed "the highest level of trust" twice as often as the control group. Subjects who were told that they were interacting with a computer showed no such reaction, leading to the conclusion that oxytocin was not merely affecting risk-aversion.[28] Nasally administered oxytocin has also been reported to reduce fear, possibly by inhibiting the amygdala (which is thought to be responsible for fear responses).[29]
"      
    "
Oxytocin secreted from the pituitary gland cannot re-enter the brain because of the blood-brain barrier. Instead, the behavioral effects of oxytocin are thought to reflect release from centrally projecting oxytocin neurons, different from those that project to the pituitary gland, or that are collaterals from them.[45] Oxytocin receptors are expressed by neurons in many parts of the brain and spinal cord, including the amygdala, ventromedial hypothalamus, septum,
Nucleus Accumbens Septi, and brainstem."    
    "Maternal behavior. Female rats given oxytocin antagonists after giving birth do not exhibit typical maternal behavior.[48] By contrast, virgin female sheep show maternal behavior toward foreign lambs upon cerebrospinal fluid infusion of oxytocin, which they would not do otherwise.[49]"  
    "
In the hypothalamus, oxytocin is made in magnocellular neurosecretory cells of the supraoptic and paraventricular nuclei and is stored in Herring bodies at the axon terminals in the posterior pituitary. It is then released into the blood from the posterior lobe (neurohypophysis) of the pituitary gland. These axons (likely, but dendrites have not been ruled out) have collaterals that innervate oxytocin receptors in the
Nucleus Accumbens Septi.[45] The peripheral hormonal and behavioral brain effects of oxytocin it has been suggested are coordinated through its common release through these collaterals.[45] Oxytocin is also made by some neurons in the paraventricular nucleus that project to other parts of the brain and to the spinal cord.[69] Depending on the species, oxytocin-receptor expressing cells are located in other areas, including the amygdala and bed nucleus of the stria terminalis. "    
    "
The oxytocin receptor in humans has several alleles, which differ in their effectiveness. Individuals homozygous for the "G" allele, when compared to carriers of the "A" allele, show higher empathy, lower stress response,[79] as well as lower prevalence of autism and of poor parenting skills.[80]
"    
    "
Virtually all vertebrates have an oxytocin-like nonapeptide hormone that supports reproductive functions and a vasopressin-like nonapeptide hormone involved in water regulation. The two genes are usually located close to each other (less than 15,000 bases apart) on the same chromosome and are transcribed in opposite directions ... It is thought that the two genes resulted from a gene duplication event; the ancestral gene is estimated to be about 500 million years old and is found in cyclostomata (modern members of the Agnatha).[34]
"    



Brain oxytocin: a key regulator of emotional and s... (PubMed) 
Only abstract available online. 
"
In addition to various reproductive stimuli, the
Neuropeptides  oxytocin (OXT) is released both from the neurohypophysial ( Posterior Pituitary ) terminal into the blood stream and within distinct brain regions in response to  Stressful or social stimuli. Brain OXT  Receptor-mediated actions were shown to be significantly involved in the regulation of a variety of behaviours. ... Also, in male rats, activation of the brain OXT system is essential for the regulation of sexual behaviour, and increased OXT system activity during mating is directly linked to an attenuated anxiety-related behaviour.


Oxytocin: the great facilitator of life (PubMed)  - 2009  
Full length HTML and PDF available online for free  . 
"
 Although Oxt is implicated in a variety of "non-social" behaviors, such as learning, anxiety, feeding and pain perception, it is Oxt's roles in various social behaviors that have come to the fore recently. Oxt is important for social memory and attachment, sexual and maternal behavior, and Aggression. Recent work implicates Oxt in human bonding and trust as well. Human disorders characterized by aberrant social interactions, such as autism and schizophrenia, may also involve Oxt expression. Many, if not most, of Oxt's functions, from social interactions (affiliation, aggression) and sexual behavior to eventual parturition, lactation and maternal behavior, may be viewed as specifically facilitating species propagation." 
 


Evolutionary precedents for behavioral actions of oxytocin and vasopressin.
http://www.ncbi.nlm.nih.gov/pubmed/1626827









Comments