Arginine Vasopressin

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Vasopressin (Wiki)   
http://en.wikipedia.org/wiki/Vasopressin     
    "Arginine vasopressin (AVP), also known as vasopressin, argipressin or antidiuretic hormone (ADH), is a neurohypophysial hormone found in most mammals, including humans.[1]
    "It is derived from a preprohormone precursor that is synthesized in the hypothalamus and stored in vesicles at the posterior pituitary. Most of it is stored in the posterior pituitary to be released into the bloodstream; however, some AVP is also released directly into the brain, where it plays an important role in social behavior and bonding.
"   
    "Vasopressin released within the brain has many actions:
  • It has been implicated in memory formation, including delayed reflexes, image, short- and long-term memory, though the mechanism remains unknown; these findings are controversial. However, the synthetic vasopressin analogue desmopressin has come to interest as a likely nootropic.
  • Vasopressin released from centrally projecting hypothalamic neurons is involved in aggression, blood pressure regulation and temperature regulation.
  • Selective AVPr1a blockade in the ventral pallidum has been shown to prevent partner preference, suggesting that these receptors in this ventral forebrain region are crucial for pair bonding.[2]

    In recent years, there has been particular interest in the role of vasopressin in social behavior. It is thought that vasopressin, released into the brain during sexual activity, initiates and sustains patterns of activity that support the pair-bond between the sexual partners; in particular, vasopressin seems to induce the male to become aggressive towards other males.[4]"   
    "Moreover, studies involving either injecting AVP agonists into the brain or blocking the actions of AVP support the hypothesis that vasopressin is involved in aggression towards other males."   
    "The structure of oxytocin is very similar to that of the vasopressins: It is also a nonapeptide with a disulfide bridge and its amino acid sequence differs at only two positions. The two genes are located on the same chromosome separated by a relatively small distance of less than 15,000 bases in most species. The magnocellular neurons that make vasopressin are adjacent to magnocellular neurons that make oxytocin, and are similar in many respects. The similarity of the two peptides can cause some cross-reactions: oxytocin has a slight antidiuretic function, and high levels of AVP can cause uterine contractions.[16][17]"  


Chronic psychosocial stress enhances vasopressin, but not Corticotropin-releasing hormone (CRH), in the external zone of the median eminence of male rats: relationship to subordinate status.  (PubMed)  - 1992   
Only abstract available online.     
    "
Colony-housed subordinates were compared to control rats housed in male-female pairs. Classical parameters of chronic 
Stress (thymus involution, impaired somatic growth, and elevated resting plasma corticosterone ( Cortisol ) level) were found in all subordinate rats.  
    Changes in vasopressin (AVP) and
Corticotropin-releasing hormone (CRH) stored in the external zone of the median eminence (ZEME) were measured by quantitative immunocytochemistry. Chronic psychosocial  Stress for 19-28 days increased AVP immunostaining in the ZEME to 160-190% of that in pair-housed controls, whereas Corticotropin-releasing hormone (CRH) immunostaining in the ZEME remained unchanged. 
   
Within colonies, subordinates differed in avoidance behavior and aggression received (subordinate status). This intracolony subordination rank was correlated with AVP in the ZEME (P less than 0.01). Although resting corticosterone
( Cortisol ) was elevated in subordinate rats (P less than 0.01), the increase in AVP was not associated with detectable secretion of AVP and/or Corticotropin-releasing hormone (CRH) from the ZEME, as measured after blockade of axonal transport. 
    
Subordinates showed suppressed
Hypothalamic (AVP depletion), Pituitary Gland (plasma  ACTH ) and Adrenal Cortex (plasma corticosterone ( Cortisol )) responses to interaction with the dominant male, which may reflect suppressive actions of elevated corticosterone (Cortisol ) on Corticotropin-releasing hormone (CRH) neurons or suprahypothalamic centers."    


Vasopressin and the regulation of hypothalamic-pituitary-adrenal axis (HPA Axis )function: implications for the pathophysiology of depression (PubMed) 
Only abstract available online.  
from the abstract 
    "
VP is released from two sites in the
Hypothalamus; the parvicellular division of the Paraventricular nucleus (PVN), where Corticotropin-releasing hormone (CRH) is also formed, and from the magnocellular neurons of the supraoptic nucleus (SON) and the PVN. The intricate interaction with CRH, the other main ACTH secretagogue, and with Glucocorticoids, the inhibitory feedback component of hypothalamic-pituitary-adrenal-axis (HPA Axis) activity, is outlined."     
    "I
n animal models there is clear evidence that chronic psychological 
Stressors increase the ratio of AVP to  Corticotropin-releasing hormone (CRH) production. Psychosocial  Stressors are intrinsically linked with depressive illness. The finding of elevated levels of AVP in postmortem studies of depressives and the lowering of Cerebrospinal Fluid  AVP levels by antidepressants, raises the question of the precise role of AVP in the overactivity of the HPA Axis in depression, a finding that is currently attributed to overdrive of its HPA Axis regulatory companion,  Corticotropin-releasing hormone (CRH) ."    
 

Response of the hypothalamic-pituitary-adrenal axis  (HPA Axis) to small dose arginine-vasopressin and daily urinary free Cortisol before and after alprazolam pre-treatment differs in obesity (PubMed) 
Only abstract available online.    - 2004 
Non-printable PDF free with registration (I haven't yet), 
from the abstract   
    "
Arginine vasopressin (AVP) has a central role in the response of the hypothalamic-pituitary-adrenal axis
(HPA Axis) to stress conditions. A low dose of AVP has been shown to have a modest, but significant effect on ACTH response in normal weight subjects. The aim of this study was to test the response of the HPA Axis in obese subjects in order to assess eventual primary neuroendocrine alterations, previously demonstrated by using AVP combined with Corticotropin-releasing hormone (CRH)."  


An overview of SSR149415, a selective Nonapeptide vasopressin V(1b) Receptor antagonist for the treatment of  Stress-related disorders.  (PubMed) 
Only abstract available online.     
    "
Vasopressin (AVP) and
Corticotropin-releasing hormone (CRH) (CRF) are key mediators in the organism's neuro-adaptive response to  Stress . Through Pituitary Gland-Posterior Pituitary and central vasopressin V(1b) Receptors , AVP participates in the control of the hypothalamic-pituitary-adrenal axis  (HPA Axis) and is involved in various emotional processes."  


An investigation of hypothalamic-pituitary-adrenal axis (HPA Axis) hyperactivity in anorexia nervosa: the role of Corticotropin-releasing hormone (CRH) and AVP (PubMed)    - 2007 
Only abstract available online.    
from the abstract   
    "We hypothesised that hypothalamic-pituitary-adrenal axis (HPA Axis) hyperactivity in anorexia nervosa (AN) is associated with (a) elevated arginine vasopressin (AVP) activity and (b) enhanced Pituitary Gland sensitivity to AVP, as it is in depressive illness."    
    "
Thus, contrary to the hypotheses, we did not find (a) evidence of upregulated AVP activity or (b) enhanced
Pituitary Gland sensitivity to AVP in AN. These findings suggest that the mechanism of HPA Axis hyperactivity differs in depression and AN, with greater involvement of AVP in depressive disorder and perhaps more reliance on Corticotropin-releasing hormone (CRH) to drive the axis in AN. The powerful anorexigenic effect of Corticotropin-releasing hormone (CRH) could contribute to the severity of weight loss associated with AN."    


The hypothalamic-pituitary-adrenal axis (HPA Axis) response to  Stress in mice lacking functional vasopressin V1b Receptors. (PubMed)  - 2007   Full length HTML and PDF available online for free.    
The "Related citations" and "Cited by ..." sections contained many other references re: V1b knockout mice.     
from the abstract       
     "The role of arginine vasopressin (Avp) as an adrenocorticotropin (ACTH) secretagogue is mediated by the Avp 1b receptor (Avpr1b) found on Anterior Pituitary corticotropes. Avp also potentiates the actions of Corticotropin-releasing hormone (CRH) and appears to be an important mediator of the hypothalamic-pituitary-adrenal axis (HPA Axis) response to chronic  Stress."  
    "
The data suggests that the Avpr1b is required for the normal
Pituitary Gland and Adrenal Gland response to some acute  Stressful stimuli, and is necessary only for a normal ACTH response during chronic  Stress."    


Vasopressin: Behavioral Roles of an “Original” Neuropeptide (PubMed) 
Full length HTML and PDF available online for free. 
    "
Vasopressin (Avp) is mainly synthesized in the magnocellular cells of the 
Hypothalamic supraoptic (SON) and Paraventricular nucleus (PVN) whose axons project to the Posterior Pituitary. Avp is then released into the blood stream upon appropriate stimulation (e.g., hemorrhage or dehydration) to act at the kidneys and blood vessels. The brain also contains several populations of smaller, parvocellular neurons whose projections remain within the brain. These populations are located within the Paraventricular nucleus (PVN), Bed Nucleus of the Stria Terminalis (BNST), medial Amygdala  (MeA) and suprachiasmatic nucleus (SCN)."   
    "
Avp is evolutionarily well-conserved as even the primitive organism hydra expresses an Avp-like peptide (Grimmelikhuijzen and Spencer, 1984). The evolutionary progenitor of the vertebrate Avp, vasotocin, is found in birds and reptiles (Acher, 1990).
"     
    "
There are three major
Receptor types for Avp: Avpr1a, Avpr1b, and Avpr2. The Avp Receptors have seven transmembrane domains: Avpr1a and Avpr1b couple to Gαq/11 GTP binding proteins, which along with Gβλ, activate phospholipase C activity whereas Avpr2 couples to Gs and acts through the cyclic AMP system (Michell et al., 1979; Jard et al., 1987).
    "
Avp plays a prominent role in the regulation of
Aggression, generally of facilitating or promoting it. Affiliation and certain aspects of pair-bonding are also influenced by Avp. Memory, one of the first brain functions of Avp that was investigated, has been implicated especially strongly in social recognition. The roles of Avp in  Stress, anxiety, and depressive states are areas of active exploration."   
    "
In humans, heightened
Aggression is associated with increased Impulsivity and is a characteristic of individuals with personality disorders. There is a positive correlation of Cerebrospinal Fluid Avp concentration with a life history of non-directed general aggression (including temper tantrums and property assault) as well as aggression towards individuals (Coccaro et al., 1998)."  
    "
Given the difficulty of studying and the complexity of aggression in humans, the concordance between the findings of the animal work and that of the human literature implicating Avp in the regulation of aggression is compelling. It appears that the role of Avp in the regulation of aggression is highly conserved.
"   


Pheromones enhance somatosensory processing in newt brains through a vasotocin-dependent mechanism  (PubMed)  - 2008   
Full length HTML and PDF available online for free. 
"
In summary, we have shown that social stimuli processed within one sensory modality can affect how sensory information coming in through other sensory modalities is processed in male roughskin newt brains, most likely by inducing endogenous VT release.
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