Central cardiovascular actions of agmatine, a putative clonidine-displacing substance, in conscious rabbits

@article{Head1997CentralCA,
  title={Central cardiovascular actions of agmatine, a putative clonidine-displacing substance, in conscious rabbits},
  author={Geoffrey A. Head and Candy King-Chi Chan and Shirley J. Godwin},
  journal={Neurochemistry International},
  year={1997},
  volume={30},
  pages={37-45}
}
Central Actions of Agmatine in Conscious Spontaneously Hypertensive Rats
TLDR
Agmatine neither did mimic nor block the antihypertensive response to rilmenidine and clonidine at well-tolerated doses, yet agmatine produced a small tachycardia at relatively low doses and was able to reverse the bradycardia induced byClonidine.
Agmatine, an endogenous ligand at imidazoline binding sites, does not antagonize the clonidine‐mediated blood pressure reaction
TLDR
Investigating whether agmatine can mimic CDS‐induced cardiovascular reactions in organ bath experiments, pithed spontaneously hypertensive rats (SHR) and anaesthetized SHR found that it may modulate noradrenaline release in the same way that clonidine does, i.e. via imidazoline binding sites.
Cardiovascular effects of agmatine within the rostral ventrolateral medulla are similar to those of clonidine in anesthetized rats
TLDR
It is concluded that agmatine exerts a similar cardiovascular effect to clonidine, with less potency within the RVLM.
Agmatine inhibits arginine vasopressin-stimulated urea transport in the rat inner medullary collecting duct.
TLDR
Agmatine inhibits AVP stimulated Pu by a cAMP-dependent mechanism and the possibility exists of an unknown agmatine-selective receptor modulating urea transport in the rat IMCD.
Harmane produces hypotension following microinjection into the RVLM: possible role of I1‐imidazoline receptors
TLDR
The β‐carboline, harmane produces dose dependent hypotension when microinjected unilaterally into the rostral ventrolateral medulla of the anaesthetized rat, and is the first report of an endogenous ligand for I1‐receptors that has central effects on blood pressure.
Agmatine: multifunctional arginine metabolite and magic bullet in clinical neuroscience?
TLDR
The agmatinergic system is currently one of the most promising candidates in order to pharmacologically interfere with some major diseases of the central nervous system, which are summarized in the present review.
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References

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Cardiovascular responses to agmatine, a clonidine-displacing substance, in anesthetized rat.
TLDR
The results suggest that earlier cardiovascular actions of partially purified CDS were either attributable to contaminating molecules and/or that CDS may be a family of molecules.
Central cardiovascular effects of alpha adrenergic drugs: differences between catecholamines and imidazolines.
TLDR
The results suggest that alpha-2 selective catecholamines are not active in the nucleus reticularis lateralis region, whereas imidazolines induce a hypotensive effect whatever their affinity for one subtype of alpha adrenoceptors.
Central Cardiovascular Effects of a Noncatecholamine Endogenous Ligand for Clonidine Receptors
TLDR
It is concluded that CDS is an endogenous non‐catecholamine ligand for receptors involved in the hypotensive effect of clonidine and is a candidate as a neuromodulator or a neurotransmitterinvolved in the blood pressure regulation at least in the NRL region.
Role of imidazoline receptors in the cardiovascular actions of moxonidine, rilmenidine and clonidine in conscious rabbits.
TLDR
A higher selectivity of the second generation agents moxonidine and rilmenidine for I1-IR over alpha 2 adrenoceptors, compared with the first generation agent clonidine appears to be necessary for this effect to be manifested in their hypotensive actions.
L 4 ‐ IMPORTANCE OF IMIDAZOLINE RECEPTORS IN THE CARDIOVASCULAR RESPONSES TO CLONIDINE AND RILMENIDINE IN CONSCIOUS RABBITS
The present paper summarizes our studies concerning the involvement of imidazoline and α2‐adrenoceptors in the cardiovascular actions of centrally acting drugs rilmenidine, clonidine and methyldopa.
Comparison of the properties of agmatine and endogenous clonidine-displacing substance at imidazoline and alpha-2 adrenergic receptors.
TLDR
The results do not rule out agmatine as an I1 transmitter but suggest that other I-receptor ligands might exist within endogenous CDS.
Evidence for the involvement of imidazoline receptors in the central hypotensive effect of rilmenidine in the rabbit
TLDR
Rilmenidine exhibited in the rabbit a central hypotensive effect which originated in the same area as where clonidine acts, and specific imidazoline‐preferring receptors appear to be involved in this hypotensiveEffect.
Importance of Imidazoline Receptors in the Cardiovascular Actions of Centrally Acting Antihypertensive Agents fn1
  • G. Head
  • Biology, Chemistry
    Annals of the New York Academy of Sciences
  • 1995
TLDR
It is found that the hypotensive effects of rilmenidine and moxonidine at moderate intracisternal doses were more readily reversed by the imidazoline antagonists than by 2-methoxy-idazoxan, indicating that IR were largely responsible for their hypotensive actions.
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