INVESTIGADORES
BERNABEU Ramon Oscar
libros
Título:
Muscarinic toxins from the verom of Elapid snakes.
Autor/es:
JERUSALINSKY, D., RASCOVSKY, S., KORNISIUK, E., BERNABEU, R. AND CERVEÑANSKY, C.
Editorial:
.Eds. F. Dajas and K. Tipton
Referencias:
Año: 1992 p. 162
Resumen:
<!--
/* Font Definitions */
@font-face
{font-family:"Book Antiqua";
panose-1:2 4 6 2 5 3 5 3 3 4;
mso-font-charset:0;
mso-generic-font-family:roman;
mso-font-pitch:variable;
mso-font-signature:647 0 0 0 159 0;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{mso-style-parent:"";
margin:0cm;
margin-bottom:.0001pt;
mso-pagination:widow-orphan;
font-size:12.0pt;
font-family:"Times New Roman";
mso-fareast-font-family:"Times New Roman";}
@page Section1
{size:595.3pt 841.9pt;
margin:70.85pt 3.0cm 70.85pt 3.0cm;
mso-header-margin:35.4pt;
mso-footer-margin:35.4pt;
mso-paper-source:0;}
div.Section1
{page:Section1;}
-->
Muscarinic toxins from the venom of Dendroaspis
snakes with agonist-like
actions. Toxicon 33,
389-397, 1995.-The venom of some Dendroaspis
snakes
contains small proteins (7500 mol. wt) that inhibit the
binding of radiolabelled
muscarinic antagonist to brain synaptomal membranes.
There were no peptides
described among muscarinic ligands until Adem et al.
(Biochim. biophys. Acta
968,
34&345, 1988) reported that
muscarinic toxins (MTxs), MTxl and 2 were
able to inhibit 3H-QNB binding to rat brain membranes.
Since MTxs inhibit
around half of specific binding of 3H-quinuclidinyl
benzilate (3H-QNB) and
3H-N-methyl-scopolamine ( 3H-NMS), which do not discriminate
between
subtypes of muscarinic receptors, it has been proposed
that MTxs might
selectively bind to some subtype. MTxl and 2 from Dendroaspis
angusticeps
almost completely inhibit the binding of 3H-pirenzepine
( 3H-PZ), a preferential
M, muscarinic receptor subtype ligand to cerebral
cortex synaptosomal membranes.
A much higher concentration was needed to inhibit
partially 3H-PZ
binding to atria1 muscarinic receptors. These results
support the hypothesis that
MTxl, and 2 may be M, selective muscarinic ligands.
Similar activities have
been found in Dendroaspis
polylepis and D.
viridis venoms, but with lower
affinities. The Ki obtained from inhibition curves of
the binding of 3H-PZ
showed that MTxl has higher affinity for the putative
Ml muscarinic receptor
subtype, followed by MTx2. DpMTx has lower affinity,
while DvMTx seems
to have the lowest affinity. All these peptides are
devoid of anticholinesterase
activity. Dendrotoxin and fasciculin from D.
angusticeps venom do not inhibit
the binding of muscarinic radioligands to cerebral
cortex membranes. The
injection of MTxs into dorsal hippocampus of rats
immediately after training
in an inhibitory avoidance task improves memory
consolidation, as does
oxotremorine. This improvement is antagonized by the
joint administration of
the muscarinic antagonist scopolamine. These results
suggest that MTxs behave
as a muscarinic agonist, at least in this case.
Therefore, the muscarinic toxins
from elapid snakes may be useful tools since they are
proteins that might be
selective muscarinic ligands, that seem to be agonists
in the case of MTxs from
D. angusticeps venom.