Molecular Human Reproduction, Vol 4, 769-773, Copyright © 1998 by Oxford University Press
MN Ritta, JC Calamera and DE Bas
Gamma-aminobutyric acid (GABA) concentrations in seminal plasma and washed
spermatozoa from normal donors were assessed by a sensitive radioreceptor
assay, and were detectable in both fractions. Specific binding of
[3H]-muscimol was shown to be dependent on protein concentration,
temperature and incubation time. [3H]-muscimol specific binding to human
sperm membranes was significantly inhibited by the GABA type A receptor
(GABA(A)) antagonist, bicuculline, and by the GABA(A) agonists, muscimol
and isoguvacine, but not by the GABA type B receptor (GABA(B)) agonist
baclofen. Scatchard analysis of [3H]- muscimol binding yielded a linear
plot consistent with a single population of binding sites with a
dissociation constant in the low nanomolar range. Incubation with GABA at a
high micromolar concentration for 3 h under capacitating conditions
resulted in an increase in the percentage of spermatozoa showing
hyperactivated motility as assessed by computerized motility analyser.
However, low micromolar concentrations of the GABA(A) agonist, muscimol,
were sufficient to significantly increase sperm hyperactivity. These
results suggest that the effect of GABA on human sperm motility might be
mediated through a specific GABA(A) receptor.
JOURNAL ARTICLE
Occurrence of GABA and GABA receptors in human spermatozoa
Instituto de Biologia y Medicina Experimental, Buenos Aires, Argentina.
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