Human follicular fluid stimulates the sperm acrosome reaction by interacting with the gamma-aminobutyric acid receptors.
OBJECTIVE
To evaluate whether gamma-aminobutyric acid receptors are involved in human sperm acrosome reaction induced by the follicular fluid (FF).


METHODS
Random selection of normal sperm samples.


METHODS
Normal men in an university clinic of andrology.


METHODS
Men with normal sperm analysis parameters.


METHODS
None.


METHODS
Acrosome reaction on motile spermatozoa.


RESULTS
Follicular fluid stimulated the acrosome reaction dose-dependently. The effect of a maximally effective concentration of FF (30%, vol/vol) was significantly suppressed by bicuculline, a GABAA receptor antagonist, and saclofen, a GABAB receptor antagonist, added concomitantly. Each of the two antagonists used alone was devoid of effect. Because the GABAA receptor is linked to the chloride channel, we tested whether picrotoxin, a blocker of this channel, could modulate the effects of the FF. Picrotoxin alone did not have any effect on the acrosome reaction induced by the FF, whereas it had a significant suppressive effect if coincubated with saclofen. The acrosome reaction induced by the FF was also inhibited by picrotoxin plus verapamil, a calcium channel blocker, whereas verapamil alone had no significant effect. This suggested that both chloride and calcium ions mediated the acrosome reaction induced by the FF.


CONCLUSIONS
The simultaneous blockade of GABAA and GABAB receptors suppressed the acrosome reaction induced by the FF. This finding suggested that GABA receptors play a physiologic role in sperm activation and shed further light on the mechanism of FF action on human sperm acrosome reaction.
Section of Endocrinology, Andrology and Internal Medicine, Department of Biomedical Sciences, and Master School in Andrological and Human Reproduction Sciences, University of Catania, Catania, Italy.
Nunziatina
N
Burrello
Enzo
E
Vicari
Letizia
L
D'Amico
Annalisa
A
Satta
Rosario
R
D'Agata
Aldo E
AE
Calogero
D020101:Acrosome Reaction / Q000187:drug effects / Q000502:physiology*; D000704:Analysis of Variance; D001418:Baclofen / Q000031:analogs & derivatives* / Q000494:pharmacology; D001640:Bicuculline / Q000494:pharmacology; D005260:Female; D015571:Follicular Fluid / Q000502:physiology*; D018756:GABA Antagonists / Q000494:pharmacology; D058787:GABA-A Receptor Antagonists; D058788:GABA-B Receptor Antagonists; D006801:Humans; D008297:Male; D009994:Osmolar Concentration; D010852:Picrotoxin / Q000494:pharmacology; D011963:Receptors, GABA-A / Q000502:physiology*; D018080:Receptors, GABA-B / Q000502:physiology*; D013081:Sperm Motility; D013094:Spermatozoa / Q000502:physiology*
D001418:Baclofen; D001640:Bicuculline; D018756:GABA Antagonists; D058787:GABA-A Receptor Antagonists; D058788:GABA-B Receptor Antagonists; D010852:Picrotoxin; D011963:Receptors, GABA-A; D018080:Receptors, GABA-B; C080629:saclofen