Evidence for prejunctional GABAB receptors mediating inhibition of ovarian follicle contraction induced by nerve stimulation

• The motor effects of gamma-aminobutyric acid (GABA) on the bovine ovarian follicle were studied in vitro using strips from follicle walls. Electrical field stimulation of nerves in the preparation, secured by tetrodotoxin blockade, caused a contraction that was almost totally abolished by phentolamine and only slightly affected by atropine. This mainly adrenergic neurogenic response was inhibited by GABA in a dose-dependent way. The GABAA-receptor antagonists, bicuculline and picrotoxin, did not affect the GABA action whereas the GABAB-receptor antagonist, homotaurine, significantly inhibited the GABA effect. The GABAA-receptor agonist, muscimol, did not affect the contractile response while the GABAB-receptor agonist, baclofen, imitated the action of GABA. On the other hand, GABA had no direct contractile or relaxing effect on the follicle strips nor did it interfere with the contractile response induced by noradrenaline or acetylcholine. The findings suggest that activation of prejunctional GABAB receptors inhibits transmitter release from mainly adrenergic nerves associated with the follicle, thereby affecting nerve-mediated tension in the follicle wall.

Subject headings

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Cell- och molekylärbiologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Cell and Molecular Biology (hsv//eng)

Keyword

Animals

Atropine/pharmacology

Baclofen/pharmacology

Bicuculline/pharmacology

Cattle

Electric Stimulation

Female

In Vitro Techniques

Muscle Contraction/drug effects

Muscle, Smooth/physiology

Ovarian Follicle/innervation

Phentolamine/pharmacology

Receptors, GABA-A/physiology

Synaptic Membranes/physiology

Taurine/analogs & derivatives

Tetrodotoxin/pharmacology

gamma-Aminobutyric Acid/pharmacology

Publication and Content Type

art (subject category)

ref (subject category)