Effects of exogenous retinoic acid on forelimb and hind limb bud culture of rat in vitro

γ-aminobutyricacid (GABA), a major neurotransmitter in the central nervous system, also acts as a paracrine or autocrine signaling molecule in endocrine tissues such as the pancreatic islets, adenohypophysis, and testis. It has been demonstrated that metabolites of progesterone and corticosterone naturally act via the GABAA – membrane receptor and they have sedative–hypnotic, anxiolytic, anticonvulsant, muscle-relaxant and anesthetic drugs properties. Also the brain as a steroidogenic organ contributes to produce these steroids. The aim of this study was to find out the steroids participation on the GABA- related activities. An injection canula was inserted into lateral ventricle of the sham and experimental adult female rats by stereotaxic surgery. One week late, at proesterus day, diazepam (GABAA–receptor agonist) with doses of 250 and 500ng/rat, bicuculine (GABAA–receptor antagonist) with doses of 1.5 and 3 ng/rat, baclofen (GABAB –receptor agonist) with doses of 4.27 and 8.54 ng/rat and CGP35348 (GABAB –receptor antagonist) with doses of 3 and 5 µg/rat were intracerebroventriculary (ICV) injected to the experimental groups, while equal volume (2µl) of artificial CSF was injected to the sham operated group. Blood samples were collected thrice at 9 AM, 11 AM and 1PM. The serum progesterone level was determined using RIA method. Data were analyzed by one way ANOVA and Duncan's test at p<0.05 for the significant level. The results showed that GABAergic system activity via both GABAA and GABAB receptors has significantly changed the serum progesterone level. Comparing the results of this research with earlier studies, it is concluded that GABAergic system has a close relation with steroidogenesis and the steroids participate in GABA-related activities