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gamma-Amino butyric-N-acid sensitivity of mouse and human oocytes
Abstract:
gamma-Aminobutyric acid (GABA)-sensitivity was studied in mouse and human oocytes using electrophysiological techniques. Isolated mouse oocytes at the germinal vesicle (GV) or metaphase II stage, and human oocytes at the GV stage or following resumption of meiosis in culture, were sensitive to GABA. The transmitter usually hyperpolarized the membrane, with a concomitant decrease followed by an increase in membrane conductance, at threshold concentrations as low as 10(-10) M. GABA response was not evoked in Cl-free medium. Bicuculline (10(-5)-10(-6) M) reversibly blocked GABA (10(-9)-10(-4) M) responses. In contrast mouse fertilized eggs were insensitive to GABA at concentrations of 10(-5) M or lower. A possible biological role of the neurotransmitter GABA is discussed.
Insights
Mouse and human oocytes are sensitive to gamma-aminobutyric acid (GABA), a neurotransmitter that hyperpolarizes the cell membrane. Fertilized mouse eggs, however, showed no GABA sensitivity, suggesting a specific role in oocyte development.
Area of Science:
- Neuroscience
- Reproductive Biology
- Cell Physiology
Background:
- gamma-Aminobutyric acid (GABA) is a primary inhibitory neurotransmitter in the central nervous system.
- The presence and function of GABA receptors in oocytes are not well understood.
- Investigating neurotransmitter sensitivity in gametes is crucial for understanding reproductive processes.
Purpose of the Study:
- To investigate the sensitivity of mouse and human oocytes to GABA.
- To characterize the electrophysiological response of oocytes to GABA.
- To explore the potential role of GABA in oocyte maturation and fertilization.
Main Methods:
- Electrophysiological techniques were used to study GABA-sensitivity in isolated mouse and human oocytes.
- Oocytes were studied at various developmental stages, including germinal vesicle (GV) and metaphase II (MII).
- Responses were measured in the presence of GABA and its antagonist bicuculline, and in chloride-free medium.
Main Results:
- Both mouse and human oocytes, at GV and MII stages, exhibited sensitivity to GABA.
- GABA (as low as 10(-10) M) induced membrane hyperpolarization and changes in conductance.
- Responses were chloride-dependent and reversibly blocked by bicuculline.
- In contrast, fertilized mouse eggs were insensitive to GABA at concentrations up to 10(-5) M.
Conclusions:
- Oocytes possess functional GABA receptors mediating specific electrophysiological responses.
- GABA sensitivity appears to be stage-specific, potentially playing a role in oocyte development or regulation.
- The lack of sensitivity in fertilized eggs suggests GABA's role may be limited to the pre-fertilization stages.