Effects of [italic]In Vivo[/italic] Testosterone and Estradiol Administration on Electrophysiological Responses of Hippocampal Slices.
Abstract number :
2.076
Submission category :
Year :
2001
Submission ID :
2994
Source :
www.aesnet.org
Presentation date :
12/1/2001 12:00:00 AM
Published date :
Dec 1, 2001, 06:00 AM
Authors :
M.D. Smith, Ph.D., Pharmacology & Physiology, University of South Carolina School of Medicine, Columbia, SC; L.S. Jones, Ph.D., Pharmacology & Physiology, University of South Carolina School of Medicine, Columbia, SC; M.A. Wilson, Ph.D., Pharmacology & Ph
RATIONALE: [italic]In vivo[/italic] fluctuations in gonadal hormones modulate both physiological and pathological hippocampal processes. Our initial experiments comparing CA1 responses in slices from intact male and female rats and gonadectomized male (ORCH) and female (OVX) rats demonstrated sex differences in excitatory postsynaptic potential (EPSP) amplitudes, population spike (PS) amplitudes, and spontaneous burst (SB) rates (Male[gt]Female). In addition, [italic]in vitro[/italic] application of testosterone to slices from ORCH and OVX rats significantly increased EPSP and PS amplitudes and SB rates. To further clarify the nature of the hormonal responses observed and to assess hormonal influences on excitability [italic]in vivo[/italic], extracellular CA1 field responses were compared in slices from gonadectomized male and female rats injected subcutaneously with gonadal steroids.
METHODS: OVX rats were injected with oil, 17[beta]-estradiol benzoate (10[mu]g EB s.c. in oil), or EB+progesterone (0.5 mg P s.c. in oil). ORCH rats were injected with oil or testosterone proprionate (0.1mg TP s.c. in oil). EB and TP injections were given 48 and 24 hours before testing, whereas P was injected 4 hours before testing.
RESULTS: TP-treated ORCH rats had significantly increased EPSP and PS amplitudes versus ORCH males. The SB rate of ORCH rats (1.5[plusminus]0.8 bursts/min) was not significantly increased by TP (2.9[plusminus]1.6 bursts/min). Although EB injection slightly increased EPSP (1.2[plusminus]0.2 mV versus 1.8[plusminus]0.2 mV) and PS (2.2[plusminus]0.3 mV versus 3.5[plusminus]0.5 mV) amplitudes compared with OVX rats, these differences failed to attain statistical significance.
CONCLUSIONS: These results support earlier findings suggesting excitatory influences of testosterone in the hippocampus and further demonstrate that gonadal hormones modulate hippocampal excitability. Current experiments are examining hormonal effects on bicuculline-induced seizures.
Support: KO2DA00249 to MAW & EFA Predoctoral Fellowship to MDS