Estrogen biphasically modifies hypothalamic GABAergic function concomitantly with negative and positive control of luteinizing hormone release - PubMed (original) (raw)

Stimulation of GABAB receptors inhibits POA neurons by activating a K+ conductance.a, Successively increasing doses of baclofen (1, 3, 10, and 30 μ

m

) hyperpolarized this POA neuron (resting V_m_ = −55 mV) at 8.5, 11, 16, and 18 mV, respectively. b, An I/_V_plot derived from a POA neuron just before (control; open circles) and near the end of the application of a maximal concentration of baclofen (100 μ

m

; filled circles) is shown. The reversal potential for the baclofen response was −94 mV, and a Δ_g_ of 0.67 nS between −60 and −80 mV and a Δ_g_ of 1.63 nS between −100 and −130 mV were also observed. c, Dose–response relationship from the cell shown in a is then generated in the presence of CGP 52,432 (1 μ

m

). Successively increasing doses of baclofen (10, 30, 100, and 300 μ

m

) elicited hyperpolarizations of 2.5, 4.5, 11, and 12.5 mV, respectively. d, Composite baclofen dose–response curves in the absence (open circles) and presence (filled circles) of CGP 52,432 (1 μ

m

) are shown. Cells were perfused with successively higher concentrations of baclofen (1, 3, 10, 30, 100, and 300 μ

m

; 4–7 min/dose; n = 2–10).Symbols represent means, and vertical lines are 2 SEMs of the baclofen-induced hyperpolarization normalized to the ΔVmax. Before CGP 52,432, the mean baclofen EC50 value was 2.3 ± 0.5 μ

m

, whereas in the presence of CGP 52,432, the EC50 was shifted to 33.0 ± 10.0 μ

m

. The estimated_K_ i for CGP 52,432 was 64.0 n

m

. BAC, Baclofen.