Electrophysiological recordings were used to investigate the role of the local synthesis of 17β-estradiol (E2) and 5α-dihydrotestosterone (DHT) on synaptic long-term effects induced in the hippocampal CA1 region of male rat slices. Long-term depression (LTD) and long-term potentiation (LTP), induced by different stimulation patterns, were examined under the block of the DHT synthesis by finasteride, and the E2 synthesis by letrozole. We used low frequency stimulation (LFS) for LTD, high frequency stimulation (HFS) for LTP, and intermediate patterns differing in duration or frequency. We found that finasteride reverted the LFS-LTD into LTP and enhanced LTP induced by intermediate and high frequency stimulations. These effects were abolished by exogenous DHT at concentration higher than the basal one, suggesting a stimulus dependent increase of DHT availability. No effect on the synaptic responses was observed giving DHT alone. Moreover, we found that the inhibition of E2 synthesis influenced the HFS-LTP by reducing its amplitude, and the exogenous E2 either enhanced HFS-LTP or reverted the LFS-LTD into LTP. The equivalence of the E2 concentration for rescuing the full HFS-LTP under letrozole and reverting the LFS-LTD into LTP suggests an enhancement of the endogenous E2 availability that is specifically driven by the HFS. No effect of finasteride or letrozole was observed on the responses to stimuli that did not induce either LTD or LTP. This study provides evidence that the E2 and DHT availability combined with specific stimulation patterns is determinant for the sign and amplitude of the long-term effects. This article is protected by copyright. All rights reserved.

Different synaptic stimulation patterns influence the local androgenic and estrogenic neurosteroid availability triggering hippocampal synaptic plasticity in the male rat

DI MAURO, MICHELA;
2016

Abstract

Electrophysiological recordings were used to investigate the role of the local synthesis of 17β-estradiol (E2) and 5α-dihydrotestosterone (DHT) on synaptic long-term effects induced in the hippocampal CA1 region of male rat slices. Long-term depression (LTD) and long-term potentiation (LTP), induced by different stimulation patterns, were examined under the block of the DHT synthesis by finasteride, and the E2 synthesis by letrozole. We used low frequency stimulation (LFS) for LTD, high frequency stimulation (HFS) for LTP, and intermediate patterns differing in duration or frequency. We found that finasteride reverted the LFS-LTD into LTP and enhanced LTP induced by intermediate and high frequency stimulations. These effects were abolished by exogenous DHT at concentration higher than the basal one, suggesting a stimulus dependent increase of DHT availability. No effect on the synaptic responses was observed giving DHT alone. Moreover, we found that the inhibition of E2 synthesis influenced the HFS-LTP by reducing its amplitude, and the exogenous E2 either enhanced HFS-LTP or reverted the LFS-LTD into LTP. The equivalence of the E2 concentration for rescuing the full HFS-LTP under letrozole and reverting the LFS-LTD into LTP suggests an enhancement of the endogenous E2 availability that is specifically driven by the HFS. No effect of finasteride or letrozole was observed on the responses to stimuli that did not induce either LTD or LTP. This study provides evidence that the E2 and DHT availability combined with specific stimulation patterns is determinant for the sign and amplitude of the long-term effects. This article is protected by copyright. All rights reserved.
17β-estradiol; 5α-dihydrotestosterone; hippocampus; long-term depression; long-term potentiation
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/20.500.11769/252256
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