The neuropeptide corticotropin releasing factor (CRF) is known to play a role in the stress response in the central nervous system. CRF is co-localized with noradrenaline (NE) and serotonin (5-HT), as well as with glutamate (Glu) and GABA in brain areas involved in the modulation of mood and behaviour (1). Electrophysiological and immunocytochemical studies have shown complex interactions between CRF, monoamines and amino acid transmitters (2, 3). Aim of the present study was to directly investigate the influence exerted by CRF on 5-HT and NE release, with an in vitro approach. Rat hippocampal slices (400 µm thick) were labelled with either [3H]-NE or [3H]-5-HT (0.1 µM) and superfused with Krebs solution, containing either 1 µM desipramine or 3 µM paroxetine. Electrical 1 Hz stimulation was applied for 2 min at the 45th (St1) and the 75th (St2) min of superfusion, and the St2/St1 ratio was calculated (4). CRF, 10-300 nM, added to the superfusion medium from the 75th min onward, concentration-dependently increased [3H]-NE efflux (Emax = 133±8% of the controls, P<0.05). The effect was prevented by the antagonist α-helical-CRF(9-41), 300 nM. To test the hypotesis that the observed effects were indirect, the influences of glutamate and GABA antagonists were challenged. In the presence of the NMDA antagonist MK 801, 10 µM, and of the AMPA/KA antagonist CNQX, 10 µM, the facilitation induced by 300 nM CRF on [3H]-NE efflux was not only prevented, but even reversed into inhibition (70±9%, P< 0.05 vs. controls and vs. CRF alone). The latter was cancelled by the GABA antagonist, bicuculline, 10 µM. Serotonin neurotransmission was modulated by CRF in an opposite way: the neuropeptide, 10-100 nM, inhibited in a concentration-dependent manner 5-HT efflux from electrically stimulated hippocampal slices (Emax = 49±6% of the controls, P<0.01). Both α-helical-CRF(9-41) and bicuculline prevented CRF effect, suggesting the involvement of GABA in the neuropeptide action. These findings, consistent with data obtained on prefrontal cortex and locus coeuruleus neurons (2, 3), suggest that CRF is able to modulate monoaminergic transmission in the hippocampus, and that this action involves aminoacidergic neurotransmission. 1) Carrasco G. A. and Van de Kar L. D.(2003) Eur. J. Pharmacol., 463:235-272. 2)Tan H., Zhong O. and Yan Z. (2004) J. Neurosci. 24: 5000-5008. 3) Valentino R. J. et al. (2001) Neuroscience 106: 375-384. 4) Siniscalchi A. et al. (2002) Br. J. Pharmacol. 136: 1178-1184.
EFFECTS OF CORTICOTROPIN RELEASING FACTOR ON MONOAMINE RELEASE IN RAT HIPPOCAMPAL SLICES.
CAVALLINI, Sabrina;BEANI, Lorenzo;BIANCHI, Clementina;SINISCALCHI, Anna
2005
Abstract
The neuropeptide corticotropin releasing factor (CRF) is known to play a role in the stress response in the central nervous system. CRF is co-localized with noradrenaline (NE) and serotonin (5-HT), as well as with glutamate (Glu) and GABA in brain areas involved in the modulation of mood and behaviour (1). Electrophysiological and immunocytochemical studies have shown complex interactions between CRF, monoamines and amino acid transmitters (2, 3). Aim of the present study was to directly investigate the influence exerted by CRF on 5-HT and NE release, with an in vitro approach. Rat hippocampal slices (400 µm thick) were labelled with either [3H]-NE or [3H]-5-HT (0.1 µM) and superfused with Krebs solution, containing either 1 µM desipramine or 3 µM paroxetine. Electrical 1 Hz stimulation was applied for 2 min at the 45th (St1) and the 75th (St2) min of superfusion, and the St2/St1 ratio was calculated (4). CRF, 10-300 nM, added to the superfusion medium from the 75th min onward, concentration-dependently increased [3H]-NE efflux (Emax = 133±8% of the controls, P<0.05). The effect was prevented by the antagonist α-helical-CRF(9-41), 300 nM. To test the hypotesis that the observed effects were indirect, the influences of glutamate and GABA antagonists were challenged. In the presence of the NMDA antagonist MK 801, 10 µM, and of the AMPA/KA antagonist CNQX, 10 µM, the facilitation induced by 300 nM CRF on [3H]-NE efflux was not only prevented, but even reversed into inhibition (70±9%, P< 0.05 vs. controls and vs. CRF alone). The latter was cancelled by the GABA antagonist, bicuculline, 10 µM. Serotonin neurotransmission was modulated by CRF in an opposite way: the neuropeptide, 10-100 nM, inhibited in a concentration-dependent manner 5-HT efflux from electrically stimulated hippocampal slices (Emax = 49±6% of the controls, P<0.01). Both α-helical-CRF(9-41) and bicuculline prevented CRF effect, suggesting the involvement of GABA in the neuropeptide action. These findings, consistent with data obtained on prefrontal cortex and locus coeuruleus neurons (2, 3), suggest that CRF is able to modulate monoaminergic transmission in the hippocampus, and that this action involves aminoacidergic neurotransmission. 1) Carrasco G. A. and Van de Kar L. D.(2003) Eur. J. Pharmacol., 463:235-272. 2)Tan H., Zhong O. and Yan Z. (2004) J. Neurosci. 24: 5000-5008. 3) Valentino R. J. et al. (2001) Neuroscience 106: 375-384. 4) Siniscalchi A. et al. (2002) Br. J. Pharmacol. 136: 1178-1184.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
