Abstract
Evoked striatal field potentials are seldom used to study corticostriatal communication in vivo because little is known about their origin and significance. Here we show that striatal field responses evoked by stimulating the prelimbic cortex in mice are reduced by more than 90% after infusing the AMPA receptor antagonist CNQX close to the recording electrode. Moreover, the amplitude of local field responses and dPSPs recorded in striatal medium spiny neurons increase in parallel with increasing stimulating current intensity. Finally, the evoked striatal fields show several of the basic known properties of corticostriatal transmission, including paired pulse facilitation and topographical organization. As a case study, we characterized the effect of local GABAA receptor blockade on striatal field and multiunitary action potential responses to prelimbic cortex stimulation. Striatal activity was recorded through a 24 channel silicon probe at about 600 µm from a microdialysis probe. Intrastriatal administration of the GABAA receptor antagonist bicuculline increased by 65±7% the duration of the evoked field responses. Moreover, the associated action potential responses were markedly enhanced during bicuculline infusion. Bicuculline enhancement took place at all the striatal sites that showed a response to cortical stimulation before drug infusion, but sites showing no field response before bicuculline remained unresponsive during GABAA receptor blockade. Thus, the data demonstrate that fast inhibitory connections exert a marked temporal regulation of input-output transformations within spatially delimited striatal networks responding to a cortical input. Overall, we propose that evoked striatal fields may be a useful tool to study corticostriatal synaptic connectivity in relation to behavior.
Highlights
Synaptic transmission and plasticity are customarily studied in brain slices
After baseline (ACSF) recordings, we studied the effect of the competitive glutamate AMPA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, Sigma) at 100 or 200 mM or the competitive GABAA receptor antagonist bicuculline at 100 mM
In order to unequivocally determine whether striatal evoked field potentials are synaptically originated, we studied the effect of intrastriatal microinfusion of the AMPA receptor antagonist CNQX by means of reverse microdialysis
Summary
Recent studies tried to fill the gap between findings in brain slices and behavior by using evoked local field responses as readout of synaptic transmission in vivo. In the hippocampus it has been possible to study changes in evoked local field responses in parallel with learning as well as interactions between changes in synaptic efficacy and learning in vivo [1,2]. Using evoked local field potentials as a readout of corticostriatal synaptic transmission proved to be more difficult, because of concerns that they could be contaminated through volume conduction from neighboring structures. Concerning local inhibition, slice physiology studies have demonstrated that collateral inhibition and GABAergic interneurons both have synaptic influences on the medium spiny projection neurons (MSNs) of the striatum [10,11,12,13]. In vivo studies have demonstrated an influence of local GABAergic networks on single MSNs [14,15], little is known about the temporal and spatial effects of GABAergic regulation at the network level
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
