Dopamine has bidirectional effects on synaptic responses to cortical inputs in layer II of the lateral entorhinal cortex.
Dopaminergic modulation of neuronal function has been extensively studied in the prefrontal cortex, but much less is known about its effects on glutamate-mediated synaptic transmission in the entorhinal cortex. The mesocortical dopamine system innervates the superficial layers of the lateral entorhinal cortex and may therefore modulate sensory inputs to this area. In awake rats, systemic administration of the dopamine reuptake inhibitor GBR12909 (10 mg/kg, ip) enhanced extracellular dopamine levels in the entorhinal cortex and significantly facilitated field excitatory postsynaptic potentials (fEPSPs) in layer II evoked by piriform cortex stimulation. An analysis of the receptor subtypes involved in the facilitation of evoked fEPSPs was conducted using horizontal slices of lateral entorhinal cortex in vitro. The effects of 15-min bath application of dopamine on synaptic responses were bidirectional and concentration dependent. Synaptic responses were enhanced by 10 microM dopamine and suppressed by concentrations of 50 and 100 microM. The D(1)-receptor antagonist SCH23390 (50 microM) blocked the significant facilitation of synaptic responses induced by 10 microM dopamine and the D(2)-receptor antagonist sulpiride (50 microM) prevented the suppression of fEPSPs observed with higher concentrations of dopamine. We propose here that dopamine release in the lateral entorhinal cortex, acting through D(1) receptors, can lead to an enhancement of the salience of sensory representations carried to this region from adjacent sensory cortices.
Caruana
Douglas A
DA
Center for Studies in Behavioral Neurobiology, Department of Psychology, Concordia University, 7141 Sherbrooke Street W., Rm. SP-244, Montreal, Quebec, Canada H4B 1R6.
Sorge
Robert E
RE
Stewart
Jane
J
Chapman
C Andrew
CA
D000818:Animals; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D002851:Chromatography, High Pressure Liquid; D004298:Dopamine / Q000494:pharmacology*; D018492:Dopamine Antagonists / Q000494:pharmacology; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D018728:Entorhinal Cortex / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D018698:Glutamic Acid / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D017551:Microdialysis; D009434:Neural Pathways / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D010879:Piperazines / Q000494:pharmacology; D051381:Rats; D020318:Rats, Long-Evans; D011954:Receptors, Dopamine / Q000187:drug effects; D013569:Synapses / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects
D018492:Dopamine Antagonists; D018765:Dopamine Uptake Inhibitors; D010879:Piperazines; D011954:Receptors, Dopamine; D018698:Glutamic Acid; C043425:vanoxerine; D004298:Dopamine