In vivo temporal property of GABAergic neural transmission in collateral feed-forward inhibition system of hippocampal-prefrontal pathway.
Anatomical evidence suggests that rat CA1 hippocampal afferents collaterally innervate excitatory projecting pyramidal neurons and inhibitory interneurons, creating a disynaptic, feed-forward inhibition microcircuit in the medial prefrontal cortex (mPFC). We investigated the temporal relationship between the frequency of paired synaptic transmission and gamma-aminobutyric acid (GABA)ergic receptor-mediated modulation of the microcircuit in vivo under urethane anesthesia. Local perfusions of a GABAa antagonist (-)-bicuculline into the mPFC via microdialysis resulted in a statistically significant disinhibitory effect on intrinsic GABA action, increasing the first and second mPFC responses following hippocampal paired stimulation at interstimulus intervals of 100-200 ms, but not those at 25-50 ms. This (-)-bicuculline-induced disinhibition was compensated by the GABAa agonist muscimol, which itself did not attenuate the intrinsic oscillation of the local field potentials. The perfusion of a sub-minimal concentration of GABAb agonist (R)-baclofen slightly enhanced the synaptic transmission, regardless of the interstimulus interval. In addition to the tonic control by spontaneous fast-spiking GABAergic neurons, it is clear the sequential transmission of the hippocampal-mPFC pathway can phasically drive the collateral feed-forward inhibition system through activation of a GABAa receptor, bringing an active signal filter to the various types of impulse trains that enter the mPFC from the hippocampus in vivo.
Takita
Masatoshi
M
Cognition and Action Group, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8566, Japan. takita.m@aist.go.jp
Kuramochi
Masahito
M
Izaki
Yoshinori
Y
Ohtomi
Michiko
M
D000344:Afferent Pathways; D000704:Analysis of Variance; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation / Q000379:methods; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D018682:GABA Agents / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology*; D008297:Male; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D009474:Neurons / Q000145:classification / Q000502:physiology* / Q000528:radiation effects; D017397:Prefrontal Cortex / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D013997:Time Factors; D005680:gamma-Aminobutyric Acid / Q000378:metabolism* / Q000494:pharmacology
D018682:GABA Agents; D005680:gamma-Aminobutyric Acid