Application of caffeine reveals input frequency-dependent determination of signal-traveling routes between primary and secondary visual cortices in rats.
Upon entering the neocortex, neural signals are required to select which neocortical circuits to propagate through. The present study focused attention on use-dependent selection of signal-traveling routes. Rat brain slices including primary visual cortex (Oc1) and the medial part of the secondary visual cortex (Oc2M) were prepared. Electrical stimulation was delivered to white matter in Oc1 and spatiotemporal aspects of traveling signals were observed using optical recording methods under caffeine application. With an interstimulus interval (ISI) of 4-8s, signals traveled horizontally along deep layers from Oc1 to Oc2M, climbed within Oc2M, then returned along layer II/III from Oc2M to Oc1. Conversely, with an ISI of 40-64s, signals climbed within Oc1 and traveled horizontally along layer II/III from Oc1 to Oc2M in parallel with signals traveling along deep layers. Pharmacological experiments with antagonists for ionotropic glutamate receptors revealed that signal-traveling routes under higher-frequency stimulation were N-methyl-d-aspartate (NMDA) receptor activity-dependent, while those at the lower-frequency were non-NMDA receptor activity-dependent. These results suggest that neural circuits between Oc1 and Oc2M possess an input frequency-dependent gating system, in which signal-traveling routes might be affected by the relative balance of receptor activities between NMDA and non-NMDA receptors.
Department of Oral and Maxillofacial Surgery, Kanazawa Medical University, Uchinada-cho, Ishikawa 920-0293, Japan. hyoshimu@kanazawa-med.ac.jp
Hiroshi
H
Yoshimura
Tokio
T
Sugai
Miho
M
Honjo
Keiseki
K
Kaneyama
Natsuki
N
Segami
Nobuo
N
Kato
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000008:administration & dosage; D000818:Animals; D000831:Animals, Newborn; D001703:Biophysics / Q000379:methods; D001931:Brain Mapping; D002110:Caffeine / Q000494:pharmacology*; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D004558:Electric Stimulation / Q000379:methods; D005071:Evoked Potentials / Q000187:drug effects* / Q000502:physiology; D018691:Excitatory Amino Acid Antagonists / Q000008:administration & dosage; D066298:In Vitro Techniques; D007478:Iontophoresis / Q000379:methods; D009415:Nerve Net / Q000187:drug effects* / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D014793:Visual Cortex / Q000033:anatomy & histology*; D014795:Visual Pathways / Q000187:drug effects / Q000502:physiology
D000697:Central Nervous System Stimulants; D018691:Excitatory Amino Acid Antagonists; D002110:Caffeine; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D015763:2-Amino-5-phosphonovalerate