Effects of temperature increase on the propagation of presynaptic action potentials in the pathway between the Schaffer collaterals and hippocampal CA1 neurons.
Effects of temperature increase on the neuronal activity of hippocampal CA2-CA1 regions were examined by using optical and electrophysiological recording techniques. Stimulation of the Schaffer collaterals at the CA2 region evoked depolarizing optical signals that spread toward the CA1 region at 32 degrees C. The optical signal recorded by 49 pixels was characterized by fast and slow components that were closely related to presynaptic action potentials and excitatory postsynaptic responses, respectively. The optical signal was depressed by temperature increase to 38-40 degrees C. The temperature increase to 38 degrees C produced a hyperpolarization and a depression of the excitatory postsynaptic potential (EPSP) in single hippocampal CA1 pyramidal neurons. The depression of the neuronal activity induced by temperature increase was attenuated by application of glucose (22 mM) or pyruvate (22 mM). Adenosine (200 microM) did not block the presynaptic action potential but strongly depressed the excitatory postsynaptic response. 8-Cyclopentyl-1,3-dimethylxanthine (8-CPT) (10 microM), an antagonist for adenosine A(1) receptors, attenuated the depression of the excitatory postsynaptic response but not the inhibition of the presynaptic action potential at 38 degrees C. These results suggest that adenosine mediates the high-temperature-induced depression of the excitatory synaptic transmission but not that of action potential propagation in rat CA1 neurons.
Takeya
Mitsue
M
Health Sciences, Kurume University Graduate School of Medicine, Kurume University School of Medicine, Kurume 830-0011, Japan.
Hasuo
Hiroshi
H
Akasu
Takashi
T
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000241:Adenosine / Q000502:physiology; D000818:Animals; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D006358:Hot Temperature; D066298:In Vitro Techniques; D008297:Male; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D017729:Presynaptic Terminals / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013696:Temperature
D000241:Adenosine