Relations between acetylcholine release and electrophysiological characteristics of theta rhythm: A microdialysis study in the urethane-anesthetized rat hippocampus

doi:10.1016/S0361-9230(96)00200-6

Brain Research Bulletin

Volume 42, Issue 2, 1997, Pages 141-146

https://doi.org/10.1016/S0361-9230(96)00200-6 Get rights and content

Abstract

In urethane-anesthetized rats, recording electrodes were implanted in the left dorsal hippocampus and a dialysis probe was placed in the contralateral dorsal or ventral hippocampus. Samples of extracellular acetylcholine (ACh) levels were assessed at 10-min intervals over a period of 30 min using microdialysis with high-performance liquid chromatography with electrochemical detection. EEG was recorded during the same period and amplitude, frequency, and duration of theta rhythm were calculated for each of the three 10-min intervals. Data were analyzed using the two-tailed Spearman rank-order correlation test. A positive and high rank correlation coefficient (rho = 0.90, p < 0.01, n = 8) was seen between the average ACh cutflow in the dorsal hippocampus and the average theta amplitude, both being calculated for the entire collection period. A lower but statistically significant positive correlation (rho = 0.59, p < 0.01) between dorsal hippocampus ACh output and theta amplitude was also found when the couples of values collected for the 30-min period were pooled (n = 20). In contrast, frequency and duration of theta were not significantly correlated with dorsal hippocampus ACh release. Also, no statistically significant correlation (p > 0.05) was found between ACh output in the ventral hippocampus and theta parameters. Because changes in hippocampal ACh outflow are believed to be the reflection of changes in number and/or level of activity of cholinergic afferents to the dorsal hippocampus, our present findings support the view that, at least in the dorsal hippocampus of the urethane-anesthetized rat, the septohippocampal cholinergic projection regulates the theta amplitude but not frequency. Finally, the possibility that ACh outflow increase and tonic release in the hippocampus is not a sufficient condition to induce and maintain theta in the urethane-anesthetized rat is discussed.

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ArticleRelations between acetylcholine release and electrophysiological characteristics of theta rhythm: A microdialysis study in the urethane-anesthetized rat hippocampus

Abstract

Brain Res.

Prog. Neurobiol.

Brain Res.

Brain Res.

Brain Res.

Neuropharmacology

Brain Res.

Brain Res.

Exp. Neurol.

Neuroscience

Physiol. Behav.

Brain Res.

Brain Res.

Brain Res.

Trends Neurosci.

Article
Relations between acetylcholine release and electrophysiological characteristics of theta rhythm: A microdialysis study in the urethane-anesthetized rat hippocampus