Modulation of low calcium induced field bursts in the hippocampus by monoamines and cholinomimetics

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Abstract
The influence of monoamine transmitter candidates, acetylcholine and related substances on rhythmic depolarization shifts (field bursts) in the CA1 area of hippocampal slices from rats in low calcium (0.2 mmol·l−1) high magnesium (4 mmol·l−1) was investigated. Acetylcholine (ACh), histamine (HA) and H2-agonists, noradrenaline (NA) and beta-agonists at nano- to micromolar concentrations as well as dopamine (DA) and 8-bromo-cyclic AMP at 100 μmol·l−1 accelerated the field bursts. H2-antagonists blocked HA actions, beta-antagonists blocked NA actions selectively; muscarinic antagonists blocked ACh, HA and NA actions. H1-agonists, serotonin, dopamine and adenosine slowed the field bursts at micromolar concentrations. These effects parallel the action of the tested substances on afterhyperpolarizations in CA 1 pyramidal cells. High sensitivity and specificity make this response of the field bursts an excellent model to study postsynaptic transmitter actions in the central nervous system.