Electrophysiological Analysis of Effects of Exogenous and Endogenous Adenosine in Hippocampal Slices

Little doubt remains that adenosine serves a modulatory role in the nervous system (Sattin and Rail, 1970; Shimizu and Daly, 1970; Fredholm and Hedqvist, 1980; Phillis and Wu, 1981; Stone, 1981; Daly et al., 1984; Dunwiddie, 1985). While electrophysiologically active concentrations of adenosine have been found in the extracellular fluid, the source and control of the levels of this active adenosine are unclear. There are indications that adenosine is released (or coreleased) from synaptic endings, fulfilling a typical transmitter role (Burnstock, 1975, 1981; Nagy et al., 1986). A synaptic hyperpolarization in autonomic neurons has been identified as an adenosine-mediated potential (Akasu et…

Abstract of the 68th Meeting (Spring Meeting) 6–9 March 1990, Heidelberg

Long-Term Potentiation in the Recurrent Inhibitory Circuit of the Dentate Gyrus

The question of whether long-term potentiation occurs in the inhibitory circuits of the hippocampus remains controversial. Buszaki and Eidelberg (1982), recording extracellularly from putative interneurones (basket cells) in the dentate gyrus and area CAl of the anaesthetized rat, found a prolonged increase in probability of cell firing to afferent stimulation after high-frequency stimulation of Schaffer-commissural fibres, and concluded that LTP occurs at excitatory feedforward synapses onto interneurones. Similarly, Kairis et al (1987) have presented field potential evidence for LTP in feedforward synapses onto inhibitory neurones in the dentate gyrus of the anaesthetized rat. In the hipp…

Special Features of the Hippocampal Formation with Respect to Seizure Conditions

The hippocampus has long been known as a region particularly prone to epileptiform discharges (Kandel et al. 1961). Connections and physiology of this archaic cortical structure are relatively well charac-terized and a wealth of information on features favoring exaggerated neuronal activity has emerged in recent years. The lamellar organization of the hippo-campus (Andersen et al. 1971) may be one of these features; it certainly has facilitated their investigation. Tissue slices cut along the lamellae, perpendicular to the axis of the structure, contain a relatively undisturbed chain of neurons which can be rigorously investigated in vitro. The results from such experiments have allowed mod…