Quantitative relationship between post-tetanic biochemical and electrophysiological changes in rat hippocampal slices.

Slices of rat brain hippocampus were tetanized in the perforant path fibers. In individual slices long-term changes of the electrophysiological parameters were determined simultaneously with post hoc endogeneous phosphorylation of proteins in a lyzed crude mitochondrial/synaptosomal fraction. A quantitative relation between the electrophysiological parameters and the degree of phosphorylation of a 52K protein was found to follow a non-linear function.

Differential effects of enkephalin within hippocampal areas.

The synthetic opiate D-Alanine-methionine enkephalin (D-Ala) affects neuronal activity of the fascia dentata (FD). D-Ala causes a depression of the population spike evoked by stimulation of the perforant path, which is antagonized by naloxone. In so called "Tandem" experiments it was shown that D-Ala had opposite effects on the CA1 pyramidal and FD granule cells. It is likely that in the FD the site of action of D-Ala is at the afferent synapses.

Differential conduction velocities in perforant path fibres in guinea pig.

Conduction velocities (c.vs) of different hippocampal fibre groups have been measured in slices in vitro. In the mossy fibres, Schaffer collaterals and Str. oriens fibres the c.v. varied from 0.36-0.38 m/s; in the alveus c.v. was 1.20 m/s. In the perforant path (p.p.) two groups of c.vs were found: in the medial p.p. the mean (+/- s.e) c.v. was 0.32 +/- 0.02 m/s, whereas in the lateral p.p. it was 1.36 +/- 0.14 m/s.

An olfactory input to the hippocampus of the cat: field potential analysis.

Hippocampal responses to electrical stimulation of the prepyriform cortex in the cat were studied both in acute experiments under halothane anesthesia and in awake cats with chronically indwelling electrodes. Analysis of field potentials and unit activity indicated the extent to which different hippocampal subareas were activated, the laminar level at which the synaptic action took place and the dynamics of the evoked responses. It was found that: (1) the main generator of evoked responses in the hippocampus upon prepyriform cortex stimulation is localized in the fascia dentata and CA3 (CA1 pyramidal cells, and probably also subiculum cells, are activated but in a lesser degree); (2) the initial synaptic activity takes place at the most distal part of the dendrites of fascia dentata granuhat leads to a transient increase in the firing rate of the hippocampal units, which is often followed by a long-lasting decrease in firing rate. We conclude that the pathway from the prepyriform cortex via lateral entorhinal cortex to hippocampal neurons may enable olfactory inputs to effectively excite hippocampal neurons.

Haemodynamic changes in the cerebral circulation of the cat during occlusion of the middle cerebral artery.

In a group of 21 cats, the middle cerebral artery pressure (MCAP) was recorded by means of a catheter introduced into the artery at its origin, just distal to the occlusion. The effects of hypertension, hypercapnia, and hypocapnia were studied. In a group of five cats, both middle cerebral arteries (MCA) were catherized and the pressure was recorded simultaneously on both sides. In another group of five cats, O2 tension measurements were made with the aid of oxygen electrodes in the brain tissue, the occluded MCA, and the common carotid artery. Some of the results obtained in this study are compared with the results of a previous study where monkeys were used as experimental animals.