Dentate Gyrus Of Hippocampal Slices Research Articles

Noradrenaline blocks potassium conductance in rat dentate granule cells in vitro

The actions of noradrenaline and the β-adrenergic agonist, isoproterenol, were studied on the dentate gyrus in hippocampal slices from rats using extra- and intracellular recording. These agents facilitated field EPSPs (excitatory postsynaptic potentials) and population spikes evoked by perforant path stimulation. Intracellular recording revealed an attenuation of the long lasting afterhyperpolarization (AHP) and the accommodation of cell discharge in response to depolarizing current injection. It is suggested that β-receptor activation blocks a calcium-dependent potassium current.

Blockade of norepinephrine-induced long-lasting potentiation in the hippocampal dentate gyrus by an inhibitor of protein synthesis

The mechanism of action of norepinephrine (NE)-induced potentiation of the population spike in the dentate gyrus of hippocampal slices was examined and compared with NE effects in field CA1. NE-induced potentiation was confined to the dentate gyrus, where slices perfused for 30 min with concentrations of NE as low as 5 μM exhibited potentiation of the perforant path evoked population spike. Potentiation began within 15 min, and lasted many hours after NE was washed out. Experiments where slices were pre-incubated with the protein synthesis inhibitor emetine indicated that there are two distinct phases to NE-induced potentiation. The initial short-term NE-induced potentiation (NEP) seen during NE application was not affected by a 30 min pre-incubation with emetine, whereas the long-lasting potentiation (NELLP) which persists after NE washout was completely blocked by emetine at a concentration which we have previously shown to be effective in blocking hippocampal long-term potentiation (LTP). Additional experiments indicated that both phases of NE-induced potentiation were completely blocked by the β-antagonist propranolol and theβ 1-antagonist metoprolol. Furthermore, pre-incubation of slices with the direct-acting adenylate cyclase stimulant forskolin shifted the dose-response curves for both phases of NE-induced potentiation to the left. These results suggest that NE-induced potentiation is probably mediated byβ 1-receptor stimulation of adenylase cyclase. We have previously shown an importance forβ 1-receptor stimulation of adenylate cyclase in the production of LTP in the dentate. Thus, these results demonstrate a number of similarities between hippocampal LTP and NELLP in the dentate gyrus.

Large long-lasting potentiation in the dentate gyrus in vitro during blockade of inhibition

The generation of long-lasting synaptic potentiation was studied in the dentate gyrus of hippocampal slices before and after blockade of inhibition by application of GABA antagonists. Field potential analysis showed that inhibition in the dentate gyrus is to a large extent dendritically located. During blockade of inhibition, induction of long-lasting potentiation was facilitated, together with a large increase in the maximal potentiation that could be produced. It is suggested that the enhanced production of long-lasting potentiation in inhibition-free slices is related to an increased postsynaptic in granule cell dendrites.

Acidic amino acid antagonists of lateral perforant path synaptic transmission: agonist—antagonist interactions in the dentate gyrus

Acidic amino acid antagonists were tested for their ability to block depolarizations produced by excitatory amino acids in the outer molecular layer of the dentate gyrus in hippocampal slices. 2-Amino-4-phosphonobutyraic (APB) and serine-O-phosphate (SOP), potent synaptic blockers of the lateral perforant path input to this system, are moderately selective antagonists of kainate and N-methyl- dl-aspartate depolarizations, but not depolarization produced by l-glutamate, quisqualate, or serine-O-sulfate, N-Methyl- dl-aspartate responses were potently blocked by 2-amino-5-phosphonovalerate, but this antagonist is less potent than APE or SOP against the synaptic response.

Penicillin-induced interictal discharges from the cat hippocampus. I. Characteristics and topographical features.

Penicillin-induced interictal discharges from the cat hippocampus. I. Characteristics and topographical features.