Emergence of preconfigured and plastic time-compressed sequences in early postnatal development

When and how hippocampal neuronal ensembles first organize to support encoding and consolidation of memory episodes, a critical cognitive function of the brain, are unknown. We recorded electrophysiological activity from large ensembles of hippocampal neurons starting on the first day after eye opening as naïve rats navigated linear environments and slept. We found a gradual age-dependent, navigational experience-independent assembly of preconfigured trajectory-like sequences from persistent, location-depicting ensembles during postnatal week 3. Adult-like compressed binding of adjacent locations into trajectories during navigation and their navigational experience-dependent replay during sleep emerged in concert from spontaneous preconfigured sequences only during early postnatal week 4. Our findings reveal ethologically relevant distinct phases in the development of hippocampal preconfigured and experience-dependent sequential patterns thought to be important for episodic memory formation.

Interactions between hippocampus and medial septum during sharp waves and theta oscillation in the behaving rat

The medial septal region and the hippocampus are connected reciprocally via GABAergic neurons, but the physiological role of this loop is still not well understood. In an attempt to reveal the physiological effects of the hippocamposeptal GABAergic projection, we cross-correlated hippocampal sharp wave (SPW) ripples or theta activity and extracellular units recorded in the medial septum and diagonal band of Broca (MSDB) in freely moving rats. The majority of single MSDB cells (60%) were significantly suppressed during SPWs. Most cells inhibited during SPW (80%) fired rhythmically and phase-locked to the negative peak of the CA1 pyramidal layer theta waves. Because both SPW and the negative peak of local theta waves correspond to the maximum discharge probability of CA1 pyramidal cells and interneuron classes, the findings indicate that the activity of medial septal neurons can be negatively (during SPW) or positively (during theta waves) correlated with the activity of hippocampal interneurons. We hypothesize that the functional coupling between medial septal neurons and hippocampal interneurons varies in a state-dependent manner.

Inhibitory effect of disodium edetate on gastric secretion

Disodium edetate (ethylenediaminetetraacetic acid, disodium salt; disodic EDTA), 3 g, was given, via an intravenous normal saline drip of 30 min, to 25 patients in order to assess a benefit for anaesthesia practice. A significant reduction of both volume and acidity of the gastric secretion was found in all the 10 patients with peptic ulcer having received the drug. The peak of the change was 1 h after administration. In other 10 non-ulcer patients undergoing orthopaedic surgeries under epidural anaesthesia with lidocaine 2%, 5 mg kg-1, pH of the gastric juice unanimously rose, from 2.24 +/- 0.28 to 4.10 +/- 0.21 1 h after EDTA with a P derived from paired difference analysis of less than 0.001. A similar group of patients receiving only normal saline showed no important changes in pH (from 2.37 +/- 0.24 to 2.34 +/- 0.19). The pH of the fundic surface, measured directly under fiberscopic control in further 5 patients suffering from peptic ulcer, was found also to rise from 1.84 +/- 0.21 to 4.62 +/- 0.34 1 h after EDTA, P less than 0.001. Total and ionized calcium changed unsignificantly. Disodic EDTA in the dose and manner used in this study showed no clinical side-effects. The constant and obvious effect of inhibition of the gastric secretion as well as the dynamics of such an action recommend disodic EDTA to be tried in reducing the aspiration pneumonia morbidity.