Biomedical subjects

M Serafin

Publications and source records attributed to M Serafin.

43 records · Page 3Linked to original sources

PubMed1991

Medial vestibular nucleus in the guinea-pig. II. Ionic basis of the intrinsic membrane properties in brainstem slices.

In the preceding paper, medial vestibular nuclei neurones (MVNn) were shown to belong to two main classes, A MVNn and B MVNn, depending on their membrane properties in brainstem slices. In the following study we attempted to confirm this segregation by studying some of the ionic conductances that these cells are endowed with. Type A MVNn demonstrated small high threshold calcium spikes that could be potentiated by barium, a 4-AP resistant A-like conductance and a calcium-dependent afterhyperpolarization. Type B MVNn, in contrast, had large high threshold calcium spikes and prolonged calcium-dependent plateau potentials. In addition, they had a calcium-dependent afterhyperpolarization as well as a subthreshold persistent sodium conductance. A subpopulation of B MVNn had also low threshold calcium spikes that gave them bursting properties. These data confirm the segregation of MVN neurones into two main classes and will be discussed with respect to the firing characteristics of vestibular neurones in vivo.

4-Aminopyridine↗

PubMed1990

Electrophysiology and lucifer yellow injection of nucleus gigantocellularis neurones in an isolated and perfused guinea pig brain in vitro.

Intracellular recordings from nucleus gigantocellularis (NGC) neurones were obtained in isolated and perfused whole brains of guinea pigs in vitro. A majority of cells (90%) were characterized by an action potential of short duration (0.3 ms) followed first by a fast and then by a slower afterhyperpolarization (AHP). Their firing pattern was mostly irregular. These cells were shown to have high threshold calcium spikes and plateau potentials. The other cell type represented only 10% of the recorded cells in the NGC. It was characterized by a wider (0.6 ms) action potential, a large single AHP, the presence of a transient rectification presumably due to an A-current and a rather regular resting discharge. Using Lucifer yellow injections in brainstem slices, both cell types were shown to correspond to gigantocellular neurones.

Action Potentials↗

PubMed1990

Opiates inhibit pedunculopontine neurones in guinea pig brainstem slices.

Intracellular recordings were obtained from pedunculopontine neurones in guinea-pig brainstem slices. These cells were characterized by a broad action potential, an A-like conductance and fired spontaneously in a regular manner. These neurones were inhibited by bath-application of both carbachol and serotonine at concentrations of 10(-4) M. Opioid peptides induced a dose-dependent hyperpolarization and a reduction in the spontaneous firing. These latter effects could be blocked by the opiate antagonist naloxone and were direct as they persisted in presence of tetrodotoxine or high magnesium/low calcium-containing salines. They were mediated by an opiate receptor of the mu type since they were obtained with the mu-preferring enkephalin analogues FK 33-824 and DAGO, but neither with the delta nor the kappa analogues such as DPLPE or U-50,488.

Animals↗

PubMed1990

Thalamic spindles in an isolated and perfused preparation in vitro.

Intracellular recordings were obtained from thalamic nuclei neurones in isolated and perfused whole brains of adult guinea pigs in vitro. Thalamic neurones presented the same basic membrane properties in this preparation as in slices. The majority of cells displayed, in addition, spontaneous spindle oscillations similar to those observed in the cat in vivo. This activity could be blocked by the cholinergic agonist carbachol perfused at 10(-4) M. Thalamic spindles could also be recorded in decorticated preparations, in which perfusion to the cerebral cortex was interrupted. Such preparations could be useful for studying in vitro the spindle generating mechanism in rodents as well as some aspects of brainstem/diencephalic interactions related to the control of sleep and arousal.

Animals↗

PubMed1990

Histamine excites pedunculopontine neurones in guinea pig brainstem slices.

Intracellular recordings were obtained from pedunculopontine tegmental nuclei neurones in guinea pig brainstem slices. These neurones were characterized by the presence of a slow regular firing (around 3 spikes/s), a broad action potential (more than 1 ms) and a transient rectification indicating the presence of an A current. Bath-application of histamine at 10(-4) or 10(-5) M induced a reversible increase in spontaneous firing. In presence of tetrodotoxin (1 microM), the effect of histamine was a reversible membrane depolarization. It was a direct effect as it persisted in presence of a low calcium/high magnesium solution. This excitatory action was presumably mediated by histamine H1 receptors as it could be blocked by the H1 receptor antagonist mepyramine but not by the H2 receptor antagonist cimetidine. A role in arousal is discussed.

Action Potentials↗

PubMed1990

Low threshold calcium spikes in medial vestibular nuclei neurones in vitro: a role in the generation of the vestibular nystagmus quick phase in vivo?

Intracellular recordings were obtained from medial vestibular nuclei neurones in guinea-pig brainstem slices. A subpopulation of neurones in this nucleus was found to have burst firing properties. Using ionic channel blockers the underlying mechanism was shown to be a low threshold calcium spike. It is speculated that this property could be implicated in the generation of the quick phase of the vestibular nystagmus in the behaving guinea-pig.

Action Potentials↗

PubMed1990

Design of a microprocessor-controlled thermoregulated chamber for perfusing in vitro mammalian brain preparations.

A system is described that allows to perfuse in vitro isolated mammalian brain preparations obtained from adult guinea-pigs. It consists of a microprocessor controlled thermoregulation unit, a perfusion line and a perfusion/recording chamber. The main features of the thermoregulation unit include the ability to maintain stable temperatures between 10 and 37 degrees C and to precisely control the time course of the temperature changes. Using this system, perfused tissue blocks can be kept viable for 8-10 h.

Animals↗