PubMed Health⌕ Search

Biomedical subjects

B Hamon

Publications and source records attributed to B Hamon.

25 records · Page 2Linked to original sources
PubMed1984

GABA and baclofen reduce changes in extracellular free calcium in area CA1 of rat hippocampal slices.

Reductions in extracellular free Ca2+-concentration [( Ca2+]o) result from neuronal activation and can be induced by repetitive electrical stimulation or by application of excitatory amino acids. They reflect Ca2+-movements along its electrochemical gradient into pre- and postsynaptic elements. Amino acid-induced reductions in [Ca2+]o are predominantly caused by postsynaptic Ca2+ entry. Under conditions of blocked chemical synaptic transmission, a presynaptic component of extracellular Ca2+ loss becomes apparent during stimulation of the Schaffer collateral/commissural fibers system in stratum radiatum/moleculare. GABA, both iontophoretically and bath applied, always reduces pre- and postsynaptic components of [Ca2+]o changes. Baclofen regularly affects postsynaptic Ca2+ entry and has frequently also a suppressant action on presynaptic Ca2+ entry in area CA1.

Animals↗
PubMed1983

Effect of striatal stimulation on cellular activities of medial thalamic neurons studied in rats.

Medial thalamic cells responded to stimulation of the striatum in either lightly anaesthetized or chronically implanted awake rats. Orthodromic and antidromic short-latency excitatory responses were associated with a pause in spontaneous activity followed by bursting activity. The thalamic distribution of the different types of response is given; the main nuclei involved were parafascicularis, centrum medianum, centralis lateralis, habenula and lateralis posterior. When observed with intracellular electrodes the pause in spontaneous activity was accompanied by a long hyperpolarisation. The possibility that this effect could be due either to inhibition or to disfacilitation is examined. Electrophysiological evidence is given to show that a direct striatothalamic pathway does not exist. Different relayed pathways which could be responsible for the observed responses are proposed and their possible role is discussed on the basis of anatomical and electrophysiological findings obtained in cats and rats. A role for a pathway making a cortical detour is suggested.

Animals↗
PubMed1980

Pharmacological blockade of the globus palidus-induced inhibitory response of subthalamic cells in the rat.

The aim of the present study was to investigate, with extracellular recording and microiontophoretic techniques, the possibility that gamma-aminobutyric acid (GABA) is the transmitter substance in the pallido-subthalamic (GP-STN) pathway. Experiments were carried out in 94 rats, anesthetized with ketamine. Among the 236 recorded STN neurons, 85 were inhibited by GP stimulation. This inhibition lasted 10--20 msec (mean duration +/- S.E.M. 13.45 +/- 0.5 msec). Control stimulations located either in the internal GP or in the striatum never elicited the same type of response as they did in the STN. STN neurons were inhibited by microiontophoretically applied GABA or muscimol. Iontophoretically applied bicuculline or picrotoxin reversibly blocked the GP-evoked inhibition at doses which blocked the GABA inhibitory responses but not those produced by glycine. The results are consistent with the hypothesis that GABA is the transmitter releasted by the inhibitory pallido-subthalamic pathway, and are in agreement with recent biochemical data. Nevertheless, on a few cells, strychnine blocked the GP-induced inhibition. This results is discussed in relation to the specificty of GABA and glycine antagonists.

Animals↗
PubMedDate not supplied

[Apolipoprotein E and bleomycin hydrolase. Polymorphisms: association with neurodegenerative diseases].

Several studies indicate a possible association between different genes and chronic neurodegenerative diseases including Alzheimer's disease (DTA). To further investigate, we have analyzed association between the apolipoprotein E (apo E) and bleomycin hydrolase (BH) polymorphisms and three groups of elderly patients: control subjects (T) (n = 68), late-onset sporadic DTA patients (DTAst) (n = 65) and other non vascular neurodegerative diseases (MNDA) (n = 52). Apo E-epsilon4 and BH-G alleles frequencies (%) are: 8.2 (T), 31.5 (DTAst), 16.4 (MNDA) and 41.4 (T), 35.6 (DTAst). No association has been observed between carrying the G allele and DTA in epsilon4 negative subjects but, our data have confirmed the earlier reports: carrying the epsilon4 allele is a dose-dependent risk factor for the DTAst (OR: 6.0, IC 95 %: 2.6-13.7) and decrease the age of symptom onset (p < 0.005). They have also suggested that apo E genotyping may be of interest to perform differential diagnosis of neurodegenerative diseases in elderly subjects.

Aged↗
PubMedDate not supplied

[Does the placebo effect exist in newborn infants?].

Although comparison with a placebo is necessary to demonstrate the "true" effect of a drug, neonatologists are usually reluctant to use a placebo. The reason given is the lack of placebo effect in neonates. We studied heart and respiration rates and behaviour in normal neonates during heelstick for diagnosis of phenylketonuria. In this open randomized study we compared no treatment with an "analgesic" treatment consisting of water and sucrose. There was no difference in heart and respiration rates and behaviour between the two groups. These results do not demonstrate a "suggested" placebo effect and can in part be explained by the model and tools used to measure pain. The results do not support the non-use of placebo in drug evaluation trials in children.

Female↗