Presynaptic GABA-A receptors prevent depression of nicotinic transmission in rabbit coeliac ganglion neurones.

We investigated the involvement of GABA-A receptors in the modulation of the nicotinic transmission of central origin in isolated rabbit coeliac ganglia. Our study was performed in vitro and the electrical activity of the ganglionic neurones was recorded using intracellular recording techniques. During iterative stimulation of the splanchnic nerves, the synaptic action potential probability decreased gradually, indicating a depression of the nicotinic activation. Pharmacological agents acting at GABA-A receptors modulated the action potential probability during the train of pulses. Muscimol (a GABA-A receptor agonist), diazepam (a benzodiazepine site agonist) and 1-[2-[[(diphenylmethylene)imino]oxy]ethyl]-1,2,5,6-tetrahydro-3-pyridinecarboxylic acid hydrochloride (a GABA uptake blocker) increased this probability. Conversely, gabazine or bicuculline (two GABA-A receptor antagonists), picrotoxin (a picrotoxin site agonist) and flumazenil (a benzodiazepine site antagonist) reduced it. These results demonstrate that endogenous GABA, released during the train of pulses, facilitates the central nicotinic activation of the ganglionic neurones by acting on GABA-A receptors. Muscimol also reduced the amplitude ratio of excitatory postsynaptic potentials triggered during the paired-pulse protocol without any change in postsynaptic properties. This result is consistent with a presynaptic action of GABA-A receptors. Our study shows that presynaptic GABA-A receptors facilitate the central nicotinic activation of prevertebral ganglionic neurones and thus play a novel role in the integrative properties of the sympathetic prevertebral ganglia.

[Unhealthy homes: possible interventions and their efficacy]. / Risques liés à l'habitat: les interventions possibles et leur efficacité.

Numerous health risks have been identified in dwellings and are a public health priority. Homes most often accumulate several different risks. Intervention programs must take this reality into account. Identification of a source of chemical pollution in the home makes it possible to correct indoor air quality quickly and inexpensively and provides immediate health benefits. Extermination of mites requires implementation of a group of complementary techniques in all contaminated areas, with help, when possible, from an indoor environment counselor. A team of multidisciplinary indoor habitat and health advisors must assess the health risks of the home. This inexpensive strategy reduces risks, although its effectiveness still requires confirmation. When the building has structural defects or abnormalities, more complex methods of renovation, or even moving, are necessary. There again, a complete assessment of their benefits to occupants' health is necessary.