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S Arbilla

Publications and source records attributed to S Arbilla.

63 records · Page 4Linked to original sources
PubMed1979

Presynaptic GABA autoreceptors on GABAergic nerve endings of the rat substantia nigra.

The release of 3H-GABA evoked by exposure to 30 mM potassium during 1 min was found to calcium independent in the rat occipital cortex and calcium dependent in the substantia nigra. Exposure to either muscimol 1 microM or GABA 1 microM inhibited the potassium-evoked release of 3H-GABA from the substantia nigra but not from the occipital cortex. The inhibitory effect of muscimol 1 microM on the potassium-evoked release of 3H-GABA from the substantia nigra was significantly antagonized by picrotoxin 10 microM. Exposure to either 10 or 100 microM pricrotoxin alone did not affect the potassium-evoked release of 3H-GABA. These results are compatible with the presence of a negative feedback mechanism in bagaergic nerve terminals of the rat substantia nigra which is mediated by presynaptic GABA autoreceptors. In addition, these results emphasize the importance of the calcium-dependent nature of the release of the neurotransmitter for demonstrating the modulation of transmitter release through presynaptic receptors.

Animals↗
PubMed1978

Differences between presynaptic and postsynaptic alpha-adrenoceptors in the isolated nictitating membrane of the cat: effects of metanephrine and tolazoline.

The alpha-adrenoceptor blocking agent, tolazoline, and the O-methylated metabolite of adrenaline, metanephrine, produced a concentration-dependent increase of tension in the smooth muscle of the cat isolated nictitating membrane. These effects were considered to be due to the activation of postsynaptic alpha-adrenoceptors. 2 The responses to nerve stimulation of this muscle were neither potentiated nor blocked by tolazoline (0.1 to 10 micrometer) or metanephrine (1 to 10 micrometer). 3 3H-transmitter overflow evoked by electrical stimulation was not modified by tolazoline or metanephrine in concentrations in which these drugs stimulated the postsynaptic alpha-adrenoceptors. 4 Since tolazoline and metanephrine failed to activate the presynaptic alpha-adrenoceptors of the cat nictitating membrane under experimental conditions in which they stimulated the postsynaptic alpha-adrenoceptors, these results further support the view that the presynaptic (alpha2) adrenoceptors differ from the postsynaptic (alpha1) adrenoceptors.

Animals↗
PubMedDate not supplied

[A specific domain (the omega 1 site) of the GABA(A) receptor may be implicated in the hypnotic effects of zolpidem].

Zolpidem (Stilnox) is a new hypnotic belonging to the imidazopyridine series. In animals, in contrast to the benzodiazepines which alter sleep architecture, zolpidem induces a physiological pattern of deep sleep. Zolpidem also differs from the benzodiazepines by its hypnoselective profile (its sedative effects are seen at doses much lower than those needed for anticonvulsant or myorelaxant effects). In this review, the authors analyze the hypothesis that the hypnoselective profile of zolpidem is linked to its interaction with a specific domain, the omega 1 site, of the GABAA receptor complex. This hypothesis is supported by: 1) the high selectivity of zolpidem for omega 1 as compared to omega 2 sites and its high intrinsic activity, 2) autoradiographic studies of the regional distribution of omega 1 and omega 2 sites in the human and non-human primate brains showing that omega 1 sites are located preferentially in sensorimotor cortical regions whereas omega 2 sites predominate in the limbic system and spinal cord. The selectivity of zolpidem for omega 1 sites could also account for the fact that in contrast to the benzodiazepines, this compound does not alter memory functions at hypnotic doses.

Animals↗