Showing papers by "Christelle Peyron published in 1998"

The hypocretins: Hypothalamus-specific peptides with neuroexcitatory activity

Abstract: We describe a hypothalamus-specific mRNA that encodes preprohypocretin, the putative precursor of a pair of peptides that share substantial amino acid identities with the gut hormone secretin. The hypocretin (Hcrt) protein products are restricted to neuronal cell bodies of the dorsal and lateral hypothalamic areas. The fibers of these neurons are widespread throughout the posterior hypothalamus and project to multiple targets in other areas, including brainstem and thalamus. Hcrt immunoreactivity is associated with large granular vesicles at synapses. One of the Hcrt peptides was excitatory when applied to cultured, synaptically coupled hypothalamic neurons, but not hippocampal neurons. These observations suggest that the hypocretins function within the CNS as neurotransmitters.

Neurons Containing Hypocretin (Orexin) Project to Multiple Neuronal Systems

Abstract: The novel neuropeptides called hypocretins (orexins) have recently been identified as being localized exclusively in cell bodies in a subregion of the tuberal part of the hypothalamus. The structure of the hypocretins, their accumulation in vesicles of axon terminals, and their excitatory effect on cultured hypothalamic neurons suggest that the hypocretins function in intercellular communication. To characterize these peptides further and to help understand what physiological functions they may serve, we undertook an immunohistochemical study to examine the distribution of preprohypocretin-immunoreactive neurons and fibers in the rat brain. Preprohypocretin-positive neurons were found in the perifornical nucleus and in the dorsal and lateral hypothalamic areas. These cells were distinct from those that express melanin-concentrating hormone. Although they represent a restricted group of cells, their projections were widely distributed in the brain. We observed labeled fibers throughout the hypothalamus. The densest extrahypothalamic projection was found in the locus coeruleus. Fibers were also seen in the septal nuclei, the bed nucleus of the stria terminalis, the paraventricular and reuniens nuclei of the thalamus, the zona incerta, the subthalamic nucleus, the central gray, the substantia nigra, the raphe nuclei, the parabrachial area, the medullary reticular formation, and the nucleus of the solitary tract. Less prominent projections were found in cortical regions, central and anterior amygdaloid nuclei, and the olfactory bulb. These results suggest that hypocretins are likely to have a role in physiological functions in addition to food intake such as regulation of blood pressure, the neuroendocrine system, body temperature, and the sleep–waking cycle.

Anatomical demonstration of a medullary enkephalinergic pathway potentially implicated in the oro-facial muscle atonia of paradoxical sleep in the cat.

Abstract: The present study was aimed to compare in detail the distribution within the rostral ventromedial medulla of Methionin-Enkephalin-immunoreactive neurons with efferent projections to the facial or trigeminal motor nuclei, using a double immunostaining technique in colchicine-treated cats. Following cholera toxin B subunit injections in the facial or trigeminal motor nuclei, we found that respectively 55% and 65% of the medium to large-sized retrogradely labeled cells in the lateral part of the nucleus reticularis magnocellularis were Methionin-Enkephalin-positive. For both motor nuclei, the double-labeled neurons had similar morphology and size and were located exactly in the same area. They could therefore belong to the same population of reticular enkephalinergic neurons. Based on these and previous anatomical and electrophysiological data, we propose that these enkephalin-containing neurons could participate in the hyperpolarization of brainstem and spinal somatic motoneurons during paradoxical sleep.