Françoise Petitjean

The raphe nuclei of the cat brain stem: A topographical atlas of their efferent projections as revealed by autoradiography

Stereotaxic injections of [14C]leucine were made in nulei raphe centralis superior, raphe dorsalis, raphe magnus and raphe pontis of the cat. The organization of the regional connections was outlined in a stereotaxic atlas using the autoradiographic tracing method: the majority of the ascending pathways from the rostral raphe nuclei are directed mainly through a ventrolateral bundle via the ventral tegmental area of Tsai, with some lateral extensions to the substantia nigra, and then through the fields of Forel and the zona incerta. More rostrally the fibers are joined to the medial forebrain bundle through the hypothalamic region up to the preoptic area or the diagonal band of Broca. Multiple divisions leave this tract towards the epithalamic or the intralaminar thalamic nuclei, the stria terminalis, the septum, the capsula interna and the ansa lenticularis. The bulk of the rostral projections terminates in the frontal lobe, while some labeling is scarcely distributed throughout the rest of the neocortex. The projections of nucleus (n.) raphe centralis superior are specifically associated with the n. interpeduncularis, the mammillary bodies and the hippocampal formation while the n. raphe dorsalis innervates selectively the lateral geniculate bodies, striatus, piriform lobes, olfactory bulb and amygdala. The rest of the ascending fibers form the centrolateral or the dorsal ascending tracts radiating either in the reticular mesencephalic formation or in the periventricular gray matter. On the contrary there are heavy descending projections from n. raphe centralis superior which distribute to the main nuclei of the brain stem, the central gray matter and the cerebellum. The ascending projections form the caudal raphe nuclei are much less dense. They disseminate mainly in the colliculus superior, the pretectum, the nucleus of the posterior commissure, the preoculomotor complex and the intralaminar nuclei of the thalamus. From n. raphe pontis, a dense labeling is selectively localized at the n. paraventricularis hypothalami with some rostral extensions to limbic areas. Diffuse caudal and rostral projections from both nuclei are observed in the mesencephalic, pontobulbar reticular formation and the cerebellum. The main differences come from the specific localization of their descending bulbospinal tracts inside the lateroventral funiculus of the spinal cervical cord.

Hypersomnie par lésion isthmique chez le chat. II.Étude neurophysiologique et pharmacologique

Summary (1) The bilateral destruction of the region of the dorsal norepinephrine bundle in the isthmus or in the mesencephalon induces a significant increase of both paradoxical sleep (PS) (up to 400%) and of slow-wave sleep (SWS). The increase of PS lasts for 4–5 days while the increase of SWS lasts at least 8–10 days. The same phenomenon is observed after total hypophysectomy. (2) Control lesions effectuated in the isthmus outside the area of the dorsal norepinephrine bundle do not affect significantly the sleep-waking cycle. (3) Pretreatment with p-chrophenylalanine suppresses the increase of sleep if the lesion is effectuated at the time maximum insomia, while a significant increase of PS is still observed if the lesion is made at the time of the recovery of sleep. (4) The mechanisms of this hypersomnia are discussed in light of the biochemical results showing an increase of the biosynthesis of serotonin in the rostral raphe system. It is postulated that some neurons of the dorsal norepinephrine bundle might tonically control the activity of the raphe system.

Effets du chloramphénicol sur le sommeil du chat -- comparaison avec le thiamphénicol, l'érythromycine et l'oxytétracycline.

The effects of various antibiotics, which inhibit protein synthesis, has been studied on the sleepwaking cycle of cats. Chloramphenicol (CAP) selectively inhibits paradoxical sleep (SP). Thiamphenicol (TAP) and oxytetracycline however are ineffective; erythromycine induces only a small decrease of SP. When CAP is injected after TAP, the SP inhibition is longer than after CAP alone. Combining erythromycine and CAP produces the same effect as one or other of the antibiotic alone, depending only on the interval between administration of the two drugs. Slow wave sleep is decreased only with high doses of CAP and is unaffected by TAP, oxytetracycline or erythromycine. These results suggest that CAP may inhibit a peptide or protein synthesis involved in the mechanisms of SP.The effects of various antibiotics, which inhibit protein synthesis, has been studied on the sleep-waking cycle of cats. Chloramphenicol (CAP) selectively inhibits paradoxical sleep (SP). Thiamphenicol (TAP) and oxytetracycline however are ineffective; erythromycine induces only a small decrease of SP. When CAP is injected after TAP, the SP inhibition is longer than after CAP alone. Combining erythromycine and CAP produces the same effect as one or other of the antibiotic alone, depending only on the interval between administration of the two drugs. Slow wave sleep is decreased only with high doses of CAP and is unaffected by TAP, oxytetracycline or erythromycine. These results suggest that CAP may inhibit a peptide or protein synthesis involved in the mechanisms of SP.

Hypersomnie par lésion isthmique chez le chat. I.Étude du métabolisme des monoamines cérébrales

Summary (1) A significant increase of 5-HT synthesis is observed in several areas of the cat brain 24 h after the bilateral destruction of the dorsal noradrenergic bundle in the isthmus. This stimulation of the synthesis was simultaneously observed at the level of serotonergic cell bodies (anterior part of the raphe system) and of 5-HT terminals (cortex, thalamus, mesencephalon, medulla oblongata). Conversely, a significant decrease of 5-HT synthesis was found in the caudal part of the raphe and in the hypothalamus. The possibility of a catecholaminergic control of 5-HT synthesis by neurons passing through the isthmus is discussed. (2) In the same experimental conditions, an important decrease of endogenous dopamine content without any subsequent change of noradrenaline concentration was observed in the thalamus, the geniculate body and the pons. This important decrease could be due to a greater utilization of dopamine into hypothetical dopaminergic terminals localized in these structures.