[Wakefulness and central basal nuclei: experimental observations and possible implications in Parkinson's disease]. / Vigilance et noyaux gris centraux: observations expérimentales et possibles implications dans la maladie de Parkinson.

Movement disorders in Parkinson disease, notably dampened during sleep, are associated with hyperactivity of the subthalamic nucleus (STN), whose origin is controversial. We have studied, on non-anaesthetized head-restrained rats, the STN spontaneous unit activity and the one of its principal GABAergic afferents, the globus pallidus (GP). In normal rats, STN neurons shifted from a random discharge in wakefulness (W) to a bursting pattern in slow wave sleep (SWS), without any change in their mean firing rate. In contrast GP neurons, with a mean firing rate higher in W than in SWS, exhibited a relatively regular discharge rate whatever the vigilance state. During paradoxical sleep, both STN and GP neurons increased markedly their firing rate. When applied during W, GABA-A antagonists increased the STN firing rate but did not change the typical W random pattern. When applied during SWS, they strongly reinforced the spontaneous burst pattern into a particularly marked one with instantaneous frequencies reaching 500Hz. SWS-W transitions occurring during ongoing antagonist iontophoresis invariably disrupted this burst pattern into a random one. On 6-OHDA unilaterally treated rats, the ipsilateral STN was hyperactive whatever the vigilance state (with an abnormal burst pattern during W on some neurons), but this hyperactivity did not seem to be associated with a GP hypoactivity. These results show that STN activity is not inversely correlated with GP activity, that its discharge pattern is strongly dependent on vigilance states, that GABA receptors do not play an exclusive role in regulating its firing pattern, and question the depolarization block hypothesis during STN high frequency stimulation.

Unrelated course of subthalamic nucleus and globus pallidus neuronal activities across vigilance states in the rat.

The pallido-subthalamic pathway powerfully controls the output of the basal ganglia circuitry and has been implicated in movement disorders observed in Parkinson's disease (PD). To investigate the normal functioning of this pathway across the sleep-wake cycle, single-unit activities of subthalamic nucleus (STN) and globus pallidus (GP) neurons were examined, together with cortical electroencephalogram and nuchal muscular activity, in non-anaesthetized head-restrained rats. STN neurons shifted from a random discharge in wakefulness (W) to a bursting pattern in slow wave sleep (SWS), without any change in their mean firing rate. This burst discharge occurred in the 1-2 Hz range, but was not correlated with cortical slow wave activity. In contrast, GP neurons, with a mean firing rate higher in W than in SWS, exhibited a relatively regular discharge whatever the state of vigilance. During paradoxical sleep, both STN and GP neurons increased markedly their mean firing rate relative to W and SWS. Our results are not in agreement with the classical 'direct/indirect' model of the basal ganglia organization, as an inverse relationship between STN and GP activities is not observed under normal physiological conditions. Actually, because the STN discharge pattern appears dependent on coincident cortical activity, this nucleus can hardly be viewed as a relay along the indirect pathway, but might rather be considered as an input stage conveying corticothalamic information to the basal ganglia.

[Carcinoma arising within mammary fibroadenomas. A study of six patients]. / Carcinomes développés sur adénofibromes mammaires. A propos de six observations.

We report six cases of carcinomas arising within fibroadenomas. Fibroadenoma is a benign neoplasm occurring in young women. Its association with carcinomas is unfrequent and particularly reported in older women. Few data are available on the histologic features of fibroadenomas harboring malignant lesions. In this study, most cases of fibroadenomas showed cysts, sclerosing adenosis, epithelial calcifications or papillary apocrine changes. These fibroadenomas are classified as complex and are a long-term risk factor for breast cancer. The complex fibroadenoma may be specific of fibroadenoma associated with carcinoma.

Inhibition of noradrenergic locus coeruleus neurons by C1 adrenergic cells in the rostral ventral medulla.

Recent anatomical and physiological experiments indicate that the nucleus locus coeruleus receives a predominant excitatory amino acid input, as well as a substantial inhibitory input, from the nucleus paragigantocellularis in the ventrolateral medulla. To determine whether C1 adrenergic neurons are involved in the inhibitory projection, the effects of the alpha-2 adrenoceptor antagonist, idazoxan, on inhibitory responses of locus coeruleus neurons to paragigantocellularis stimulation were characterized in the rat. Intravenous administration of idazoxan (0.2-1 mg/kg) attenuated paragigantocellularis-evoked inhibition, and often revealed an underlying weak excitation. Intraventricular administration of kynurenate, an excitatory amino acid antagonist, eliminated excitation from paragigantocellularis and disclosed an underlying inhibitory response in many locus coeruleus neurons that were previously excited by paragigantocellularis stimulation. These results revealed that about 90% of locus coeruleus neurons receive inhibition from the paragigantocellularis. Intravenous idazoxan significantly reduced such paragigantocellularis-evoked inhibition, completely blocking this response in three of eight locus coeruleus cells tested. Idazoxan was much more potent when locally infused into the locus coeruleus. Local infusion of idazoxan (0.1-2.5 ng) into locus coeruleus produced a dose-dependent decrease of paragigantocellularis-evoked inhibition and completely blocked the inhibition in 10/33 locus coeruleus neurons, indicating that the site of idazoxan action was in the locus coeruleus. These results extend our previous anatomical studies of adrenergic input to locus coeruleus, and indicate that C1 adrenergic neurons in the paragigantocellularis provide a direct inhibitory input to the great majority of locus coeruleus noradrenergic neurons. In addition, this is the first report of a neuronal response to activation of C1 adrenergic cells indicating that these neurons are strongly inhibitory when acting at alpha-2 receptors in vivo.

Afferent regulation of locus coeruleus neurons: anatomy, physiology and pharmacology.

Tract-tracing and electrophysiology studies have revealed that major inputs to the nucleus locus coeruleus (LC) are found in two structures, the nucleus paragigantocellularis (PGi) and the perifascicular area of the nucleus prepositus hypoglossi (PrH), both located in the rostral medulla. Minor afferents to LC were found in the dorsal cap of the paraventricular hypothalamus and spinal lamina X. Recent studies have also revealed limited inputs from two areas nearby the LC, the caudal midbrain periaqueductal gray (PAG) and the ventromedial pericoerulear region. The pericoeruleus may provide a local circuit interface to LC neurons. Recent electron microscopic analyses have revealed that LC dendrites extend preferentially into the rostromedial and caudal juxtaependymal pericoerulear regions. These extracoerulear LC dendrites may receive afferents in addition to those projecting to LC proper. However, single-pulse stimulation of inputs to such dendritic regions reveals little or no effect on LC neurons. Double-labeling studies have revealed that a variety of neurotransmitters impinging on LC neurons originate in its two major afferents, PGi and PrH. The LC is innervated by PGi neurons that stain for markers of adrenalin, enkephalin or corticotropin-releasing factor. Within PrH, large proportions of LC-projecting neurons stained for GABA or met-enkephalin. Finally, in contrast to previous conclusions, the dorsal raphe does not provide the robust 5-HT innervation found in the LC. We conclude that 5-HT inputs may derive from local 5-HT neurons in the pericoerulear area. Neuropharmacology experiments revealed that the PGi provides a potent excitatory amino acid (EAA) input to the LC, acting primarily at non-NMDA receptors in the LC. Other studies indicated that this pathway mediates certain sensory responses of LC neurons. NMDA-mediated sensory responses were also revealed during local infusion of magnesium-free solutions. Finally, adrenergic inhibition of LC from PGi could also be detected in nearly every LC neuron tested when the EAA-mediated excitation is first eliminated. In contrast to PGi, the PrH potently and consistently inhibited LC neurons via a GABAergic projection acting at GABAA receptors within LC. Such PrH stimulation also potently attenuated LC sensory responses. Finally, afferents to PGi areas that also contain LC-projecting neurons were identified. Major inputs were primarily autonomic in nature, and included the caudal medullary reticular formation, the parabrachial and Kölliker-Fuse nuclei, the PAG, NTS and certain hypothalamic areas.(ABSTRACT TRUNCATED AT 400 WORDS)

Anatomical evidence for multiple pathways leading from the rostral ventrolateral medulla (nucleus paragigantocellularis) to the locus coeruleus in rat.

Using retrograde transport of Fluoro-Gold (FG) combined with immunofluorescence for phenylethanolamine-N-methyltransferase (PNMT), we have examined afferents to the nucleus locus coeruleus (LC) from the rostral ventrolateral medulla (nucleus paragigantocellularis; PGi) in rats sustaining lesions of the medullary adrenergic bundle (MB). In lesioned rats, very few adrenergic LC-projecting neurons persist in the PGi ipsilateral to the lesion, representing a 90% decrease in comparison to non-lesioned animals. These results indicate that almost all adrenergic input to the LC from C1 neurons in PGi is conveyed by the MB. In contrast, the number of non-adrenergic LC afferent neurons in the PGi ipsilateral to the lesion only decreased by 48% after such lesions. Thus, this pathway also provides non-adrenergic projections to LC from PGi, but many of these are conveyed by other route(s) as well.

Adrenergic innervation of noradrenergic locus coeruleus neurons. A dual labeling immunocytochemical study in the rat.

By means of dual immunocytochemistry, synaptic associations between adrenergic terminals and noradrenergic neurons were directly demonstrated in the rat locus ceruleus (LC). It could be estimated that every adrenergic afferent contacts at least one noradrenergic dendrite in the nucleus. An adrenergic innervation of non-noradrenergic targets was also evidenced. These data add to our knowledge on the synaptic circuitry by which activation of the adrenergic input could affect central mechanisms known to be influenced by LC neurons.

Are adrenergic neurons subject to a serotoninergic influence in the nucleus tractus solitarii? A morphological and biochemical study in the rat.

The possible relationships between adrenaline-synthesizing neurons and serotoninergic afferent fibers in the nucleus tractus solitarii of the rat were investigated both morphologically and biochemically. Adrenergic elements (cell bodies, dendrites and nerve endings) were detected simultaneously with serotoninergic axonal varicosities in the same electron-microscopic sections by means of combined phenylethanolamine-N-methyltransferase immunocytochemistry and [3H]serotonin-uptake radioautography. Among some 500 serotoninergic varicosities scanned in the areas of significant overlap between the 2 types of labeling, only 3 were directly apposed to an adrenergic process, identified as a dendrite in each case. No synaptic membrane differentiations were seen at these occasional sites of contact. Destruction of the serotonin input by 5,7-dihydroxytryptamine had no significant effect on the tyrosine hydroxylase dopamine-beta-hydroxylase and phenylethanolamine-N-methyltransferase enzymatic activities in the C2 adrenergic region, but induced 22% and 38% increases of tyrosine hydroxylase and dopamine-beta-hydroxylase activities, respectively, in the neighboring A2 noradrenergic area. Taken together, these results suggest that serotoninergic and adrenergic neurons do not significantly interact in the nucleus tractus solitarii; this implies that the possible catecholaminergic relays for the action of serotonin in autonomic regulation at this level could consist of noradrenergic neurons rather than of their adrenergic counterparts.

Immunohistochemical evidence for the adrenergic medullary longitudinal bundle as a major ascending pathway to the hypothalamus.

Three weeks after unilateral electrolytic lesion of the longitudinal axon bundle in the medulla oblongata of the rat, we observed a decrease in the number of phenylethanolamine-N-methyltransferase (PNMT)-immunoreactive (IR) nerve fibers in virtually all the regions of the diencephalon ipsilaterally to the lesion, especially in the dorsomedial nucleus and the paraventricular nucleus of the hypothalamus. These results indicate that the hypothalamic PNMT-IR terminal-like fibers originate in the ipsilateral medulla oblongata presumptive adrenaline-containing (Ad) neurons especially through ascending projections provided in majority by the longitudinal axon bundle. Further, no PNMT-IR cell bodies were detected in the hypothalamus even after colchicine treatment.

Immunohistochemical evidence for the adrenergic medullary longitudinal bundle as a major ascending pathway to the locus coeruleus.

The present study describes the first experimental evidence for a direct projection of the medulla oblongata adrenergic (Ad) neurons to the rat pontine structures by using the indirect immunoperoxidase technique. Three weeks after unilateral electrolytic lesion of the longitudinal axon bundle in the medulla oblongata, the morphological changes of the phenylethanolamine-N-methyltransferase (PNMT)-immunoreactive (IR) structures located in the rat brainstem have been analysed. In the lesioned rats we observed a decrease in the number of PNMT-IR structures in virtually all regions of the brainstem ipsilateral to the lesion, especially in the locus coeruleus (LC). These results indicate that the PNMT-IR terminal-like fibers of the LC are derived from the ipsilateral medulla oblongata Ad neurons and are mainly provided by the longitudinal axon bundle.

Biochemical evidence for an interaction between adrenaline and noradrenaline neurons in the rat brainstem.

In this study, we sought to determine if there was an interaction between the C2 adrenaline-containing (A) neurons of the rat medulla oblongata and the noradrenaline-containing (NA) cell bodies of the locus coeruleus (LC). For this purpose, the biochemical response of the NA cell bodies of the LC after a lesion of the C2 region was studied by using as markers the in vitro activities of the catecholamine synthesizing enzymes: tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH) and phenylethanolamine-N-methyltransferase (PNMT). An increase in TH activity, not associated with any change in DBH or PNMT activity, was found in the LC (+104%, P less than 0.001) 4 days after a bilateral electrolytic lesion (3 mA for 5 s) of the C2 region. Conversely, the electrolytic lesioning of the neighboring A2 region of NA neurons did not modify the TH activity of the LC. These results suggest the existence of an ascending adrenergic inhibitory control of the NA cell bodies of the LC.

Central and peripheral catecholamine synthesizing enzymes during the development of two-kidney, one clip hypertension in rats.

The activities of the catecholamine synthesizing enzymes have been determined in discrete brain areas and in peripheral tissues of rats, at different times after clipping the left renal artery (two-kidney Goldblatt hypertension, 2KGH) and in sham operated animals. Three days after clipping the only enzymatic change was a slight decrease in plasma dopamine-beta-hydroxylase (DBH) activity. Ten days after clipping no change in enzymatic activity was found at the central level. However, the DBH and the phenylethanolamine-N-methyltransferase (PNMT) activities were increased in the adrenal medulla (+49.0%, P less than 0.001 and +36.6%, P less than 0.001, respectively) and DBH activity was also increased in the superior cervical ganglia (+22.8%, P less than 0.01). These data suggest that sympathetic hyperactivity is present in 2KGH rats when hypertension is established. In addition, as this type of hypertension does not alter the PNMT activity in brainstem areas, it seems that the alterations in PNMT activity reported for genetically hypertensive rats are unlikely to be secondary to the elevated blood pressure.

Adrenaline and noradrenaline neurons in rat lower brain stem: anatomical and pharmacological neurochemistry.

Since there was no study available on the comparative anatomical neurochemistry of the noradrenaline (NA) and adrenaline (A) containing neurons of the lower brain stem, we studied the distribution of the activities of the three major catecholamines (CA)-synthesizing enzymes in coronal sections of the rat medulla oblongata dissected into microcubes. In the dorso-medial region, there was a 1500 micron rostro-caudal difference in the localization of the peak of PNMT activity compared with the peaks of TH and DBH activities. This result led to a new microdissection technique allowing the preferential microdissection of the C2 A neurons versus the A2 NA neurons. The response of these two populations of CA neurons was then studied after a sustained decrease in blood pressure induced in young SHR by a 14 days dihydralazine treatment. The C2 adrenergic region exhibited an overall increase in TH, DBH and PNMT activity (+69%, +45% and +33%; p less than 0.01 respectively) while the A2 noradrenergic region was unaffected. Thus, the NA and A neurons of the rat dorso-medial lower brain stem do not seem to exhibit the same biochemical response after a prolonged hypotension. This preliminary result favors the hypothesis of a different functional role for the neighboring A2 and C2 neurons in central control of blood pressure.