The medial forebrain bundle (MFB) and ascending monoaminergic pathways in the cat.
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The monoamine-containing neurons in the brain of the garfish, Lepisosteus osseus.
The morphological organization of monoamine (MA)-containing neurons in the brain of the longnose gar (Lepisosteus osseus) was studied by means of fluorescence histochemical methods. In this species, one of the few living representatives of the holostean group of actinopterygian fishes, by far the largest number of MA cells is found within the preoptico-hypothalamic complex. Multitudinous small-sized MA cells, with a short club-like process protruding into the third ventricle, are present along the ependymal wall of the lateral and posterior hypothalamic recesses. This population of CSF-contacting MA cells, comprising both catecholamine (CA) and serotonin (5-HT) type cells, gives rise to numerous efferent fibers, some of which proceed rostrally toward the telencephalon while others course dorsally to reach the midbrain tegmentum and optic tectum. Many fibers, however, arborize directly within the hypothalamus, particularly around blood vessels where they form patches of highly fluorescent material. Small CA cells are also scattered along the preoptic recess wall. They do not directly contact the CSF but also appear to contribute to the CA innervation of telencephalon. At brain stem levels, a few CA cells are scattered at the base of the rostral midbrain, in the isthmal tegmentum, and in the central and dorsal (vagal lobe) portions of the medulla. Some CSF-contacting CA cells are also present around the central canal at upper spinal cord levels. One of the most striking features of the MA systems in Lepisosteus is the remarkable development of the 5-HT neuronal network. A prominent 5-HT cell column extends rostrocaudally in the raphe region from the caudal midbrain to upper spinal cord levels. In the caudal midbrain and isthmus, the 5-HT, cells also invade the lateral tegmentum and profusely innervate various brain stem structures as well as large portions of telencephalon, particularly the dorsal nucleus of area ventralis (Vd). The CA innervation of telencephalon is relatively weak, except in the olfactory bulb where numerous CA varicosities were found. These findings in Lepisosteus suggest that the pattern of MA system organization in the holostean brain is far more similar to that seen in primitive vertebrates, such as cyclostomes--where the 5-HT systems are highly elaborated relative to the CA systems--than it is to the pattern in more advanced fishes such as teleosts.
Animals↗
Axonal arborizations of corticostriatal and corticothalamic fibers arising from the second somatosensory area in the rat.
Corticostriatal and corticothalamic projections arising from the second somatosensory area in the rat were studied after labeling small pools of neurons in laminae V and VI with biocytin. Tracing the axon of single neurons revealed the following principles of organization: (i) all corticostriatal and corticothalamic projections arising from layer V cells are collaterals of long-range corticofugal axons that also project below the thalamic level; (ii) all layer V cells that project to the thalamus also project to the striatum; (iii) all layer VI corticothalamic cells project exclusively to the thalamus; (iv) cells of the upper part of lamina VI send collaterals to the thalamic reticular nucleus and arborize in the ventrobasal complex forming rod-like terminal fields; and (v) cells of the lower part of lamina VI also send collaterals to the thalamic reticular nucleus, give off few branches in the ventrobasal complex and terminate principally in the caudal part of the posterior thalamic group. On the basis of these findings, and in the light of previous anatomical studies, it is proposed that the above mentioned organizing principles represent general rules that also apply to corticostriatal and corticothalamic pathways arising from other areas of the neocortex.
Animals↗
Axonal arborization of corticostriatal and corticothalamic fibers arising from prelimbic cortex in the rat.
This study aimed at elucidating the branching pattern of striatal and thalamic projections arising from prelimbic (Cg3) cortex in the rat. Small pools (5-15 cells) of neurons were microiontophoretically injected with biotin-dextran or biocytin and their labeled axons were individually reconstructed from serial horizontal sections immunostained for calbindin-D28k to delineate striatal patch/matrix compartments. Reconstruction of > 40 axons shows that all Cg3 corticofugal fibers, including corticothalamic axons from layer VI, course through the patch network in the rostromedial sector of the striatum. Corticostriatal projections arise from two types of layer V cells: (i) long-range corticofugal neurons, whose main axons reach the brainstem and/or spinal cord, and (ii) neurons arborizing into both striatum and claustrum, either ipsi-, contra- or bilaterally. The axons of these two types of neurons arborize profusely in striatal patches and only sparsely in the matrix. Layer VI neurons do not arborize in the striatum but target principally the thalamus. The same corticothalamic axon can innervate the anterior, rostral intralaminar and mediodorsal thalamic nuclei. These findings support the concept that no corticofugal fiber system exists that is solely devoted to the striatum. They also shed new light on how neural information from prelimbic cortex is conveyed to various subcortical limbic structures in the rat.
Animals↗
Cyclophosphamide for the treatment of progressive low-grade astrocytoma: a Pediatric Oncology Group phase II Study.
PURPOSE: Results of a phase II trial of cyclophosphamide (CPM) for children with progressive low-grade astrocytoma are reported. PATIENTS AND METHODS: Fifteen patients with a median age of 39 months (range, 2 to 71) were included in this study. The tumors of 11 children were located in the optic pathway, hypothalamus, or thalamus. Four courses of intravenous CPM 1.2 g/m2 were administered every 3 weeks during the upfront window portion of this protocol. Subsequently, chemotherapy was to continue with CPM, vincristine, and carboplatin for 2 years. RESULTS: By study design, the first 14 patients were centrally reviewed after completion of the initial 4 CPM courses. Toxicity was primarily hematologic. One patients had a complete response, 8 had stable disease, and 5 had progressive disease (PD). The excessive number of children with PD prompted study closure. CONCLUSION: CPM as used in this protocol showed insufficient activity against astrocytoma to justify further patient accrual.
Antineoplastic Combined Chemotherapy Protocols↗
[Compartmentalized organization of human corpus striatum].
INTRODUCTION: The compartmentalization of the human striatum was first established thanks to the pioneer work of Graybiel and Ragsdale in 1978. These authors described in the human striatum, as well as in the cats and primates, zones poorly stained for the enzyme acetylcholinesterase, which they termed striosomes, that lie in more intensely stained matrix. The striosome/matrix subdivision of the striatum is supported by the distribution of a wide variety of transmitter-related substances and by the organization of striatal afferent and efferent connections. DEVELOPMENT: The results of many studies performed in different species in the last twenty years have indicated that the chemical heterogeneity of striatum is more complex than the simple subdivision into striosomes and matrix compartments. Thus, a further subdivisions of the dual striosome/matrix system has been proposed on the basis of the results of a huge amount of works combining tract tracing methods with histochemical techniques. The matrix has been demonstrated to be heterogeneous by containing numerous functional modules that were termed matrisomes. Furthermore, the most recent study of the distribution of a wide variety of neurochemical markers in the striosomal compartment of the human striatum, has revealed that the striosomes are themselves heterogeneous, being composed of a central core and a peripheral region. CONCLUSIONS: Since it is now twenty years from the first description of the striosome/matrix organization of the striatum, in this review we intend to summarize the major finding regarding the compartmental organization of this subcortical structure that have been obtained during this period of time.
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