Effect of quipazine, a serotonin-like drug, on striatal cholinergic interneurones

Quipazine (30 mg/kg i.p., 60 min), a serotonin-like drug increased ACh levels in the striatum (37%) but was without effect on the transmitter content in the hippocampus and the parietal cortex of the rat. Added in vitro(10(-5) M) or injected in vivo, quipazine did not affect choline acetylase and cholinesterase activities in striatal tissue. The drug effect on striatal ACh levels did not appear to be related to an interaction with dopamine metabolism. Indeed quipazine still increased striatal ACh levels after degeneration of the dopaminergic neurons had been induced by local injection of 6-OH-DA. p-Chlorophenylalanine (PCPA) pretreatment (300 mg/kg, 48 and 24 h before the experiment) definitely prevented the quipazine effect on ACh levels. This result suggested that the drug may partially act by its interference with 5-HT metabolism. 5-Methoxy-N,N-dimethyltryptamine (10 mg/kg, i.p., 30 min), a serotonergic agonist, induced a weak but significant increase in ACh levels. These data provide some preliminary evidence for the existence of an inhibitory control of the cholinergic interneurones by the serotonergic neurones projecting to the striatum. However, the lack of effect of 5-hydroxytryptophan (100 mg/kg i.p.), PCPA (2 x 300 mg/kg i.p.) and of Lilly 110 140 (10 mg/kg i.p.) and chlorimipramine (10 mg/kg i.p.), two potent inhibitors of 5-HT uptake, on striatal ACh levels indicate that further experiments are required to retain this hypothesis.

A Golgi study of neuronal types in the neostriatum of monkeys

Examination of the nestriatum of monkeys prepared by the Golgi-Kopsch perfusion method revealed the presence of at least 6 neuronal types. The spiny type I is medium size with a high density of dendritic spines. The axon extends well beyond the dendritic field and gives off many collaterals. The spiny type II is either medium or large size, has long thick dendrites with a relatively low density of spines, and an axon similar to that of the previous type but with fever collaterals. The aspiny type I is medium size with varicose dendrites and a thin axon arborizing in the immediate vicinity of the soma. The aspiny type II is large, with many thick and thin varicose dendrites. The aspiny type III is medium size with smooth dendrites and an axon ramifying profusely within the dendritic field. The neurogliform cell is small with many branching processes. Findings indicate that the neostriatum has 2 distinct types of spiny neurons with long axons (spiny I and II), some of which may contribute to the efferent system. There are also 2 (aspiny I and III) or perhaps as many as 4 categories (aspiny I, II, III and neurogliform) of typical Golgi type II cells. Large neurons belong to 2 separate populations, one with dendritic spines and a long axon (large version of spiny II), and one with varicosities and presumably a short axon (aspiny II). A realistic interpretation of neurophysiologic data on the neostriatum must take into account all cell types instead of the current view of considering it as a pool of interneurons with few output cells.

The rodent neostriatum: a Golgi analysis

In the adult rodent, coronal sections of Golgi impregnations of the neostriatum display a compact segregation of axon fascicles, neuronal clusters, and dendritic bundles thus forming an areolar configuration. Isolated neurons are rarely seen. The dorsomedial region of the neostriatum appears free of axon fascicles and dendritic bundles. Horizontal and sagittal sections of the neostriatum show clusters of cells parallel to axon fascicles. The neurons exhibit spine-laden dendrites with an initial spine-free segment. Neonatal impregnations exhibit a different configuration. Neonatally, cells tend to cluster but there is no bundling of dendrites. Neurons are spine-free or have protospines on the soma and the dendrites, including the initial segment. Transition from neonate to adult configuration is discernible at about 15 days after birth. The neostriatum of carnivores exhibits a different structure from the rodent neostriatum. This difference is associated with a developed anterior limb of the internal capsule in the carnivore. The axon fascicle-free portion of the carnivore neostriatum lacks dendritic bundles and pallisades. Portions near the capsule with axon fascicles appear similar to the rodent neostriatum with dendritic bundlings and pallisading. Such findings emphasize the importance of total neuronal configuration (neuronal-architectonics) in morphologic analyses.

Enzyme histochemistry of rat interfascicular oligodendroglia, with special reference to 5'-nucleotidase

The interfascicular oligodendroglia of the rat striatum nucleus is studied in control animals and under experimentally induced brain edemas. Enzyme histochemical studies were performed. Normal oligodendrocytes show two different enzymatic distributions. While Mg2+-ATPase, TPPase, TPPase, adenylate cyclase and SDH are shown to be situated at the cell bodies and some proximal processes, 5'-nucleotidase reaction is seen at the cell fine distal processes. In spite of its trong activity in oligodendroglial endings the latter enzyme is not seen at the myelin sheath. This sheath and the interfascicular cells being intimately related, 5'-nucleotidase appears to be important not only during myelination, as almost all authors emphasize, but also in the adult myelin metabolism. Experimental brain edema shows some changes in the interfasicular oligodendroglia enzymatic activites for 5'-nucleotidase, Mg2+-ATPase and adenylate cyclase. A progressive disappearance of the former enzyme is observed. These features and those of derived from local ionic alterations may be concerned with the special susceptibility of white matter for some types of brain swellings.

Acetylcholinesterase-containing neurons in the neostriatum and substantia nigra revealed after punctate intracerebral injection of di-isopropylfluorophosphate

Infusion of 1 mul arachis oil containing 1.5 mug bis-(1 -methylethyl)phosphorofluoridate (di-isopropylfluorophosphate: DFP) into the caudate--putamen nucleus and substantia nigra of rats produced a considerable reduction of histochemical staining for acetylcholinesterase (AChE) in these two brain regions 30--120 min after injection. Thereafter, regeneration of AChE occurred within the zone of DFP effect. These new stores of AChE were associated with discrete neuronal perikarya and their processes. Intracerebral DFP administration had little or no histochemically detectable effect on NADH-diaphorase. Thionin staining was similarly unaffected. The results with punctate intracerebral application of DFP were replicated by intramuscular injection of 1.5 mg/kg DFP. Although the significance of dopaminergic--cholinergic interactions in the neostriatum could not be elucidated on the basis of these histochemical data, the thesis was advanced that dopamine neurons in the pars compacta of the substantia nigra also contained AChE, possibly to inactivate acetylcholine released from cholinergic fibers afferent to this neural structure.