Preface. Acknowledgements. Introduction. References. List of Structures. Index of Abbreviations. Diagrams.

The Rat Brain in Stereotaxic Coordinates

A complete stereotaxic neuroanatomical atlas of the rat hindbrain was prepared using transverse serial sections stained with Luxol fast blue and cresyl violet. Catecholamine-containing cell bodies and fiber terminals were identified by the histofluorescence method. The acetylcholinesterase distribution was histochemically localized. A detailed stereotaxic atlas of the catecholaminergic and acetylcholinesterase-containing structures is presented.

Topographic atlas of catecholamine and acetylcholinesterase-containing neurons in the rat brain. I. Forebrain (telencephalon, diencephalon).

The specificity of synapses in the mammalian brain cannot possibly be accounted for by one-to-one biochemical matching. The alternative proposed in this article is that connections are genetically specified between classes of cells, but the final wiring pattern depends on the refinement of those collections by selective stabilisation during neuronal activity.

Selective stabilisation of developing synapses as a mechanism for the specification of neuronal networks.

Molecular and cellular biology of cholinesterases

The new Conductivity Bridge derives its bridge source. voltage from a self-contained vacuum tube oscilltor adjusted to approximately 1,000 cycles. Voltage for the amplifier and null indicator tubes is provided by a.builtin D.C. power supply which operates directly from the A.C. power source. 9-324 Conductivity Bridge, without Conductivity Cell, for use with 110 volts 5060 cycle A.C. 9-351.Cosi~uCvity Cell, for use with Conductivity Bridge, constant 0.8, $20.00

The Vertebrate Eye and Its Adaptive Radiation.

SummaryA histochemical method is presented for localizing ChE activity by incubating tissue sections in a medium containing acetylthiocholine, copper glycinate and copper thiocholine. Results obtained with several tissues containing specific ChE are described and illustrated.

A histochemical method for localizing cholinesterase activity.

1. Histochemical studies using thin (10 micra) fresh frozen sections indicated the occurrence of artifacts of localization of ChE9s with a previously published method as the result of enzymatic diffusion; confirmatory evidence of such was obtained by manometric measurements of the ChE activities of liver homogenates and isolated nuclei. 2. By means of recovery tests, it was found that purified specific (bovine erythrocyte) and non-specific (horse serum) ChE9s were practically completely precipitated at pH 6.0 in the presence of 20 and 24 per cent Na 2 SO 4 , respectively. Crude preparations of cat specific and non-specific ChE9s were completely recovered following precipitation at pH 6.0 with 24 and 28 per cent Na 2 SO 4 , respectively. The effects of precipitation by Na 2 SO 4 on the activities of the enzymes were determined. 3. The earlier histochemical method was modified in accordance with the foregoing findings and by certain minor changes to eliminate enzymatic diffusion artifacts and to enhance the accuracy of the cellular localizations of the ChE9s. 4. Specific ChE activity was found principally in the dendrites, cell bodies, axons and terminations of cholinergic neurons (anterior and lateral horn cells, certain autonomic ganglion cells), at the motor endplates of striated muscle, and in low concentrations in sensory neurons (dorsal root and nodose ganglion cells.) 5. Non-specific ChE activity was localized in the capsular glial cells of sensory and autonomic ganglion cells, in certain Schwann9s sheath cells, in groups of chemoreceptor cells, in the cells lining the sinusoids of the liver, and in the smooth muscle fibers, stellate cells and occasional ganglion cells of the ileum. 6. Physiological implications of the present findings are discussed, particularly in regard to the probable roles of ACh and the ChE9s in conduction and transmission.

The elimination of enzymatic diffusion artifacts in the histochemical localization of cholinesterases and a survey of their cellular distributions

1. The rates of hydrolysis of several choline esters and their thio-analogues have been studied, using purified enzymes and homogenates of cat tissue. The effects of DFP, Nu 683 and Nu 1250 on specific and non-specific ChE's of the cat have been compared.

2. Based on the findings, a histochemical procedure for localizing ChE activity has been modified to permit the individual localizations of the two types of enzyme in cat tissues. The pH of the original incubation solution has been buffered to 6.4 to obtain sharper localization than was obtained previously.

3. Sites of specific ChE activity were stained by incubating tissues in 10-6 M DFP, followed by incubation in a medium containing AThCh. BuThCh was used as the substrate for localizing non-specific ChE.

4. Sites of activity of the two types of enzymes in several tissues are described and illustrated. In general, regions of the central nervous system examined, skeletal muscle and smooth muscle in some regions were found to contain specific ChE almost exclusively, whereas the reverse was true in sensory ganglia, the adrenal pericapsular ganglia, the hepatic cells, the carotid body and smooth muscle from other sites. Both types of enzyme were revealed in most autonomic ganglia and effector cells.

5. Present results indicate that non-specific ChE plays a role in synaptic transmission similar to that of specific ChE at certain sites in the cat. Previous work which suggests this conclusion is reviewed.

6. Findings are discussed in relation to the older literature and to recent histological and physiological studies.

7. A statement is made concerning the possible pharmacological application of the present technique.

The histochemical differentiation of types of cholinesterases and their localizations in tissues of the cat.

Identical, or adjacent, fresh-frozen sections of the vas deferens (guinea pig, cat), uterus and fallopian tube (cat), and nictitating membrane (cat, rabbit) were examined for catecholamines (modified formaldehyde vapor technique) and acetycholinesterase (AChE) activity (thiocholine technique). In the vas deferens and nictitating membrane, the distribution and density of catecholamine-fluorescent nerve tracts were similar in the cat and in time other species, but AChE staining was much more restricted in the corresponding tissues of the cat, whereas it approximated the pattern of catecholamine fluorescence in the other species. Thus, in these cases the species variations in the AChE activities of the peripheral, presumably postganglionic sympathetic nerve fibers reflect those noted previously in the corresponding sympathetic ganghion cells. The uterus and fallopian tube of the cat, on the other hand, showed a much more extensive distribution of fibers having low but definite AChE activity, corresponding with the patterns of those exhibiting catecholamine fluorescence, than noted in the other organs of this species. These findings were considered in terms of the Burn and Rand hypothesis, that the release of norepinephrine from postganglionic adrenergic fibers is mediated or facilitated by acetylcholine. It was concluded that the present results are consistent with the occurrence of such a mechanism in the vas deferens of the guinea pig and nictitating membrane of the rabbit, but probably not in the same organs of the cat: in the cat uterus and fallopian tube, however, the hypothesis could apply. In order to obtain more direct information by this type of approach, it will be necessary to develop methods which permit the definite localization within individual nerve fibers of the transmitters or their related enzymes, by electron microscopy.

Histochemical correlations of acetylcholinesterase and catecholamines in postganglionic autonomic nerves of the cat, rabbit, and guinea pig.

The location of the external, or functional, AChE of autonomic ganglia of the cat was determined by comparing histochemically the sites of AChE-inhibition by ambenonium in normal and preganglionically denervated ganglia. In the stellate and superior cervical ganglia, essentially all the functional AChE was found to be presynaptic; this was noted with synapses involving ganglion cells which give rise to either adrenergic or cholinergic postganglionic fibers. The ciliary ganglion presented a different pattern: here, functional AChE was observed both pre- and postsynaptically. Findings with the sphenopalatine ganglion were similar to those with the ciliary, but less conclusive.

From the present results, and observations cited from the literature, it is proposed that the primary physiological role of the functional AChE of autonomic ganglia, and possibly of other cholinergic neurons as well, is the prevention of postsynaptic activation by ACh liberated by the preganglionic fibers during the resting stage. Possible secondary functions might include prevention of accumulation and spread of ACh during the course of repeated preganglionic volleys, and protection of the presynaptic terminals against initiation of antidromic firing by ACh.

George B. Koelle

Papers

A histochemical method for localizing cholinesterase activity.

The elimination of enzymatic diffusion artifacts in the histochemical localization of cholinesterases and a survey of their cellular distributions

The histochemical differentiation of types of cholinesterases and their localizations in tissues of the cat.

Histochemical correlations of acetylcholinesterase and catecholamines in postganglionic autonomic nerves of the cat, rabbit, and guinea pig.

The localization of external or functional acetylcholinesterase at the synapses of autonomic ganglia