Historical review: The golden age of the Golgi method in human neuropathology.

Golgi methods were used to study human neuropathology in the 1970s, 1980s, and 1990s of the last century. Although a relatively small number of laboratories applied these methods, their impact was crucial by increasing knowledge about: (1) the morphology, orientation, and localization of neurons in human cerebral and cerebellar malformations and ganglionic tumors, and (2) the presence of abnormal structures including large and thin spines (spine dysgenesis) in several disorders linked to mental retardation, focal enlargements of the axon hillock and dendrites (meganeurites) in neuronal storage diseases, growth cone-like appendages in Alzheimer disease, as well as abnormal structures in other dementias. Although there were initial concerns about their reliability, reduced dendritic branches and dendritic spines were identified as common alterations in mental retardation, dementia, and other pathological conditions. Similar observations in appropriate experimental models have supported many abnormalities that were first identified using Golgi methods in human material. Moreover, electron microscopy, immunohistochemistry, fluorescent tracers, and combined methods have proven the accuracy of pioneering observations uniquely visualized as 3D images of fully stained individual neurons. Although Golgi methods had their golden age many years ago, these methods may still be useful complementary tools in human neuropathology.

Zones in the cerebellar cortex: the adventures of one participant in the unfolding story.

Prior to the late 1960s, a variety of studies suggested that a general zonal pattern existed within the cerebellar cortex. The hypothesis proposed by Voogd, based on the organization of the subcortical white matter, indicated that this pattern may be very detailed, and he noted that "a further analysis of the corticonuclear projection is still necessary." This brief paper chronicles the approach used by the author to formulate a plan, initiate a large series of experiments (over 250), and follow the sometimes confusing results to finally arrive at an understanding of the details of cerebellar corticonuclear projections. It was discovered that a series of mediolateral cortical zones were present that were topographically related to the underlying cerebellar nuclei, and within each zone, the cortex projected in a rostrocaudal sequence to a specific cerebellar nucleus. The hypothesis proposed by Voogd was fundamentally proven.

Lennart Heimer: concepts of the ventral striatum and extended amygdala.

Dr. Lennart Heimer, the famous neuroanatomist of Swedish descent, died last year but left a legacy that will impact the neurosciences and potentially psychosurgery for years to come. He developed an anatomical technique for demonstrating the terminal boutons that helped to delineate basal forebrain anatomy. During these studies, he realized the relationship of basal forebrain structures to the limbic system, thus initiating the concept of the ventral striatum and parallel basal ganglia circuitry. Heimer excelled as a teacher as well and honed his brain dissection technique to one of the most effective tools for understanding neuroanatomy. His legendary sessions with neurosurgical residents resulted in his recognition as one of the world's leading fiber tract dissectors. His gentle, engaging manner has been documented in several media formats.

How the 1906 Nobel Prize in Physiology or Medicine was shared between Golgi and Cajal.

In 1906 the Nobel Prize in Physiology or Medicine was shared between Camillo Golgi and Ramón y Cajal in recognition of their work on the structure of the nervous system. Golgi's most impressive contribution was his method, described in 1873. This was applied in studies of the cerebellum, the olfactory bulb, hippocampus and the spinal cord. These studies together with his earlier work were included in his Opera Omnia, published in 1903. His method was highly praised by Cajal. His adherence to the reticular theory was opposed by Cajal, however, who had spelled out the neuron theory already in the late 1800s. Cajal's extraordinary contributions to the structure of the nervous system, based largely on the Golgi method and Ehrlich's methylene blue stain, were published in his Textura del Sistema Nerviosa de Hombre y de los Vertebrados, three volumes published from 1897 to 1904. Documents from the Nobel Archives reveal that Kölliker, Retzius and Fürst were the ones who proposed Golgi and Cajal for a shared prize. Golgi was nominated by Hertwig, as well. Cajal was proposed by Ziehen and Holmgren, and also by Retzius, as an alternative to a shared prize. Holmgren, who was commissioned to write the report to the Nobel Committee, found Cajal far superior to Golgi. Sundberg, asked for another evaluation, was more positive to Golgi's contributions than Holmgren. Gadelius supported Holmgren's views. The final vote gave a majority for a shared prize. The prize ceremony and the lectures were described in detail in Cajal's autobiography.

Neuroanatomy: Cajal and after Cajal.

This essay commences with a consideration of the relative contributions of Cajal and Golgi to the study of the anatomy of the nervous system. It demonstrates the extent to which Cajal depended upon Golgi's work and how his modifications of the Golgi technique permitted a remarkable series of investigations in which the foundations of the neuron doctrine were laid and in which the intrinsic connectivity of virtually every part of the central nervous system was charted. Cajal's readiness to seize on and develop new techniques was one of the many keys to his success. After him, neuroanatomical studies tended to be focused more on long tract connectivity, using techniques such as those of Nissl and Marchi that had been in place before Cajal commenced his studies. Development of degeneration-based techniques of tracing connections in the late 1950s spearheaded a revolution in neuroanatomy while introduction of mixed aldehyde fixation made possible similarly intensive studies of the fine structure of the nervous system. At this time, the Golgi technique experienced a brief resurgence as neuroanatomists made efforts to bridge the gap between light and electron microscopy. Later developments in techniques for tracing connections included anterograde tracing by autoradiography and retrograde tracing by horseradish peroxidase. These were soon superseded by tracing techniques of increasing sensitivity and specificity that rely upon the cellular and molecular biology of neurons. Although neuroanatomy in its traditional form is perhaps no longer fashionable as a discipline, the techniques of neuroanatomy remain preeminent in many, perhaps all areas of neuroscience.

A historical reflection of the contributions of Cajal and Golgi to the foundations of neuroscience.

In 1906, the Spaniard Santiago Ramón y Cajal and the Italian Camillo Golgi shared the Nobel Prize in Physiology or Medicine, in recognition of their work on the structure of the nervous system. Although both were well-known scientists who had made a large number of important discoveries regarding the anatomy of the nervous system, each defended a different and conflicting position in relation to the intimate organization of the grey matter that makes up the brain. In this communication we will review the importance of Cajal's studies using the method of impregnation discovered by Golgi, as well as the relevant studies carried out by Golgi, the concession of the Nobel Prize and the events that occurred during the Nobel conferences. In summary, we will précis the important contribution of both scientists to the founding of modern Neuroscience.

The sensory neuron and the triumph of Camillo Golgi.

While Golgi's concept of the sensory neuron provided sound reasons for his rejection of the polarity principles underlying the 'neuron doctrine', it is now apparent that his concern about recovery of function after injury and the vast modern findings of ephemerality of connexin-clustered connections in the cerebral cortex and elsewhere in the central nervous system, and credibly termed 'reticularist', has somewhat eclipsed the polarized neuron doctrine of reflex physiology with the "fixed and immutable" connections championed by Cajal. Although Golgi's view was not the result of incisive reasoning based on subsequently confirmed observation, both principles espoused by these combatant Nobel laureate partners have proven robustly operative in different spheres and time frames of neural activity that have vastly enhanced contemporary understanding of neural connectivity.

One century of progress in neuroscience founded on Golgi and Cajal's outstanding experimental and theoretical contributions.

Since the discovery and mapping of the neuronal circuits of the brain by Golgi and Cajal neuroscientists have clearly spelled the fundamental questions which should be answered to delineate the arena for a scientific understanding of brain function: How neurons communicate with each other in a network? Is there some basic principle according to which brain networks are organised? Is it possible to map out brain regions specialised in carrying out some specific task? As far as the first point is concerned it is well known that Golgi and Cajal had opposite views on the interneuronal communication. Golgi suggested protoplasmic continuity and/or electrotonic spreading of currents between neurons. Cajal proposed the so-called "neuron doctrine", which maintained that neurons could communicate only via a specialised region of contiguity, namely the synapse. The present paper has the first and second points as main topics and last century progresses in these fields are viewed as developments of Golgi and Cajal's findings and above all, hypotheses. Thus, we will briefly discuss these topics moving from the transmitter based mapping, which brought neurochemistry into the Golgi-Cajal mapping of the brain with silver impregnation techniques. The mapping of transmitter-identified neurons in the brain represents one of the major foundations for neuropsychopharmacology and a reference frame for the biochemical and behavioural investigations of brain function. Biochemical techniques allowed giving evidence for multiple transmission lines in synapses interacting via receptor-receptor interactions postulated to be based on supramolecular aggregates, called receptor mosaics. Immunocytochemical and autoradiographic mapping techniques allowed the discovery of extra-synaptic receptors and of transmitter-receptor mismatches leading to the introduction of the volume transmission concept by Agnati-Fuxe teams. The Volume Transmission theory proposed the existence of a three-dimensional diffusion of e.g. transmitter and ion signals, released by any type of cell, in the extra-cellular space and the cerebrospinal fluid of the brain. Thus, a synthesis between Golgi and Cajal's views became possible, by considering two main modes of intercellular communication: volume transmission (VT) and wiring transmission (WT) (a prototype of the latter one is synaptic transmission) and two types of networks (cellular and molecular networks) in the central nervous system. This was the basis for the suggestion of two fundamental principles in brain morphological and functional organisation, the miniaturisation and hierarchic organisation. Finally, moving from Apathy's work, a new model of brain networks has recently been proposed. In fact, it has been proposed that a network of fibrils enmeshes the entire CNS forming a global molecular network (GMN) superimposed on the cellular networks.

Cajal: lessons on brain development.

In 1906, Santiago Ramón y Cajal was awarded the Nobel Prize in Physiology or Medicine in recognition of his work on the structure of the nervous system. At that time, almost all of Cajal's work was carried out using the Golgi method, a technique devised by the Italian scientist Camillo Golgi, with whom he shared this prize. Cajal introduced several modifications to the method developed by Golgi and, to avoid the problems encountered in staining myelinated neurons, part of his studies were carried out on embryos and very young animals (the "ontogenetic method"). In this way, Cajal begin to describe aspects of the development of the nervous system. Here, we review some of his wonderful discoveries (for example, the description of the axonal growth cone) from which he derived some of his main theories on the anatomy and physiology of the nervous system: the chemotactic hypothesis and the neuron doctrine.

The dorsal raphe nucleus--from silver stainings to a role in depression.

Over a hundred years ago, Santiago Ramón y Cajal used a new staining method developed by Camillo Golgi to visualize, among many other structures, what we today call the dorsal raphe nucleus (DRN) of the midbrain. Over the years, the DRN has emerged as a multifunctional and multitransmitter nucleus, which modulates or influences many CNS processes. It is a phylogenetically old brain area, whose projections reach out to a large number of regions and nuclei of the CNS, particularly in the forebrain. Several DRN-related discoveries are tightly connected with important events in the history of neuroscience, for example the invention of new histological methods, the discovery of new neurotransmitter systems and the link between neurotransmitter function and mood disorders. One of the main reasons for the wide current interest in the DRN is the nucleus' involvement in depression. This involvement is particularly attributable to the main transmitter of the DRN, serotonin. Starting with a historical perspective, this essay describes the morphology, ascending projections and multitransmitter nature of the DRN, and stresses its role as a key target for depression research.

The Nobel Prize of 1906.

December 2006 marked 100 years since the Nobel Prize in Physiology or Medicine was awarded jointly to 2 pioneers in the cellular anatomy of the central nervous system (CNS), Camillo Golgi and Santiago Ramon y Cajal. Golgi developed the silver impregnation method for studying nerve cells, a technique that clearly showed entire cells with their arborizing dendrites and axons for the first time. Ramon y Cajal seized on the method for a series of groundbreaking studies that provided convincing support for what came to be known as the neuron theory, in opposition to the reigning model of the time, the reticular theory. The retina was one of Ramon y Cajal's favorite tissues for study. Although he was perplexed by the horizontal and amacrine cells, he was remarkably prescient in his analysis of retinal and CNS cellular anatomy. Few scientists have cast such a long shadow in their field, but Ramon y Cajal did not establish the neuron theory single-handedly, and the real tale is much more complicated.

Whither withered Golgi? A retrospective evaluation of reticularist and synaptic constructs.

The 100th anniversary of the shared first Nobel prize in neuroscience by Camillo Golgi and Ramon y Cajal invites reappraisal of the merits of the arguments adduced by these two combative scientists in the light of contemporary knowledge. Guided by cogent reasons for reluctance in accepting the inviolable polarity principle of the neuron doctrine and concern for explaining cerebral recovery of function, Golgi joined the 'reticularists' of his generation. Modern observations of axo-axonic and dendro-dendritic synapses, gap-junction interconnections, rules for the direction and mode of analog or impulse conduction, the myriad diversity of ion channels and gating principles and the complexities of synaptic plasticity have eclipsed the polarized neuron doctrine explanations of reflex physiology and the 'fixed and immutable' connections successfully championed by Cajal. Without violating the cell theory, expanded modes of neuronal and glial communication have encompassed reticularist notions and provided insight into the long-term changes underlying synaptic and extra-synaptic neural patterns. Both laureates espoused operative principles that have survived in different modes and distinctive temporal domains. Together, they reflect the roots of our contemporary understanding of neural interaction.

The contribution of Camillo Golgi to our understanding of the structure of the nervous system.

A hundred years ago Camillo Golgi and Santiago Ramón y Cajal were awarded the Nobel Prize for Physiology or Medicine for their investigations on the structure of the nervous system. The work of Cajal is universally acknowledged, whereas Golgi's contribution is less well known. This article reviews the main achievements of Golgi in that field. In addition to Golgi's most important results, the errors he made in interpreting his own findings are examined. These errors contributed notably to a widespread neglect and underestimation of his important contributions to our understanding of the structure of the nervous system.

Sesquicentenary of the birthday of Santiago Ramón y Cajal, the father of modern neuroscience.

The appearance of Santiago Ramón y Cajal in the world of neuroscience provoked a radical change in the course of its history. Cajal's studies of the microanatomy of virtually the whole CNS and his observations regarding degeneration and regeneration, together with his theories about the function, development and plasticity of the nervous system, had a profound impact on researchers of his era. These studies represent the roots of what are today some of the most exciting areas of discovery in terms of the structure and function of the brain in both sickness and health.

[The Golgi silver impregnation method: commemorating the centennial of the Nobel Prize in medicine (1906) shared by Camillo Golgi and Santiago Ramón y Cajal]. / La técnica de impregnación argéntica de Golgi. Conmemoración del centenario del premio nobel de Medicina (1906) compartido por Camillo Golgi y Santiago Ramón y Cajal.

The Golgi silver impregnation technique is a simple histological procedure that reveals complete three-dimensional neuron morphology. This method is based in the formation of opaque intracellular deposits of silver chromate obtained by the reaction between potassium dichromate and silver nitrate (black reaction). Camillo Golgi, its discoverer, and Santiago Ramón y Cajal its main exponent, shared the Nobel Prize of Medicine and Physiology in 1906 for their contribution to the knowledge of the nervous system structure, Their successes were largely due to the application of the silver impregnation method. However, Golgi and Cajal had different views on the structure of nervous tissue. According to the Reticular Theory, defended by Golgi, the nervous system was formed by a network of cells connected via axons within a syncytium. In contrast, Cajal defended the Neuron Doctrine which maintained that the neurons were independent cells. In addition, Golgi had used a variant of his "black reaction" to discover the cellular organelle that became known as the Golgi apparatus. Electron microscopy studies confirmed the postulates of the Neuron Doctrine as well as the existence of the Golgi complex and contributed to a resurgence of use of the Golgi stain. Although modern methods of intracellular staining reveal excellent images of neuron morphology, the Golgi technique is an easier and less expensive method for the study of normal and pathological morphology of neurons.

Pioneering a golden age of cerebral microcircuits: the births of the combined Golgi-electron microscope methods.

Theodor W. Blackstad devised methods by which the synaptic connectivity of neuron somata and their dendritic and axonal processes in the CNS could be analyzed by the combined use of light and electron microscope techniques. His first publication on that subject dates from 1965 and was contemporary to the independent research by William K. Stell. The Golgi method was an obvious neuronal marker at those times, and Blackstad and Stell showed that the Golgi precipitate is electron-dense and intracellular and, therefore, it could help identify in the electron microscope, with great accuracy, profiles of neurons initially visualized in light microscopy. Besides this convergent research, Blackstad demonstrated for the first time that anterograde axonal degeneration could be combined with the Golgi-electron microscope method, allowing the identification of the neurons whose dendritic or somatic profiles were postsynaptic to the severed axonal afferent projections. Last, but not least, Blackstad pioneered de-impregnation techniques for electron microscopy of Golgi preparations. This had a great impact in the study of synaptic circuitry. The present account is a remembrance of the events that linked these early attempts with the development of a de-impregnation method based on gold toning by Alan Peters and the present author.