A Durable Nissl Stain for Frozen and Paraffin Sections

Anticataleptic activity of nicotine in rats: involvement of the lateral entorhinal cortex

RATIONALE

Recently, it was found that cyclosomatostatin-induced catalepsy in middle-aged rats is accompanied by neuronal hypoactivation in the lateral entorhinal cortex (LEntCx); this hypoactivation was reversed by systemic administration of nicotine combined with diphenhydramine. These findings suggest the ability of nicotine to regulate catalepsy and the involvement of the LEntCx in this nicotine effect.

OBJECTIVES

The study was aimed to assess whether nicotine alone influences catalepsy when injected into the LEntCx and some other neuroanatomical structures.

METHODS

Experiments were conducted with male Wistar rats of 540-560 days of age. Catalepsy was induced by intracerebroventricular injection of cyclosomatostatin and assessed by the standard bar test. Nicotine was injected into the LEntCx, prelimbic cortex (PrCx), or basolateral amygdala (BLA). The tissue levels of tyrosine hydroxylase, dopamine, and DOPAC in the substantia nigra pars compacta and dorsal striatum were measured with use of HPLC and ELISA.

RESULTS

Injections of nicotine into the LEntCx but not into the PrCx and BLA produced anticataleptic effect; the nicotine effect was significantly reversed by intra-LEntCx administration of NMDA and non-NMDA glutamate receptor antagonists. Nicotine also attenuated cataleptogen-induced changes in nigrostriatal dopamine metabolism.

CONCLUSIONS

This may be the first demonstration of anticataleptic activity of nicotine. The results show that the effect is mediated by nicotine receptors in the LEntCx, via a glutamatergic mechanism. These findings may help advance the development of novel treatments for extrapyramidal disorders, including parkinsonism.

Medicinal Plant Analysis: A Historical and Regional Discussion of Emergent Complex Techniques

The analysis of medicinal plants has had a long history, and especially with regard to assessing a plant's quality. The first techniques were organoleptic using the physical senses of taste, smell, and appearance. Then gradually these led on to more advanced instrumental techniques. Though different countries have their own traditional medicines China currently leads the way in terms of the number of publications focused on medicinal plant analysis and number of inclusions in their Pharmacopoeia. The monographs contained within these publications give directions on the type of analysis that should be performed, and for manufacturers, this typically means that they need access to more and more advanced instrumentation. We have seen developments in many areas of analytical analysis and particularly the development of chromatographic and spectroscopic methods and the hyphenation of these techniques. The ability to process data using multivariate analysis software has opened the door to metabolomics giving us greater capacity to understand the many variations of chemical compounds occurring within medicinal plants, allowing us to have greater certainty of not only the quality of the plants and medicines but also of their suitability for clinical research. Refinements in technology have resulted in the ability to analyze and categorize plants effectively and be able to detect contaminants and adulterants occurring at very low levels. However, advances in technology cannot provide us with all the answers we need in order to deliver high-quality herbal medicines and the more traditional techniques of assessing quality remain as important today.

Effects of stimulation of the insular cortex on execution of the antrofundal reflex in conscious dogs

Neuroanatomical studies demonstrated the existence of direct descending projections from the insular cortex to the area of the solitary tract nucleus responsible for mediating the vagovagal reflexes of the proximal part of the gastrointestinal tract. These studies provided grounds for suggesting that one of the mechanisms mediating the influences of the insular cortex on stomach function may be modulation of its vagovagal reflex reactions, one of which is the antrofundal inhibitory reflex. Experiments on conscious dogs were performed to study the effects of electrical stimulation of the insular cortex on execution of the antrofundal gastric reflex in conditions of intermittent gastrointestinal tract activity during fasting. Stretching of the walls of the antral segment of the stomach during the active period of intermittent gastric activity led to suppression of contractions in the fundal segment. Electrical stimulation of the insular cortex was found to prolong this reflex reaction. Thus, one result of activation of the insular area of the cortex is enhancement of the inhibitory vagovagal gastric reflexes, in all probability occurring as a result of modulation of neurotransmission in the vagovagal reflex arc system.

Identification of a respiratory related area in the rat insular cortex

The aim of this study was to map areas within the rat insular cortex from which respiratory responses originate and compare those sites with gastrointestinal control regions. The insular cortex was systematically microstimulated and histological location of responsive sites determined. Increased inspiratory airflow and decreased respiratory cycle duration were considered to be respiratory excitatory responses. The responses were localized in dysgranular and agranular insular cortex at levels caudal to the joining of the anterior commissure. More rostrally, respiratory inhibitory responses were elicited: these were manifested as a decrease in inspiratory airflow without a significant alteration in respiratory cycle duration. Respiratory inhibitory responses were usually accompanied by changes in gastric motility. These results suggest that the respiratory area in the rat insular cortex consist of two distinct zones which overlap a region modulating the gastrointestinal activity.Key words: rats, insular cortex, respiration, gastrointestinal motility.

Gastric related neurons in the rat medial vestibular nucleus

Some structural and functional peculiarities of the rat vestibular nuclei neurones involved in realisation of vestibular-gastrointestinal reflectory reactions were studied. After microinjection of a horseradish peroxidase solution in the 'gastric' area of the nucleus tractus solitarius, retrogradely-labelled cell bodies were found in caudal part of the medial vestibular nucleus. Electrical stimulation of these neurons resulted in the decrease of gastric tone. The respiratory arrest was registered simultaneously. The results suggest that activation of the identified vestibular neurons can induce coordinated changes in visceral systems which are peculiar to a vomiting reaction.

Localization of neurons innervating the upper portion of the duodenum in the motor nucleus of the vagus nerve

Using the method of the retrograde axonal transport of horseradish peroxidase and a microelectrode technique, a population of neurons sending axons to the upper portion of the duodenum was identified in the dorsal motor nucleus of the vagus nerve. It was established that the maximal number of such neurons was located 1.0-2.5 mm rostral to the obex. The effects of their stimulation on the electrical activity of the smooth muscles of the duodenum was studied.

Distribution of carbonic anhydrase activity in the rat central nervous system, as revealed by a new semipermeable technique

Results obtained with a new method provided evidence for the extraneuronal localization of CA and supports the idea that the enzyme is very widespread in non-neuronal cell types of the CNS. Most of these cells were considered to be oligodendroglia, but probably the astrocytes also contributed to the reactivity of the neuropil. The perineuronal CA activity observed in the spinal cord, brainstem, cerebellum, and hippocampus could be astrocytic in origin. Our observations concerning the widespread CA staining of the CNS vessels pointed to the possible functional significance of CA in the vessel wall. This activity could be due not only to pericytes but also to astrocytic processes. We have not found stained myelin sheats although biochemically the myelin contained the enzyme. Might be that our histochemical reaction was not sensitive to the membrane bound form of the CA. The fact that the reaction of the nucleoli did not disappear after acetazolamide treatment could be explained on the basis of binding of the cobalt-phosphate complex to the proteins of the nucleolus.

Cytoarchitecture of the avian ventral lateral geniculate nucleus

The avian thalamic ventral lateral geniculate nucleus (GLv) was studied by light microscopic techniques in order to understand its anatomy, neuronal composition, and the nature of its retinal and tectal afferents. The avian GLv is of considerable interest because physiological experiments show that it is the brain structure with the highest percentage of color-opponent responses (Maturana and Varela, '82). We used adult pigeons and quail for the present study. With Nissl techniques a predominance of medium-size neurons (58%) constitute the GLv. The shape, size, and orientation of the different neurons is highly variable throughout the GLv. With the Golgi methods, 5 classes of neurons are distinguished: I and IV (large), II (medium-size), III and V (small). Some class IV large neurons have bifurcated axons; no axons were distinguished on the small neurons. Optic fibers penetrating the GLv are often collateral branches of retinal axons that continue elsewhere. Fink-Heimer methods show that retinal axon terminals end around large and medium-size neurons and also reach the internal lamina of the GLv. HRP tracing shows that the large and medium-size neurons of the GLv project to the optic tectum. On the basis of comparisons between the cytoarchitecture of the GLv described here and the physiological findings previously reported (Maturana and Varela, '82; Pateromichelakis, '79), we suggest that: (1) large GLv neurons are the color-opponent units, (2) medium-size neurons are the movement-sensitive units, and (3) small neurons are either interneurons (local circuit neurons), or they might project to the area pretectalis or to some other GLv projection region not yet described.

The anatomical organization of retinal projections in the shark Scyliorhinus canicula with special reference to the evolution of the selachian primary visual system

The retinal projections of the shark Scyliorhinus canicula were investigated using both the degeneration technique after eye removal and the radioautographic method following the intraocular injection of various tritiated tracers (proline, leucine, fucose, adenosine). The results showed contralateral projection via different optic tract components (TOM, AOT, TOm, TOl, ROVm, RODm) to various areas and nuclei of the hypothalamus (NSC), thalamus (NODLAT, NODMAT, NTTOM, NOVT, NODPT), pretectum (NOPC, NOCPd, NOCPv), tectum (SFGS, SGI) and mesencephalic tegmentum (AOTMd, NOTMv). Ipsilateral retinal projections were found to arborize within 7 distinct zones at the hypothalamic (NSC), thalamo-pretectal (NODLAT, NTTOM, NOVT, NOPC, NOCpd) and tectal (SFGS) levels. A comparison of the data with those previously obtained in different species of elasmobranchs and batoids indicate the existence of a common and consistent pattern of organization of the primary visual system in all selachians. Many of the discrepancies reported in studies on the organization of selachian retinal projection may be listed to methodological differences and/or interspecies variations in the cytoarchitecture of the different visual centers. Moreover, a comparison of the primary visual system of more primitive squalomorph sharks with that of the more advanced galeomorph sharks and batoids suggests that this system evolved through an increase in the neuronal density of the target structures and transformations in the dendritic configurations of the postsynaptic neurons rather than through an increase in the total number of projection zones.

Incomplete maturation of brainstem auditory nuclei in genetically induced early postnatal cochlear degeneration

In the Shaker-2 mouse mutant, a cochleo-saccular type of genetically induced inner ear degeneration occurs. Morphological signs of degeneration are evident in the 3rd postnatal week and a severe and almost total degeneration has occurred by the age of 6-9 weeks. There are no qualitative differences between the brain of the normal CBA/J mouse and that of the Shaker-2 mouse. The growth of the auditory brainstem nuclei (dorsal cochlear nucleus and ventral cochlear nucleus) in the mutant Sh-2 mouse has stopped by 14 days of age--but not in the normal CBA/J mouse. The brainstem as a whole continues to grow between 14 and 140 days of age in both strains. The early cochlear degeneration coincides with the critical period when a normal input from the peripheral receptor organ is necessary for the maturation of the central auditory pathway.

Subdivisions of the inferior colliculus in the barn owl (Tyto alba)

The inferior colliculus in the barn owl contains three subdivisions: the central (ICC), external (ICX), and superficial (ICS) nuclei. The nuclei are distinguished on the basis of their cyto- and myeloarchitecture, connectivity, and physiological properties. The ICC may be further divided into dorsal (ICCd) and ventral (ICCv) parts. Auditory fibers ascending in the lateral lemniscus enter the ICCd and ICCv, but not the ICX or ICS. The ICX receives its auditory input from the ICC. The ICC and ICX in owls are similar in position, anatomy, connectivity, and physiology to the ICC and ICX in mammals, suggesting that these structures are homologous. Units in the ICC are organized tonotopically, whereas units in the ICX are organized according to the locations of their spatial receptive fields. This implies that a transformation from a tonotopic to a spatiotopic organization takes place in the ICX of the owl.

The retinofugal pathways in a primitive actinopterygian, the chondrostean Acipenser güldenstädti. An experimental study using degeneration, radioautographic and HRP methods

Experimental study of the retinofugal pathways in Acipenser güldenstädti was carried out on 109 specimens using 3 experimental tracing methods: Fink-Heimer (after retinal ablation), radioautography (after intraocular injection of tritiated markers) and HRP (after intraocular injection of HRP or iontophoretic deposit of HRP on the optic nerve). The optic fiber was found to partially decussate at the chiasm and to project to 5 contralateral regions: (1) hypothalamus (area optica hypothalami); (2) thalamus (area optica dorsalis thalami, area optica mediale thalami, nucleus thalamicus tractus optici marginalis, nucleus laminaris ventralis); (3) pretectum (nucleus pretectalis ventralis, nucleus commissurae posterioris, nucleus intercalaris lateralis); (4) optic tectum (superficial layers); and (5) mesencephalic tegmentum (area optica accessoria). The ipsilateral component was well developed and innervated the same regions mentioned above. A few contralateral optic fibers crossed again in the posterior commissure and terminated within ipsilateral visual pretectal structures. Although the architecture of the visual centers was less elaborated in this paleopterygian than in neopterygians (holosteans, teleosteans), we observed that the general organization of the retinal contralateral projections in this fish was comparable to that of more advanced actinopterygians. Our results indicate that this pattern was probably set at a very early date, perhaps as soon as the emergence of the chondrostean grade at the beginning of the Devonian.

The medial accessory nucleus of Bechterew: a cell group within the anatomical limits of the rostral oculomotor complex receives a direct prefrontal projection in the monkey

The medial accessory nucleus of Bechterew, a vertically oriented cell group in the rostral lateral oculomotor nucleus (OMN), contiguous dorsally with the nucleus of Darkschewitsch (ND) and ventrally with the parvocellular red nucleus, is separated from the interstitial nucleus of Cajal (IC) by a small paraoculomotor fascicle (POF) that forms the anatomical limits of the OMN. Horseradish peroxidase (HRP) gel implants in the prearcuate frontal cortex dorsal to the caudal third of the principal sulcus in the monkey resulted in an anterogradely labeled bilateral projection to this paraoculomotor cell group. The functional role of this largely overlooked nucleus is yet to be determined. However, the failure to retrogradely label following HRP injections involving both the extraocular muscles and ciliary ganglion suggests that it cannot be classified as belonging to either the somatic or the visceral cell column at the present time. We suggest that, like IC and ND, it probably contributes to the POF of the medial longitudinal fasciculus and may be involved in internuclear connections. There is little doubt that it has been involved inadvertently in studies of oculomotor connections.

Retinal projections in the African cichlid fish, Haplochromis burtoni

The retinal projections of the African cichlid fish, Haplochromis burtoni, have been traced by two different methods. Following unilateral enucleation, a modified Nauta technique was used to demonstrate degenerating axons and terminals. Some degeneration was found after 5 days but optimal survival time was 20-25 days. Orthograde transport of horseradish peroxidase (HRP) into the cut optic nerve also was used to examine retinal fiber distribution in the brain. The optic nerve is completely crossed and gives rise to two major tracts, the tractus opticus dorsomedialis and the tractus opticus ventrolateralis, as well as minor fascicles. Projections were found in the suprachiasmatic nucleus, ventral thalamus, dorsal thalamus, the pretectal complex, and the tectum opticum. The optic tectum is large and laminated and the great majority of the optic fibers terminate there. Degeneration methods revealed projections in the tectum to the stratum opticum, stratum griseum et fibrosum superficiale, and stratum album centrale. HRP staining confirmed these projections and revealed another projection to the stratum griseum centrale.

Cochlear nuclear complex of mice

Using serial sections stained with luxol fast blue-cresyl violet, the cochlear nuclei of CBA/J mice were parcellated into the same cytoarchitectonic areas and layers that Osen (1969) used in cats. Within the spherical cell areas, the distribution of Nissl substance is more reliable than soma shape in identifying the spherical cells. The area of large spherical cells is extremely small in CBA/J mice but does contain significantly larger neurons than the small spherical cell area. In Golgi preparations, bushy cells are found in all areas of the ventral cochlear nucleus except in the octopus cell area and granule cell layer. They are more numerous anteriorly than posteriorly and details of their morphology are quite variable. Stellate cells are found throughout the ventral cochlear nuclei but are present in greatest numbers in the multipolar cell area; they are rare in the large spherical cell area and octopus cell area. Because size, soma morphology, and dendritic arborization vary on a continuum rather than in discrete steps, we have not subcategorized these neurons. Octopus cells are restricted to the posterior, dorsomedial area of the ventral cochlear nucleus. In the central region of the dorsal cochlear nucleus, stellate cells abound and are categorized as vertical, elongate, or radiate cells. In the granule layer of the dorsal cochlear nucleus there are both fusiform and Purkinje-like neurons, so named because of their resemblance to cerebellar Purkinje cells. These Purkinje-like cells differ from fusiform cells in having 1) a smaller cell body, spherical in shape, 2) no basal dendrites, 3) a sagittal dendritic orientation, 4) elaborate dendritic branching, and 5) abundant dendritic spines.

The retinofugal pathways in the primitive African bony fish Polypterus senegalus (Cuvier, 1829)

Retinal projections were studied using Fink-Heimer and radioautographic methods in Polypterus senegalus, a species which is representative of a small group of African fresh-water bony fish often considered to be very primitive. The large optic nerve showed partial decussation at the chiasm. Two major contralateral tracts were observed: the axillary and marginal optic tracts, with the latter being subdivided posteriorly into the tractus opticus medialis and tractus opticus lateralis. The retina projected onto the: (1) hypothalamus (area optica postoptica); (2) thalamus (nucleus opticus dorsolateralis thalimi, nucleus dorsomedialis thalami, corpus geniculatum laterale, area optica dorsolateralis thalami, area optica ventrolateralis thalami); (3) pretectum (nuclei commissurae posterioris, pretectalis ventralis, pretectalis dorsalis); and (4) optic tectum (stratum marginale, stratum opticum, stratum griseum et fibrosum superficiale, stratum griseum et album centrale, stratum griseum et fibrosum periventriculare). Ipsilateral retinal projections were demonstrated to the same 4 levels and more precisely to the nucleus opticus dorsolateralis thalami, area optica dorsolaterale thalami, nucleus commissurae posterioris, stratum marginale and stratum griseum et album centrale. The existence of a retinal projection to the mesencephalic tegmentum is discussed. Comparing the primary optic system of Polypterus with that of other jawed vertebrates, and particularly with that of other bony fish, indicated that this species possesses a combination of characteristics which are both actinopterygian and sarcopterygian. The phylogenetic significance of this mozaic anatomical arrangement is discussed.

Fine structure of the superficial layers of the viper optic tectum. A Golgi and electron-microscopic study

The superficial layers of the viper optic tectum, which receive fibers from he retina, were studied using both light and electron microscopes. The optic fibers layer, or stratum opticum, is composed of 200 to 250 tight fascicles containing thin fibers, nearly all of which are myelinated. The main optic terminal layers, the stratum griseum et fibrosum superficiale, the greatest part of the cellular population is composed of small vertically oriented neurons and horizontal nerve cells, many of which are probably local circuit neurons. The neuropil of the stratum griseum et fibrosum superficiale is made up of small nerve elements, including three types of profiles containing synaptic vesicles; 1) boutons with pleiomorphic synaptic vesicles (P), representing over 47% of the total population of profiles containing synaptic vesicles and comprising three subgroups (P1, P2, and P3); 2) boutons with spheroidal synaptic vesicles (S), forming more than 29% of the total populations of profiles containing synaptic vesicles and comprising two categories, S1 and S2 (S2, the more numerous, represents the optic boutons, which make up 22% of the total populations of profiles containing synaptic vesicles); and 3) dendrites with pleiomorphic vesicles, accounting for approximately 23% of the total populations of profiles containing synaptic vesicles. A study of synaptic patterns revealed a large number of serial synapses and a lesser number of triplets or triadic synapses. The presynaptic components are boutons containing spheroidal (S1, S2) or pleiomorphic (P1, P2, P3) synaptic vesicles. The intermediate profile was always a dendrite with synaptic vesicles which frequently belonged to the small neurons of the stratum griseum et fibrosum superficiale. Comparison of the present results with other recent data shows that the synaptic circuitry in the optic tectum of Vipera aspis closely resembles the pattern observed in the optic tectum of other vertebrates, ranging form fish to mammals. However, quantitative differences exist, especially with regard to the proportion of dendrites containing synaptic vesicles. Their number seems to be higher in sauropsidians than in mammals, particularly in primates.

Mouse brainstem auditory nuclei development

The cross-sectional areas of brainstem auditory neurons were measured in a potential developmental series of mice. There is no demonstrable neuronal growth between days 1 and 3. Between days 3 and 12 the neuronal somas grow rapidly to their adult size. Most of this growth occurs prior to any cochlear physiological activity and all of it occurs before cochlear maturation. Most brainstem auditory neurons of 45-day-old mice postnatally deprived of sound or with conductive losses are of a size comparable to normal nine-day-old mice.

Proprioceptive reflex connections of head musculature and the mesencephalic trigeminal nucleus in the carp

The location of the sensory cells concerned with the proprioception of respiratory and extraocular musculature in the carp was studied by retrograde transport of horseradish peroxidase. Sensory cell labeling after intramuscular HRP injection was exclusively found in the trigeminal-facial-anterior lateral line ganglion complex. The muscles innervated by the trigeminal system are represented in the more rostral ganglion areas, the muscles innervated by the facial system in the more caudal ganglion parts. Nearly all labeled cells were situated on the ipsilateral side. Sensory cells labeled after extraocular muscle injection were also found all over the V-VII ganglion, however, to a considerable degree also on the contralateral side. All muscle injections failed to give mesencephalic trigeminal cell labeling. The resluts of intranerve HRP injections in peripheral trigeminal nerve branches strongly suggests a perioral mechanoreceptive function for the mes.V neurons. A bisynaptic proprioceptive reflex model is described for respiratory musculature consisting of a sensory cranial ganglion component connected to the descending trigeminal nucleus, which on its turn links the proprioceptive ganglion cells to the trigeminal and facial motorneurons. Monosynaptic proprioceptive reflex circuits are discussed on neurophysiological grounds.

Afferent and efferent components of the facial nerve in the bullfrog (Rana catesbeiana)

The afferent and efferent components of the facial nerve were traced within the brain stem of Rana catesbeiana, using three different neuroanatomical techniques. Primary afferent fibers could be traced to the spinal tract of trigeminal nerve and to fasciculus solitarius as far caudally as the first or second spinal segment, using silver degeneration methods. Cobalt filling of of the entire nerve showed the same distribution of afferent fibers, as well as the filling of the cells within the mesencephalic nucleus of trigeminal, indicating the origin of a proprioceptive component of the facial nerve. Cobalt iontophoresis and horseradish perioxidase experiments showed that the motor nucleus of the facial nerve was located just ventral to the fourth ventricle, and caudal to the motor nucleus of trigeminal. The distribution of afferent fibers to fasciculus solitarius and the spinal tract of trigeminal is similar in some respects to the distribution of afferent fibers from the trigeminal and vagal nerves in the bullfrog. The afferent fibers from the three cranial nerves are found as far caudally in the brain stem as the second spinal segment.

Graphic representation of the distribution of acetylcholinesterase in cat dorsal root ganglion neurons

Acetylcholinesterase (AChE) activity of primary sensory neurons of the cat has been quantitated and correlated with cell size. Dorsal root ganglia of the fourth and fifth thoracic spinal levels were studied. Frozen longitudinal and cross-sections were collected serially and stained with Cresyl Violet for total cell counts of the ganglia on the left; the average count was 3375 cells. Ganglia from the right were stained for AChE after the method of Karnovsky & Roots (1964) as modified by El Badawi & Schenk (1967), and counterstained with Haematoxylin. Cells were counted in every fourth section and the diameter of each was recorded. AChE-positive cells were classified as brown (B1, B2, B3) and AChE-negative ones as blue (BL). An inverse correlation exists between cell size and AChE activity. High activity was demonstrated in 29% of the cells (B1), moderate activity in 52% (B2), minimal activity in 15% (B3) and 4% were classified as AChE-negative (BL). Small cells with high activity were centrally located in the ganglia whereas large AChE-negative cells were peripherally distributed. Chi-Square analysis revealed that the size of the cell was not independent of the enzyme colour category.

Cochlear nerve projections following organ of corti destruction

Experimental organ of Corti destruction results in (1) secondary loss of all type I spiral ganglion neurons, (2) development of type III spiral ganglion neurons, (3) degeneration of most cochlear nerve myelinated fibers, and (4) terminal degeneration in the ventral and dorsal cochlear nuclei. The first signs of degenerative changes occur by eight days after organ of Corti destruction and degeneration debris remains until 28 weeks after destruction.

Distinct auditory and lateral line nuclei in the midbrain catfishes

The catfish torus semicircularis (TS) comprises two major nuclei, which are specialized to process separately inputs of three acousticolateral modalities: VIII nerve acoustic input in one, and lateral line mechanoreceptive and electroreceptive input in the other. Electrophysiological recording and mapping experiments demonstrate a medial auditory region, a lateral electroreceptive region, and an intercalated mechanoreceptive region in the TS Nissl and Golgi-Cox preparations distinguished two rostrocaudally elongate, nuclear divisions, which correlate, one with the auditory and the other with the mechano- and electroreceptive regions. The medially positioned auditory nucleus is here called the nucleus centralis. The nucleus centralis appears as a rostrally flattened cylinder of uniformly packed cells, covered dorsally and laterally by a fiber rind. Cells within this nucleus conform to one of three general cell types based upon somatic and dendritic morphology: type 1 cells, which are the most abundant" have a single major primary dendrite and an axon typically arising from the same somatic pole; type 2 cells have two major primary dendrites and an axon, which issues from a third distinct somatic pole; and type 3 cells have several major primary dendrites and their axons are associated with one of the major somatic poles. No systematic orientation of dendrites could be found in the nucleus centralis. The laterally positioned lateral line nucleus, to be called the nucleus lateralis, includes two subdivisions: a large pars lateralis containing predominantly electroreceptive units, and a smaller, ventromedial pars medialis encompassing predominantly mechanoreceptive units. Each subdivision is found to be somatotopically organized, inputs from the head projecting to rostral areas and inputs from the tail to caudal areas. Although the cell types resemble those described for the nucleus centralis, a greater degree of cytoarchitectural orderliness is discernible: (a) cells in the nucleus lateralis group into four, alternating cell-poor cell-rich, layers; and (b) the dendritic fields of many type 1 and type 2 cells located in layer II tend to orient in a rostrodorsal-caudoventral attitude, perpendicular to the laminar planes. Fink-Heimer preparations of brains with unilateral, lateral line lobe lesions demonstrate heavy fiber and terminal degeneration confined to the nucleus lateralis on both sides. Lateral line fibers ascend bilaterally in the lateral halves of the lateral lemnisci. At the level of the dorsal oculomotor nucleus the lemniscal fibers in this portion split into two fascicles, one proceeding rostrally to innervate the rostral portion of the nucleus lateralis, and the other arching back dorsolaterally to innervate the caudal portions of the nucleus.

The vestibular complex of the American opossum, Didelphis virginiana. I. Conformation, cytoarchitecture and primary vestibular input

Degeneration experiments reveal that the vestibular nerve of the adult opossum distributes to an extensive and diverse area of the brainstem and, as in placental mammals, the traditionally named nuclei do not receive a uniform distribution of primary afferent fibers. Nevertheless, such nuclei as well as other nearby cell groups have been considered as vestibular since they share other mutual connections. Except for subgroups "l", "g" and the nucleus supravestibularis all of the vestibular subdivisions generally recognized in more specialized placentals (e.g., the cat) have been identified in the marsupial opossum. Each of the vestibular nuclei and "extra-nuclear" cell stations are described as to their boundaries, cytoarchitecture and dendritic domain. Whenever possible we have employed a terminology consistent with that used for the cat. In several instances we have used results from experimental degeneration material to identify nuclear boundaries and divisions which are not apparent in routine Nissl, Golgi or silver preparations.

Punch sampling technique for quantitative identification of tritiated D-amphetamine

A punch sampling, tissue solubilization, and scintillation counting technique has been devised for the quantitative identification of tritiated d-amphetamine in monkey brain tissue. The method is superior to autoradiography in identifying this water soluble radiochemical, and is easier and more anatomically precise than radiochemical assay of brain homogenates. This rapid and simple technique allows one to survey the whole brain by sampling unit volumes of individual structures verified by light microscopy. The procedure consists of six steps which may be spaced as the laboratory schedule permits: obtaining tissue blocks, preparation for sectioning, punch sampling and sectioning, preparing samples for scintillation counting, histological verification of sample sites, and analysis of scintillation count data. The technique has been successfully used to demonstrate a gradient of radioactivity following experimental intraventricular injections of 3H amphetamine.

Effects of posterior neocortical lesions on wavelength, light/dark and stripe orientation discrimination in ground squirrels

Thirteen-lined ground squirrels (Citellus tridecemlineatus) were trained on three two-choice visual discrimination problems: light/dark, color and stripe orientation. After posterior neocortical lesions in one or two stages, they were tested on all three discriminations. The results demonstrate that animals with large posterior neocortical lesions which produced retrograde changes throughout the dorsal lateral geniculate (LGNd) were capable of light/dark and wavelength discrimination. These animals were not able to discriminate stripe orientation. It is proposed that wavelength discrimination depends on extrageniculostriate mechanisms in posterior neodecorticates of this species.

Telencephalic projections in two teleost species

The efferent pathways of the telencephalon were investigated in the percomorph Eugerres and the berycomorph Holocentrus. One telencephalic hemisphere was resected by suction and the animals were perfused 7-35 days thereafter. The brains were processed according to a modification (Method 7 in Ebbesson, '70) of the Fink-Heimer ('67) technique for selective silver impregnation of degenerating axons and terminals. Some fibers emerging from the lesioned telencephalic hemisphere terminate upon the contralateral hemisphere. The large bulk of efferent fibers, however, descends into the ipsilateral diencephalon and gives off the so-called strio-tectal bundle (STB) as well as the medial forebrain bundle (MFB). The remaining contingent eventually splits into the so-called strio-lobar bundle (SLB) and the lateral forebrain (LFB), but, previous to splitting, it contributes most of the telencephalic projection to the optic tectum in Eugerres, and gives abundant terminals to the ipsilateral nucleus rotundus or prethalamicus in both Eugerres and Holocentrus. The STB conveys all telencephalo-tectal fibers in Holocentrus, and some of them in Eugerres. Telencephalic efferents teminate ipsilaterally in the middle level of the tectum's stratum griseum centrale; in Holocentrus there is also a small projection to the stratum opticum. The MFB terminates at the caudal hypothalamus and gives terminals all along its course. The LFB also gives terminals all along its course and terminates upon a nucleus located between the midline and the corpus glomerulosum. The SLB spreads out and terminates in the inferior lobe of the hypothalamus.

Projections of the optic tectum in two teleost species

The efferent pathways of the optic tectum have been investigated in the percomorph Eugerres and the berycomorph Holocentrus. A portion of the dorsal-dorsolateral region of the optic tectum was unilaterally resected by suction. The animals were perfused 6-30 days thereafter, and the brains were processed according to a modification (Method 7 in Ebbesson, '70) of the Fink-Heimer ('67) technique for the selective silver impregnation of degenerating axons and terminals. Three groups of fibers emerge from the lesioned region (a) a medial group, which runs towards the midline and terminates in the ipsilateral torus longitudinalis and the contralateral tectum; (b) an ascending group, which enters the dorsocaudal region of the diencephalon and terminates in pretectal cell groups, in the dorsomedial optic thalamic nucleus, and in the nucleus rotundus or prethalamicus; and (c) a descending group, which funnels down into the midbrain tegmentum. Here abundant terminals are given to dorsolateral cell groups and to the nucleus isthmi. A recurrent fascicle leaves the mainstream and ascends to terminate in scattered diencephalic cell groups, in the nucleus geniculatus posterior pars ventralis, and in the nucleus rotundus or prethalamicus. The bulk of descending fibers then forms an ipsilateral bundle, which gives terminals to the lateral reticular formation of mesencephalon and rhombencephalon, and a contralateral (i.e., the predorsal) bundle, which terminates in the medial reticular formation of mesencephalon and rhombencephalon.

Axonal projections and connections of the principal sensory trigeminal nucleus in the monkey

To date, anatomical studies of ascending principal sensory trigeminal nuclear (PrV) axons in the monkey have been restricted to few incomplete investigations utilizing the Marchi method. In the present study total or partial unilateral stereotaxic lesions of PrV were made in cebus and rhesus monkeys and analyzed with the aid of a variety of Nauta silver impregnation techniques applied to frozen sections. Analysis of the fiber degeneration emanating from PrV lesions indicates that PrV fibers form an ascending system composed of two distinct components. Most PrV axons project ventromedially from PrV through the ventral pontine tegmentum and gradually decussate across the midline in the mesencephalic tegmentum up to the level of the caudal pole of nucleus interpeduncularis. These decussated fibers form the trigeminal lemniscus, which courses dorsomedial to the medial lemniscus during its ascent into the diencephalon. A few whorls of preterminal fiber degeneration separating from the trigeminal lemniscus first appear in the magnocellular area of the thalamus medial to the medial geniculate body. The lemniscal PrV axons terminate densely throughout most, but not all, of the magnocellular part of nucleus ventralis posteromedialis (VPM) contralateral to the side of their origin. Some collateral-like fibers from the trigeminal lemniscus also were observed ending in the ventral segment of the zona incerta. Other axons, arising chiefly from the dorsal one-third of PrV form a smaller ipsilateral trigeminothalamic projection. These fibers all remain on the side of their origin and terminate consistently in a discrete dorsomedial paralaminar portion of VPM that does not receive lemniscal PrV connections. A commissural fiber system at the pontine level connects parvicellular reticular cells with their counterparts and the motor trigeminal nucleus of the opposite side. These interconnections appear to provide an anatomical link for the integration of bilateral trigeminal sensory information and motor function.

The visual connections of the adult flatfish, Achirus lineatus

Metamorphosis in the flatfish is characterized by the migration of one eye around the dorsal surface of the head to a position adjacent to the other eye on the new top side of the animal. The visual connections of the adult flatfish, Achirus lineatus, were examined. Either the migrating or non-migrating eye was removed and the animal allowed to survive for one to three weeks. Alternate sections of the brain were stained by a modification of the Fink-Heimer technique, or with cresyl violet. The diencephalic visual connections of the flatfish were similar to those of other teleosts with contralateral projections to the nuclei corticalis, dorsomedialis thalami, pretectalis, and the corpus geniculatum laterale. The distribution of the retinal efferents to the optic tectum is unique in the flatfish. In the medial one-third of the tectum, terminal degeneration was found in three bands in the stratum opticum (SO) and the stratum griseum et fibrosum superficiale (sgfs). In the middle part of the tectum, two bands of degeneration remained over the sgfs. The lateral part of the tectum has only a very small amount of degeneration distributed radomly in scattered clusters over the deep SO and superficial sgfs. The Nissl preparations also reflected the differences between the medial and lateral parts of the tectum. Distinct layer was lacking in the medial tectum with a conspicuously absent large cell layer in the stratum griseum centrale (sgc). In contrast, the lateral tectum had a typical tectal stratification. Most notable were the large neurons of the sgc.

A golgi study of the optic tectum of the tegu lizard, Tupinambis nigropunctatus

The dendritic patterns of cells in the optic tectum of the tegu lizard, Tupinambis nigropunctatus, were analyzed with the Ramon-Moliner modification of the Golgi-Cox technique. Cell types were compared with those described by other authors in the tectum of other reptiles; particular comparisons of our results were made with the description of cell types in the chameleon (Ramń, 1896), as the latter is the most complete analysis in the literature. The periventricular gray layers 3 and 5 consist primarily of two cell types--piriform or pyramidal shaped cells and horizontal cells. Cells in the medial portion of the tectum, in an area coextensive with the bilateral spinal projection zone, possess dendrites that extend across the midline. The latter cells have either fusiform or pyramidal shaped somas. The central white zone, layer 6, contains fibers, large fusiform or pyramidal shaped cells, fusiform cells, and small horizontal cells. The central gray zone, layer 7, is composed predominately of fusiform cells which have dendrites extending to the superficial optic layers, large polygonal cells, and horizontal cells. The superficial gray and white layers, layers 8-13, contain polygonal, fusiform, stellate, and horizontal elements. Layer 14 is composed solely of afferent optic tract fibers. Several differences in the occurrence and distribution of cell types between the tegu and the other reptiles studied are noted. Additionally, the laminar distribution of retinal, tectotectal, telencephalic, and spinal projections in the tegutectum can be related to the distribution of cell types, and those cells which may be postsynaptic to specific inputs can be identified. The highly differentiated laminar structure of the reptilian optic tectum, both in regard to cell type and to afferent and efferent connections, may serve as a model for studying some functional properties of lamination common to cortical structures.

Cytoarchitecture of the optic tectum in the nurse shark

The cytoarchitecture of the optic tectum of the nurse shark is described and related to the arrangements of afferents from retina, telencephalon and contralateral tectum. Its lamination is not pronounced when compared to tecta of most other non-mammalian species but more comparable to those of mammals. The absence of highly differentiated cells such as pyramidal and true horizontal cells is perhaps correlated with the poor differentiation in general, including the apparent partial overlap of inputs. Some neurons near the midline were found to possess dendrites extending into the contralateral tectum.

Modulation of cortical and pyramidal tract induced motor responses by electrical stimulation of the basal ganglia

Two general mechanisms based on anatomical studies are possible for modulation of motor activity by the caudate nucleus and globus pallidus. These mechanisms are: (1) modulation of the output of cortical neurons that exert motor influences; and (2) modulation of subcortical neurons that exert motor influences. Differentiation between these two mechanisms was accomplished in the present study by two experimental approaches, both of which employed the conditioning-test paradigm. The first approach was an investigation of caudate nucleus or globus pallidus modulation (conditioning stimulus) of flexor responses of the anterior tibialis muscle elicited by electrical stimulation of the sensorimotor cortex (test stimulus) or pyramidal tract (test stimulus). These investigations were carried out in the intact and in decorticate cats. The second approach was an analysis of modulation or cortically induced pyramidal tract responses (direct and indirect, D-I potentials) by conditioning shock trains delivered to various loci within the caudate nucleus or globus pallidus. Both approaches were designed to determine whixh inhibitory and facilitatory motor influences of the basal ganglia occurred at a cortical or subcortical level. Simultaneous stimulation of a locus within the caudate nucleus and the sensorimotor cortex evoked either an enhancement, reduction or no alteration of the cortically induced increase in flexor responses (measured by Ia afferent activity, EMG, myogram). In contrast, no inhibitory influences occurred from caudate nucleus stimulation upon pyramidal tract induced flexor responses in either the intact or decorticate preparation. Inhibitory loci were distributed toward the rostral portion of the caudate nucleus, whereas facilitatory loci were distributed throughout; this distribution was statistically significant (chi2; P less than 0.01). Only enhancement or no influence upon cortical induced or pyramidal tract induced responses were obtained by conditioning stimuli to the globus pallidus. In the unanesthetized but immobilized cat, trains of shocks delivered to the caudate nucleus enhanced, reduced or had no influence upon the cortically evoked direct (D) and indirect (I) potentials recorded in the bulbar pyramidal tract. The distribution of facilitatory and inhibitory loci was organized in a similar fashion as in theanesthetized preparation. From these observations, a model was proposed in which the output of the caudate nucleus exerts both facilitatory or inhibitory modulation of the tonically active globus pallidus cells. The latter in turn predominantly or exclusively facilitate output of pyramidal tract neurons as well as the output of subcortical structures; both effects facilitate motor responses at the spinal level.

P-Chloramphetamine: Selective neurotoxic action in brain

Injection of 2.5,5, 10, or 20 milligrams of p-chloroamphetamine per kilogram of body weight into rats produced evidence of cytopathological changes in sections of brain stained by a Nissl or silver method. As early as 1 day after drug injection cells demonstrated an intense Nissl staining, intense argyrophilia, cellular shrinkage, and perineuronal spaces. At 30 days after injection both stains revealed cellular debris and glial reactions characteristic of cellular dissolution. The neurotoxic effects of 2.5, 5, or 10 milligrams of p-chloroamphetamine per kilogram were primarily restricted to an area of the ventral midbrain tegmentum corresponding to the distribution of the B-9 serotonergic cell group. After 20 milligrams of p-chloroamphetamine per kilogram there was also evidence of neurotoxic effects on cells within the substantia nigra. These results confirm previous suggestions that the long-term reduction in serotonin content of brain, tryptophan-5-hydroxylase activity, and uptake of serotonin after injection of p-chloroamphetamine is due to a neurotoxic effect of the drug or some metabolite on serotonergic cell bodies.

The basilar pontine gray of the opossum: a correlated light and electron microscopic analysis

Neurons within the basilar pontine gray (BPG) of the American opossum can be subdivided into four major nuclei which are named medial, lateral, ventral and peripeduncular in accordance with previous studies. In addition, several smaller subnuclei, such as the median and dorsolateral cell groups, are present, as well as two longitudinal columns of neurons within the ventral nucleus. Neurons in the BPG range in size from 9 to 35 mu and appear randomly distributed so that none of the subdivisions contains exclusively nerve cells of the same perikaryal dimension. Projection neurons as shown in Golgi impregnations have a variable dendritic pattern; those in peripeduncular zones exhibit dendrites closely applied to the surface of the cerebral peduncle, whereas those in other regions generally have a radial type of arrangement. Certain projection neurons can be distinguished on the basis of their dendritic surface, which bears either claw-like protrusions or stalked appendages. Smaller nerve cells measuring less than 18 mu may be intrinsic neurons, since axon-like processes arise from their dendrites and course for some distance near the parent cell before becoming thin and beaded. Ultrastructural observations show profiles of neurons comparable in size to those seen in Golgi impregnations and suggest at least four classes of presynaptic profiles. One category ranges in size from 2 to 8 mu, contains round vesicles (average diameter 450 A) and characteristically forms multiple asymmetric synaptic contacts with several small postsynaptic profiles, some of which appear to be the dendritic claws mentioned above. The other three types of axon terminals measure less than 2 mu in their greatest dimension and are distinguished by their synaptic vesicles; one group containing round vesicles with an average diameter of 380 A, a second group exhibiting larger round vesicles with an average diameter of 500 A and a third group containing flatened or eliptical vesicles. Transection of the superior cerebellar peduncle produces early filamentous and later electron dense degenerative changes in some, but not all, of the larger types of presynaptic profiles. Subsequent to large motor-sensory cortex ablations both filamentous and dark degenerating profiles are simultaneously observed at all survival times. In one case with a cortical lesion restricted to the motor-sensory cortex, mainly dark degenerating terminals are apparent in the ipsilateral pontine gray, whereas in a lesion confined to the visual cortex only filamentous degeneration was observed. It is suggested, therefore, that some of the dark degenerating profiles represent the terminals of collaterals of corticospinal axons and the filamentous boutons are terminal expansions of direct corticopontine fibers.