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The median eminence (ME) of the hypothalamus is known to be an important brain site where hypophysiotropic release might be regulated by excitatory and inhibitory signals impinging on their neuronal terminals. Since a role for neuropeptide Y (NPY) on preovulatory luteinizing hormone (LH) release has been suggested, we hypothesized that NPY might act at the ME to control preovulatory gonadotropin-releasing hormone (GnRH) release and thus the onset of the preovulatory surge of LH. To examine this possibility, we used the ewe as an animal model to determine: (a) immunocytochemical distribution of GnRH and NPY in the ewe ME; (b) changes in in vivo release of NPY and GnRH using ME push-pull cannula (PPC) perfusate samples, as well as in plasma LH, during the luteal, follicular and preovulatory phases of a synchronized estrous cycle, and (c) effects of ME perfusion of NPY or a Y1-NPY antagonist, or an NPY antiserum on in vivo release of ME-GnRH and plasma LH during a synchronized follicular phase. Immunolocalization reveals a dense plexus of beaded GnRH-containing neurites in the arcuate nucleus and in its vicinity, the pituitary stalk and the palisade. In contrast, a dense plexus of NPY-containing neurites occurs in the internal layer, with occasional fibers found in the intermediate and lateral external zone of the ME. In the area between the lateral internal and lateral external layers, both NPY and GnRH-containing processes were found, thus providing opportunities for synaptic and/or paracrine interactions between NPY- and GnRH-containing neurons. Hormonal analysis indicated that a synchronized preovulatory surge of LH is elicited within a 2-hour window by the sequential implantation and removal of silastic-encased estradiol (E2) or progesterone (P4) implants. In this paradigm, there was a parallel increase in ME release of both NPY and GnRH preceding the synchronized LH surge. The onset of this synchronized LH surge was advanced by ME perfusion of exogenous NPY and was both delayed and blunted by ME perfusion with the NPY antagonist (both were perfused through the PPC probe for 2 h, starting 2–3 h before the expected onset of the LH surge). In addition, NPY perfusion in the ME increases, while perfusion of the Y1-NPY antagonist or of the NPY antiserum decreases ME-PPC GnRH content and plasma levels of LH in early follicular ewes. Finally, perfusion of NPY antiserum during an ongoing LH surge disrupted LH release. These results suggest that interactions between NPY and GnRH neurons are important in controlling the timing, magnitude and maintenance of the preovulatory LH surge.Copyright © 2003 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Objectives: Behavioral variant frontotemporal dementia (bvFTD) is characterized by early atrophy in the frontotemporoinsular regions. These regions overlap with networks that are engaged in social cognition-executive functions, two hallmarks deficits of bvFTD. We examine (i) whether Network Centrality (a graph theory metric that measures how important a node is in a brain network) in the frontotemporoinsular network is disrupted in bvFTD, and (ii) the level of involvement of this network in social-executive performance., Methods: Patients with probable bvFTD, healthy controls, and frontoinsular stroke patients underwent functional MRI resting-state recordings and completed social-executive behavioral measures., Results: Relative to the controls and the stroke group, the bvFTD patients presented decreased Network Centrality. In addition, this measure was associated with social cognition and executive functions. To test the specificity of these results for the Network Centrality of the frontotemporoinsular network, we assessed the main areas from six resting-state networks. No group differences or behavioral associations were found in these networks. Finally, Network Centrality and behavior distinguished bvFTD patients from the other groups with a high classification rate., Conclusions: bvFTD selectively affects Network Centrality in the frontotemporoinsular network, which is associated with high-level social and executive profile.

Ataxia-telangiectasia (A-T) is a human disorder with pleiotropic manifestations that include neoplasms, immune dysfunction and neurodegeneration. The disorder is due to mutations in the gene known as ATM (A-T, mutated), which causes a deficiency in its protein product (Atm in mice) that is necessary for DNA damage surveillance. This nuclear function of Atm explains in principle the propensity to cancer and immunodeficiency in A-T, but not the neurodegeneration which results in the earliest clinical manifestations and causes progressive disability. Here we report ultrastructural evidence of cytoplasmic localization of Atm-like immunoreactivity (ALI) within endosomes in murine cerebellocortical neurons, one of the principal targets of A-T. The ALI was obtained with two separate monoclonal antibodies that recognize Atm specifically. By contrast, electron-dense endosomes that could be confused with ALI occur in negligible amounts in both wild-type mice and in mice deficient in Atm ("knockout" mice). Furthermore, there was a marked preferential distribution of Atm-immunopositive endosomes in the granule cell layer - where they are present in granule neurons - with a much lower density in the Purkinje and molecular layers. These observations suggest that endosome-bound Atm may be more important for the function of certain neurons than others - or that it is processed differently among them - and that this protein may be involved in molecular sorting in the cytoplasm. This is relevant to elucidating the role of Atm deficiency in the pathobiology of neurodegeneration in A-T.

Learning disabilities present a diagnostic and therapeutic management challenge that requires an interdisciplinary approach initiated and coordinated by the child neurologist. An optimal evaluation for these conditions must include an extensive knowledge of the types and range of these disorders, a complete neurological and laboratory examination, a neuropsychological assessment tailored to the individual needs of the patient, a speech pathological evaluation when pertinent, and special attention to the frequent co-occurrence of more than one condition susceptible of interfering with learning.

Ataxia-telangiectasia (A-T) is a pleiotropic, multi-system disorder with manifestations that include immune deficiency, sensitivity to ionizing radiation and neoplasms. Many of these manifestations are understood in principle since the identification in A-T patients of mutations in a gene encoding a protein kinase that plays a key role in signaling and repair of DNA damage. However, the cause of the neurodegeneration that afflicts patients with A-T for at least a decade before they succumb to overwhelming infections or malignancy remains mysterious. Based on our work in a mouse model of A-T and previous evidence of extra-neural autoimmune disorders in A-T, we postulate that the neurodegenerative process in A-T is not due to a function for A-T mutated (ATM) essential for the postnatal brain, but to an autoimmune process (hence 'horror autotoxicus', Paul Ehrlich's term for autoimmune disorder). This hypothetical mechanism may be analogous to that in the so-called 'paraneoplastic' neurodegenerative syndromes in patients with various malignancies. Thus, alterations in the balance between cellular and humoral immunity in A-T probably result in autoantibodies to cerebral epitopes shared with cells of the immune system. This hypothesis has important implications for the understanding and development of effective palliative and even preventative strategies for A-T, and probably for other so far relentlessly progressive neurodegenerative disorders.

Nitric oxide (NO) synthase (NOS)-containing cerebrocortical neurons degenerate in patients with amyotrophic lateral sclerosis (ALS) and dementia, and in transgenic mice expressing a mutated superoxide dismutase gene (G93A) associated with familial ALS. The cerebral cortex of transgenic mice displayed decreased NOS activity (p<0.001) and cGMP levels (p<0.01), but no changes in NOS content indicating that less NO is produced. Therefore, NOSN degeneration is not caused by elevated NO., (Copyright 1999 Elsevier Science B.V.)

Tangential sections of the primary visual (striate) cerebral cortex from five patients with histopathologically verified Alzheimer's disease were used to study the laminar and tangential disposition of senile plaques. These lesions were visualized with thioflavin S or the modified Bielschowsky method, and classified into four different, purely morphological types: "classical", (predominantly) "neuritic", (primarily amyloid) "core" and "diffuse", which were charted and analyzed using computer-assisted three- and two-dimensional reconstruction and mapping methods. These analyses reveal a tendency for a selective laminar disposition of the lesions (preferentially in layers II/III and V) which is generally consistent with previous reports performed at lower resolution, yet the specific pattern is highly variable among patients, and among plaque subtypes within individual patients. In addition, we observed a clustering of senile plaques in the tangential domain (i.e. parallel to the pial surface) in layers II/III, that suggests a selective involvement of iterated circuits within the "units", "modules", or "hypercolumns" that some believe compose this region of the cortex. These findings also imply an intriguing relative sparing of immediately adjacent components of the modular circuitry of the cerebral cortex, in the same cytoarchitectonic layers. Taken together, these findings indicate that: (1) senile plaques may arise in functionally and anatomically distinct subsets of iterated neuronal circuits that cannot be reduced to schemes based on traditional cytoarchitectonic layers; and (2) that individual variability in the patterns of striate cortex involvement and clinical manifestations must be taken into consideration when addressing the specific mechanisms underlying visual dysfunction in Alzheimer's disease.

Neural degeneration is one of the clinical manifestations of ataxia-telangiectasia, a disorder caused by mutations in the Atm protein kinase gene. However, neural degeneration was not detected with general purpose light microscopic methods in previous studies using several different lines of mice with disrupted Atm genes. Here, we show electron microscopic evidence of degeneration of several different types of neurons in the cerebellar cortex of 2-month-old Atm knockout mice, which is accompanied by glial activation, deterioration of neuropil structure, and both pre- and postsynaptic degeneration. These findings are similar to those in patients with ataxia-telangiectasia, indicating that Atm knockout mice are a useful model to elucidate the mechanisms underlying neurodegeneration in this condition and to develop and test strategies to palliate and prevent the disease.

A 65-year-old woman with progressive visuospatial dysfunction for 2 years complained of later-onset associated memory impairment. MRI revealed diffuse cerebrocortical atrophy, which was especially severe in both parieto-occipital regions but spared the calcarine and pericalcarine cortices. Examination 5 years after onset revealed left visual hemi-neglect, oculomotor apraxia, optic ataxia, simultanagnosia, verbal alexia, lexical and spatial agraphia, and anterograde amnesia. This patient's disorder is considered in the context of previous reports on the array of cognitive disturbances associated with posterior cortical atrophy (pCA). Special emphasis is made on her reading and writing disturbances, because their prevalence and range of individual variability have not been established in pCA. This array of neuropsychological manifestations may help to distinguish among different clinical and etiological types of pCA, and to elucidate the pathophysiology of a syndrome that has been associated with conditions as diverse as Alzheimer's disease, subcortical gliosis, and prion diseases. The parameters described in our case may thus help to address these issues in clinico-pathological studies with large numbers of patients with pCA.

Cognitive impairment in the absence of lesions indicative of Alzheimer's disease and other dementing conditions has long been recognized in a subgroup of patients with motor neuron disease MND), including amyotrophic lateral sclerosis. However, the mechanisms underlying this cognitive deterioration and its relationship with the relatively selective involvement of motor neurons remains elusive. We used histo- and immunocytochemical labeling methods to study the nitrogen monoxide (NO; a.k.a. nitric oxide) synthase (NOS)-/NADPH diaphorase-containing neurons (NOSN) in three patients with MND and dementia (MND+D), two patients with MND without dementia, and 19 controls that included patients with Alzheimer and non-Alzheimer dementias. Patients with MND+D, but not those with MND without dementia, exhibit numerous dystrophic perikarya and neurites throughout all sensory, motor, association, and limbic neocortices examined. Interestingly, affected NOSN appear to correspond to some subtypes (smooth stellate and spiny neurons), while other neurons containing the same molecular phenotype (such as layer I local circuit neurons and layer II granule cells) are either spared or significantly less affected. These observations indicate that cognitive impairment and dementia in MND may be due, at least in part, to a pancortical involvement of certain types of NOSN. Consequently, the elucidation of the factors that make NOSN vulnerable in MND, and the prevention or pharmacological palliation of their loss, may eventually help to prevent or ameliorate cognitive impairment in MND and may also shed some light on the nature of the insult that targets motor neurons.

The pulvinar nucleus of the thalamus has been implicated in visual attention and in the control of eye movements, and may also help mediate attention-dependent tasks in the auditory and somatosensory systems. Consequently, a hypothetical disruption of functions mediated by the pulvinar may help understand common visual and nonvisual symptoms in patients with Alzheimer's disease. To test this hypothesis, the pulvinar nuclei of nine patients with histologically confirmed Alzheimer's disease and twelve young (9-28 years of age) and age-matched controls (without dementia and with non-Alzheimer dementias) were examined using a battery of histopathological methods. All patients with Alzheimer's disease had numerous amyloid plaques and some neuritic plaques throughout the various subdivisions of the pulvinar. Neuropil threads were also present among the senile plaques, and neurofibrillary tangles occurred in clusters throughout the nucleus. Control patients with and without dementia had very few Alzheimer lesions, which should be expected in normal elderly individuals. The lesions in the pulvinar may help understand some of the clinical manifestations of Alzheimer's disease, including deficits in attention and in a host of visual disturbances. Such deficits may be the result of involvement of reciprocal thalamo-cortical and corticothalamo-cortical circuits that appear to be critical for the function of a vast expanse of association cortices interconnected with the pulvinar, which are heavily laden with lesions themselves.

Using monoclonal antibodies to the three known human leukocyte IgG receptors, Fc gamma R, we examined the expression of Fc gamma R in normal brains and in Alzheimer's disease. We found Fc gamma RI, II and III immunoreactivity in senile plaques and on ramified microglia throughout the cortex and white matter of normal and Alzheimer's disease brains. Fc gamma RI expression was independently confirmed by a murine isotype binding study. These findings suggest that intrinsic Fc gamma R may play an important role in normal and disordered immune-related processes in the brain. They support the idea that microglia are brain macrophages.

Beta-endorphin (beta-END) is an inhibitory factor in the neuroendocrine control of luteinizing hormone (LH) release and thus, presumably also of hypophysiotropic luteinizing hormone-releasing hormone (LHRH) release. In order to address if the median eminence (ME) is a site of beta-END action, we studied its functional role in ewes by assessing: (a) the hypothalamic distribution of beta-END using immunolabeling and by comparing this distribution with our data on the localization of LHRH; (b) the ME in vivo release of LHRH and beta-END during the luteal (day 12) and the follicular (day 15) phases of the estrous cycle; (c) the in vivo release of LHRH from the posterior-lateral ME, as assessed by push-pull cannula (PPC) sampling, before, during, and after infusion of increasing doses of beta-END or naloxone through the PPC, during the follicular phase; and (d) the in vivo release of ME-LHRH and serum LH, before, during, and after infusion of beta-END or naloxone in luteal and follicular ewes. In the ewe, beta-END-containing perikarya are located in and around the arcuate nucleus. Their processes are also present in the diagonal band, medial septal nucleus, and medial and lateral hypothalamic areas, including the preoptic region and posterior ME. Perikarya containing LHRH are located in the preoptic area and project also to the ME, providing opportunities for synaptic interactions between beta-END and LHRH-containing perikarya and processes at these levels. ME in vivo release of LHRH and beta-END increase from the luteal (low LH/high progesterone, P4) to the follicular phase (high LH/low P4). In follicular ewes, in vivo LHRH and LH release is decreased, in a dose-dependent manner, by beta-END infused through the PPC probe into the posterior-lateral ME. In contrast, infusion of naloxone under similar conditions increases LHRH and LH release, also in a dose-dependent fashion. The inhibitory effect of beta-END on LHRH and LH, as well as the stimulatory effect of naloxone on LHRH and LH, were only marginally apparent in luteal ewes. These results suggest that the ME is a major control site where beta-END exerts its influence on hypophysiotropic LHRH release. The strength of this inhibitory effect apparently increases throughout the follicular phase, and might prevent the premature onset of the preovulatory surge of LHRH and LH.

Analysis of neuronal interactions at the median eminence (ME) that control anterior pituitary function requires sampling of in vivo release of specific hypophysiotropic components and of putative inputs that might regulate such a release. We developed a multiple guide cannula assembly (MGCA) to sample repetitively discrete areas of the ewe ME, using removable push-pull cannula (PPC) probes. The MGCA is attached to the skull over the ME using stereotaxic surgery. A specific guide cannula of the assembly (1 of 48 guides) located on the midline and directly on top of the central portion of the ME is selected based on roentgenograms obtained after infusion of radiopaque contrast material into the third ventricle. The MGCA and the large size of the ewe brain allows the simultaneous positioning of a PPC probe, an infusion cannula or another removable probe in additional discrete hypothalamic and extrahypothalamic areas. To determine the capabilities of this sampling technique, we assessed in vivo release of LHRH from the extracellular space at the posterior-lateral ME, under various reproductive conditions that have well-defined LH-secretory patterns. The pulsatile profile of both LHRH and LH was significantly lower in anestrus than during the follicular phase of cycling ewes. In vivo pulsatile release of LHRH was higher in the follicular than in the midluteal phase of ewes sampled repetitively from the same ME site during three consecutive estrous cycles. All ewes showed increased midluteal progesterone levels. In vivo LHRH release, as determined by PPC sampling of the extracellular fluid at the posterior-lateral ME, probably reflects a mix of hypophysiotropic and nonhypophysiotropic LHRH components. Histological analysis revealed a well-organized, pallisade-like array of astroglial processes along the track of chronically implanted cannulae. This glial scar is disrupted along the tracks of acutely reimplanted cannulae but without apparent difference in the yield of the method. Our method increases the efficiency and versatility of ME PPC sampling providing an additional tool to assess the role of the ME as the final neuroendocrine control site of anterior pituitary function.

Specialized areas in the cerebral cortex are essential to mediate the various sensory modalities and are crucial to their recovery in disease. We recently observed that prenatal photoreceptor cues are not indispensable for the development of the elaborate modular organization of the primate primary visual (striate) cortex (Kuljis, R. O. and P. Rakic. 1990. Proc. Natl. Acad. Sci. USA 87: 5303-5306). By contrast, the elegant experiments of Woolsey, Van der Loos, and collaborators (Van der Loos, H., and T. A. Woolsey. 1973. Science 179: 395-398; Van der Loos, H. and J. Dörfl. 1978. Neurosci Lett. 7: 23-30; Woolsey, T. A. 1967. John Hopkins Med. J. 121: 91-112; Woolsey, T. A. and H. Van der Loos. 1970. Brain Res. 17: 205-242) indicate that postnatal vibrissal receptor input is necessary for the development of modular organization in the posteromedial barrel subfield (PMBSF) of the rodent somatosensory cortex. The present report is part of a series of studies designed to address the variables that result in seemingly different results in these two models. Here, I address the role of pre- and postnatal tactile experience in the development of the rat homologue of the mouse PMBSF using mutants that lack vibrissae. Mutants exhibit cytoarchitectonic units in layer IV similar to those in controls, as revealed by NissI stains and histochemistry for succinate dehydrogenase and cytochrome oxidase. Sections from flat mounts of the vibrissal pad reveal that all mutants contain vibrissal follicles with stumps of sinus hairs in a geometric array and number similar to that in controls, and that the follicles are innervated heavily by fascicles of fibers from the infraorbital nerve.(ABSTRACT TRUNCATED AT 250 WORDS)

Seventy-two hybridoma lines that produce monoclonal antibodies to molecules of a rat synaptosomal plasma membrane fraction (SPM) were generated. The topographical distribution of the antigens in the cerebellum and other areas of the brain was studied by light microscopy immunocytochemistry. Some of the antibodies recognize exclusively neuronal antigens while others bind to specific glial molecules. Some of the antigens have a distribution limited to certain classes of neurons. There are antigens localized in both the cell bodies and processes while others are present only in the latter. Immunoblots of SPM proteins indicate that some antibodies react specifically with one or few of these proteins while other antibodies react with many. The latter antibodies also generally react with many brain cell types. Particularly interesting is the monoclonal antibody 8-6A2 which binds to many SPM proteins but only recognizes large neurons with long axons. A further characterization of the antigens was done by enzyme-linked immunosorbent assays and immunoblots of known purified proteins. The results indicate that antibody 8-2H5 binds specifically to clathrin, 8-7A5 to actin, 8-1E7 to the glial fibrillary acidic protein and both 8-3A5 and 7-2C12 to collagen. In contrast, the antibodies 4-4C3, 2-4H3, 4-4G7 and 6-6A8 bind to antigenic determinants present in many purified proteins.

Twenty-five specimens of Rana pipiens were subjected to a unilateral crush of the optic nerve. Substance P (SP)-, leucine enkephalin (LENK)-, cholecystokinin octapeptide (CCK8)-, and bombesin (BOM)-like immunoreactivities were analyzed in the retinae, optic nerves, and optic tecta, 9 days to 9 months postoperatively, by means of immunohistochemical methods. Peptide-like immunoreactivity was observed in axons within the optic nerve stump retinal to the crush, as in previous studies (Kuljis and Karten, '83b, Kuljis et al., '84). Peptide-containing retinofugal axons began traversing the lesion site between 10 and 20 days postoperatively, in progressively increasing numbers. Ten to 20 days following crush of the optic nerve SP-, LENK-, and CCK8-containing axons could be found in the cerebral stump of the optic nerve and in the optic chiasm, advancing to the side of the brain deafferented by the crush. The number of axons displaying peptide-like immunoreactivity within the optic nerve, retinal or cerebral to the crush, and within the optic chiasm gradually decreased after 2-3 months. The optic nerve contralateral to the procedure displayed only occasional isolated peptide-containing fibers, as in normal optic nerves. The retinae ipsilateral and contralateral to the crush exhibited no change in the normal pattern of peptide-like immunoreactivity, including the absence of demonstrable peptide-like immunoreactivity in the somata of retinal ganglion cells. The optic tectum deafferented by the procedure underwent modifications in the pattern of peptide-like immunoreactivity identical to those reported following unilateral eye enucleation (Kuljis and Karten, '82a, '83a). The patterns of LENK-, CCK8-, and BOM-like immunoreactivities in the tectum were identical to those following irreversible retinal deafferentation as long as 9 months postoperatively. SP-like immunoreactivity, however, was gradually restored in layer 11 of Ramón y Cajal ('46; layer D of Potter, '69) of the superficial (retinorecipient) neuropil 4-6 months postoperatively. The persistence of lamina-specific depletion patterns of LENK-, CCK8-, and BOM-like immunoreactivities in reafferented tecta represents a puzzling observation. The latter findings contrast sharply with the recovery of SP-like immunoreactivity, which occurs long after apparently complete restitution of the retinofugal projection, as shown by anatomical (Stelzner et al., '81), physiological (Maturana et al., '59), and behavioral (Sperry, '44) methods.(ABSTRACT TRUNCATED AT 400 WORDS)

A population of neurons situated in the human cerebral neocortex contains mRNA coding for tyrosine hydroxylase, the key enzyme for catecholamine biosynthesis. Phosphorylated neurofilament-containing cytoplasmic inclusions occur in these neurons in diffuse Lewy body disease, indicating a tendency for selective involvement that is shared with subcortical catecholamine-containing neurons. These findings are relevant to the pathophysiology of several neurologic and psychiatric illnesses in which the monoamine-containing neurons of the neocortex may participate.

A moderately compressive tubulation procedure has been devised to improve regeneration that follows fascicular neurorrhaphy. The early phases of the regenerative process were analyzed to identify the underlying cellular mechanisms. Adult Sprague-Dawley rats were subjected to bilateral fascicular neurorrhaphy involving tubulation on one side with a dura mater sheet closely apposed to the suture site. One to 16 days postoperatively the nerves were processed for histological analysis. Compared with nontubulated nerves, the cuffed side displayed a longer extent of retrograde myelin and axonal degeneration, a faster rate of orthograde remyelination, axonal invasion of the suture plane at about the same period (fifth postoperative day), larger contingent of regenerating fibers invading the distal stump, more longitudinally oriented fibers at the repair level, no escape of regenerating fibers into the extraneural tissue through the repair borders, and less intraneural edema. These findings have implications for the potentially beneficial effects of mechanically restricting post-traumatic intraneural edema buildup during nerve regeneration.

Unilateral section, crush, or ligation of the optic nerve was performed in Rana pipiens. Following optic nerve disruption, Substance P (SP)-, leucine-enkephalin (LENK)-, cholecystokinin octapeptide (CCK8)-, and bombesin (BOM)-like immunoreactivities were analyzed in the retinae and optic nerves. Peptide-like immunoreactivity developed in the retinal stump of disrupted optic nerves within 1 hour after surgery and was retained until at least 30 days. Peptide-positive staining in the retinal stump of the optic nerves was abolished by preabsorption of each of the antibodies/antisera with the corresponding synthetic substances. No massive peptide-like immunoreactivity was observed in the cerebral stump of the ligated side, nor in the contralateral, nonoperated, optic nerve. No change in the pattern of peptide-like immunoreactivity was apparent in the retina ipsilateral or contralateral to the experimental procedure. The optic tectum contralateral to the surgical procedure displayed those changes in peptide-like immunoreactivity described previously following retinal deafferentation (Kuljis and Karten, '82a, '83a). Peptide-like immunoreactivity in the stump retinad to the surgical procedure occurred in the form of beaded and fibrillar elements often ending in an irregular expansion near the lesion site. Fluorescent double-label antibody methods demonstrated that SP-like immunoreactivity is present in different processes than those containing LENK, CCK8, or BOM. Electron microscopical immunocytochemistry revealed that peptide-like immunoreactivity is contained within unmyelinated and possibly also within myelinated axons in the stump retinad to the traumatic procedure. Radioimmunoassay studies of SP demonstrated a four- to sixfold increase in SP-like content in the retinal stump of ligated nerves, compared with both the cerebral stump and with the contralateral nonoperated optic nerves. These findings demonstrate the presence of peptide-like immunoreactivity in retinal ganglion cell processes, which is compatible with either a posttraumatic expression of previously repressed peptide-like phenotypes, or, most likely, with the existence of various classes of peptide-containing retinal ganglion cells. The latter prospect strongly suggests that peptide-specific subsets of retinal ganglion cells terminate in highly specific laminae in the optic tectum (Kuljis and Karten, '81, '82a-83a) and presumably differ in their physiological role in vision.(ABSTRACT TRUNCATED AT 400 WORDS)

Layers II/III of the primary visual cortex contain a regular pattern of histochemically detectable cytochrome oxidase (CO)-rich "puffs," which differ from the interpuff regions in their thalamo-cortical and cortico-cortical connectivity, receptive-field properties, and the density of inhibitory GABA-containing synaptic terminals. We used an immunocytochemical method, in combination with cytochrome oxidase histochemistry, to analyze the spatial relationship between neurons that contain neuropeptide Y (NPY) and the CO puffs. Of a total of 606 neurons, only 2.6% of the NPY-containing cells are located in the puffs, whereas the rest are situated in the interpuffs, or at the interface between puffs and interpuffs. The number of NPY-containing neurons in the puffs is substantially less than that expected in an equal volume of the interpuffs (X2 = 13.86; df = 1; P less than 0.001). These observations indicate that columns containing the puffs may differ also from those in the interpuff regions in that they contain a unique array of chemically and morphologically distinct local circuit neurons.

Substance P (SP)-, leucine-enkephalin (LENK)-, cholecystokinin octapeptide (CCK8)-, bombesin (BOM)-, and avian pancreatic polypeptide (APP)-like immunoreactivities were analyzed in the optic tectum of Rana pipiens 5-99 days after unilateral eye enucleation, or optic nerve ligation, by means of the peroxidase-antiperoxidase and indirect fluorescence single and double labeling methods. The normal pattern (Kuljis and Karten, '81, '82c) of peptide-like immunoreactivity was observed ipsilaterally to the operation. Contralateral deafferented tectae displayed conspicuous modifications in the normal pattern of peptide-like immunoreactivity unique to each of the substances studied. The modifications of peptide-like immunoreactivity observed varied depending both on the survival time and on the particular peptide analyzed, with either increment or diminution or disappearance--or combinations thereof--in the staining intensity of some of the peptide-positive bands in the superficial one-third (superficial neuropil) of the tectum. The onset of these changes is detectable immunocytochemically between the sixth and tenth day following deafferentation. By 2-4 weeks full expression of the long-term changes is reached with no apparent further modification up to the 99th postoperative day. The rapid onset of these phenomena suggests the existence of a previously unrecognized retinal ganglion cell terminal peptidergic contribution to the tectum and/or rapid transsynaptic effects. The former possibility is suggested by recent observations demonstrating peptide-like immunoreactivity for SP, LENK, CCK8 and BOM in the retinal stump of ligated optic nerves (Kuljis and Karten, '82b). The fact that no vertebrate retinal ganglion cells have been shown to contain any of these peptides (Brecha et al., '79; Famiglietti et al., '80; Eldred and Karten, '81; Karten et al., '82), however, argues against the possibility of a retinal terminal contribution to peptide-like immunoreactivity in the tectum and suggests that transsynaptic phenomena are involved.

The avidin-biotin-peroxidase method was used at the light and electron microscopic levels to analyze neuropeptide Y (NPY)-containing neurons in the neocortex of six adult macaque monkeys. Regions studied included various sensory, motor, limbic, and association areas, designated as 17, 18, 7, 22, 3, 4, 6, 24, and 9 by Brodmann (Beiträge zur Histologischen Lokalisation der Grosshirnrinde. Leipzig: Barth, '06). Several types of NPY-containing neurons can be distinguished by their laminar location, by the size of their perikarya, and by the size, shape, and pattern of ramification of their processes: 1) layer I small local circuit neurons; 2) layer II granule cells; 3) aspiny stellate cells located in layers II-III and V-VI, with long, slender dendrites; 4) sparsely spiny stellate cells; 5) aspiny stellate cells with long, horizontally oriented dendrites, whose cell body is situated in layer VI; 6) Martinotti cells in areas 9, 7, and 24; and 7) multipolar neurons situated in the white matter subjacent to the cortical gray. The possibility of additional neuronal types containing NPY is suggested by labeled densely spinous dendrites in area 6 and recurving axons and axonal loops in the supragranular layers in areas 7 and 9. No NPY-containing neurons were found in layer IV of any area, except layers IVA and B of the visual cortex. Likewise, nonneuronal elements were not labeled. The regional differences in the distribution of some NPY-containing neuron types may reflect adaptations of local neuronal circuits for specialized functions.

Autoradiographic labelling has been employed to analyze the morphogenesis of the neostriatum. Pregnant rabbits received a single intraperitoneal injection of tritiated thymidine at different stages of gestation. Careful microscopical observation of the autoradiographs shows that cellular components of the neostriatum originate between days 15 and 18 of the intrauterine life from a layer of proliferating matrix cells that lies on the floor of the anterior part of the lateral ventrical (ganglionic eminence). From this proliferating layer, precursor cells migrate outwards to reach the developing neostriatum in a sequential fashion according to two gradients of histogenesis. Thus, it was found that neurons formed at early stages occupy a ventromedial position in the neostriatum, while those formed at later stages occupy a dorsolateral position (ventromedial to dorsolateral gradient). Furthermore, the present study indicates that the rostral regions of the neostriatum arise somewhat later than the caudal ones, demonstrating the existence of a caudocephalic gradient of cytogenesis.

Synaptic-terminal degeneration was analyzed in 18 specimens of Octodon degus after stereotaxic lesions in the pulvinar nucleus. Aside from the cortical targets of the pulvinar (Kuljis et al. 1979), a conspicuous projection towards the nucleus lateralis dorsalis of the thalamus (LD) was observed. The LD is known to receive fibers from the fornix (Valenstein and Nauta 1959), and to project heavily over the cingulate cortex (Locke et al. 1964; Ajmone Marsan 1965; Graybiel 1974); we have confirmed the latter projection in 3 operated specimens of Octodon degus. The possibility is discussed, in the light of these findings, that the pulvino-LD pathway may be important for the purposes of visuo-limbic interactions.

Recent immunocytochemical studies indicate the existence of several classes of peptide- (PRGC) and catecholamine-containing retinal ganglion cells in anurans, birds, and mammals. Different classes of PRGC project to discrete and seemingly unique layers in the retino-recipient portion of the anuran and avian optic tectum. Peptide-containing retinofugal projections to the frog tectum originate early in development, and are reestablished by some classes of PRGC during regeneration of the optic nerve. These findings indicate that chemically specific, parallel retinofugal pathways presumably subserve different functional aspects of vision in vertebrates. Exciting prospects for research include the correlation of physiologically with immunocytochemically defined classes of retinal ganglion cells, the analysis of the possible role of neuroactive peptides in retinofugal transmission, and the pharmacological manipulation of putative peptidergic retinofugal pathways to analyze their role in visual function.

Generation and regeneration of the Nervous System are considered essentially similar processes since the pioneering studies of Cajal (15). The present paper is a hypothetical attempt to explain the puzzling internal-to-external histogenetic pattern of the mammalian neocortex(4), largely on the basis of various observations made by Cajal on the developing and regenerating Central and Peripheral Nervous System. Fundamental to our model are the principles of excitatory neurocladism and of reciprocal homotropism as described by Cajal. By assuming that both latter principles are valid for the early stages of neocortical development, an explanation can be given for most of the main events of neocortical histogenesis that is consistent with known facts. Our main conclusion is that neocortical neurogenesis differs from that of any other area of the neural tube due to the interposition of the corticipetal fiber system in between the cortical matrix layer and the cortical plate. The mechanical obstacle thus posed to neuroblast migration by this fiber system appears responsible - by activating the operation of the aforementioned principles of Cajal - for both the cellular and topographical neurogenetic sequences of neocortical development, as well as the growth predominantly in width, all features that are unique to the neocortex as compared to the rest of the neural tube.

The laminar and areal distribution of neuropeptide Y (NPY)-containing perikarya and their processes was analyzed immunocytochemically in Brodmann's neocortical areas 17, 18, 7, 22, 3, 4, 24, and 9 (Walker's area 46) in seven macaque monkeys. Most NPY-containing cells are distributed in two broad bands in layers II-III and V-VI in all areas; relatively few cells can be found in layer I and virtually none in layer IV. Numerous NPY-containing cells are situated in the white matter immediately subjacent to the cortical gray. Severalfold regional and individual differences in the density of NPY-positive somata were found in supra- and infragranular layers. However, the interareal variations in the density of NPY-containing somata do not conform to a universal pattern, because of either individual variability or inherent difficulties in standardizing immunocytochemical labeling. In contrast, the laminar differences in the distribution of NPY-containing axons among cortical areas are consistent in all animals. In general, primary sensory and motor areas have a lesser density of NPY-containing axons than association and limbic areas. Within the general pattern, area-specific laminar segregation of NPY-containing axons occurs. The regional differences in the distribution of NPY-like immunoreactivity in the neocortex may reflect innate characteristics of local neuronal circuits serving specialized functions.

After performing eye enucleations or restricted lesions in the superior colliculus or the pulvinar nucleus, the degeneration patterns provoked by these procedures were analyzed by means of the Nissl and the Fink-Heimer methods in 30 specimens of Octodon degus. The pulvinar or lateroposterior nucleus can be subdivided into 3 regions (rostrolateral, rostromedial and caudal), on the basis of cytoarchitecture, tectofugal afferent and efferent connections to the cerebral cortex. In addition, this nucleus projects to the ipsilateral tail of the caudate nucleus and the nucleus lateralis dorsalis of the thalamus, which has been shown to project over the cingulate cortex in this animal 43. These findings support the possibility that the pulvinar may have an important role visuo-limbic interactions, by way of its connections with the nucleus lateralis dorsalis. Another highly interesting finding from the phylogenetic point of view is that the organization of the pulvinar in the Octodon degus is remarkably similar to that of the inferior pulvinar described for the owl monkey 46. Furthermore, the fact that the organization of the retino-tecto-thalamo-cortical pathways described in the grey squirrel 54 and in the tree shrew 33 is strikingly similar to those found in the Octodon degus, a semi-fossorial South American rodent that has evolved in isolation from the two former species for about 40 million years, makes it impossible to explain the organization of this pathway by advocating convergent evolution, due to environmental pressures determined by arboreal life, as postulated by kaas et al 39.

Peptide, 5-hydroxytryptamine (5-HT)-, tyrosine hydroxylase (TOH)-, and glial fibrillary acidic protein (GFAP)-like immunoreactivity was studied in the optic tectum of Rana pipiens. Peroxidase-antiperoxidase and indirect immunofluorescence single- and double-labeling methods were used to compare differential laminar distribution of each of these substances. Substance P (SP), leucine-enkephalin (LENK), cholecystokinin octapeptide (CCK8), bombesin (BOM), avian pancreatic polypeptide (APP), and possibly neurotensin display unique individual patterns of laminar distribution of processes and cell bodies throughout the tectum. A correlative analysis of the topographical distribution of SP, LENK, BOM, and APP on the basis of double-labeled sections shows a precise laminar segregation of these substances. Vasoactive intestinal peptide-, beta-endorphin-, and ranatensinlike immunoreactivity is consistently absent from our material. 5HT- and TOH-like immunoreactivity discloses a reticular array of fibers without clear evidence of laminar organization. This peptide-like laminar organization is particularly elaborate throughout the superficial neuropil of the optic tectum, the major retinorecipient zone. The pattern of lamination demonstrated in the present study differs in several important features from that previously described on the basis of several histological methods. The cells of origin of processes (axons and/or dendrites) in the superficial tectal neuropil may be either intrinsic or extrinsic to the tectum. Special reference is made to conflicting evidence regarding the possibility of a retinal contribution to peptide-like tectal lamination.

Immunocytochemical labeling revealed that the arcuate nucleus (ARN) of the ewe's hypothalamus contains numerous tyrosine hydroxylase (TH)-positive neurons, that appear to lack dopamine-beta-hydroxylase (DBH)-like immunoreactivity. Axons of these presumed dopaminergic neurons converge in the median eminence (ME) with Luteinizing Hormone Releasing Hormone (LHRH)-containing axons originating mostly from neurons situated in the medial preoptic area. Electron microscopic double labeling revealed synaptic contacts between TH-positive presynaptic profiles and LHRH-containing postsynaptic elements. Samples of ME, ARN, paraarcuate and lateral hypothalamus were dissected and incubated to assess LHRH release and tissue content. Only ME-LHRH release was significantly reduced in the presence of dopamine (DA). All other regions released equal amounts with and without DA. Thus, a presynaptic dopaminergic inhibition of LHRH-containing axons at the level of the ME might contribute to the regulation of LHRH release into the portal vessels.

Tritiated thymidine autoradiography was used to analyze the site, time of origin, and developmental gradients of the specialized lining of the ependymal surface of the third ventricle. Cells destined to form the ependyma are generated between days 15 and 22 of embryogenesis (gestation: 30 +/- 2 days), the majority of the cells undergoing final division on the 18th day of gestation. Ependymal cells originate in an orderly fashion according to 3 gradients. Two gradients of opposite direction (ventrodorsal and dorsoventral) are found in the parasaggital plane. Both gradients start at the level of the hypothalamic sulcus, progressively departing from this anatomical landmark as histogenesis progresses. A third gradient occurs in the caudorostral axis, such that cells located in caudal regions originate earlier than those located in rostral sectors. Thus, an orderly relationship exists between the time of origin of ependymal cells and their final location within the lining of the ventricular wall. These findings indicate, once again, the topographic nature of the gradients of histogenesis. The histogenic gradients displayed by the ependymal lining of the third ventricle appear strongly related to those exhibited by other diencephalic derivatives. The latter suggests that common factors govern the developmental sequence of all diencephalic derivatives as a function of their relative topographic location, independently of their functional role in the adult.