Unique contributions of distinct cholinergic projections to motor cortical plasticity and learning.

The cholinergic basal forebrain projects throughout the neocortex, exerting a critical role in modulating plasticity associated with normal learning. Cholinergic modulation of cortical plasticity could arise from 3 distinct mechanisms by 1) "direct" modulation via cholinergic inputs to regions undergoing plasticity, 2) "indirect" modulation via cholinergic projections to anterior, prefrontal attentional systems, or 3) modulating more global aspects of processing via distributed inputs throughout the cortex. To segregate these potential mechanisms, we investigated cholinergic-dependent reorganization of cortical motor representations in rats undergoing skilled motor learning. Behavioral and electrophysiological consequences of depleting cholinergic inputs to either motor cortex, prefrontal cortex, or globally, were compared. We find that local depletion of cholinergic afferents to motor cortex significantly disrupts map plasticity and skilled motor behavior, whereas prefrontal cholinergic depletion has no effect on these measures. Global cholinergic depletion perturbs map plasticity comparable with motor cortex depletions but results in significantly greater impairments in skilled motor acquisition. These findings indicate that local cholinergic activation within motor cortex, as opposed to indirect regulation of prefrontal systems, modulate cortical map plasticity and motor learning. More globally acting cholinergic mechanisms provide additional support for the acquisition of skilled motor behaviors, beyond those associated with cortical map reorganization.

Topical ointment for preventing infection in preterm infants.

BACKGROUND: Nosocomial sepsis is a frequent and serious complication of premature infants. The increased susceptibility of ELBW infants to infection has been attributed to less effective immune function compared to mature newborns and the invasive nature of necessary supportive care. Breakdown of the barrier function of the skin may be an additional risk factor for nosocomial sepsis. OBJECTIVES: To assess the effect of prophylactic application of topical ointment on nosocomial sepsis rates and other complications of prematurity in preterm infants. SEARCH STRATEGY: Searches were made of the Cochrane Central Registry of Controlled Trials (CENTRAL, The Cochrane Library, Issue 2, 2003), Ovid DC MEDLINE through June 2003, previous reviews including cross references, abstracts, conference and symposia proceedings, expert informants, and journal hand searching in the English language. SELECTION CRITERIA: Randomized controlled trials which compared the effect of prophylactic application of topical ointment to routine (standard) skin care or as needed topical therapy in preterm infants are included in this review. DATA COLLECTION AND ANALYSIS: Data regarding clinical outcomes including infection [including any bacterial infection, bacterial infection with a known pathogen, coagulase negative staphylococcal infection, fungal infection, and any nosocomial infection (bacterial or fungal)], patent ductus arteriosus, oxygen requirement at 28 days, chronic lung disease and mortality were excerpted from the reports of the clinical trials by the reviewers. Data analysis was done in accordance with the standards of the Cochrane Neonatal Review Group. MAIN RESULTS: Four randomized controlled trials were identified. All four studies reported improved skin condition in infants treated with prophylactic topical ointment (results not reported here). All four studies reported on the incidence of any nosocomial infection, fungal infection and coagulase negative staphylococcal infection. Infants treated with prophylactic topical ointment are at increased risk of coagulase negative staphylococcal infection (typical relative risk 1.31, 95% CI 1.02, 1.70; typical risk difference 0.04, 95% CI 0.00, 0.08); and any nosocomial infection (typical relative risk 1.20, 95% CI 1.00, 1.43; typical risk difference 0.05, 95% CI 0.00, 0.09). A trend toward increased risk of any bacterial infection was found in infants treated with prophylactic topical ointment (typical relative risk 1.19, 95% CI 0.97, 1.46; typical risk difference 0.04, 95% CI -0.01, 0.08). There was no significant difference found in the risk of bacterial infection with a known pathogen, fungal infection, or other complications related to prematurity. REVIEWER'S CONCLUSIONS: Prophylactic application of topical ointment increases the risk of coagulase negative staphylococcal infection and any nosocomial infection. A trend toward increased risk of any bacterial infection was noted in infants prophylactically treated. Topical ointment should not be used routinely in preterm infants.

Modulation of neuronal survival and axonal growth in vivo by tetracycline-regulated neurotrophin expression.

Vector systems for the regulated and reversible expression of therapeutic genes are likely to improve the safety and efficacy of gene therapy for medical disease. In the present study, we investigated whether the expression of genes transferred into the central nervous system by ex vivo gene therapy can be regulated in vivo leading to controlled neuronal survival and axonal growth. Primary rat fibroblasts were transfected with a retrovirus containing a tetracycline responsive promoter for the expression of the neurotrophin nerve growth factor (NGF) or green fluorescent protein as a control (GFP). After lesions of basal forebrain cholinergic neurons, NGF-mediated neuronal rescue and axonal growth could be completely controlled over a 2-week period by the addition or removal of the tetracycline modulator doxycycline in the animals' drinking water. Further, continued expression of the reporter gene GFP could be reliably and repeatedly turned on and off in the injured CNS for at least 3 months post-grafting, the longest time point investigated. These data constitute the first report of regulated neuronal rescue and axonal growth by controlled neurotrophin gene delivery and long-term, regulated expression using ex vivo CNS gene therapy.

Nontropic actions of neurotrophins: subcortical nerve growth factor gene delivery reverses age-related degeneration of primate cortical cholinergic innervation.

Normal aging is associated with a significant reduction in cognitive function across primate species. However, the structural and molecular basis for this age-related decline in neural function has yet to be defined clearly. Extensive cell loss does not occur as a consequence of normal aging in human and nonhuman primate species. More recent studies have demonstrated significant reductions in functional neuronal markers in subcortical brain regions in primates as a consequence of aging, including dopaminergic and cholinergic systems, although corresponding losses in cortical innervation from these neurons have not been investigated. In the present study, we report that aging is associated with a significant 25% reduction in cortical innervation by cholinergic systems in rhesus monkeys (P < 0.001). Further, these age-related reductions are ameliorated by cellular delivery of human nerve growth factor to cholinergic somata in the basal forebrain, restoring levels of cholinergic innervation in the cortex to those of young monkeys (P = 0.89). Thus, (i) aging is associated with a significant reduction in cortical cholinergic innervation; (ii) this reduction is reversible by growth-factor delivery; and (iii) growth factors can remodel axonal terminal fields at a distance, representing a nontropic action of growth factors in modulating adult neuronal structure and function (i.e., administration of growth factors to cholinergic somata significantly increases axon density in terminal fields). These findings are relevant to potential clinical uses of growth factors to treat neurological disorders.

Neonatal intensive care: satisfaction measured from a parent's perspective.

Health care systems today are complex, technically proficient, competitive, and market-driven. One outcome of this environment is the recent phenomenon in the health care field of "consumerism." Strong emphasis is placed on customer service, with organized efforts to understand, measure, and meet the needs of customers served. The purpose of this article is to describe the current understanding and measurement of parent needs and expectations with neonatal intensive care services from the time the expectant parents enter the health care system for the birth through the discharge process and follow-up care. Through literature review, 11 dimensions of care were identified as important to parents whose infants received neonatal intensive care: assurance, caring, communication, consistent information, education, environment, follow-up care, pain management, participation, proximity, and support. Five parent satisfaction questionnaires-the Parent Feedback Questionnaire, Neonatal Index of Parent Satisfaction, Inpatient Parent Satisfaction-Children's Hospital Minneapolis, Picker Institute-Inpatient Neonatal Intensive Care Unit Survey, and the Neonatal Intensive Care Unit-Parent Satisfaction Form-are critically reviewed for their ability to measure parent satisfaction within the framework of the neonatal care delivery process. An immense gap was found in our understanding about what matters most and when to parents going through the neonatal intensive care experience. Additional research is required to develop comprehensive parent satisfaction surveys that measure parent perceptions of neonatal care within the framework of the care delivery process.

Anterograde transport of neurotrophin proteins in the CNS--a reassessment of the neurotrophic hypothesis.

The basic tenets of the neurotrophic hypothesis are that i) limiting quantities of a given factor are produced in specific target tissues; ii) responsive neurons projecting to these targets compete for the limiting amounts of the factor; iii) the factor is bound within the target by selective receptors on afferent terminals, internalized, and retrogradely transported to the neuronal cell body where it provides signals affecting neuronal survival and differentiation. Although originally formulated on the basis of evidence for NGF's actions on peripheral sensory and sympathetic neurons, the neurotrophic hypothesis appeared to be upheld for CNS neuronal systems as well, where NGF was found to function primarily as a target-derived trophic factor for basal forebrain cholinergic neurons. With the discovery of additional neurotrophins sharing considerable structural homology with NGF, the question arose of whether the neurotrophic hypothesis held true for all members of this protein family. Recent investigations into the localization and function of neurotrophins other than NGF, particularly BDNF and NT-3, have provided evidence indicating that these molecules may not act in a manner consistent with the neurotrophic hypothesis, as originally postulated. Numerous studies in the peripheral and central nervous systems have now demonstrated that BDNF (and NT-3) may be preferentially trafficked anterogradely along axonal processes and stored within pre-synaptic terminals. Other studies have suggested that these factors may be released in an activity-dependent, rather than constitutive, manner and can act in autocrine or paracrine fashions to subserve an assortment of biological functions including anterograde effects on cell survival and differentiation, as well as more novel roles in synaptic transmission. These recent findings strongly suggest that, while the various neurotrophin proteins may be grouped into a single family based upon their structural homology, they should be considered as a heterogeneous group of trophic factors based upon function and mode of action.

Development and characterization of monoclonal antibodies specific to the serotonin 5-HT2A receptor.

Serotonin (5-hydroxytryptamine, 5-HT) mediates many functions of the central and peripheral nervous systems by its interaction with specific neuronal and glial receptors. Fourteen serotonin receptors belonging to seven families have been identified through physiological, pharmacological, and molecular cloning studies. Monoclonal antibodies (MAbs) specific for each of these receptor subtypes are needed to characterize their expression, distribution, and function in embryonic, adult, and pathological tissues. In this article we report the development and characterization of MAbs specific to the serotonin 5-HT2A receptor. To generate MAbs against 5-HT2AR, mice were immunized with the N-terminal domain of the receptor. The antigens were produced as glutathionine S-transferase (GST) fusion proteins in insect cells using a Baculovirus expression system. The hybridomas were initially screened by ELISA against the GST-5-HT2AR recombinant proteins and subsequently against GST control proteins to eliminate clones with unwanted reactivity. They were further tested by Western blotting against recombinant GST-5-HT2AR, rat and human brain lysate, and lysate from cell lines transfected with 5-HT2AR cDNA. One of the MAbs G186-1117, which recognizes a portion of the 5-HT2AR N-terminus, was selected for further characterization. G186-1117 reacted with a band of molecular size 55 kD corresponding to the predicted size of 5-HT2AR in lysates from rat brain and a 5-HT2AR-transfected cell line. Its specificity was further confirmed by adsorption of immunoreactivity with recombinant 5-HT2AR but not with recombinant 5-HT2BR and 5-HT2CR. Rat brain sections and Schwann cell cultures were immunohistochemically labeled with this MAb. G186-1117 showed differential staining in various regions of the rat brain, varying from regions with no staining to regions of intense reactivity. In particular, staining of cell bodies and dendrites of the pyramidal neurons in the cortex was observed, which is in agreement with observations of electrophysiological studies.

Partial cortical devascularization results in elevations of cortical nerve growth factor and increases nerve growth factor protein within basal forebrain cholinergic neurons.

Previous studies have demonstrated that partial cortical devascularization results in increased levels of nerve growth factor protein within the tissue immediately surrounding the infarcted region. In the present study, we have used this lesion model to further characterize the nerve growth factor increase by investigating: (i) the time course for this phenomenon; (ii) the impact of the devascularizing lesion on cortical regions not directly impinged upon by the lesion; and (iii) the response of nerve growth factor-sensitive nucleus basalis neurons providing afferent cortical innervation to the increased availability of nerve growth factor within their target territory. Our results indicate that, within the infarcted cortex, nerve growth factor levels increase rapidly following the lesion (up 51% by one day post lesion), reach a maximum of 136% above controls by three days and undergo a slow decline back to baseline levels by 23 days. Within the frontal and cingulate cortices, which are not devascularized by the lesion and show no signs of pathological damage, nerve growth factor levels increase over a similar time course, and with a similar magnitude, to those in the lesioned cortex. Nerve growth factor-sensitive nucleus basalis neurons on the side ipsilateral to the lesion respond to increased cortical nerve growth factor levels with an increased accumulation of nerve growth factor within their cell bodies (revealed by nerve growth factor immunohistochemistry and quantitative enzyme-linked immunosorbent assay) which was apparent at three days following the lesion, but no longer discernible at seven or 14 days or later. The present study investigated a model of cortical devascularization for its ability to alter nerve growth factor levels within the cortex. Nerve growth factor levels were rapidly increased within the infarcted cortical tissue beneath the lesion but were also elevated to a similar extent, and with a similar time course, in cortical regions not directly impinged upon by the lesion. The retrograde impact of elevated cortical nerve growth factor levels was demonstrated by an increased accumulation of nerve growth factor within the cell bodies of nucleus basalis neurons providing innervation to the cortex. This lesion model should provide a potential avenue for investigating the functional role(s) of nerve growth factor in the intact and lesioned adult central nervous system, as well as the internal mechanisms for regulating its synthesis, release, uptake, and degradation.

Developmental profile of NGF immunoreactivity in the rat brain: a possible role of NGF in the establishment of cholinergic terminal fields in the hippocampus and cortex.

In the current investigation, we have examined the developmental profile of nerve growth factor immunoreactivity (NGF-ir) in the postnatal rat. During the first 3 weeks after birth, NGF-ir was observed within the hippocampal mossy fiber region, where it persists throughout adulthood and appeared transiently within three additional zones-the dentate gyrus supragranular zone, the tenia tecta/intermediate lateral septum, and the cingulate/retrosplenial cortex. In all cases, the appearance of NGF-ir progressed in a rostrocaudal pattern over time. A strong correlation was seen between the pattern of NGF-ir and cholinergic innervation in the dentate gyrus supragranular zone, both spatially and temporally, suggesting that NGF may direct the innervation of cholinergic afferents to this region. A spatial correlation was also observed between NGF-ir and cholinergic innervation within the retrosplenial cortex and tenia tecta. With our current techniques, however, we were unable to determine at what point during development the adult-like pattern of cholinergic terminal innervation in these regions occurred and, thus, were not able establish a temporal correlation in these regions. Within the cingulate cortex, there was no evidence suggesting that the developmental appearance of NGF-ir in this region was associated with a specific enhancement of cholinergic innervation. Thus, the results of the current investigation clearly identify the presence of transiently occurring zones of NGF-ir during postnatal CNS development, although defining their exact functional role will require additional investigation.

Distribution of brain-derived neurotrophic factor (BDNF) protein and mRNA in the normal adult rat CNS: evidence for anterograde axonal transport.

A sensitive immunohistochemical technique was used, along with highly specific affinity-purified antibodies to brain-derived neurotrophic factor (BDNF), to generate a detailed mapping of BDNF immunoreactivity (BDNF-ir) throughout the adult rat CNS. A parallel analysis of sites of BDNF synthesis was performed with in situ hybridization techniques using a cRNA probe to the exon encoding mature rat BDNF protein. These combined data revealed (1) groups of cell bodies containing diffuse BDNF-ir throughout the CNS that were strongly correlated with fields of cells containing BDNF mRNA; (2) varying degrees of BDNF-ir outside of cell bodies, in what appeared to be fibers and/or terminals; and (3) many regions containing extremely heavy BDNF-immunoreactive fiber/terminal labeling that lacked BDNF mRNA (e.g., medial habenula, central nucleus of the amygdala, bed nucleus of stria terminalis, lateral septum, and spinal cord). The latter observation suggested that in these regions BDNF was derived from anterograde axonal transport by afferent systems. In the two cases in which this hypothesis was tested by the elimination of select afferents, BDNF immunostaining was completely eliminated. These data, along with the observation that BDNF-ir was rarely found within dendrites or fibers en passage, suggest that BDNF protein produced in adult CNS neurons is polarized primarily along axonal processes and is preferentially stored in terminals within the innervation target.

Anterograde transport of brain-derived neurotrophic factor and its role in the brain.

The role of neurotrophins as target-derived proteins that promote neuron survival following their retrograde transport from the terminals to the cell bodies of neurons has been firmly established in the developing peripheral nervous system. However, neurotrophins appear to have more diverse functions, particularly in the adult central nervous system. Brain-derived neurotrophic factor (BDNF), for example, produces a variety of neuromodulatory effects in the brain that are more consistent with local actions than with long-distance retrograde signalling. Here we show that BDNF is widely distributed in nerve terminals, even in brain areas such as the striatum that lack BDNF messenger RNA, and that inhibition of axonal transport or deafferentation depletes BDNF. The number of striatal neurons that contain the calcium-binding protein parvalbumin was decreased in BDNF+/- and BDNF-/- mice in direct proportion to the loss of BDNF protein, which is consistent with anterogradely supplied BDNF having a functional role in development or maintenance. Thus the anterograde transport of BDNF from neuron cell bodies to their terminals may be important for the trafficking of BDNF in the brain.

The role of NGF and afferent denervation in the process of sympathetic fiber ingrowth into the hippocampal formation.

Nerve growth factor (NGF) has been postulated to play an important role in the process of sympathetic sprouting into the septally deafferented hippocampal formation. In the current investigation we have used transplants of NGF-dependent neonatal superior cervical ganglion (SCG) neurons to investigate the influence of NGF and septal denervation (either alone or in combination with one another) upon neuronal survival and intrahippocampal sprouting. In the current model, SCG transplants were placed onto the dorsal surface of the CA1 hippocampal subfield and a continuous infusion device was used to deliver either NGF or vehicle into the hippocampal parenchyma. Following 15 days of vehicle infusion, little or no sympathetic neuronal survival was observed and no hippocampal fiber outgrowth was detected. NGF infusions, however, promoted both neuronal survival and intrahippocampal fiber outgrowth directed mainly toward the location of the infusion cannula. Septal denervation, achieved by either a septal ablation or fimbria-fornix transection, had no discernible impact upon SCG neuronal survival or fiber outgrowth, with or without NGF infusions. Similar results were also obtained when SCG were transplanted directly within the cortex, with or without an intracortical infusion. It appears, therefore, that NGF may be a sufficient, as well as necessary, component for eliciting and guiding the invasion of a tissue by NGF-sensitive fibers.

Distribution of brain-derived neurotrophic factor in the rat pituitary gland.

Immunohistochemical techniques were used to determine the distribution of brain-derived neurotrophic factor (BDNF) in the adult rat pituitary gland. In the posterior lobe, BDNF staining was found only within fibers. Within the intermediate lobe, nearly all cells were labeled intensely for BDNF. In the anterior lobe, varying degrees of BDNF immunoreactivity were observed exclusively in cells shown by double-labeling techniques to contain thyroid stimulating hormone (TSH), although not all TSH-positive cells contained detectable BDNF labeling. These results are consistent with and extend information from previous studies demonstrating BDNF expression in the pituitary gland and further support the idea that this neurotrophin plays a role in endocrine function.

Nerve growth factor (NGF) content in adult rat brain tissues is several-fold higher than generally reported and is largely associated with sedimentable fractions.

Initial studies had revealed that the bioactivity of nerve growth factor (NGF) in sonicates of adult rat hippocampal formation (HF) is several-fold greater in their pellet than their supernatant fractions. Such observations have prompted an analysis of NGF antigen (NGF-Ag) contents in pellets and supernatants from a variety of adult rat CNS tissues, both in the absence and the presence of exogenous beta-NGF. With HF tissues, NGF-Ag in the supernatants was comparable to most literature values, but pellet NGF-Ag was 3 to 5 times that amount. All other CNS tissue sonicates also revealed 3-6 fold higher NGF-Ag in their pellets than their supernatants, hence overall NGF-Ag contents were greatly in excess of reported ones. Presentation of mouse beta-NGF to a tissue, its sonicate, or its standard pellet resulted in a transfer to the final pellet of 30-50% of the added soluble NGF-Ag (and 30% of the added bioactivity). This percentage is much lower than that present in native pellets (80%), suggesting that the association of endogenous NGF with particulate matter may involve at least two compartments. Treatments of pellets with salt, alkaline pH, and/or the detergent Triton X-100 have revealed a third subset, namely additional pellet NGF-Ag that was not initially recognized by the antibody in our ELISA assay. The treatments also caused substantial release of NGF from pellet to supernatant. Further studies should clarify the nature of the association between NGF and the three subsets of pellet NGF and allow the investigation of the pellet molecules responsible for it.

Maintenance of sympathetic innervation into the hippocampal formation requires a continuous local availability of nerve growth factor.

The sprouting of peripheral sympathetic fibers into the septally denervated hippocampal formation is a well-characterized model of lesion-induced plasticity. While various studies have demonstrated the importance of nerve growth factor for evoking sympathetic sprouting, little is known concerning whether nerve growth factor continues to be required for maintaining innervation once it has occurred. In the present study we have addressed this point by (i) investigating the consequences of withdrawing exogenous nerve growth factor support from rats in which sympathetic innervation was enhanced by a nerve growth factor infusion and (ii) using blocking antibodies to interfere with the actions of endogenous nerve growth factor. The results of this investigation clearly indicate that a continuous supply of nerve growth factor (either exogenous or endogenous) is required to maintain sympathetic innervation within the hippocampal formation. Evidence is also provided demonstrating that the nerve growth factor must be made available locally within a given region to evoke and maintain the sympathetic innervation within this location. Axonal rearrangement within the developing and adult brain is believed to be an important mechanism underlying learning and memory is crucial for lesion-related plasticity. In various experimental paradigms, nerve growth factor has been shown to be an important cue for initiating axonal remodeling. In the current study, we have demonstrated that once such rearrangements have taken place, nerve growth factor may also be required to maintain them.

Characterization of antibodies to nerve growth factor: assay-dependent variability in the cross-reactivity with other neurotrophins.

The neurotrophin family of growth factors consists of proteins sharing a sizable degree of amino acid sequence and structural homology. These similarities greatly increase the probability that antibodies directed against any single neurotrophin may cross-react with other family-members. Various investigators have documented such cross-reactivity can occur under experimental conditions, although the extent of cross-reactivity reported in different studies has varied greatly. Although the use of different antibody preparations may have contributed to the differing degrees of cross-reactivity observed, it is important to note that different assay conditions were also used to evaluate cross-reactivity in the various studies. Little information is currently known about how antibody-antigen interactions vary as a function of the assay conditions used for the evaluation. The present study addressed this question by evaluating the cross-reactivity occurring between various neurotrophins and a single preparation of antibodies directed against purified mouse nerve growth factor-beta (beta-NGF) in a wide variety of immunological assay systems. Our results indicate that cross-reactivity between NGF antibodies and related neurotrophins can vary greatly depending upon the assay system chosen for the evaluation. These data strongly argue against transferring cross-reactivity data across various assay systems.

Effects of exogenous nerve growth factor upon sympathetic sprouting into the hippocampal formation.

Following septal denervation of the hippocampal formation, sympathetic fibers from a transplanted superior cervical ganglion will innervate hippocampal tissue in a topographically restricted manner. Previously, we have shown a strong correlation between the regions innervated by the sprouting sympathetic axons and the distribution of NGF immunoreactivity in the hippocampal formation, suggesting that a restricted availability of NGF trophic support may regulate the topography of innervation by the NGF-sensitive sympathetic fibers. It was possible, however, that other molecular cues were responsible for restricting neurite outgrowth to selected hippocampal regions. In the current investigation, this idea was explored by experimentally altering the distribution of hippocampal NGF using a continuous intraparenchymal infusion device. Our results indicate that some hippocampal regions, not innervated by sympathetic fibers in control animals, do become occupied when the necessary trophic factor is provided, suggesting that these regions already contained an appropriate substratum for sympathetic neurite outgrowth but lacked the necessary trophic stimulus. Other regions, however, did not become innervated even though infused NGF was verifiably present in them. Together, these findings propose that a spatial restriction of NGF may be a crucial molecular mechanism for controlling the distribution of sprouting NGF-sensitive sympathetic fibers but that other endogenous signals may regulate NGF's ability to stimulate local terminal sprouting. The data are also consistent with the idea that a limited availability of endogenous NGF is regulating both the density of sympathetic innervation into the hippocampal formation and the extent of neuronal survival within the transplanted ganglion.

NGF modulates sympathetic innervation of lymphoid tissues.

Immune tissues are known to be innervated by the sympathetic nervous system, but little is known of what directs the innervation to specific tissue compartments. This report examines the sympathetic innervation of immune tissues in transgenic mice that overexpress nerve growth factor (NGF) in skin and other epithelial structures. NGF transgenic mice exhibited dramatic hyperinnervation in the splenic marginal zone, and the medulla and capsule of peripheral lymph nodes. In contrast, the transgenic mesenteric lymph nodes showed no hyperinnervation. This difference correlated with the location of these nodes; peripheral lymph nodes drain skin where the transgene was expressed while mesenteric lymph nodes drain non-transgene-expressing structures. In addition, the level of innervation correlated with the level of NGF peptide content as assayed by ELISA (3- and 13-fold increase in transgenic spleen and axillary lymph nodes, respectively; no increase in mesenteric nodes) and immunocytochemistry. RT-PCR showed that the NGF transgene was not being expressed in the immune tissues, suggesting that immune tissues can concentrate transgene-produced NGF. It was also demonstrated that the change in innervation had functional consequences. The mitogen response to concanavalin A (ConA) by spleen cells was decreased in the transgenics suggesting that elevated catecholamines or NGF can modulate the proliferative response of these cells. These mice demonstrate that NGF can modulate the sympathetic innervation and function of the immune system.

Nerve growth factor in Alzheimer's disease: defective retrograde transport to nucleus basalis.

NGF immunohistochemistry was combined with quantitative optical densitometry to evaluate whether retrogradely transported NGF is altered within cholinergic basal forebrain (CBF) neurons in Alzheimer's disease (AD). In normal aged humans, almost all CBF neurons stained for NGF. Although fewer in total number, remaining CBF perikarya in AD displayed diminished (32%) or undetectable NGF immunoreactivity. Based upon these data we hypothesize that there is a defect in retrograde transport of NGF in AD which may be due to a abnormal production and/or utilization of the trk receptor. This defect may be a primary event mediating the degeneration of CBF neurons in AD.