Bioavailability of vitamin D biofortified pork meat: results of an acute human crossover study in healthy adults

Vitamin D intakes are concerningly low. Food-based strategies are urgently warranted to increase vitamin D intakes and subsequently improve 25-hydroxyvitamin D (25(OH)D) concentrations. This acute randomised three-way crossover study investigated the efficacy of vitamin D biofortified pork derived from pigs exposed to UVB light to increase serum 25(OH)D₃ concentrations, compared to a dose-matched vitamin D₃ supplement and control pork in adults (n = 14). Blood samples were obtained at baseline and then 1.5, 3, 6, 9 and 24 h postprandially. There was a significant effect of time (p < 0.01) and a significant treatment*time interaction (p < 0.05). UV pork and supplement significantly increased within-group serum 25(OH)D₃ concentrations over timepoints (p < 0.05) (max. change 0.9 nmol/L (2.2%) UV pork, 1.5 nmol/L (3.5%) supplement, 0.7 nmol/L (1.9%) control). Vitamin D biofortified pork modestly increased 25(OH)D₃ concentrations and produced a similar response pattern as a dose-matched vitamin D supplement, but biofortification protocols should be further optimised to ensure differentiation from standard pork.

Impact of molecular medicine on neuropsychiatry: the clinician's perspective

Clinical neuropsychiatry has traditionally relied on individual practitioner experience or the apprentice-training model for formulating cases and choosing treatment. Scientifically-based diagnostic criteria and treatment algorithms have been lacking in the overlap area between psychiatry and neurology, owing largely to the complexity of this population population. However, the novel application of new molecular technologies is promising to change the care of neuropsychiatric patients. This review will highlight recent advances in molecular medicine pertaining to neuropsychiatry.Introduction

Pharmacologic therapy for behavioral symptoms of alzheimer's disease

Behavioral signs and symptoms in dementia are common, morbid, classifiable, and treatable. The current state-of-the-art approach is to evaluate carefully for social or environmental causes, intercurrent medical conditions, or other triggers of the behavior and attempt to deal with those directly. When these conservative steps fail, there may be a role for medication. A rational approach typically hinges on matching the most dominant behavioral target symptoms to the most relevant medication class, the key information of which is summarized.

Prenatal availability of choline alters the development of acetylcholinesterase in the rat hippocampus

Choline (Ch) supplementation during embryonic days (ED) 12-17 enhances spatial and temporal memory in adult and aged rats, whereas prenatal Ch deficiency impairs attention performance and accelerates age-related declines in temporal processing. To characterize the neurochemical and neuroanatomical mechanisms that may mediate these behavioral effects in rats, we studied the development [postnatal days (PD) 1, 3, 7, 17, 27, 35, 90, and 26 months postnatally] of acetylcholinesterase (AChE) activity in hippocampus, neocortex and striatum as a function of prenatal Ch availability. We further measured the density of AChE-positive laminae (PD27 and PD90) and interneurons (PD20) in the hippocampus as a function of prenatal Ch availability. During ED11-ED17 pregnant Sprague-Dawley rats received a Ch-deficient, control or Ch-supplemented diet (average Ch intake 0, 1.3 and 4.6 mmol/kg/day, respectively). Prenatal Ch deficiency increased hippocampal AChE activity as compared to control animals in both males and females from the 2nd to 5th week postnatally. Moreover, prenatal Ch supplementation reduced hippocampal AChE activity as compared to control animals over the same developmental period. There was no effect of prenatal Ch status on either cortical or striatal AChE activity at any age measured, and by PD90 the effect of Ch on hippocampal AChE was no longer observed. In order to localize the early changes in hippocampal AChE activity anatomically, frozen coronal brain sections (PD20, PD27, PD90) were stained histochemically for AChE. Consistent with biochemical results, the AChE staining intensity was reduced in PD27 hippocampal laminae in the Ch-supplemented group and increased in the Ch-deficient group compared to control animals. There was no effect of the diet on hippocampal AChE staining intensity on PD90. In addition, the prenatal Ch availability was found to alter the size and density of AChE-positive PD20 interneurons. These results show that prenatal Ch availability has long-term consequences on the development of the hippocampal cholinergic system.

Physiologic and neuroendocrine responses to intravenous naloxone in subjects with Alzheimer's disease and age-matched controls

BACKGROUND

Prior work showed that administration of naloxone HCl had different behavioral effects in patients with Alzheimer's disease (AD) than controls. The aim of the present study was to contrast the physiologic and neuroendocrine responses to administration of a wide range of doses of intravenous naloxone of patients with probable Alzheimer's disease to aged-matched controls.

METHODS

This was a double-blind, placebo-controlled, study of 12 patients with probable Alzheimer's disease and 8 age-matched normal controls who each received intravenous infusions of naloxone HCl on 3 different days in doses of 0.1 mg/kg and 2.0 mg/kg preceded by test doses of 0.5 mcg/kg. Order of treatment condition was randomized. Vital signs and plasma cortisol and prolactin were obtained at regular intervals.

RESULTS

Both groups showed increased cortisol after naloxone 0.1 mg/kg and 2.0 mg/kg (p < .0001), but the increase was significantly greater and longer lived in controls than in patients. Patients, but not controls, also experienced a significant hypothermic response after naloxone 2.0 mg/kg (p < .05). Prolactin, heart rate, and blood pressure did not change following naloxone and did not differ between groups.

CONCLUSIONS

These findings support a growing body evidence that HPA axis activity is increased in AD, and further suggest that at least part of this may be due to decreased opiatergic tonic inhibition.

Hypertrophy of basal forebrain neurons and enhanced visuospatial memory in perinatally choline-supplemented rats

The effects of choline supplementation during two time-frames of early development on radial-arm maze performance and the morphology of basal forebrain neurons immunoreactive for the P75 neurotrophin receptor (NTR) in male and female Sprague-Dawley rats were examined. In the first experiment, rats were supplemented with choline chloride from conception until weaning. At 80 days of age, subjects were trained once a day on a 12-arm radial maze for 30 days. Compared to control littermates, supplemented rats made fewer working and reference memory errors; however, the memory enhancing effects of choline supplementation were greater in males than females. A morphometric analysis of NTR-immunoreactive cell bodies at three levels through the medial septum/diagonal band (MS/DBv) of these rats revealed that perinatal choline supplementation caused the somata of cells in the MS/DBv to be larger by 8-15%. In a second experiment, choline supplementation was restricted to embryonic days 12-17. A developmental profile of NTR immunoreactive cell bodies in the MS/DBv of 0-, 8-, 16-, 30- and 90-day old male and female rats again revealed that cell bodies were larger in choline-supplemented rats than controls. As in the behavioral studies, the effect of choline supplementation was greater in male than female rats. These data are consistent with the hypothesis that supplementation with choline chloride during early development leads to an increase in the size of cell bodies of NTR-immunoreactive cells in the basal forebrain and that this change may contribute to long-term improvement in spatial memory.

Apoptosis is induced by choline deficiency in fetal brain and in PC12 cells

Treatment of rats with choline during critical periods in brain development results in long-lasting enhancement of spatial memory in their offspring. Apoptosis is a normal process during brain development, and, in some tissues, is modulated by the availability of the nutrient choline. In these studies, we examined whether availability of choline influences apoptosis in fetal brain and in the PC12 cell line derived from a rat pheochromocytoma. Timed-bred Sprague Dawley rats were fed a choline-deficient (CD), choline-control, or choline-supplemented (CS) diet for 6 days and, on embryonic day 18, fetal brain slices were prepared and apoptosis was assessed using terminal dUTP nucleotide end labeling (TUNEL) to detect DNA strand breaks and by counting of apoptotic bodies. TUNEL-positive cells were detected in 15.9% (P < 0.01), 8.7% and 7.2% of hippocampal cells from fetuses of dams fed the CD, control or CS diets, respectively. A similar inverse relationship between dietary intake of choline and TUNEL positive cells was detected in an area of cerebral cortex from these fetal brain slices. Counts of apoptotic bodies in fetal brain slices correlated inversely with choline intake of the mothers (6.2% (P < 0.01), 2.5% and 1.9% of hippocampal cells had apoptotic bodies in fetuses of dams fed the CD, control and CS diets, respectively). PC12 cells were grown in DMEM/F12 media supplemented with 70 microM choline or with 0 microM choline. The number of apoptotic bodies in PC12 cells increased when cells were grown in 0 microM choline medium (1.5%; P < 0.05) compared to 70 microM choline medium (0.55%). In PC12 cells, TUNEL labeling (DNA strand breaks) increased in choline deficient (13.5%, P < 0.05) compared to sufficient medium (5.0%). In addition, cleavage of genomic DNA-into 200 bp internucleosomal fragments was detected in choline-deficient cells. These results show that choline deficiency induces-apoptotic cell death in neuronal-type cells and in whole brain. We suggest that variations in choline availability to brain modulate apoptosis rates during development.

Retrograde axonal transport and lesion-induced upregulation of the TrkA high-affinity NGF receptor

Long-term physiological responses of nerve growth factor (NGF) and other neurotrophins require gene regulation and likely depend on retrograde axonal transport of NGF or a signaling molecule activated by ligand-receptor interaction. The low-affinity neurotrophin receptor p75LANR is retrogradely transported, but this receptor is not sufficient for NGF-dependent cell survival or differentiation. In this study we examined the distribution and transport of the TrkA NGF receptor using two anti-peptide polyclonal antibodies and a monoclonal antibody, all of which are TrkA specific. We find that (1) in the adult rat brain TrkA-like immunoreactivity is similar with all antibodies in striatal and basal forebrain neurons, (2) TrkA is upregulated in neuronal and nonneuronal cells near the sites of injury, and (3) TrkA immunoreactivity builds up within the proximal and distal segments of transected fimbrial axons, which is consistent with its transport in the anterograde and retrograde directions. Thus, TrkA may itself be, or be a component of, the neurotrophic intraaxonal messenger by which NGF regulates gene expression in sensitive neurons.

Regional CNS uptake of blood-borne nerve growth factor

Nerve growth factor (NGF), in addition to being a neurotrophic substance, has effects on the endocrine and immune systems. For example, intravenous injection of NGF results in a cascade of events leading to an increase in glucocorticoid secretion. While this response appears to be mediated centrally, there has been no evidence that circulating NGF has access to the CNS. Using intravenous injections of 125I-NGF, we find specific uptake at 1 hr but none at 6 hr, into homogenates of the basal forebrain, cerebellum, frontal cortex, hippocampus, and olfactory bulb. By autoradiography, uptake is localized to circumventricular organs, deep layers of the cerebellum, and all layers of the hippocampal region CA1, but not the dentate gyrus. Thus, uptake of blood-borne NGF could affect the hypothalamic-pituitary-adrenal axis via binding to NGF receptors present in the hippocampus. However, the sources of endogenous NGF, the mechanism of access through the blood-brain barrier, the eventual fate of NGF entering from the blood, and the physiological significance of this uptake remain to be elucidated.

Relationship of APP mRNA transcripts and levels of NGF and low-affinity NGF receptors to behavioral measures of age-related cognitive dysfunction

This study was designed to examine the relationship between cognitive function and endogenous levels of NGF, low-affinity NGF receptor (LNGFR), and amyloid precursor protein (APP) mRNAs. Using 3 month (n = 5), 18 month (n = 40), and 29 month (n = 17) Fischer-344 male rats, cognitive function was assessed with the Morris water maze, reverse transcription and polymerase chain reaction were used to quantify APP mRNAs, and NGF and LNGFR levels were determined with an ELISA. Cognitive function declined progressively with age from 3 months to 18 months, and from 18 months to 29 months, but only RNA content in the tissue declined significantly from 3 months to 18 months. Between 18 month and 29 month rats were small but statistically significant decreases only for Kunitz protease inhibitor (KPI)-inclusive mRNAs and cortical NGF levels. There was a small but statistically significant correlation between cognitive function and %KPI (the amount of KPI APP mRNAs relative to the total amount of APP mRNA), with lower %KPI related to more impaired spatial learning. No other statistically significant correlation or linear relationship could be detected between cognitive function and any of the other neurological measures or any combination of these measures (i.e., hippocampal levels of APP 695 mRNA, cortical and hippocampal levels of NGF, and cortical, hippocampal, and basal forebrain levels of LNGFR).(ABSTRACT TRUNCATED AT 250 WORDS)

Increased levels of truncated nerve growth factor receptor in urine of mildly demented patients with Alzheimer's disease

OBJECTIVE

In Alzheimer's disease, cholinergic basal forebrain neurons, which have receptors for nerve growth factor (NGF), degenerate, while NGF receptors increase in some areas of the neocortex. Levels of the truncated, extracellular portion of the NGF receptor (NGF-Rt) are elevated in urine of patients with peripheral neuropathies and in animals with peripheral-nerve injury, but it has not been determined whether urine levels of NGF-Rt are altered by the presence and/or progression of dementia-related neuropathologic changes in patients with Alzheimer's disease. In this study, we developed an enzyme-linked immunosorbent assay to determine whether urine levels of NGF-Rt are altered in patients with Alzheimer's disease.

DESIGN

Survey of urine NGF-Rt levels in neurologically normal (n = 19), mildly demented (n = 31), and moderately to severely demented (n = 31) patients.

SETTING

Subjects were participants in the Rochester Alzheimer's Disease Project and mildly demented patients about to begin a clinical drug study.

PATIENTS

All patients met established criteria for a clinical diagnosis of probable Alzheimer's disease. Aged, nondemented, neurologically normal controls were selected from the families of the demented subjects.

RESULTS

Urine NGF-Rt levels were substantially elevated in mildly demented patients relative to those of nondemented controls.

CONCLUSIONS

These results suggest that an enzyme-linked immunosorbent assay on urine samples may provide an antemortem measure of dementia-related neuropathologic changes, but further study is needed to determine the source and potential clinical utility of increased NGF-Rt levels in urine of mildly demented patients.

Developmental regulation of human truncated nerve growth factor receptor

Monoclonal antibodies (designated XIF1 and IIIG5) recognizing distinct epitopes of the human truncated nerve growth factor receptor (NGF-Rt) were used in a two-site radiometric immunosorbent assay to monitor levels of NGF-Rt in human urine as a function of age. Urine samples were collected from 70 neurologically normal subjects ranging in age from 1 month to 68 years. By using this sensitive two-site radiometric immunosorbent assay, NGF-Rt levels were found to be highest in urine from 1-month old subjects. By 2.5 months, NGF-Rt values were half of those seen at 1 month and decreased more gradually between 0.5 and 15 years. Between 15 and 68 years, urine NGF-Rt levels were relatively constant at 5% of 1-month values. No evidence for diurnal variation of adult NGF-Rt was apparent. Pregnant women in their third trimester showed significantly elevated urine NGF-Rt values compared with age-matched normals. Affinity labeling of NGF-Rt with 125I-NGF followed by immunoprecipitation with ME20.4-IgG and gel autoradiography indicated that neonatal urine contained high amounts of truncated receptor (Mr = 50 kd); decreasingly lower amounts of NGF-Rt were observed on gel autoradiograms with development, indicating that the two-site radiometric immunosorbent assay correlated well with the affinity labeling technique for measuring NGF-Rt. NGF-Rt in urines from 1-month-old and 36-year-old subjects showed no differences in affinities for NGF or for the monoclonal antibody IIIG5. These data show that NGF-Rt is developmentally regulated in human urine, and are discussed in relation to the development and maturation of the peripheral nervous system.(ABSTRACT TRUNCATED AT 250 WORDS)

Localization of NGF receptors in normal and Alzheimer's basal forebrain with monoclonal antibodies against the truncated form of the receptor

Four new monoclonal antibodies to the extracellular domain of the nerve growth factor receptor (NGFR) have been evaluated for their specificity to NGFR and their utility in localizing NGFR in human brain. All four antibodies, as well as Me20.4, show similar cellular localization and patterns of immunoreactivity in basal forebrain neurons. NGFR monoclonal antibody XIF1 stains optimally over the widest range of concentrations, with staining being reduced only slightly at less than 10 pg/ml or more than 100 ng/ml, and produces the lowest background of those tested. Staining with all NGFR monoclonal antibodies is blocked by the addition of as little as 5-fold excess human recombinant truncated NGFR protein. The distribution of NGFR-containing neurons is similar to that previously described in normal human forebrain, as is the reduction in cell size in nucleus basalis (Ch4am) in brains from patients with Alzheimer's disease. In addition, we find evidence in the two Alzheimer's cases examined for a previously unreported loss of cells in the horizontal limb nucleus of the diagonal band (Ch3) in Alzheimer's disease. The loss of these neurons, which in normal brain have characteristic varicose dendritic processes extending to the pial surface adjacent to the cisternal space, may indicate a change in the relationship of NGF-sensitive neurons to the vasculature. Since these neurons project to olfactory bulb and cortex in rodent and primate brains, their loss may also reflect damage to the olfactory system in Alzheimer's disease.

Loss of NGF receptor immunoreactivity in basal forebrain neurons of aged rats: correlation with spatial memory impairment

Nerve growth factor (NGF) has recently been implicated as a trophic agent in the survival and maintenance of basal forebrain cholinergic neurons. To test the hypothesis that NGF may play a role in the age-related decline of cerebral cholinergic function and loss of cognitive ability, we investigated the possible correlation between the loss of basal forebrain neurons that stain for NGF receptor, and impairment of spatial reference memory performance in aged rats. Our results suggest that NGF receptor-positive basal forebrain neurons undergo marked cell atrophy and loss of neuropil staining in aged rats exhibiting impaired spatial learning and memory performance. Conversely, numerous, densely immunoreactive perikarya and a profuse neuritic plexus within the basal forebrain nuclei was consistently observed in behaviorally intact rats. Overall, the mean number of NGF receptor-positive basal forebrain neurons both in the nucleus of the diagonal band and nucleus basalis correlated with retention of the spatial task (r = 0.84 and r = 0.67, respectively; P less than 0.01). Our results support the view that progressive failure of retrograde trophic support due to the age-related loss of NGF receptors may promote degenerative changes in basal forebrain cholinergic neurons, and contribute to deterioration of cognitive ability in senescence.

Localization and development of nerve growth factor-sensitive rat basal forebrain neurons and their afferent projections to hippocampus and neocortex

In order to understand further the role of NGF in the development of NGF-sensitive basal forebrain neurons and their afferent connections to the hippocampus and neocortex, we have used monoclonal antibody 192 IgG to detect and localize NGF receptors immunocytochemically in the developing rat brain. NGF receptor immunoreactivity (NGF-RI) is first visible at embryonic day 13 (E 13) in the ventrolateral telencephalic wall and follows a caudal-to-rostral gradient in its initial appearance. NGF-RI neuronal number and neuropil staining undergo substantial increases before birth, and extensive dendritic growth and increases in perikaryal size continue during the first 3 weeks of postnatal life. This growth and cellular differentiation, however, is followed in the fourth postnatal week and later by an apparent decrease in dendritic arborization and 50% shrinkage in the size of perikarya. Initial NGF-RI fiber outgrowth from immature basal forebrain neurons directed toward appropriate target fields is observed as early as E 15. The formation of a laminar pattern by septal axons in the hippocampal terminal fields and invasion of NB afferents into the cortex occur postnatally over a protracted time. In the hippocampus, NGF-RI is initially diffusely distributed, and wide bands of immature granule and pyramidal cells are almost devoid of immunoreactive fibers; however, with maturity, septal axon terminals become concentrated in narrow zones closely associated with the cellular layers. In the neocortex, early-arriving basal forebrain afferents accumulate in the intermediate zone underneath the darkly immunoreactive subplate before they enter The cortex. Dense subplate and transiently present, radially aligned fiber staining completely disappear in later postnatal week and are gradually replaced by specific axonal and terminal staining associated with NB afferents. The expression of NGF receptor in the subplate zone at the time afferents arrive and its subsequent disappearance with the specific terminal formation suggest that NGF receptor and concomitant accumulation of NGF in the subplate may act as a temporary target for the early-arriving basal forebrain afferents; ingrowing afferents may then be guided by radially oriented NGF-RI fibers to proper synaptic sites.

Evaluation and therapy of polycystic ovarian syndrome

The amenorrhea associated with bilateral polycystic ovaries, described by Stein and Leventhal, actually represents a syndrome involving various organs and systems. Clinically, this symptom complex commonly presents as menstrual disturbances, infertility, excessive body weight, and hirsutism. An understanding of the pathophysiology that underlies these symptoms provides a logical basis for evaluation and treatment of the syndrome. The diagnostic approach may involve biochemical determinations (baseline, stimulated, and suppressed) and radiologic testing. Therapy is directed at chronic anovulation, the hyperandrogenism responsible for hirsutism and acne, and the prophylaxis against endometrial and breast carcinomas. Ovulation can be induced with various agents, many of which have a risk of ovarian hyperstimulation in the PCOD patient. The use of GnRH agonists with HMG or FSH for ovulation induction will probably increase in the future. Although classic wedge resection has little place in modern management of PCOD, the recent laparoscopic ovarian cautery remains largely unstudied with respect to long-term postoperative plasma androgen levels and pelvic adhesions. It is too premature to evaluate this new surgical therapy. Hirsutism is effectively treated with estrogen-progestin combinations, medroxyprogesterone acetate, androgen receptor blockers (spironolactone, cimetidine, cyproterone acetate, and cyproheptadine), and glucocorticoids. To date, the available GnRH agonists have not been found selective enough to be used in the treatment of hirsutism, owing to possible long-term complications. Most medical approaches should include electrolysis for permanent hair removal. At present, gynecologic surgery seems to have little place in the management of hirsutism.

Autoradiographic localization of estradiol-binding neurons in the rat hippocampal formation and entorhinal cortex

This study has examined the distribution of [3H]estradiol and [1 alpha,2 alpha-3H]testosterone uptake in the hippocampal formation and entorhinal cortex of male and female rats. In both males and females, [3H]estradiol-binding neurons in Ammon's horn are located deep in stratum pyramidale and may correspond either to polymorphic interneurons or to early maturing pyramidal cells. Interneurons of strata oriens, lucidum and radiatum of Ammon's horn and of stratum moleculare of the subiculum also bind [3H]estradiol, as do basket cell interneurons in the polymorphic, infragranular layer of the dentate gyrus. While no granule cells appear to accumulate [3H]estradiol, these cells may be affected transsynaptically by gonadal steroids via their afferent contacts with the entorhinal cortex, which, of the areas examined, contains the greatest number of [3H]estradiol-binding neurons. While relatively few neurons concentrate [3H]estradiol in the hippocampal formation, these are localized to specific subpopulations, which may enhance their functional significance. Because there is no significant nuclear accumulation of [3H]-alpha-testosterone in either the entorhinal cortex or hippocampal formation, it appears that aromatase enzyme activity is not a major contributor to estrogen receptor occupancy in adult rats.

Transplantation of male mouse submaxillary gland increases survival of axotomized basal forebrain neurons

Transection of the fimbria-fornix results in a loss of magnocellular neurons in the medial septum and vertical limb of the diagonal band (MS/VDB), possibly due to the deprivation of a retrogradely transported trophic substance, such as nerve growth factor (NGF), derived from the hippocampal formation. We have utilized a transplantation model in which grafts of NGF-rich male mouse submaxillary gland were placed in the lateral ventricle adjacent to the MS/VDB of rats with transections of the fimbria-fornix. At 2-4 weeks following transection, animals with grafted submaxillary glands exhibited enhanced survival of MS/VDB neurons, which stained positive for acetylcholinesterase and were immunoreactive for the NGF receptor. These experiments demonstrate that grafts of male mouse submaxillary gland can facilitate the survival of axotomized MS/VDB cholinergic neurons and may therefore prove beneficial in promoting regeneration of damaged neural systems.

Age-related loss of nerve growth factor sensitivity in rat basal forebrain neurons

Nerve growth factor (NGF) has recently been implicated as a trophic agent in the survival and maintenance of basal forebrain cholinergic neurons. To test the hypothesis that NGF may play a role in the age-related degeneration of basal forebrain neurons and decline of cerebral cholinergic function, we have used a monoclonal antibody to the NGF receptor, 192 IgG, to immunocytochemically visualize and compare rat basal forebrain neurons responsive to NGF in aged (30 months) and young adult (10 months) rats. In a subpopulation of aged rats, NGF receptor-immunoreactive cells in the basal forebrain appear vacuolated and shrunken, and the neuropil staining is markedly reduced. While no substantial decline in cell density is apparent in Nissl-stained sections, the number of NGF receptor-positive cell profiles within the vertical limb of diagonal band nuclei is reduced by an average of 32% in aged rats. Marked reduction in the expression of NGF receptors in aged rats may signify loss of capacity of the basal forebrain neurons to bind and transport NGF from their terminals in the hippocampus and cortex, subsequent decrease in NGF delivered to the cell bodies, and eventual cellular dysfunction and death of neurons in aging.

Sexually dimorphic development of cholinergic enzymes in the rat septohippocampal system

Cholinergic enzyme activity is sexually dimorphic in the rat hippocampal formation. Acetylcholinesterase (AChE) activity is greater in females than males in Ammon's horn/subiculum on the day of birth, but is equivalent in males and females at all older ages, suggesting an earlier maturation. Choline acetyltransferase (ChAT) activity also reaches adult levels earlier in female septum, and at day 18 and in adults is greater in the female dentate gyrus compared to males. Hippocampal weight relative to body weight is consistently greater in females at all ages, particularly in Ammon's horn/subiculum. Such regional sex differences during development and in adulthood suggests that cholinergic enzyme activity is regulated locally in the hippocampal target tissue.

Regional analysis of age-related changes in the cholinergic system of the hippocampal formation and basal forebrain of the rat

In an attempt to clarify conflicting reports of age-related changes in cholinergic systems of the rat hippocampal formation and basal forebrain, we compared aged (40 months) and adult (12 months) male rats using quantitative, regional receptor autoradiography in addition to radiolabelled assays of choline acetyltransferase (ChAT) and acetylcholinesterase (AChE). The activities of ChAT and AChE in Ammon's horn/subiculum are 24% and 38% lower, respectively, in the aged brains. There is also a drop in both ChAT (38%) and AChE (28%) activities in the septum, and a 46% drop in ChAT activity in the nucleus basalis of aged rats. In the septal pole of the hippocampal formation there is no significant change with age in binding of the muscarinic antagonist, tritiated quinuclidinyl benzylate (3H-QNB) in any hippocampal subregion. However, specific binding in the temporal pole is higher in the subiculum (40%), CA (27%), and dentate gyrus (25%) of the aged animals. Because some of the neurons of the diagonal band of Broca project to the temporal areas of the hippocampal formation by way of a ventral pathway, it is possible that with age this septohippocampal pathway is selectively affected. Particularly in Ammon's horn and the subicular regions of the aged rat hippocampus, postsynaptic muscarinic receptors may upregulate to compensate for decreases in presynaptic cholinergic activity.

Demonstration of the retrograde transport of nerve growth factor receptor in the peripheral and central nervous system

NGF acts on responsive neurons by binding to specific NGF receptors on axonal termini, after which a critical biochemical signal is retrogradely transported to the cell body. The identity of the signal(s) is unknown; candidates include NGF itself or some other "second messenger." A possible second messenger is the NGF receptor. As a first step in assessing the possible role of NGF receptor in the generation of the NGF-dependent signal, and in understanding the economy of NGF receptor synthesis and utilization, we determined whether the NGF receptor is retrogradely transported. Using immunohistochemical staining with a monoclonal antibody (192-IgG) against rat NGF receptor, we looked for accumulation of NGF receptor molecules distal (retrograde transport), as well as proximal (anterograde transport), to sites of axonal ligation or transection. By 10-12 hr in both the ligated sciatic nerve and the lesioned fimbria-fornix, accumulated NGF receptor was detected proximal and distal to the ligation/lesion site. The transported receptor presumably was located in sympathetic and sensory neurons in the sciatic nerve and in forebrain cholinergic neurons projecting from the medial septum to the hippocampus. In both anatomical sites, accumulation of NGF receptor on the proximal (anterograde) side occurred in streams of fine axonal processes, whereas staining on the distal (retrograde) side occurred in varicose or granular configurations. These results raise the possibility that the NGF receptor has a role in the mechanism of NGF beyond the initial binding event at the plasma membrane of the axonal terminus.

Basal forebrain magnocellular neurons stain for nerve growth factor receptor: correlation with cholinergic cell bodies and effects of axotomy

Recent evidence has demonstrated the presence of nerve growth factor (NGF) in areas of the central nervous system characterized by cholinergic innervation. We report that a unique population of rat basal forebrain magnocellular neurons that project to the cortex and hippocampus are immunoreactive to a monoclonal antibody to the NGF receptor. Removal of target contact results in a time-dependent loss or shrinkage of cells in the basal forebrain that stain for NGF receptor and acetylcholinesterase, suggesting that under normal conditions, basal forebrain cholinergic neurons utilize NGF for trophic support.

Intrahippocampal injections of antiserum to nerve growth factor inhibit sympathohippocampal sprouting

Following lesions of the fimbria/fornix system in the rat, noradrenergic sympathetic fibers grow into the hippocampal formation. It has been postulated that these fibers collateralize in response to the presence of a neurotrophic substance similar to Nerve Growth Factor (NGF). We tested this by injecting into the rat hippocampus antibody to NGF, or control serum (contralateral control), immediately prior to a bilateral fimbria/fornix transection. In fluorescent histochemical preparations at four to five weeks following surgery, there are fewer large, brightly fluorescent fibers around the injection site on the experimental side when compared with the contralateral control side. These results support the hypothesis that NGF, or an NGF-like substance, plays an important role in the sprouting of sympathetic fibers into the denervated hippocampal formation.

Up-regulation of serotonergic binding sites labeled by [3H]WB4101 following fimbrial transection and 5,7-dihydroxytryptamine-induced lesions

Lesions of the serotonergic afferents to the hippocampus, by fimbrial transection or by 5,7-dihydroxytryptamine treatment, produce an increase in the Bmax of [3H]WB4101 to its nanomolar affinity binding site, with no effect on its picomolar affinity binding site or on [3H]prazosin binding. The nanomolar site is serotonergic as the serotonergic agonists, serotonin and 8-hydroxydipropylaminotetraline (8-OH-DPAT) have nanomolar affinity for [3H]WB4101 binding when studied in the presence of a prazosin mask (30 nM) of the alpha-1 component of [3H]WB4101 binding. The serotonin receptor antagonists metergoline, lysergic acid diethylamide and lisuride also have high nanomolar affinities while ketanserin, yohimbine, prazosin and noradrenergic agonists have affinities in the micromolar range. Fimbrial transection or 5,7-dihydroxytryptamine injections produced 32% and 44% increases in the Bmax of [3H]WB4101 binding in the presence of a prazosin mask. Serotonin competition for [3H]WB4101 binding was identical in control and experimental tissue from each lesion experiment. Although specific binding of [3H]WB4101 was increased, there was no change in the affinities or the percentages of the two binding components for serotonin competition with [3H]WB4101. These data suggest that removal of the serotonergic input to the hippocampus produces an increase in the Bmax of serotonin receptor binding sites labeled by [3H]WB4101.

Alteration of nicotinic cholinergic agonist binding sites in hippocampus after fimbria transection

Nicotinic cholinergic agonist binding sites were studied in rat hippocampus by the binding of [3H]acetylcholine in the presence of 1.5 microM atropine sulfate. Following transection of the fimbria/fornix there was a 49% increase in the binding of [3H]acetylcholine reflecting an increase in the affinity of the receptor binding site from Kd = 18.82 +/- 3.6 nM in control animals to Kd = 9.06 +/- 1.2 nM in experimental tissue. Chronic administration of the agonist nicotine (4 mg/kg/day) by osmotic minipumps produced an increase in the binding of 10 nM [3H]acetylcholine after 14 days (49% increase over control) and after 28 days (141% increase over controls). These data are consistent with the suggestion that [3H]acetylcholine labels a nicotinic cholinergic receptor in rat brain. Further they support the notion that some of the termination sites of the septal-cholinergic projection to the hippocampus are nicotinic.

Computer-assisted image analysis to quantify regional and specific receptor ligand binding: upregulation of [3H]QNB and [3H]WB4101 binding in denervated hippocampus

Quantitative regional analysis of receptor autoradiographs using the Nikon Magiscan image analysis system permits resolution of regional variations in specific binding in non-homogeneous CNS structures, such as the hippocampus. Cholinergic denervation, produced by fimbrial transections, elicits a 24% increase in atropine-displaceable [3H]QNB binding in whole coronal sections of the hippocampal formation, which is greatest in the dorsal subiculum, CA3 and dentate gyrus. This lesion also elicits a 69% increase in lower affinity [3H]WB4101 binding which is displaceable by phentolamine, but not by prazosin. This represents a sum of increases and decreases in binding in several subregions. Taken together, these findings serve to emphasize the need for normalized regional evaluation of subtracted images which have been calibrated, and linearized or transformed, to reveal binding specific to a single site.

Septal deafferentation increases hippocampal adrenergic receptors: correlation with sympathetic axon sprouting

Denervation of the hippocampal formation in adult rats through lesion of the medial septum and diagonal band or by transection of the fimbria/fornix elicits an increase in the number of putative alpha-adrenergic receptor binding sites labeled by the antagonist ligand [3H]WB4101 [2-(2,6-dimethoxyphenoxyethyl)-aminomethyl-1,4-benzodioxane]. This increase in [3H]WB4101 binding is observable at 6 days postlesion, preceding the ingrowth of sympathetic axons into the partially denervated regions of the hippocampus. The receptor up-regulation is specific for lesions of the septal (primarily cholinergic) innervation of the hippocampus. Damage to noradrenergic, dopaminergic, or serotonergic afferents as well as kainate injections in the lateral septum had no effect on [3H]WB4101 binding levels. In vivo muscarinic/cholinergic-receptor blockade does not mimic the effects of the lesion on receptor binding levels or upon axonal sprouting of the sympathetic neurons. Although [3H]WB4101 binding consistently increased after septal deafferentation, there was no clear-cut effect upon the other adrenergic ligands, including [3H]prazosin, [3H]yohimbine, P-[3H]aminoclonidine, or [3H]dihydroalprenolol. These observations can be interpreted as demonstrating a unique and selective adrenergic receptor increase after a nonadrenergic denervation but accompanying the ingrowth of anomalous adrenergic fibers. We suggest several possible relationships between the new binding sites and the ingrowing axons.

Sprouting of sympathetic fibers in the hippocampus in the absence of major target cell candidates

Noradrenergic fibers of sympathetic origin enter the hippocampal formation following removal of the cholinergic septal afferents. These sympathetic fibers apparently form synaptic contacts with cells in the hippocampus, but the identity of the postsynaptic cell is unknown. As the two major cell types of the hippocampal formation are the pyramidal cells and the dentate granule cells, we sought to determine how their absence would affect the ingrowth and distribution of the sympathetic fibers following septal lesions. Hippocampal pyramidal cells were selectively removed with kainic acid and granule cells were selectively removed with colchicine 4 days before lesions were placed in the medial septal-diagonal band nuclear complex. Animals were sacrificed 4-5 weeks after the septal lesions and the brains prepared for catecholamine fluorescence histochemistry. Sympathetic fibers innervate the hippocampal formation of brains depleted of pyramidal cells or granule cells. Thus, it appears that neither cell type is an obligatory postsynaptic target or is necessary for the ingrowth of sympathetic fibers. The anomalous sympathetic fibers may be contacting interneurons or glia.

Nest-building behavior in two cerebellar mutant mice: staggerer and weaver

Nest-building behavior was studied in two separate (different genes) but phenotypically similar autosomal recessive neurological (cerebellar) mutants, staggerer and weaver, as well as their wild-type siblings. None of the test animals or their parents had previous experience with the nesting materials used in these experiments. All of the mice, with the exception of the staggerer mutant, exhibited the nest-building behavior. This observation, coupled with other phenotypes expressed in this mutant, suggest the mutation may more generally affect neuroendocrine development and/or regulation rather than be restricted to cerebellar development.

Hormonal regulation of axonal sprouting in the hippocampus

Removal of septal fibers to the rat hippocampal formation is followed by an ingrowth of sympathetic axons into the deafferented regions. We have shown previously that the pattern of sprouting is more restricted in males than in females when the lesions are made in mature animals, but is almost the same if lesions are made during the early postnatal period. In the present study, the relationship of circulating sex hormones to the sprouting response was investigated by comparing the extent of sympathetic axon ingrowth following fimbrial lesions in intact or gonadectomized adult male and female rats. The effects of manipulating sex steroids during development was examined by comparing sympathetic axonal sprouting after fimbrial lesions in rats which were castrated (male) or treated with testosterone (females and castrated males) on postnatal day 2. We find that (1) gonadectomy of either adult female or male rats does not affect the sprouting response, but (2) neonatal castration of male rats permits sprouting in a pattern similar to normal females, and neonatal testosterone treatment of females or castrated males results in the more limited sprouting response characteristic of normal males. These results indicate that the sex-related differential response to fimbrial lesions may be determined by developmental differences in endogenous steroid levels.

Association of sympathetic axons in denervated hippocampus to intracerebral vasculature. I. Fluorescence histochemistry combining glyoxylic acid and pontamine sky blue

Combining glyoxylic acid and pontamine sky blue fluorescence methods allows simultaneous visualization of catecholamine fibers and the intra-hippocampal vascular bed. The normal noradrenergic innervation of the hippocampal formation is not closely associated with the vasculature in any region. However, following lesions of the septo-hippocampal fibers, norepinephrine-containing sympathetic fibers course along the penetrating arterioles into the parenchyma of regio inferior and the area dentata. Within the respective cell layers, the anomalous sympathetic axons collateralize freely, thus suggesting a dual relationship with the vasculature and with the neuropil of selective hippocampal zones.

Interaction of age and sex in sympathetic axon ingrowth into the hippocampus following septal afferent damage

Damage to the medial septal nucleus or to the fimbria/fornix in the adult rat elicits sprouting of vascular sympathetic fibers into the deafferented regions of the hippocampal formation. The following study examines the effects of developmental stage and sex on this sprouting phenomenon using both fluorescence histochemistry and high affinity uptake of noradrenaline. We find that (1) the sprouting, which is reduced in adult and juvenile males relative to females, is equivalent in the two sexes after transections at postnatal day 3, and (2) the period of maximum ingrowth is sexually regulated, occurring near postnatal day 3 in the male and postnatal day 13 in the female.

A delayed sprouting response to partial hippocampal deafferentation: time course of sympathetic ingrowth following fimbrial lesions

Sympathetic, noradrenaline-containing fibers grow into the hippocampal formation following lesions of the medial septum or fimbria/fornix. Fluorescent histochemical analysis reveals that these fibers begin to arise as collateral sprouts of the normal sympathetic innervation of the internal and external transverse hippocampal arteries at 9 days post-lesion. These initial fibers are oriented orthogonally to the septo-temporal axis of the hippocampal formation. They grow towards the granule cells of the fascia dentata and the CA3 pyramidal cells, where they begin to proliferate at 14 days post-lesion. This process continues until 29 days, resulting in a final distribution of fibers in areas of septal deafferentation: stratum lucidum, the inner one-third of stratum oriens and stratum pyramidale of CA3; and the hilus, the inner one-third of stratum moleculare and stratum granulosum of the fascia dentata. The time course of this sprouting response is relatively late in onset and slow in completion when compared to sprouting responses of intrinsic afferent systems of the hippocampal formation following entorhinal cortical or commissural deafferentation.

Sexual dimorphism in extent of axonal sprouting in rat hippocampus

Sympathetic axons, normally innervating the extracerebral vasculature, sprout into denervated regions of the hippocampal formation after lesions of the medial septal nucleus or fimbria in adult female rats. Similar lesions in adult males also elicit the sympathetic ingrowth; however, the number of anomalous axons is greatly reduced and their distribution is altered. In adult males the sympathetic axons do not send out collaterals within the stratum oriens of region CA3 or the molecular layer or deep hilar regions of the area dentata, as they do in adult females. Lesions in juveniles of both sexes result in more vigorous sprouting than in their adult counterparts. In the young males the anomalous axons are distributed more extensively into the dentate molecular layer; in the young females the axons merely send out more collaterals within the same regions as in the adults. This sexually dimorphic response to central nervous system damage suggests either that the sprouting is affected by the hormonal environment of the mature hippocampal system or that this brain region, like the hypothalamus, may express permanent morphological or physiological differences as a result of exposure to sex steroids during development.

Noradrenergic innervation of the adult rat hippocampal formation

The noradrenaline (NA)-containing innervation of the hippocampal formation arises exclusively in the brainstem nucleus locus coeruleus. The projection is 75--90% ipsilateral, originating predominantly in the large, multipolar cells of the compact component of the nucleus. The axons course into the hippocampal formation by three pathways. Ammon's horn receives its NA innervation principally through the ventral amygdaloid bundle-ansa peduncularis, with smaller contributions from the fornix and ipsilateral fasciculus cinguli. The innervation of the area dentata is to a larger extent bilateral, with the greatest contribution arising from the ipsilateral fasciculus cinguli and approximately equal proportions of fibers traveling via the contralateral cingulum, fornix, and the ventral path. In general, the endogenous content of NA is greater in the area dentata than in Ammon's horn, and in both structures is greater in the temporal than in the septal ends. The pattern of NA innervation is similar at all septotemporal levels, however. The dense plexuses of preterminal and terminal elements appear in the infragranular hilus of the area dentata, stratum lucidum of CA3, and in the molecular layer of the subiculum. Fluorescent varicosities often appear in perisomatic clusters, or, closely apposed to dendrites of granule and pyramidal cells.

Ontogeny of the noradrenergic innervation of the rat hippocampal formation

The noradrenergic (NA) innervation of the rat hippocampal formation arrives embryonically into a structure in which cytogenesis and cell migration are still active processes. At embryonic day 18 (E18) the first fluorescent axons appear in the septal end of CA3 at the boundary of the marginal zone and cortical plate, the future stratum lucidum. By birth axons invade the subiculum and also course along the septo-temporal axis in a longitudinal associational system in stratum moleculare of CA3. The innervation of the area dentata increases significantly by postnatal day four (P4). The innervation pattern throughout the dentate and Ammon's horn is fairly complete by P10. High affinity uptake of 3H-NA also matures embryonically and correlates postnatally with the extent of innervation estimated by fluorescence histochemistry. The levels of endogenous NA develop more slowly, showing only 60--80% of older adult values by P48. Compared to the maturation of other hippocampal afferents, the NA innervation is extremely precocious. It is localized in areas which could allow it to have significant trophic functions during early stages of histogenesis. In addition, its presence in the rapidly developing structure may contribute to its eventual distribution in a relatively less organized terminal pattern than that of the later-arriving entorhinal, commissural and septal afferents.

Development of afferent lamination in the fascia dentata of the rat

In the present study we examine the development of afferent lamination in the fascia dentata of the postnatal rat, as a first step in determining possible mechanisms controlling synaptic specificity in this system. This analysis is based on degeneration-induced argyrophilia as well as autoradiographic labeling of the entorhinal and commissural/associational afferents. Both methods show that in spite of the immaturity of the neonatal fascia dentata, these afferent systems have already established territorial relationships by 4 days of age which persist into adulthood. At 4 days, the entorhinal projection is restricted approximately to the outer 45 mum of the 80 mum wide molecular layer. The commissural/associational projection occupies appoximately the inner 35 mum of the molecular layer. At older ages the commissural/associational zone increases in width very slowly relative to the entorhinal zone. We also discuss these results in relation to potential mechanisms of afferent development and dendritic differentiation.