Biomedical subjects

D M Nance

Publications and source records attributed to D M Nance.

At least 37 records · Page 2Linked to original sources

PubMed1996

Pavlovian conditioning of LPS-induced responses: effects on corticosterone, splenic NE, and IL-2 production.

The present study used a taste aversion paradigm to condition lipopolysaccharide (LPS)-induced suppression of splenic lymphocyte interleukin-2 (IL-2) production, with concurrent measurement of corticosterone production and splenic norepinephrine (NE) content). In training, two groups of rats received saccharin and IP LPS in a paired (P) manner and a third group in a specifically unpaired (U) manner. In the test, the unpaired group (group U) and one of the paired (group P) groups were re-exposed (R) to the cue and the other not (NR). An additional group controlled for the effects of cues (conditional stimulus) and fluid deprivation (negative control; NC). A robust taste aversion in the P-R group was accompanied by suppression of IL-2 production, reduced splenic NE content, and elevated corticosterone production, relative to combined controls (i.e., groups U-R, P-NR, and NC). The conditioned modulation of IL-2 secretion, along with the concomitant alteration of adrenocortical and sympathetic mediators, supports the involvement of bidirectional central nervous-immune system pathways in this paradigm.

Animals↗

PubMed1996

Activation and selectivity of splenic sympathetic nerve electrical activity response to bacterial endotoxin.

Regulatory interactions and neuroanatomic pathways have been described between the sympathetic nervous system and the immune system. It is not clear whether these pathways are activated during immune responses and if target specificity provides selective regulation of immune organs. The present study examined whether systemic injection of endotoxin [lipopolysaccharide (LPS)] induces sympathetic outflow to an immune organ (spleen). Sympathetic nerve activity was recorded from either the splenic or renal nerve of adult male rats after intravenous injections of LPS. Splenic nerve activity increased in a dose-dependent manner up to 175% of control after injection of LPS, with an onset time of 17.1-23.5 min. In contrast, renal nerve recordings showed a significantly slower onset time of 37.1-52.6 min at similar doses. In addition, splenic nerve recordings of 8/8 rats responded to 10 micrograms of LPS, whereas only 4/11 positive renal nerve responses were observed at this dose. The magnitude of the responses of both splenic and renal nerves were comparable. These data suggest that the splenic nerve responds to and is more sensitive to LPS-stimulated sympathetic activation in terms of latency and frequency of responses. Thus sympathetic outflow can be directed to an immune organ in response to a stimulus known to activate the immune system.

Animals↗

PubMed1995

Suppressed T cell and macrophage function in the "reeler" (rl/rl) mutant, a murine strain with elevated cerebellar norepinephrine concentration.

The effects of neurochemical alterations in specific brain regions on the immune system were examined in reeler (rl/rl) mice, a neurologic mutant strain having an abnormally high concentration of cerebellar norepinephrine (NE). Following immunization with sheep red blood cells, lower numbers of IgM-producing B cells were found in rl/rl mice than in B6C3Fea/a controls. Interleukin-1 (IL-1) production by splenic macrophages from rl/rl mice was reduced compared to B6C3F3a/a controls, as was the proliferative response of splenic T lymphocytes from rl/rl mice activated with an anti-CD3 monoclonal antibody. Levels of IL-4, interferon-gamma and IL-2 produced by splenic T lymphocytes from rl/rl mice were also lower than those of B6C3Fea/a controls. Rl/rl mice do not have an intrinsic defect in the ability to produce IgM, as lipopolysaccharide activated splenic lymphocytes from rl/rl mice produced levels of IgM similar to those of controls. This suggests that defective function in the T lymphocyte and/or macrophage population rather than in the B cell population may underlie the defect in IgM production. No significant alterations were observed in basal splenic levels of NE or neuropeptides in rl/rl mice relative to controls. The reeler mouse model shows that alterations in immune function are present in a strain with inherited alterations in cerebellar noradrenergic innervation and NE concentration.

Animals↗

PubMed1995

Migration of bovine aortic smooth muscle cells after wounding injury. The role of hyaluronan and RHAMM.

The migration of smooth muscle cells is a critical event in the pathogenesis of vascular diseases. We have investigated the role of hyaluronan (HA) and the hyaluronan receptor RHAMM in the migration of adult bovine aortic smooth muscle cells (BASMC). Cultured BASMC migrated from the leading edge of a single scratch wound with increased velocity between 1 and 24 h. Polyclonal anti-RHAMM antisera that block HA binding with this receptor abolished smooth muscle cell migration following injury. HA stimulated the random locomotion of BASMC and its association with the cell monolayer increased following wounding injury. Immunoblot analysis of wounded monolayers demonstrated a novel RHAMM protein isoform that appeared within one hour after injury. At the time of increased cell motility after wounding, FACS analysis demonstrated an increase in the membrane localization in approximately 25% of the cell population. Confocal microscopy of injured monolayers confirmed that membrane expression of this receptor was limited to cells at the wound edge. Collectively, these data demonstrate that RHAMM is necessary for the migration of smooth muscle cells and that expression and distribution of this receptor is tightly regulated following wounding of BASMC monolayers.

Animals↗

PubMed1994

Cytokine-specific central monoamine alterations induced by interleukin-1, -2 and -6.

Cytokine-specific alterations of monoamine activity were evident in the hypothalamus, hippocampus and prefrontal cortex 2 h following peripheral administration of recombinant interleukin (IL)-1 beta, IL-2 and IL-6 (200 ng, i.p.) in male, BALB/c mice. IL-1 induced the broadest range of neurochemical changes, affecting central norepinephrine (NE), serotonin (5-HT) and dopamine (DA) activity. In particular, IL-1 enhanced NE turnover in the hypothalamus and hippocampus, 5-HT turnover in the hippocampus and prefrontal cortex (owing to increased utilization and reduced content of the transmitters in these brain regions), and enhanced DA utilization in the prefrontal cortex. IL-6 increased 5-HT and DA activity in the hippocampus and prefrontal cortex in a manner similar to IL-1, but failed to affect central NE activity. Moreover, IL-2 increased hypothalamic NE turnover (reflecting a profound increase in NE utilization) and enhanced DA turnover in the prefrontal cortex, but did not influence central 5-HT activity. Hence, these cytokines differentially altered neurochemical activity in brain regions that mediate neuroimmune interactions and that are influenced by physical and psychological stressors. In addition to the neurochemical changes, plasma corticosterone concentrations were profoundly enhanced in IL-1-treated animals, but not significantly altered by IL-2 or IL-6 treatment. The IL-1-induced corticosterone elevations did not significantly correlate with alterations of hypothalamic NE activity.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1994

The effects of kainic acid-induced lesions in the lateral septal area on cell-mediated immune function.

The lateral septal area (LSA) is a primary control region for psychoneuroendocrine functions, and we have previously reported that kainic acid (KA) lesions in the LSA and the hippocampus have inhibitory and facilitatory effects, respectively, on the humoral immune response of female rats. Thus, these limbic structures may selectively participate in directing neuroimmune regulation. In order to assess the fundamental role of the LSA in neuroimmune regulation, we have evaluated the effects of neurotoxic septal lesions on various cell-mediated immune measures. Animals received stereotaxically guided bilateral infusions of KA (2.0 micrograms/microliter) or physiological saline (SHAM) into the LSA. Following a 2-week recovery period, animals were sacrificed and the spleen cells analyzed for natural killer (NK) cell activity and T-cell responsiveness to mitogen (ConA) or to anti T-cell receptor mAb (R73). A separate group of LSA-lesioned animals were immunized with sheep red blood cells 4 days prior to harvesting the spleen for plaque forming cell (PFC) number determination and measurement of TNF-alpha secretion from splenic macrophages. The results indicate that rats with KA lesions in the LSA have significantly higher NK cell activity, significantly lower numbers of splenic PFCs, and significantly reduced TNF-alpha secretion from splenic macrophages, relative to controls. There was a statistical tendency (p < .1) for reduced T-cell lymphoproliferative responses to ConA stimulation in LSA-lesioned animals, relative to SHAMs. However, the T-cell lymphoproliferative response to specific activation via the T-cell receptor was not significantly different between lesioned and control groups. These results further demonstrate the importance of KA-sensitive LSA neurons in neuroimmunoregulation. Moreover, selective alterations of different components of the immune system are observed in LSA-lesioned animals, suggesting that the LSA is involved in the complex and differential regulation of immunity.

Animals↗

PubMed1994

Intracellular labeling of cat spinal neurons using a tetramethylrhodamine-dextran amine conjugate.

Tetramethylrhodamine-dextran is a highly fluorescent neuroanatomical tracer that, in its 10,000 MW form, has seen widespread use as a sensitive anterograde tract-tracing label. We report here the use of a lower molecular weight tetramethylrhodamine-dextran (3000 MW; Molecular Probes, OR) as an in vivo intracellular marker of locomotor-related spinal neurons. In the paralyzed, decerebrate cat preparation, fictive locomotion was evoked by electrical stimulation of the mesencephalic locomotor region. Extracellular and intracellular potentials of rhythmically active spinal neurons were recorded using microelectrodes filled with 2% tetramethylrhodamine-dextran (3000 MW) in 0.9% saline (impedance 5-20 Mohm). Following impalement and electrophysiological characterization, neurons were iontophoretically injected for 2-30 min with 3-10 nA of pulsed positive current. Animals were then perfused 30 min to 7 h postinjection with a variety of paraformaldehyde- and glutaraldehyde-containing fixatives. After tissue sectioning, more than 90% of the injected neurons were recovered. Choline acetyltransferase-immunoreactivity could be demonstrated in a subpopulation of tetramethylrhodamine-dextran-labeled neurons. This technique, in addition to producing high-quality electrodes, has the advantages of rapid yet extensive filling of neuronal processes, no tissue processing prior to visualization, and compatibility with immunohistochemistry.

Animals↗

PubMed1994

Neural and biochemical mediators of endotoxin and stress-induced c-fos expression in the rat brain.

We and others have reported that c-fos protein is induced in the hypothalamus and brain stem of the rat following central and peripheral injections of endotoxin (lipopolysaccharide; LPS). We have now examined possible mechanisms through which LPS induces c-fos protein. The cyclooxygenase inhibitor indomethacin and the glutamate NMDA antagonist MK801 inhibited c-fos protein in the paraventricular nucleus (PVN), supraoptic nucleus (SON), and the A1/A2 regions of the brain stem induced by IP or IV injections of LPS (40 micrograms). The H1 histamine antagonist diphenhydramine, but not the H2 histamine antagonist cimetidine, reduced the amount of c-fos labeling. MK801 also attenuated the effects of stress (foot shock) on c-fos protein; however, indomethacin had no effect on c-fos protein induced by stress. We next examined the importance of visceral afferent innervation on the response to LPS or stress. Subdiaphragmatic vagotomy completely blocked the induction of c-fos protein following IP injections of LPS; however, vagotomy had a minimal effect on c-fos protein induced in the PVN and SON following IV injections of LPS, but potentiated c-fos induction following foot shock. Thus, prostaglandin synthesis, glutamate release, histamine receptors, and visceral afferents represent functional biochemical and neural pathways through which endotoxin activates c-fos protein in specific autonomic and neuroendocrine regulatory nuclei. Activation of NMDA glutamate receptors may represent a final common pathway for the induction of c-fos protein in the brain induced by both endotoxin and stress.

Animals↗

PubMed1994

Interleukin-2-induced enhancement of an antigen-specific IgM plaque-forming cell response is mediated by the sympathetic nervous system.

Interleukin (IL)-2, a lymphokine produced by activated T-cells, stimulates T-cell proliferation and differentiation and potentiates B-cell production of antigen-specific immunoglobulins. IL-2 also increases hypothalamic norepinephrine turnover without affecting plasma corticosterone levels, which suggests that it selectively impacts on central sites that mediate sympathetic outflow to lymphoid organs. Because sympathetic stimulation during the early phases of an immunoglobulin (Ig)M plaque-forming cell (PFC) response to sheep red blood cells results in an increase in the subsequent number of antibody-forming cells, we assessed whether the enhancing effects of IL-2 on the PFC response are mediated by the sympathetic nervous system. The peak splenic IgM PFC response was increased in male Sprague-Dawley rats and BALB/c mice administered recombinant human IL-2 (50, 100 or 200 ng i.p.) in close temporal congruity with sheep red blood cell administration (i.e., 1 day before or immediately before immunization), compared with vehicle-treated controls. IL-2 administered at a later interval after immunization (i.e., 2 days) did not increase the number of antibody-forming cells. Intact sympathetic innervation of the spleen was required for the IL-2-induced immunoenhancement to occur because cutting the splenic nerve 10 days prior to IL-2 administration blocked the lymphokine's potentiation of the IgM PFC response. The immunostimulatory effects of IL-2 were also blocked in mice administered the beta adrenergic antagonist propranolol (5 mg/kg) immediately and 1 day after IL-2 administration. The alpha adrenergic antagonist phentolamine (5 mg/kg) had no effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Anomalous adrenalectomy-induced Fos-like immunoreactivity in the hypothalamic paraventricular nucleus of stress-hyporesponsive rats.

Cellular activity in the paraventricular nucleus of the hypothalamus (PVN) in response to adrenalectomy (ADX) and sham-ADX was measured in adult male rats, lactating females, and nursing pups using c-fos immunocytochemistry. Increased Fos-like immunoreactivity (FLI) was seen in the PVN of male rats at 4 h following ADX or sham-ADX but this increase was transient, and basal values were restored within 24 h. In suckling pups, ADX induced a marked FLI response in the PVN at 3 days and at 18 days postpartum. At 11 days postpartum, however, the FLI response was attenuated relative to adult animals, and 3- and 18-day-old pups. Similarly, in nursing mothers, ADX induced FLI at 3 days, but this response disappeared by 7 days and did not reappear by the end of the suckling period (day 21). These data indicate that c-fos expression is a sensitive indicator of hyporesponsiveness in the hypothalamic-pituitary-adrenal (HPA) system.

Adrenal Glands↗

PubMed1993

Central administration of interleukin-1 beta increases norepinephrine turnover in the spleen.

We have previously shown that intracerebroventricular (ICV) injection of interleukin-1 beta (IL-1 beta) suppressed splenic macrophage function. Sympathetic noradrenergic innervation of the spleen was implicated as a mediator of this IL-1 beta signal as surgical sympathectomy ablated the macrophage suppression. In this study, we have determined whether ICV administration of IL-1 beta has an effect on sympathetic outflow and norepinephrine (NE) turnover in the spleen. Adult male rats were injected with 5 ng of IL-1 or saline, and NE turnover in the spleen was determined using the rate of decline of NE content in the spleen after synthesis inhibition. The splenic NE turnover rate was increased significantly from 69.52 ng/g/h in saline-treated animals to 111.05 ng/g/h in IL-1-treated animals. In addition, serum corticosterone and ACTH were significantly elevated in IL-1 beta-treated animals 4 h postinjection. These data indicate that central administration of IL-1 beta increases both sympathetic outflow to the spleen and activates the hypothalamic-pituitary-adrenal axis during the period when IL-1 beta induces immunosuppression.

Adrenocorticotropic Hormone↗

PubMed1993

The effects of stress on splenic immune function are mediated by the splenic nerve.

Intermittent footshock (FS) suppresses immune function of spleen cells. To determine if the autonomic nervous system mediates this immunosuppression in spleen cells, we tested whether cutting the splenic nerve, which depletes splenic norepinephrine levels by 98-100% and eliminates catecholamine fibers, blocks the effects of stress. Splenic nerve sections, sham operations, or no surgery were performed on male Sprague-Dawley rats. Ten days later, rats were injected with sheep red blood cells (SRBC). Three days later, rats were placed in a chamber equipped with a shock grid. Foot shock (1.6 mA) was administered for 5 s on a VI 3.5 min schedule for 60 min. Each FS was preceded by a 15-s warning tone. Controls were treated identically except for the FS. The next day spleen cells were harvested and the number of IgM plaque-forming cells (PFCs) determined. For the sham and unoperated control animals, the number of PFCs was reduced for the stressed animals relative to the nonstressed controls, and there was no effect of the sham surgeries. In contrast, there was no difference between the stressed and nonstressed groups in which the splenic nerve had been sectioned, and their PFC response was comparable to the controls. Next we examined the effects of FS on the proliferative response to mitogens (PHA and ConA) following splenic nerve sections or sham operations. One week following surgery, animals were given a 60-min session of FS or exposed to the chamber/tone without FS. Rats were then killed, spleens harvested, and the proliferative response to mitogens determined.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Differential induction of c-Fos immunoreactivity in hypothalamus and brain stem nuclei following central and peripheral administration of endotoxin.

Lipopolysaccharide (LPS), an endotoxin associated with gram-negative bacteria, is a potent activator of the immune system. We have tested the effects of ICV infusions of LPS (10 ng) or Ringer's solution on the induction of the proto-oncogene protein c-Fos in the brain as well as plasma levels of corticosterone and splenic concentrations of norepinephrine (NE) and VIP. At 3 h post-ICV infusion of LPS, numerous labeled neurons were observed in the paraventricular nucleus (PVN) of the hypothalamus and the nucleus tractus solitarius (A2) region of the brain stem. Also, corticosterone and splenic NE and VIP levels were all elevated post-ICV LPS. Analysis of the time course for the induction of c-Fos protein in the brain following IP injections of LPS indicated that, relative to control injections, increased numbers of c-Fos-positive cells were detected in the PVN 0.5 h following IP injections (100 micrograms), peaked at 2-3 h postinjection, and then returned to control levels at later intervals. Additional dose-response data for IP LPS indicated a small increase in the number of labeled cells at a dose of 4.0 micrograms, and the number and staining intensity increased up to a dose of 100 micrograms. Corticosterone levels followed a similar pattern and were elevated at the 4.0 micrograms IP dose of LPS and increased to peak levels at 40 micrograms and higher. In contrast to ICV injections, splenic NE levels were unaltered by IP injections of LPS.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Quantitative immunohistochemical and biochemical correlates of connexin43 localization in rat brain.

We have shown by immunohistochemical methods that the gap junction protein connexin43 is heterogeneously distributed in rat brain (Yamamoto et al: J Comp Neurol 302:853, 1990). Here we have compared quantitatively the relative amount of connexin43 detected on Western blots of seven central nervous system (CNS) regions with the density of connexin43-immunoperoxidase reactivity in these regions. As has been observed on Western blots of several cell types, homogenates of these CNS regions contained two forms of connexin43, its dephospho form with an apparent mobility of approximately 41 kDa and its approximately 43 kDa phosphorylated form. While the relative quantities of connexin43 varied considerably among the brain regions, the ratio of the 43/41 kDa forms, 0.71, was relatively uniform (correlation coefficient, r = 0.92). Sections of brain processed for connexin43-immunolocalization by the peroxidase-antiperoxidase (PAP) method showed that chromogen deposition was linear with incubation time in reaction medium. Optical density of tissue connexin43-immunoreactivity in each of the seven areas plotted against the density of connexin43 bands on Western blots gave a correlation coefficient of r = 0.90. Connexin43-immunoreactivity had a similar appearance in sections processed by PAP or immunofluorescence procedures and consisted of isolated or aggregates of puncta.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Molecular cloning of a novel hyaluronan receptor that mediates tumor cell motility.

A cDNA encoding a unique hyaluronan receptor has been molecularly cloned from a lambda GT11 3T3 cDNA expression library. Immunoblot analyses of cell lysates, using antibodies to peptides encoded in the cDNA, specifically react with a 58-kD protein. This protein is regulated by the mutant H-ras gene in cells containing a metallothionein promoter H-ras hybrid gene. Further, antibodies to peptide sequences encoded in the cDNA block the increase in locomotion resulting from induction of the mutant H-ras gene in this cell line. In a transblot assay, the bacterially expressed protein binds to biotinylated hyaluronan. Antibodies to peptides encoded in the cDNA react in immunoblot assays with the 58- and 52-kD proteins of a novel hyaluronan receptor complex previously implicated in cell locomotion. Furthermore, antibodies specific to the 58- and 52-kD proteins, which block ras-induced locomotion, also cross-react with the expressed, encoded protein. The gene product described here appears to be a new type of hyaluronan receptor that is involved in cell locomotion. It is named RHAMM, an acronym for receptor for hyaluronan-mediated motility.

3T3 Cells↗

PubMed1991

Suppression of splenic macrophage interleukin-1 secretion following intracerebroventricular injection of interleukin-1 beta: evidence for pituitary-adrenal and sympathetic control.

Intracerebroventricular (ICV) injections of interleukin-1 beta (IL-1 beta) produced a dose-dependent increase in plasma corticosterone and adrenocorticotropic hormone (ACTH) within 2 hr of injection and then declined over the next 24 hr. Using a potent steroidogenic dose of IL-1 beta (5 ng), ICV injection resulted in suppression of splenic macrophage IL-1 secretion following stimulation by LPS in vitro. Macrophage TGF-beta secretion was not affected, indicating a differential action of ICV IL-1 beta on macrophage cytokine production. Following adrenalectomy (ADX), the suppressive effect of ICV IL-1 beta was reversed and resulted in stimulation of macrophage IL-1 secretion, indicating that the suppression was mediated by adrenocorticol activation. However, surgical interruption of the splenic nerve to eliminate autonomic innervation of the spleen also prevented the macrophage suppressive signal in rats given ICV IL-1 beta. Furthermore, the combination of ADX and splenic nerve section resulted in a potent stimulatory effect of ICV IL-1 beta on splenic macrophage IL-1 secretion which was greater than either ADX or splenic nerve section alone. These results support the concept of a negative feedback on macrophage IL-1 secretion by the central action of IL-1 beta and indicate that both the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system mediate this effect.

Adrenalectomy↗

PubMed1991

Differential and sex-specific effects of kainic acid and domoic acid lesions in the lateral septal area of rats on immune function and body weight regulation.

The lateral septal area (LSA) has been implicated in the control of various psychoneuroendocrine processes in the rat. Interactions between the endocrine and immune systems and sex differences in immunity reflect the interdependence of the immune and neuroendocrine systems. Kainic acid (KA) lesions in the lateral septal area not only modify neuroendocrine processes, but also produce a suppression of humoral immunity in female rats. Presently, we have evaluated the effects of neurotoxic lesions in the LSA on the humoral immune response and body weight regulation of male and female rats. Bilateral lesions in the LSA of adult male and female rats were produced by stereotaxically infusing either 0.25 microliters of kainic acid (1.5 micrograms/microliters) or 0.5 microliters of domoic acid (DA; 0.3 micrograms/microliters) into the LSA. In an additional study, LSA lesions using 0.25 microliters of DA (0.6 micrograms/microliters) were produced in female rats only. Sham operations consisted of bilateral injections of 0.9% saline into the LSA. The effects of these lesions on antibody production, following immunization with 100 micrograms ovalbumin in complete Freund's adjuvant, were examined. Blood samples were collected on Days 7 and 14 following immunization. The anti-ovalbumin IgM and IgG antibody titers were measured by an enzyme amplified ELISA assay. As found previously, KA-induced LSA lesions in adult female rats produced an increase in body weight and a suppression of the humoral immune response. However, LSA lesions produced with the neurotoxin DA had a similar effect on body weight but had no effect on humoral immunity. In male rats, neither body weight regulation nor the humoral immune response was affected by KA or DA lesions in the LSA. These results indicate that the effects of neurotoxic LSA lesions on body weight regulation and the humoral immune response are sex specific and further demonstrate that two closely related kainate neurotoxins have differential effects on the humoral immune response, but have similar effects on body weight regulation. Thus, neurons in the LSA of female rats that are involved in the inhibitory control of body weight are susceptible to both KA and DA, whereas neurons in the LSA associated with immunoregulation are differentially affected by KA and DA. Of further interest, a sex difference in DA susceptibility was noted, with male rats showing greater cell loss in the LSA following DA infusions, as compared to female rats.

Animals↗

PubMed1990

Fluorescent dextrans as sensitive anterograde neuroanatomical tracers: applications and pitfalls.

We have examined five conjugated 10,000 mol. wt. dextrans as potential anterograde tract tracers: Lucifer Yellow, Texas Red, fluorescein, Cascade Blue and tetramethylrhodamine. Pressure injections were made into the brain, dorsal root ganglia or footpads of adult rats. The retrograde tracer Fluoro-Gold was injected alone or mixed with the dextrans before injection. Three-14 days after injection, animals were perfused and sections cut with a freezing microtome. Texas Red-, fluorescein- and tetramethylrhodamine-conjugated dextrans produced intense labeling of neuronal cell bodies, axons and dendritic processes at the injection site and were transported by neurons predominantly in an anterograde direction to yield terminal and preterminal labeling. Relative to the fluorescein and tetramethylrhodamine conjugates, the quality and intensity of the anterograde labeling produced by Texas Red was variable. Results with Lucifer Yellow and Cascade Blue conjugates were negative. Optimal results were produced by slow-pressure injections via glass micropipettes. In comparison with Fluoro-Gold, retrograde transport by the dextran conjugates was present, but limited in its extent. Injections of the tetramethylrhodamine conjugate into dorsal root ganglia produced anterograde labeling of afferent fibers in visceral organs and injections into the nucleus ambiguous labeled motor fibers in the esophagus. Double/triple labeling was observed in the brain and spinal cord following multiple injections of fluorescein, tetramethylrhodamine and Fluoro-Gold. Also, Fluoro-Gold could be mixed with one of the dextrans in order to produce specific retrograde and anterograde labeling from the same injection site. The conjugates were compatible with fluorescent immunocytochemical procedures, but proved unsuitable for peripheral injections.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗