Cells Expressing mRNA for Neurotrophins and their Receptors During Embryonic Rat Development

In situ hybridization analysis of cells expressing messenger RNAs (mRNAs) for the neurotrophins nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) and their high-affinity receptors (trk, trkB and trkC) in the rat embryo revealed a complex but specific expression pattern for each of these mRNAs. For all mRNAs a developmentally regulated expression was seen in many different tissues. BDNF and NT-3 mRNAs were expressed in the sensory epithelia of the cochlea and vestibule macula of the sacculus and utricle, and both trkB and trkC mRNA were expressed in the spiral and vestibule ganglia innervating these sensory structures. NGF and NT-3 mRNA were found in the iris, innervated by the sympathetic neurons of the superior cervical ganglion and sensory neurons from the trigeminal ganglion, which expressed both trk and trkC mRNAs. Both NGF and NT-3 mRNAs were also expressed in other target fields of the trigeminal ganglion, the epithelium of the whisker follicles (NT-3 mRNA) and in the epithelium of the nose, tongue and jaw. NT-3 mRNA was found in the cerebellar external granule layer and trkC mRNA in the Purkinje layer of the cerebellar primordia. These sites of synthesis are consistent with a target-derived neurotrophic interaction for NGF, BDNF and NT-3. However, in some cases mRNAs for both the neurotrophins and their high-affinity receptors were detected in the same tissue, including the dorsal root, geniculate, superior, jugular, petrose and nodose ganglia, as well as in the hippocampus, frontal cortical plate and pineal recess, implying a local mode of action. Combined, these data suggest a broad function for the neurotrophins and their receptors in supporting neural innervation during embryonic development. The results also identify several novel neuronal systems that are likely to depend on the neurotrophins in vivo.     

Differential expression of mRNAs for the NGF family of neurotrophic factors in the adult rat central olfactory system.

The cellular localization of mRNAs for nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT3), in the rat central olfactory system was evaluated with in situ hybridization of 35S-labeled cRNA probes. In the main olfactory bulb, low levels of NGF and BDNF mRNA expression were detected. NGF mRNA was restricted to the glomerular region while BDNF mRNA was predominantly localized to the granule cell layer. No cellular hybridization to NT3 cRNA was seen. The accessory olfactory bulb did not express detectable levels of mRNA for any of the three related neurotrophic factors. Areas which receive olfactory bulb afferents expressed comparatively high levels of both NGF and BDNF mRNA. Cell labeling with cRNAs for NGF and BDNF occurred throughout the cellular layers of the anterior olfactory nucleus and in layers 2 and 3 of rostral piriform cortex. BDNF mRNA expression in these areas appeared more robust than that of NGF mRNA, while NT3 mRNA was not detectable. In contrast, tenia tecta exhibited dense labeling with the cRNAs for all three neurotrophic factors. The localization of NGF mRNA to primary target neurons of the olfactory nerve in the periglomerular region of the main olfactory bulb suggests that bulb cells may influence the ingrowth and continual turnover of olfactory sensory afferents. However, as there is a strong correlation between the distribution of neurotrophic factor mRNAs within rostral olfactory structures and the distribution of centrifugal cholinergic afferents, it is more likely that bulb-derived NGF, and possibly BDNF, act on the cholinergic neurons of the basal forebrain.     

Expression of the trk gene family of neurotrophin receptors in prevertebral sympathetic ganglia

When the phenotype of neurons in pre- and paravertebral sympathetic ganglia are compared, there are marked differences in NGF dependence, neuropeptide content, connectivity and electrophysiological properties. The trophic interactions that induce these differences are currently poorly understood. One explanation is that prevertebral neurons receive a second neurotrophic signal, other than NGF, from their target of innervation. If this is the case, neurons in the prevertebral ganglia should express another neurotrophin receptor, in addition to the NGF receptor (trk A). To test this prediction, the level of expression of three neurotrophin receptors, trk A, trk B and trk C, were examined in one paravertebral sympathetic ganglia, the SCG, and two prevertebral ganglia, the celiac and superior mesenteric ganglia. It was found that mRNA encoding the full-length form of the trkB receptor was barely expressed in the SCG. Significantly higher levels of full-length trk B mRNA expression were found in the prevertebral ganglia. Ligands of the trkB receptor may, therefore, contribute to the differentiation and/or survival of some prevertebral sympathetic neurons.     

Expression of Ciliary Neurotrophic Factor and the Neurotrophins-Nerve Growth Factor,Brain-Derived Neurotrophic Factor and Neurotrophin 3-in Cultured Rat Hippocampal Astrocytes

Cultured astrocytes are known to possess a range of neurotrophic activities in culture. In order to examine which factors may be responsible for these activities, we have examined the expression of the genes for four known neurotrophic factors – ciliary neurotrophic factor (CNTF), nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin 3 (NT3) – in purified astrocyte cultures derived from neonatal rat hippocampus. Hippocampal astrocytes were found to express mRNA for three neurotrophic factors – CNTF, NGF and NT3 – at significantly higher levels than other cultured cell types or cell lines examined. BDNF messenger RNA (mRNA), however, was undetectable in these astrocytes. The levels of CNTF, NGF and NT3 mRNA in astrocytes were largely unaffected by their degree of confluency, while serum removal caused only a transient decrease in mRNA levels, which returned to basal levels within 48 h. Astrocyte-derived CNTF was found to comigrate with recombinant rat CNTF at 23 kD on a Western blot. Immunocytochemical analysis revealed strong CNTF immunoreactivity in the cytoplasm of astrocytes, weak staining in the nucleus, but no CNTF at the cell surface. NGF and NT3 were undetectable immunocytochemically. CNTF-like activity, as assessed by bioassay on ciliary ganglion neurons, was found in the extract of cultured astrocytes but not in conditioned medium, whereas astrocyte-conditioned medium supported survival of dorsal root ganglion neurons but not ciliary or nodose ganglion neurons. This conditioned medium activity was neutralized with antibodies to NGF. Astrocyte extract also supported survival of dorsal root ganglion and nodose ganglion neurons, but these activities were not blocked by anti-NGF. Part, but not all, of the activity in astrocyte extracts which sustained nodose ganglion neurons could be attributed to CNTF.     

Dental pulp cells provide neurotrophic support for dopaminergic neurons and differentiate into neurons in vitro; implications for tissue engineering and repair in the nervous system

Glial cell line-derived neurotrophic factor (GDNF) mRNA is highly expressed by dental pulp cells (DPCs) prior to the initiation of dental pulp innervation. We show that radioactively labelled exogenous GDNF is retrogradely transported from neonatal teeth and vibrissae to the trigeminal neurons, indicating that GDNF acts as a classical neurotrophic factor in the trigeminal system. We also show that DPCs from both rats and humans produce nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and GDNF mRNAs in vitro, promote the survival and phenotypic characteristics of embryonic dopaminergic (DA) neurons and protect DA neurons against the neurotoxin 6-hydroxy-dopamine (6-OHDA) in vitro. By using inhibitory antibodies to NGF, BDNF and GDNF, we show that the promotion of DA neuron survival relates to the production and release of neurotrophic proteins by DPCs in vitro. We suggest that in vivo production of neurotrophic factors by DPCs play roles in tooth innervation. However, continued production of neurotrophic factors by the DPCs might have wider implications. We propose that the dental pulp is a viable source of easily attainable cells with possible potential for development of autologous cell transplantation therapies. We also show that a population of neural crest-derived dental pulp cells acquire clear neuronal morphology and protein expression profile in vitro, indicating the presence of a cell population in the dental pulp with neuronal differentiation capacity that might provide additional benefits when grafted into the CNS.     

Differential regulation of neurotrophin expression in basal forebrain astrocytes by neuronal signals

Nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT3) promote the function and/or survival of basal forebrain (BF) cholinergic neurons in vivo and in culture. The neurotrophin source is commonly thought to be targets of cholinergic neurons and the possibility that local glial sources support cholinergic neurons has not been well examined. These sources, however, may be critical to BF neurons before or even after they reach their targets. We investigated neurotrophin expression in BF astrocytes and its regulation by neural signals. Solution hybridization and immunocytochemical assays revealed that NGF, BDNF, and NT(3) mRNA and proteins were expressed in cultured BF astrocytes. To investigate roles of neuronal signals in neurotrophin regulation, effects of K(+), glutamate, and the cholinergic agonist carbachol were examined. These stimuli affected neurotrophin expression differentially. KCl increased BDNF mRNA but did not alter NGF or NT(3) mRNA. The effect was blocked by nifedipine, suggesting that it was mediated by L-type voltage-dependent calcium currents. Carbachol also increased BDNF mRNA levels without changing NGF or NT(3). Effects were blocked by the muscarinic antagonist, atropine. In contrast, glutamate increased both NGF and BDNF mRNA. NT(3) mRNA again was unaffected. The metabotropic agonist trans-(1S,3R)-1-amino-1,3-cyclopentanedicarboxylic acid (trans-ACPD) reproduced glutamate effects, whereas kainate or N-methyl-D-aspartate (NMDA) plus glycine did not. Lack of antagonism by ionotropic antagonists and blockade of glutamate effects by metabotropic antagonists confirmed metabotropic mediation. We suggest that BF astrocytes are local sources of neurotrophins for BF cholinergic neurons during development and are regulated differentially by specific neuronal signals. Critical neuronal-glial interactions may underlie basal forebrain function.     

Levels of nerve growth factor and neurotrophin-3 are affected differentially by the presence of p75 in sympathetic neurons in vivo

The development and survival of sympathetic neurons is critically dependent on the related neurotrophic factors nerve growth factor (NGF) and neurotrophin-3 (NT3), the actions of which must be executed appropriately despite spatial and temporal overlaps in their activities. The tyrosine receptor kinases, trkA and trkC, are the cognate receptors for NGF and NT3, respectively. The p75 neurotrophin receptor has been implicated in neurotrophin binding and signaling for both NGF and NT3. In this study, the authors used mice that overexpressed NGF (NGF-OE) or NT3 (NT3-OE) in skin and mice that lacked p75 (p75(-/-)) to understand the dynamics of sympathetic neuron response to each neurotrophin and to address the role of p75. NGF and NT3 were measured in sympathetic ganglia and skin (a major target of sympathetic neurons) by using the enzyme-linked immunosorbent assay (ELISA) technique. A three- to four-fold increase in skin NT3 was seen in both NT3-OE and p75(-/-) mice. Moreover, both mouse lines exhibited a three-fold increase in ganglionic NT3. However, the increase in ganglionic NT3 was accompanied by a decrease in ganglionic NGF in p75(-/-) mice but not in NT3-OE mice. This indicated that p75 plays an important role in determining the level of NGF within sympathetic neurons. In NGF-OE mice, the overexpression of NGF was correlated with increased ganglionic NGF and increased ganglionic expression of p75 mRNA. In addition, in NGF-OE mice, ganglionic trkC expression was decreased, as was the amount of NT3 present within sympathetic ganglia. These results indicate that the level of p75 is integral in determining the level of sympathetic NGF and that NGF competes with NT3 by increasing the expression of p75 and decreasing the expression of trkC.     

The response of chick sensory neurons to brain-derived neurotrophic factor

To determine the spectrum of activity of brain-derived neurotrophic factor (BDNF) among first-order sensory neurons, explants of the nine distinct populations of sensory neurons from embryonic chicks of 3-14 d incubation (E3-E14) were grown in collagen gels with and without BDNF in the culture medium. The explants responded to BDNF with profuse neurite outgrowth and comprised those in which neurons are derived from neural crest (the dorsomedial part of the trigeminal ganglion, rostromedial part of the trigeminal mesencephalic nucleus, jugular ganglion, and lumbosacral dorsal root ganglia) and from epibranchial placodes (the ventrolateral part of the trigeminal ganglion and the geniculate, petrosal, and nodose ganglia). This response was first clearly observed in the ventrolateral trigeminal and nodose ganglia as early as E4, but did not appear until later in other explants. The dorsomedial trigeminal, jugular, and geniculate ganglia were the latest to develop a response, which was not apparent until E8. In all explants the response was maximal between E10 and E12, and there was a decline in the magnitude of the response from E12 to E14. Although explants of the vestibular ganglion failed to respond to BDNF, the survival and growth of vestibular neurons in dissociated neuron-enriched cultures were promoted by BDNF. To investigate whether all first-order sensory neurons respond to BDNF or whether BDNF-responsive neurons comprise a distinct subset, we studied the influence of BDNF and NGF on the survival and growth of the placode-derived and the neural crest-derived neurons of the trigeminal ganglion in dissociated neuron-enriched culture.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cerebrolysin modulates pronerve growth factor/nerve growth factor ratio and ameliorates the cholinergic deficit in a transgenic model of Alzheimer's disease

Alzheimer's disease (AD) is characterized by degeneration of neocortex, limbic system, and basal forebrain, accompanied by accumulation of amyloid‐β and tangle formation. Cerebrolysin (CBL), a peptide mixture with neurotrophic‐like effects, is reported to improve cognition and activities of daily living in patients with AD. Likewise, CBL reduces synaptic and behavioral deficits in transgenic (tg) mice overexpressing the human amyloid precursor protein (hAPP). The neuroprotective effects of CBL may involve multiple mechanisms, including signaling regulation, control of APP metabolism, and expression of neurotrophic factors. We investigate the effects of CBL in the hAPP tg model of AD on levels of neurotrophic factors, including pro‐nerve growth factor (NGF), NGF, brain‐derived neurotrophic factor (BDNF), neurotropin (NT)‐3, NT4, and ciliary neurotrophic factor (CNTF). Immunoblot analysis demonstrated that levels of pro‐NGF were increased in saline‐treated hAPP tg mice. In contrast, CBL‐treated hAPP tg mice showed levels of pro‐NGF comparable to control and increased levels of mature NGF. Consistently with these results, immunohistochemical analysis demonstrated increased NGF immunoreactivity in the hippocampus of CBL‐treated hAPP tg mice. Protein levels of other neurotrophic factors, including BDNF, NT3, NT4, and CNTF, were unchanged. mRNA levels of NGF and other neurotrophins were also unchanged. Analysis of neurotrophin receptors showed preservation of the levels of TrKA and p75^NTR immunoreactivity per cell in the nucleus basalis. Cholinergic cells in the nucleus basalis were reduced in the saline‐treated hAPP tg mice, and treatment with CBL reduced these cholinergic deficits. These results suggest that the neurotrophic effects of CBL might involve modulation of the pro‐NGF/NGF balance and a concomitant protection of cholinergic neurons. © 2012 Wiley Periodicals, Inc.     

Granule cell mRNA levels for BDNF, NGF, and NT-3 correlate with neuron losses or supragranular mossy fiber sprouting in the chronically damaged and epileptic human hippocampus

This study determined in temporal lobe epilepsy patients if there were correlations among hippocampal granule cell expression of neurotrophin mRNAs, aberrant supragranular mossy fiber sprouting, and neuron losses. Consecutive surgically resected hippocampi (n=9) and comparison tissue from autopsies (n=3) were studied for:

1. Granule cell mRNA levels usingin situ hybridization for brainderived neurotrophic factor (BDNF), nerve growth factor (NGF), and neurotrophin-3 (NT-3);
2. neo-Timm supragranular mossy fiber sprouting; and
3. Ammon’s horn neuron densities.

Clinically, patients were classified into those with hippocampal sclerosis (HS;n=7) and non-HS cases (i.e., mass lesions and autopsies;n=5). Results showed that compared to non-HS cases, HS patients showed increased granule cell mRNA levels for BDNF, NGF, and NT-3 (p=0.035,p=0.04,p=0.045 respectively; one-tail directional test). Moreover, granule cell BDNF mRNA levels correlated inversely with Ammon’s horn neuron densities (p=0.02) and correlated positively with greater supragranular mossy fiber sprouting (p=0.02). NGF mRNA levels correlated inversely with Ammon’s horn neuron densities (p=0.02), and TN-3 mRNA levels correlated inversely with age at surgery (p=0.04) and correlated positively with greater mossy fiber sprouting (p=0.026). These results indicate in the chronically damaged human hippocampus that granule cells express neurotrophin mRNAs, and mRNA levels correlate with either hippocampal neuron losses or aberrant supragranular mossy fiber sprouting. These data support the hypothesis that in the epileptic human hippocampus, there may be pathophysiologic associations among mossy fiber synaptic plasticity, hippocampal neuron damage, and granule cell mRNA neurotrophin levels.     

TrkA-expressing trigeminal sensory neurons display both neurochemical and structural plasticity despite a loss of p75NTR function: responses to normal and elevated levels of nerve growth factor

In neural crest-derived sensory ganglia, approximately half of the neuronal population expresses the transmembrane trkA receptor that is required for neuronal binding of target-derived nerve growth factor (NGF). These same neurons also express the p75 neurotrophin receptor (NTR) that increases the affinity of trkA for NGF. Depleting p75NTR expression reduces both the survival of trkA-positive sensory neurons and their afferent innervation of peripheral targets. In this investigation, we assessed the neurochemical and structural plasticity of trigeminal sensory neurons in p75NTR-deficient mice in response to either normal or elevated levels of NGF during postnatal development and into adulthood. Although p75NTR-deficient mice have 30% fewer trigeminal neurons, levels of trkA mRNA expression are modestly elevated in these mutant mice as compared to control mice. The density of central afferent axons and local levels of NGF are, however, comparable between mutant and control animals. Thus, despite the survival of fewer trigeminal neurons, neither ganglionic levels of trkA mRNA expression nor the density of central afferent projections are depleted in p75NTR-deficient mice. In response to elevated levels of NGF protein, transgenic mice with and without p75NTR expression display both increased levels of trkA mRNA expression and a greater density of trigeminal central afferent axons as compared to control mice. These data further reveal that an absence of p75NTR function in trigeminal sensory neurons does not diminish their capacity for NGF-dependent plasticity, namely trkA mRNA expression and collateral growth of central afferent axons.     

Limbic seizures induce a differential regulation of the expression of nerve growth factor, brain-derived neurotrophic factor and neurotrophin-3, in the rat hippocampus.

Small unilateral electrolytic lesions placed in the hilus of the dentate gyrus produce limbic seizures. We have investigated the effects of these hilar lesions on the levels of the mRNAs encoding for 3 neurotrophic factors (NTF): nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT3). 'In situ' hybridization histochemistry with synthetic oligonucleotides was used to analyze their mRNA distribution and levels. In agreement with previously published data (Science, 245 (1989) 758-761), NGF mRNA was found bilaterally, quickly and transiently increased in granule cells of the dentate gyrus. Only 2 h after the onset of limbic seizures, mRNA levels for BDNF were also found to be dramatically elevated in both sides of the hippocampus, reaching a maximum 30-fold increase in the granule cell layer of the dentate gyrus 5 h after the lesion. Moreover, increased levels of this mRNA were also been found in the pyramidal layer of the CA3 (5-fold) and CA1 (15-fold) hippocampal fields. In contrast, NT3 mRNA was found to be clearly and bilaterally decreased in dentate gyrus granule cells, reaching 5- to 6-fold decreased levels at 12 h after lesion. Taken together, these results clearly show a different regulation of neurotrophic factors genes (NGF, BDNF and NT3) expression in the different hippocampal fields, as a consequence of seizure-producing hilar lesions.     

Neurotrophic properties of olfactory ensheathing glia

Olfactory ensheathing cells (OEC) constitute a specialized population of glia that accompany primary olfactory axons and have been reported to facilitate axonal regeneration after spinal cord injury in vivo. In the present report we describe OEC neurotrophic factor expression and neurotrophic properties of OECs in vitro. Investigation of the rat olfactory system during development and adulthood by radioactive in situ hybridization revealed positive labeling in the olfactory nerve layer for the neurotrophic molecules S-100beta, CNTF, BMP-7/OP-1, and artemin, as well as for the neurotrophic factor receptors RET and TrkC. Ribonuclease protection assay of cultured OEC revealed expression of NGF, BDNF, GDNF, and CNTF mRNA, while NT3 and NT4 mRNA were not detectable. In vitro bioassays of neurotrophic activity involved coculturing of adult OEC with embryonic chick ganglia and demonstrated increased neurite outgrowth from sympathetic, ciliary, and Remak's ganglia. However, when culturing the ganglia with OEC-conditioned medium, neurite outgrowth was not stimulated to any detectable extent. Our results suggest that the neurotrophic properties of OEC may involve secretion of neurotrophic molecules but that cellular interactions are crucial.     

Complexity in the modulation of neurotrophic factor mRNA expression by early visual experience

The expression of mRNA for brain-derived neurotrophic factor (BDNF) is regulated by early visual experience. In this study, we sought to determine whether other neurotrophic factor mRNAs are similarly regulated. We reared pigmented rats from birth to postnatal day 21 in a normal light cycle, constant light (LR) or constant darkness (DR). In the retina, superior colliculus (SC), primary visual cortex (V1), hippocampus (HIPP) and cerebellum (CBL), using a ribonuclease protection assay (RPA), we examined expression of the mRNAs for nerve growth factor (NGF), BDNF, NT3, NT4, ciliary neurotrophic factor (CNTF) and glial cell line-derived neurotrophic factor (GDNF). LR or DR alter the expression of the mRNAs for NGF, BDNF and NT3 and CNTF within the visual system. LR also upregulated BDNF mRNA expression within the cerebellum. In all of the structures examined, NT4 mRNA expression was unaltered by LR or DR and GDNF mRNA was undetectable. Notably, the same rearing condition could induce changes of opposite sign in the mRNA for a single factor in different structures or for different factors in the same structure. Thus, during developmental stages when sensory experience and neuroelectric activity are important in the shaping of visual circuitry, vision regulates the expression of multiple neurotrophic factor mRNAs and each mRNA has a unique profile with respect to the locus and sign of activity-induced changes.     

Properties of Contextual Memory Formed in the Absence of αCaMKII Autophosphorylation

Background

Sleep homeostasis is characterized by a positive correlation between sleep length and intensity with the duration of the prior waking period. A causal role for brain-derived neurotrophic factor (BDNF) in sleep homeostasis has been suggested, but the underlying mechanisms remain unclear. Cortistatin, a neuropeptide expressed primarily in a subset of cortical GABAergic interneurons, is another molecule implicated in sleep homeostasis.

Results

We confirmed that sleep deprivation leads to an increase in cortical cortistatin mRNA expression. Disruption of activity-dependent BDNF expression in a genetically modified mouse line impairs both baseline levels of cortistatin mRNA as well as its levels following sleep deprivation. Disruption of activity-dependent BDNF also leads to a decrease in sleep time during the active (dark) phase.

Conclusion

Our studies suggest that regulation of cortistatin-expressing interneurons by activity-dependent BDNF expression may contribute to regulation of sleep behavior.     

Delineating neurotrophin-3 dependent signaling pathways underlying sympathetic axon growth along intermediate targets

Postganglionic sympathetic neurons detect vascular derived neurotrophin 3 (NT3) via the axonally expressed receptor tyrosine kinase, TrkA, to promote chemo-attraction along intermediate targets. Once axons arrive to their final target, a structurally related neurotrophic factor, nerve growth factor (NGF), also acts through TrkA to promote final target innervation. Does TrkA signal differently at these different locales? We previously found that Coronin-1 is upregulated in sympathetic neurons upon exposure to NGF, thereby endowing the NGF-TrkA complex with new signaling capabilities (i.e. calcium signaling), which dampens axon growth and branching. Based on the notion that axons do not express functional levels of Coronin-1 prior to final target innervation, we developed an in vitro model for axon growth and branching along intermediate targets using Coro1a^−/− neurons grown in NT3. We found that, similar to NGF-TrkA, NT3-TrkA is capable of inducing MAPK and PI3K in the presence or absence of Coronin-1. However, unlike NGF, NT3 does not induce calcium release from intracellular stores. Using a combination of pharmacology, knockout neurons and in vitro functional assays, we suggest that the NT3-TrkA complex uses Ras/MAPK and/or PI3K-AKT signaling to induce axon growth and inhibit axon branching along intermediate targets. However, in the presence of Coronin-1, these signaling pathways lose their ability to impact NT3 dependent axon growth or branching. This is consistent with a role for Coronin-1 as a molecular switch for axon behavior and suggests that Coronin-1 suppresses NT3 dependent axon behavior.     

Neurotrophic effects of 7,8-dihydroxycoumarin in primary cultured rat cortical neurons

Objective Neuronal loss in the central nervous system is central to the occurrence of neurodegenerative diseases. Pharmaceutical companies have devoted much effort to developing new drugs against such diseases, since there are currently no effective drugs for neurodegenerative disease treatment. Promoting the capacity for nerve regeneration is an ideal treatment target. The present study aimed to investigate the neurotrophic effects of 7,8-dihydroxycoumarin (DHC) or daphnetin in primary cultured rat cortical neurons. Methods Cortical neurons were identified by microtubule-associated protein 2 (MAP2) immunostaining. Morphological observation was used to measure the average length of neurite outgrowth. MTT and lactate dehydrogenase assays were used to assess neuronal survival. The mRNA expression of MAP2 and brain-derived neurotrophic factor (BDNF) was measured by RT-PCR. Results MAP2 immunostaining showed that most of the cultured cells were neurons. Compared with the vehicle control group, DHC promoted neurite outgrowth and prolonged neuronal survival time at concentrations ranging from 2 to 8 μmol/L. Expression of both BDNF mRNA and MAP2 mRNAwas increased in the groups treated with 2, 4 and 8 μmol/L DHC. Conclusion DHC significantly increases neurite outgrowth and promotes neuronal survival in primary cultured rat cortical neurons. The neurotrophic effects of DHC are probably associated with increased BDNF expression.