Nerve Growth Factor Antiserum Research Articles

A novel method for assessing bladder-related pain reveals the involvement of nerve growth factor in pain associated with cyclophosphamide-induced chronic cystitis in mice.

Pain is a prominent feature of interstitial cystitis/painful bladder syndrome (IC/PBS), but the underlying mechanisms are not fully understood. There is a lack of well-characterized research tools, such as pain evaluation methods and experimental animal models, for investigating non-ulcerative cystitis. We developed a novel method for evaluating bladder pain in mice with cyclophosphamide (CYP)-induced cystitis. Cystitis was produced by a single intraperitoneal injection of CYP (300 mg/kg) or repeated injections of CYP (150 mg/kg once daily for 4 days). Blunt stimulation with a cotton probe was applied to the abdominal region, and the thresholds for withdrawal responses were measured quantitatively using an anaesthesiometer. The single injection of CYP provoked acute cystitis with severe bladder inflammation in mice. In these mice, we could detect an increased sensitivity to blunt stimulation, which was abolished by intravesical lidocaine. The stimulation induced phosphorylation of extracellular signal-regulated kinases in bladder-projecting sensory neurons. Chronic treatment with CYP produced persistent pain responses to the blunt stimulus. Although there were few signs of bladder inflammation in these mice, the concentration of nerve growth factor (NGF) was elevated in bladder tissue, and NGF antiserum inhibited the hypersensitivity. The blunt probe method is useful for evaluating bladder pain signalling in mice, and revealed the involvement of an NGF-sensitive pain pathway in chronic cystitis pain. This assessment method may be useful for studying the pathophysiology of bladder pain and for developing therapeutic strategies for non-ulcerative IC/PBS in patients.

Pro-apoptotic Bim Induction in Response to Nerve Growth Factor Deprivation Requires Simultaneous Activation of Three Different Death Signaling Pathways

Bim is a pro-apoptotic member of the Bcl-2 family that is induced and contributes to neuron death in response to nerve growth factor (NGF) deprivation. Past work has revealed that Bim is downstream of multiple independent transcriptional pathways in neurons, including those culminating in activation of the c-Jun, FoxO, and Myb transcription factors. This study addresses the issue of whether the three signaling pathways are redundant with respect to Bim induction or whether they act cooperatively. Examination of the proximal Bim promoter reveals binding sites for FoxO, Mybs, and, as shown here, c-Jun. We find that mutation of any one of these types of sites abolishes induction of a Bim promoter-driven reporter in response to NGF deprivation. Moreover, down-regulation of either c-Jun, FoxOs, or Mybs by short hairpin RNAs blocks induction of Bim promoter-reporter activity triggered by withdrawal of NGF. This was the case for reporters driven by either the proximal promoter or a promoter that also includes additional regulatory elements in the first intron of the Bim gene. Such short hairpin RNAs also suppressed the induction of endogenous Bim protein. These findings thus indicate that the Bim promoter acts as a coincidence detector that optimally responds to the simultaneous activation of three different pro-apoptotic transcriptional pathways. Such a mechanism provides a "fail-safe" that prevents neurons from dying by accidental activation of any single pathway. It also permits neurons to utilize individual pathways such as JNK signaling for other purposes without risk of demise.

Nerve growth factor mediates peripheral mechanical hypersensitivity that accompanies experimental cystitis in mice

Increased sensitivity to somatic stimuli has been noted in the presence of visceral inflammation. Cystitis was induced by intraperitoneal injection of cyclophosphamide (CYP) in female mice. Sensitivity of hind paws to mechanical stimuli was determined prior to and 4, 9 and 24 h after CYP, and sensitivity of the tail to thermal stimuli was determined prior to, 4 and 24 h after CYP treatment. To investigate the role of nerve growth factor (NGF) in these processes, other groups of mice received NGF antiserum, normal serum, or K252a intravenously 30 min after CYP administration. CYP induced bladder inflammation that was not ablated by treatment with NGF antiserum or K252a. Sensitivity to mechanical stimuli was increased 4 and 9 h after CYP administration. This was reversed by NGF antiserum or K252a but not by normal serum. After 24 h, no differences were observed in withdrawal threshold among groups. None of the treatments had any effect on sensitivity to thermal stimuli. To further investigate the role of NGF in this process, NGF was instilled into the bladders of mice in the presence or absence of intravenous NGF antiserum. Four hours after intravesical instillation of NGF, the threshold of the hind paws to mechanical stimulation was significantly decreased, and this effect was reversed by prior treatment with NGF antiserum. This model of visceral pain causes increased sensitivity to peripheral application of mechanical stimuli. This effect is at least partially mediated by NGF, and the bladder may be the source of NGF in this process.

Pre-weaning carvedilol treatment in spontaneously hypertensive rats

Hypertension in spontaneously hypertensive rats (SHR) has been permanently abolished by aggressive treatment regimens targeted against the sympathetic nervous system and adrenal medulla, initiated during the pre-weaning period (guanethidine and nerve growth factor antiserum combined with either adrenal demedullation or prazosin treatment). To investigate the components of the sympatho-adrenal system involved, we treated pre-weaning SHR with the combined α 1- and β-adrenoceptor antagonist carvedilol (60 mg/kg/day s.c.; postnatal days 1–21). Carvedilol treatment significantly blocked adrenoceptors during the treatment period, delayed development (eye opening), reduced growth, and reduced arterial pressure and heart rate. However, there was only modest attenuation of the subsequent development of hypertension at 10 weeks of age (mean arterial pressure 129.5±1.8 versus 136.1±1.6 mm Hg in vehicle-treated littermates; P<0.05). Thus pre-weaning carvedilol treatment slightly but significantly attenuated the development of SHR hypertension at 10 weeks, suggesting that the profound antihypertensive effects of pre-weaning sympatho-adrenal ablation are attributable to factors other than α 1- and β-adrenoceptor-mediated effects of catecholamines during this period.

Progesterone Induces the Proliferation of Urothelial Cells in an Epidermal Growth Factor Dependent Manner

We have previously reported that estrogen induced proliferation of urothelial cells is modulated by nerve growth factor (NGF). In this study we investigated whether progesterone induces urothelial cell proliferation and whether this effect is modulated by NGF or by epidermal growth factor (EGF). Experiments were performed using human urothelial cells immortalized by human papillomavirus E6. Cell proliferation was determined using the alamarBlue (Trek Diagnostic, Westlake, New York) assay. Human papillomavirus were seeded in 48-well plates. They were incubated with 5% alamarBlue and different concentrations of progesterone, EGF or NGF in the presence or absence of neutralizing EGF or NGF antibody, K252a (an inhibitor of trkA, the high affinity receptor for NGF), Ru-486 (an antagonist of progesterone and glucocorticoid receptor) or ZK 137 316 (a specific antagonist of progesterone receptor). Immunoblotting was performed using specific antibodies for progesterone receptor, glucocorticoid receptor or EGF receptor. EGF content in conditioned medium was determined by enzyme-linked immunosorbent assay. In the presence of 10 nM to 1 microM progesterone urothelial cell proliferation was significantly increased 8.6% to 51.1%. This effect was abolished by ZK137 316 or by Ru-486. Hydrocortisone also induced urothelial cell proliferation. This effect was blocked by Ru-486 but not by ZK137 316. In addition, progesterone stimulated urothelial cell proliferation was inhibited by neutralizing EGF antibody but not by NGF antiserum or K252a. We also found that EGF synthesis and release by urothelial cells was increased by exogenous progesterone. This effect of progesterone was inhibited by ZK 137 316. These findings indicate that progesterone has the capacity to induce urothelial cell proliferation through its cognate receptor and this effect is mediated by EGF but not by NGF.

Lumbar 5 ventral root transection-induced upregulation of nerve growth factor in sensory neurons and their target tissues: a mechanism in neuropathic pain

We have previously demonstrated that profound and persistent neuropathic pain as displayed by mechanical and cold allodynia and thermal hyperalgesia can be produced by a lumbar 5 ventral root transection (L5 VRT) model in adult rats in which only the motor nerve fibers were injured without axotomy of sensory neurons. However, the underlying mechanisms remain to be determined. In this study, by examining its changes in expression and by inhibiting its functions using a neutralizing antibody, we have investigated whether nerve growth factor (NGF), a neurotrophic factor known to have a function in regulating nerve injury-induced pain, is involved in the development of neuropathic pain induced by L5 VRT. Motor nerve injury by L5 VRT resulted in a de novo expression of NGF mRNA in a subpopulation of small sensory neurons and pericellular satellite cells in ipsilateral L5 dorsal root ganglion. NGF protein expression was also increased by sensory neurons with various sizes and by keratinocytes in the target tissue ipsilateral skin. Systemic administration of NGF antiserum twice within 17 days markedly attenuated L5 VRT-induced mechanical allodynia but not the cold allodynia and thermal hyperalgesia. These findings suggest that NGF is an important pain mediator in the generation of mechanical sensitivity induced by L5 VRT.

Estrogen-induced proliferation of urothelial cells is modulated by nerve growth factor.

Both nerve growth factor (NGF) and estrogen have been shown to stimulate proliferation of various cell types. Human urothelial cells (HUC) express the alpha- and beta-subtypes of the estrogen receptor (ER(alpha) and ER(beta)) as well as tyrosine kinase A (trkA), the high-affinity receptor for NGF. We investigated interactions between estrogen and NGF relative to cell proliferation using primary cultures of HUC. 17 beta-estradiol (E2) stimulated NGF synthesis by HUC, and E2 (50 nM), the ER(alpha) agonist 16 alpha-iodo-17 beta-estradiol (10 nM), or the ER(beta) agonist genistein (50 nM) each stimulated HUC proliferation, an effect that was abolished by the estrogen antagonist ICI-182,780 (100 nM). NGF (1-100 ng/ml) stimulated HUC proliferation, and this was abolished by NGF antiserum (0.1 microl/ml) or the trkA antagonist K252a (100 nM). HUC proliferation stimulated by E2 was also abolished by NGF antiserum or K252a. Finally, we observed that treatment of HUC with NGF (50 ng/ml) or E2 (50 nM) stimulated trkA phosphorylation, and this was abolished by K252a (100 nM) or NGF antiserum (0.1 microl/ml). These data indicate that the effects of ER activation on HUC proliferation at least partly involve activation of trkA by NGF.

Anti-interleukin-3 and anti-nerve growth factor increase neonatal mice survival to reovirus type 3 clone 9 per oral challenge

Reovirus type 3 clone 9 (T3C9) induces lethal encephalitis in neonatal, but not adult mice. Whether host factors that promote the development and/or functioning of nervous and gastrointestinal tissues could modulate the pathogenesis of this enteric virus was examined. The results showed that antibody specific for interleukin-3 or nerve growth factor antiserum, but not anti-interleukin-6 or anti-tumor necrosis factor-α/β increased mice survival to T3C9 and decreased viral titers in nervous tissues early after infection. These data suggest that IL-3 and NGF are involved in the pathogenesis of T3C9 infection in neonatal mice.

Neurotrophic factors and pain.

Neurotrophic factors have been shown to play significant roles in the transmission of physiologic and pathologic pain. Nerve growth factor appears to be particularly important. It is crucial for the development of sympathetic and small fiber sensory neurons that serve as nociceptors. It stimulates the expression and release of neuropeptides involved in pain transmission, and interacts with cellular and molecular mediators of inflammation. Blockade with nerve growth factor antiserum demonstrates the critical role of the growth factor in mediating inflammatory hyperalgesia. Administration of nerve growth factor to rodents results in the rapid onset of hyperalgesia. Although the exact mechanism is unknown, several possibilities have been proposed. In clinical trials for the treatment of Alzheimer disease and peripheral neuropathy, induction of pain has been the major adverse event. When administered intracebrebroventricularly, a dull constant back pain resulted. Subcutaneous injection of nerve growth factor induces injection site hyperalgesia, as well as generalized myalgias and arthralgias. Whether the mechanisms underlying these adverse events are identical to those associated with the hyperalgesia in rodents is unknown. In addition to nerve growth factor, other growth factors, such as brain-derived neurotrophic factor and glial cell-derived neurotrophic factor, may be involved in pain pathways. Their precise roles are still being defined, but evidence suggests that they may have particular relevance to neuropathic pain. Understanding the role all these factors play may change the way we approach the treatment of pain in general, and neuropathic pain in particular.

Endogenous nerve growth factor and neurotrophin-3 act simultaneously to ensure the survival of postnatal sympathetic neurons in vivo

For many years nerve growth factor was the only factor known to influence embryonic and postnatal development of sympathetic neurons. Its deprivation by antibody neutralization or gene mutation results in extensive neuron death. Recently it has been shown that these neurons also require neurotrophin-3 for survival in the late developmental period. Using neurotrophin-3 antiserum to neutralize endogenous factor in newborn rats, our laboratory has shown that extensive numbers of neurons are lost from both pre- and paravertebral ganglia, indicating a continuing requirement for neurotrophin-3. In the present study we sought to determine whether neurons could survive in vivo in the presence of excess amounts of either nerve growth factor or neurotrophin-3 alone. Consistent with previous findings, administration of antiserum to nerve growth factor or neurotrophin-3 to newborn rats for eight days, resulted in an extensive loss of sympathetic neurons. Interestingly, administration of neurotrophin-3 together with nerve growth factor antiserum or nerve growth factor with neurotrophin-3 antiserum, reversed this neuronal loss. However the latter combination was less effective than the former. Furthermore, the ability of exogenous nerve growth factor to increase both the number and size of sympathetic neurons was prevented by the simultaneous deprivation of endogenous neurotrophin-3. Unlike nerve growth factor, exogenous neurotrophin-3 failed to rescue the naturally occurring neuronal death in these newborn rats. Further evidence for a physiological role for both nerve growth factor and neurotrophin-3 was found by the detection of both trkA and trkC immunoreactivity in neurons of the superior cervical ganglion.Taken together, these results suggest that sympathetic neurons do not have an absolute requirement for either nerve growth factor or neurotrophin-3 and that the endogenous supply of either factor alone is insufficient to support neuronal survival postnatally. However, while each factor may play similar roles in the regulation of postmitotic neuronal function, some evidence for distinct functions has been identified.

Regulation of N- and L-type Ca2+ channels in adult frog sympathetic ganglion B cells by nerve growth factor in vitro and in vivo.

To examine mechanisms responsible for the long-term regulation of Ca2+-channels in an adult neuron, changes in whole cell Ba2+ current (IBa) were examined in adult bullfrog sympathetic ganglion B cells in vitro. Cells were cultured at low density in defined, serum free medium. After 15 days, total IBa was similar to the initial value, whereas IBa density was reduced by approximately 36%, presumably due to an increase in neuronal surface area. By contrast, IBa density remained constant after 6-15 days in the presence of murine beta-NGF (200 ng/ml), and total IBa was almost doubled. Inclusion of cytosine arabinoside (Ara-C; 10 microM) to inhibit proliferation of nonneuronal cells, did not affect the survival of neurons in the absence of nerve growth factor (NGF) nor did it attenuate IBa. Ara-C did not prevent the effect of NGF on IBa. There were three independent components to the action of NGF; during 6-9 days, it increased omega-conotoxin-GVIA-sensitive N-type IBa (IBa,N); increased nifedipine-sensitive L-type IBa (IBa,L) and decreased inactivation of the total Ba2+ conductance (gBa). The latter effect involved a selective decrease in the amplitude of one of the four kinetic components that describe the inactivation process. Total IBa was also 55.8% larger than control in the somata of B cells acutely dissociated from leopard frogs that had received prior subcutaneous injections of NGF. By contrast, injection of NGF antiserum decreased total IBa by 29.4%. There was less inactivation of gBa in B cells from NGF-injected animals than in cells from animals injected with NGF antiserum (P < 0.001). These data suggest that NGF-like molecule(s) play(s) a role in the maintenance of IBa in an adult amphibian sympathetic neuron; the presence of NGF may allow the neuron to maintain a constant relationship between cell size and current density. They also show that IBa inactivation in an adult neuron can be modulated in a physiologically relevant way by an extracellular ligand.

Involvement of interleukin-1 beta, nerve growth factor and prostaglandin E2 in endotoxin-induced localized inflammatory hyperalgesia.

1. Intraplantar endotoxin (ET) injection (1.25 micrograms) into the hind paw of rats resulted in a localized inflammatory hyperalgesia, as assessed by paw pressure (PP), paw immersion (PI), tail flick (TF) and hot plate (HP) tests. 2. ET injection resulted in a significant elevation in the levels of interleukin-1 beta (IL-1 beta) and nerve growth factor (NGF) in the injected foot as compared with the non-injected foot. This increase was attenuated by intraperitoneal injections of dexamethasone (200 and 400 micrograms kg-1) and to a lesser extent by indomethacin (2 and 8 mg kg-1). 3. The tripeptide Lys-D-Pro-Val, which is known to antagonize IL-1 beta and prostaglandin E2 (PGE2) reversed mechanical hyperalgesia, as assessed by the PP test, and reduced significantly thermal hyperalgesia, as assessed by the HP and TF tests. 4. IL-1ra reversed both mechanical (PP) and thermal (PI) nociceptive thresholds tested on the injected leg and significantly reduced thermal hyperalgesia, as assessed by the HP and TF tests. 5. A sheep, anti-mouse NGF antiserum reversed mechanical hyperalgesia (PP test) but had little or no effect on thermal hyperalgesia (PI, HP and TF tests). 6. Our results indicate the importance of IL-1 beta, NGF and prostaglandin E2 (PGE2) in the development of ET induced hyperalgesia and the possible existence of different mechanisms underlying thermal and mechanical as well as central and peripheral hyperalgesia.

Endogenous nerve growth factor is required for regulation of the low affinity neurotrophin receptor (p75) in sympathetic but not sensory ganglia.

During development, many sympathetic and sensory neurons are dependent on nerve growth factor (NGF) for survival. The low affinity neurotrophin receptor (p75), expressed in these neurons, is regulated by exogenous NGF in vitro and in vivo. However, whether p75 expression in vivo is under the control of endogenous NGF has not been determined. The role of NGF in regulating the expression of p75 in sympathetic and sensory nerves was investigated in Sprague-Dawley rats treated with an antiserum specific for NGF. P75 was differentially regulated. P75 immunoreactivity (-ir) within sympathetic neurons in the superior cervical ganglia (SCG) was reduced after 2 days, and disappeared after 5 days, of treatment with the NGF antiserum. In contrast, a significant increase in p75-ir was detected in nerve bundles within and close to the SCG from 3 to 14 days after treatment. A similar pattern of p75 expression was observed in the stellate and coeliac ganglia. In contrast, p75 expression in nerve terminals of the mesenteric arteries and irides was reduced. However, in the same animals the expression of p75 was not significantly affected by the treatment in dorsal root, trigeminal or nodose ganglia, salivary gland or small intestine. In contrast to p75, the NGF high affinity receptor trkA was little affected in sympathetic neurons by depletion of endogenous NGF for 2 weeks. These results indicate that endogenous NGF is required in sympathetic ganglia for the expression of p75 but not trkA in neurons, but for the down-regulation of p75 in glia. In contrast, endogenous NGF is not essential for the regulation of p75 in neurons or glia within sensory ganglia.

An improved procedure for the immunohistochemical localization of nerve growth factor-like immunoreactivity

Nerve growth factor (NGF) is a survival factor required by a number of neuronal populations including most post-ganglionic sympathetic neurones. NGF has been detected and quantified in many tissues but there is little information regarding its cellular localization. Although it has been argued that histological detection has proven difficult due to the low levels of NGF present, other factors may contribute to prevent its identification. In the present study, we report a method for the histological detection of NGF-like immunoreactivity in the rat superior cervical ganglia (SCG). Adult Wistar-Kyoto rats were perfused briefly with either a high or low pH buffer prior to fixation and routine immunohistochemistry. Polyclonal antibodies to native mouse NGF used in the present study recognized mouse NGF but not recombinant human neurotrophin 3 (rhNT3) or brain-derived neurotrophic factor (rhBDNF) by immunoblot analysis. NGF-like immunoreactivity was localized to most sympathetic neurones. Immunoreactivity was detected in the cytoplasm with dense labelling around nuclei. No stain was seen in sections incubated with normal sheep IgG or from animals perfused with phosphate buffer (pH 7.4) prior to fixation. In addition, axotomy resulted in the disappearance of NGF immunoreactivity which was confirmed by biochemical quantification. Finally, no NGF immunoreactivity was found in neurones of rats treated systemically with NGF antiserum 3 days earlier. Possible mechanisms underlying the improvement of NGF immunohistochemistry by pH manipulation before fixation are discussed.

Trophic influences of human and rat amniotic fluid on neural tube-derived rat fetal cells

Normal human (week 17–20) and rat (E16–17) amniotic fluids were used as culture media for primary cultures of rat fetal (E 16) cortical, mesencephalic and striatal cell dissociates, or astroglial subcultures from the same brain regions. Phase-bright and dark cells were identified under phase contrast microscopy and their cell processes were measured utilizing semi-automated procedures. Subcultured astroglia were immuno-reacted against glial fibrillary acidic protein and fibronectin. Rat and human amniotic fluid allowed survival and growth of neuronal and non-neuronal cells. Human amniotic fluid samples were trophic in variable degrees. Cerebral cortex subcultured astroglia usually expressed a radial-like morphotype. Although charcoal-adsorbed human amniotic fluid was trophic for primary cultures, its ability to sustain neuritic growth depended on its degree of trophism before treatment. Growth of cell processes in neuronal- and glial-like cells in primary cultures was inhibited to different degrees by the addition of antisera towards nerve or epidermal growth factors. It is concluded that amniotic fluid constitutes a trophic medium for astroglia and neurons. Both, nerve and epidermal growth factors appear to be necessary for growth of cell processes in neuronal and glial primary cultures in amniotic fluid. Trophic effect of amniotic fluid on subcultured astroglia did not seem to be diminished by nerve growth factor antiserum. The role of amniotic fluid during the early phases of brain organogenesis is discussed.

Medical futility, treatment withdrawal and the persistent vegetative state.

Why do we persist in the relentless pursuit of artificial nourishment and other treatments to maintain a permanently unconscious existence? In facing the future, if not the present world-wide reality of a huge number of persistent vegetative state (PVS) patients, will they be treated because of our ethical commitment to their humanity, or because of an ethical paralysis in the face of biotechnical progress? The PVS patient is cut off from the normal patterns of human connection and communication, with a life unlike other forms of human existence. Why the struggle to justify ending a life which, it is said, has suffered an irreversible loss of the content of consciousness? Elsewhere, the authors have addressed the ethical controversies and confusion engendered by ambiguous terminology, misuse of medical facts and the differing interpretations of what constitutes 'effective' treatment: in particular, the issue of whether in fact artificial nutrition and hydration is a medical treatment, or simply part of the obligatory care owed to all patients, permanently unconscious or not. In this paper, we intend to argue that recent analyses of medical futility, its meaning and ethical implications, despite an absence of public consensus, permit some tentative re-evaluation of our ethical obligations to the PVS patient.

Regulation of the transcription factor c-JUN by nerve growth factor in adult sensory neurons

We examined the regulation by nerve growth factor (NGF) of the immediate-early gene (proto-oncogene) c- jun in adult dorsal root ganglion (DRG) neurons using immunocytochemistry to c-JUN (the protein product of the proto-oncogene c- jun). Following a sciatic nerve crush, the injury-induced increase in c-JUN-like immunostaining was reduced in DRG neurons by continuous intrathecal infusion of NGF for one week. Conversely, in intact DRG neurons (i.e., without Wallerian degeneration), c-JUN-like immunoreactivity was markedly increased following four weeks of daily NGF antiserum injections (to remove target tissue-derived NGF) into the hindfoot. Taken together, these findings indicate that nerve transection (axotomy) results in a loss of target tissue-derived NGF leading to induction of the transcription factor c-jun which may play a role in axonal regeneration.

Administration or deprivation of nerve growth factor during development permanently alters neuronal geometry

We investigated whether the administration or deprivation of a neuronal growth factor during development can permanently alter the dendritic architecture of sensitive neurons. Nerve growth factor (NGF) or NGF antiserum treatment in the first 2-3 postnatal weeks markedly affected the survival, size, and dendritic arborization of mouse sympathetic ganglion cells acutely. Six months after the completion of treatment, the number of surviving neurons, cell body size, and higher order dendritic branching had changed considerably from their values at 3 weeks, suggesting that these parameters remain malleable throughout postnatal life. However, the number of primary dendrites, a fundamental determinant of organization within sympathetic ganglia, was permanently altered by the neonatal treatment protocol. The idea emerging from this study is that NGF influences the elaboration of primary dendrites by sympathetic ganglion cells only during a critical developmental period. In maturity, NGF acts as a "maintenance" factor necessary for normal neuronal function and survival, but neurons lose the capacity to respond with wholesale rearrangements of dendritic architecture.

Nerve growth factor (NGF) induces sprouting of specific neurons of the snail, Lymnaea stagnalis

Nerve growth factor (NGF) was examined for its ability to elicit sprouting by adult molluscan neurons. Motoneurons and interneurons (but not neurosecretory cells) from Lymnaea exhibited a sprouting response to murine 2.5S NGF in defined medium with a half-maximal response at about 150 ng/mL. Furthermore, an NGF antiserum blocked sprouting by all normally responsive neurons. We tested whether an NGF-like molecule is a component of conditioned medium (CM) by attempting to preabsorb its sprout-inducing activity with NGF antiserum. Treatment of CM with immune (but not nonimmune) serum largely blocked the response of motoneurons, but not that of neurosecretory cells, to CM. We conclude that NGF exerts neurotrophic activity on specific adult Lymnaea neurons, and suggest the possibility that an NGF-like molecule may exist in the molluscan nervous system.

Differential regulation of estrogen-dependent sexual development of rat brain by growth factors

Intraventricular infusion of antiserum to nerve growth factor (ANGF), but not that to insulin, epidermal growth factor nor normal rabbit serum, resisted estrogen-induced behavioral defeminization in the female rat neonates. A significant number of the ANGF-treated rats showed lordosis as adults despite neonatal estrogen, but positive feedback of estrogen on serum luteinizing hormone was absent. Sexual phenotype in behavioral and gonadotropic functions may be under differential developmental regulation.