Factors involved in the migration of neuroendocrine hypothalamic neurons

Neuroendocrine control of physiological functions needs a complex developmental organisation of the hypothalamic parvicellular neurons, which synthesise and release hypophysiotropic hormones. Among the hypothalamic neuroendocrine cells, Gonadotropin-releasing hormone (GnRH) neurons represent a unique class; they are generated in the olfactory placode and, during embryonic life, migrate to the septo/hypothalamic region along terminal and vomeronasal nerves. At this level GnRH neurons undergo terminal differentiation and start to release GnRH to modulate the secretion of pituitary gonadotropins. All these steps are under the strict control of several developmental cues and their defect might represent a cause of clinical disorders. A number of factors have been proposed to be involved in the migration of GnRH neurons, but their role is still unclear. By using gene knockout techniques it has been found that mice carrying a targeted deletion of Ebf2 gene, a component of Olf/Ebf bHLH transcription factors, show a defective migration of GnRH neurons, providing the first evidence of a mouse model of such defect. Since the investigation of GnRH neurons is hindered by their peculiar anatomical distribution, other studies has been forwarded by the availability of immortalized GnRH-expressing neurons (GN11 cells) that retain a strong chemomigratory response "in vitro". Among the factors analysed, we found that hepatocyte growth factor/scatter factor (HGF/SF) and vascular endothelial growth factor (VEGF) induce specific chemotaxis of GN 11 neurons, suggesting that migratory signals can arise from nasal mesenchyme and from the concomitant vasculogenesis. Finally, anosmin-1 (the product of the gene responsible of the X-linked form of Kallmann's disease) was found to induce a significant chemotactic response of GN11 cells, confirming a permissive/instructive role of KAL1 gene product in the migratory behaviour of GnRH neurons. In conclusion, the migration of the GnRH neurons appears to be a complex process, which involves the interplay of multiple molecular cues. These studies may provide new insights on the etiopathogenesis of the large proportion of reproductive dysfunctions that affect humans and could provide novel insights on common biochemical events controlling neuronal development and migration.

Bartonella species as a potential cause of epistaxis in dogs

Infection with a Bartonella species was implicated in three cases of epistaxis in dogs, based upon isolation, serology, or PCR amplification. These cases, in conjunction with previously published reports, support a potential role for Bartonella spp. as a cause of epistaxis in dogs and potentially in other animals, including humans.

Expression of functional ciliary neurotrophic factor receptors in immortalized gonadotrophin-releasing hormone-secreting neurones

Ciliary neurotrophic factor (CNTF), a cytokine of the interleukin-6 superfamily, is known to exert pleiotropic actions, including regulation of food intake and permissive effects on reproduction, by facilitating the release of gonadotrophin-releasing hormone (GnRH) and gonadotrophins. CNTF activates membrane receptors (CNTF-Rs) composed of one ligand-specific binding subunit, defined CNTFR alpha, and two signal transducing subunits, termed leukaemia inhibitory factor receptor (LIFR) and gp130. However, it is not clear whether the effects of CNTF on GnRH release result from either a direct or an indirect action on GnRH-secreting hypothalamic neurones, or from a combination of these events. The hypothesis of a direct effect of CNTF was thus tested using the GT1-7 GnRH-secreting cell line. CNTF-R expression and CNTF-induced modulation of the Janus kinase (JAK2)-signal transducer and activator of transcription 3 (STAT3) pathway and of GnRH release were evaluated. GT1-7 cells were found to express CNTFR alpha, LIFR and gp130 genes, as shown by reverse transcription-polymerase chain reaction analysis, and the corresponding proteins, analysed by immunofluorescence and western blot. CNTFR alpha, LIFR and gp130 immunoreactive bands had an approximate size of 50, 190 and 130 kDa, respectively. Treatment of GT1-7 cells with 10(-12) M CNTF for 15-60 min resulted in a marked and transient increase of STAT3 phosphorylation via activation of JAK2. A 30-min exposure of GT1-7 cells to different CNTF concentrations increased the accumulation of GnRH into the culture medium, with a maximal effect at 10(-11) M. In conclusion, the present results provide new information about the regulation of the reproductive axis by CNTF, and suggest that it might operate at the hypothalamic level by directly influencing the activity of GnRH-secreting neurones, in addition to the possible indirect effects via interneurones proposed by previous studies.

Combination of a CpG-oligodeoxynucleotide and a topoisomerase I inhibitor in the therapy of human tumour xenografts

The study was conducted to investigate the effects of a novel therapeutic approach, i.e. the combination of chemotherapy and immunotherapy, against a human prostate carcinoma xenograft. A topoisomerase I inhibitor, topotecan, and CpG-containing oligodeoxynucleotides (CpG-ODN) were combined. Athymic mice bearing the PC-3 human prostate carcinoma were treated with the maximum tolerated dose (MTD) of topotecan (3 weekly treatments) and with repeated treatments of CpG-ODN (40 and 20 microg/mouse); tumour growth and lethal toxicity were monitored. Topotecan effect on CpG-ODN-induced production of interleukin (IL) 12, interferon (IFN)-gamma and tumour necrosis factor-alpha was also assessed. Since topotecan pretreatment differentially influenced CpG-ODN-induced production of IL-12 and IFN-gamma, the antitumour effects of the two therapies were investigated in a sequential (full topotecan regimen followed by CpG-ODN) or in an alternating sequence (starting with CpG-ODN). Topotecan inhibited PC-3 tumour growth, inducing 95% tumour volume inhibition. All combined treatments resulted in a significant delay in tumour growth, compared to the effects in topotecan-treated mice (P<0.01, by analysis of tumour growth curves). The combination regimens were well tolerated, except for the alternating sequence of 40 microg CpG-ODN and topotecan, which resulted in three out of eight toxic deaths. This alternating sequence was highly toxic even when another cytotoxic drug (doxorubicin) was used in healthy mice. In conclusion, the combination of topotecan and CpG-ODN increased antitumour effects over chemotherapy alone in the growth of a human prostate carcinoma xenograft. Administration sequence was critical to the combination toxicity: the complete regimen of the cytotoxic drug followed by repeated administrations of the immunomodulator seemed the most promising for further investigations.

Characterization and pharmacological actions of tecostanine, an alkaloid of Tecoma stans

Tecostanine (1) was isolated from Tecoma stans leaves. Its sterochemistry was elucidated as well as its antihyperglycemic activity and its affinity to opioid and nicotinic receptors. The oxalate salt of 1 did not significantly affect blood glucose levels in normoglycaemic and hyperglycaemic rats. It did not appear to interact with opioid receptors (mu type) and showed only moderate affinity to the nicotinic receptor.

Hepatocyte growth factor/scatter factor facilitates migration of GN-11 immortalized LHRH neurons

The molecular cues regulating the migratory process of LHRH neurons from the olfactory placode into the brain are not well known, but gradients of chemotropic and chemorepellent factors secreted by the targets are likely to play a key role in guidance mechanisms. Hepatocyte growth factor/scatter factor (HGF/SF) is a pleiotropic cytokine inducing cell migration. It is involved in a variety of developmental processes through interaction with its receptor c-Met. Here we show that c-Met-antibody labels LHRH migrating neurons in the olfactory mesenchyme of E12 mouse and analyze the potential chemotropic effect of HGF/SF on two immortalized LHRH cell lines, GT1-7 and GN11, isolated from tumors developed in the hypothalamus and in the olfactory bulb, respectively. By RT-PCR analysis, Western blotting, and immunocytochemistry, we provide evidence for a high level of c-Met expression in GN11, but not in GT1-7, cells. In addition, HGF/SF treatment promotes specific migratory activity of GN11 cells, as demonstrated by collagen gel assay, time-lapse video microscopy, and Boyden's chamber experiments. Such promotion is inhibited by the neutralizing antibody. The data reported here represent the first direct evidence of a chemotactic effect of HGF/SF on immortalized LHRH neurons.

Tendon surgery in Brown's syndrome

PURPOSE

Longitudinal tenectomy of the reflected tendon of the superior oblique muscle resulted in full recovery in a series of cases of Brown's syndrome after surgery by one of the authors.

METHODS

A survey of the records of cases of Brown's syndrome was done to assess the criteria for patients requiring surgery and to evaluate the methods used. Included in the study were 9 eyes of patients who underwent surgery over the course of 1 year. Criteria identified in cases in this study include: preoperative compulsory head tilt in primary position of gaze, severe restriction of Hess chart in the affected eye, and an enlarged field in the healthy eye; intraoperative thickening of the tendon preventing free slippage through the trochlea in the forced duction test. The surgical method consisted of trimming a swelling that was consistently found on the reflected tendon of the superior oblique muscle in all patients undergoing surgery. Enough of the swelling was removed to allow free slippage of the tendon through the trochlea, as judged by the forced duction test. Sulphamide powder soaked in delayed action steroid compound (methylprednisolone acetate) was applied to prevent postoperative adhesions.

RESULTS

A normal head posture and a satisfactory upward vergence were achieved in all patients from the first days after surgery, and were maintained throughout the follow up, as shown in the pre- and postoperative photographs and Hess charts.

CONCLUSIONS

A preliminary exploration of the reflected tendon of the superior oblique muscle is warranted in cases of Brown's syndrome; when a thickening of the tendon is found, its surgical trimming is advised. Our findings suggest that delayed development of the trochlea may be a possible cause of Brown's syndrome.

Expression and role of functional glucocorticoid receptors in the human androgen-independent prostate cancer cell line, DU145

We investigated the presence of glucocorticoid receptors (GR) as well as the role of glucocorticoids (Gc) in the control of proliferation of the androgen-independent prostate cancer cell line, DU145. We detected the presence of a specific high affinity binding site (K(d) 2.3 nM) for [(3)H]dexamethasone ([(3)H]Dex) in the cytosolic preparations of DU145 cells; the density of these binding sites is significantly higher than that detected in HA22T/VGH and in HepG2, two hepatoma cell lines classically considered models for the study of GR. Immunocytochemistry studies confirmed the presence of GR in the cytosolic compartment of DU145 cells; GR undergo translocation to the nucleus following exposure to dexamethasone (Dex). The functional activity of GR present in DU145 cells was also studied by analyzing the potency of Dex in inducing chloramphenicol acyltransferase (CAT) activity in DU145 cells transfected with a glucocorticoid/progesterone response element (GRE/PRE) tkCAT plasmid (GRE/PREtkCAT plasmid). The results have shown that Dex stimulates the transcriptional activity of GR in transfected DU145 cells with an EC(50) of 9.65 nM and a maximal induction of sevenfold above basal levels. Finally, a dose-dependent (IC(50) 3.14 nM) decrease of DU145 cell numbers was observed after their exposure to Dex for 4 days; this effect was counteracted by the presence of the steroid antagonist, RU486. In conclusion, the present data suggest a possible role of corticoids in the control of the growth of androgen-independent prostate cancer.

A multicentre collaborative study on the use of cold scalpel and electrocautery for midline abdominal incision

BACKGROUND

Although studies in animals demonstrated a better wound healing after abdominal incision with cold scalpel than with electrocautery, clinical experiences did not confirm these findings. The purpose of this study was to compare early and late wound complications between diathermy and scalpel in gynecologic oncologic patients undergoing midline abdominal incision.

METHODS

Patients undergoing midline abdominal incision for uterine malignancies were divided into two groups according to the method used to perform the abdominal midline incision: cold scalpel and diathermy in coagulation mode. Early and late complications were compared. Logistic regressions were used for statistical analysis.

RESULTS

Nine hundred sixty-four patients were included, of whom 531 were in the scalpel group and 433 in the electrocautery group. Both groups were similar with respect to demographic, operative, and postoperative characteristics. Univariate analysis revealed a higher incidence of severe wound complications in the scalpel group than in the electrocautery group (8 of 531 versus 1 of 433, P <0.05). After adjustment for confounding variables (eg, age, body mass index) no differences were found between groups.

CONCLUSIONS

Scalpel and diathermy are similar in terms of early and late wound complications when used to perform midline abdominal incisions. Therefore the choice of which method to use remains only a matter of surgeon preference.

Growth-inhibitory activity of melatonin on human androgen-independent DU 145 prostate cancer cells

BACKGROUND

The pineal hormone melatonin has been shown to exert a direct oncostatic activity on neoplastic cells, particularly from breast cancer. In the present study, we evaluated the effects of melatonin on the proliferation and on the cell cycle distribution of human androgen-independent DU 145 prostate cancer cells. Experiments were also performed to gain insights into the possible mechanism of action of the hormone.

METHODS

The effects of melatonin on DU 145 cell proliferation was analyzed by counting the cells by hemocytometer at the end of treatment. The effects of the pineal hormone on cell cycle distribution were evaluated by FACS analysis. RT-PCR studies were performed to detect Mel(1a) and Mel(1b) expression in DU 145 cells. The cellular localization of (125)I-melatonin binding sites was investigated by radioreceptor assay. A commercially available binding-protein assay kit was utilized to evaluate intracellular cAMP levels.

RESULTS

Melatonin, in physiological doses, significantly inhibited DU 145 cell proliferation and induced cell cycle withdrawal by accumulating cells in G0/G1 phase. The mRNA for Mel(1a) receptors was found to be expressed in DU 145 cells; however, by radioreceptor assay, no binding sites for (125)I-melatonin could be detected in membrane preparations, suggesting that, in these cells, the level of translation of this mRNA is too low to possibly mediate the antiproliferative action of the hormone. In agreement with this hypothesis, melatonin did not affect forskolin-induced intracellular cAMP accumulation. Binding sites for (125)I-melatonin were found in nuclear extracts of DU 145 cells.

CONCLUSIONS

Melatonin exerts a direct oncostatic activity on human androgen-independent prostate cancer cells, by affecting cell cycle progression. This activity seems to be mediated by nuclear, but not by membrane, receptors.

Immortalized luteinizing hormone-releasing hormone neurons show a different migratory activity in vitro

The development of two cell lines (GT1 and GN) of immortalized LHRH neurons has allowed an accurate study of the mechanisms controlling the synthesis and the secretion of LHRH. These cell lines, obtained in mice by genetic targeted tumorigenesis, retain many of the phenotypic characteristics of LHRH neurons. Of interest, GT1 cells derive from an hypothalamic tumor, whereas GN cells were obtained from a tumor localized in the olfactory bulb. The different origin of these cell lines lead to hypothesize that they might represent hypothalamic postmigratory neurons (GT1 cells), or LHRH neurons blocked at an early stage of their migration (GN cells). Using different experimental procedures, we found that the two cell subclones GT1-7 and GN11 express a different morphology and migratory behavior in vitro. In particular, we found that GN11 cells, but not GT1-7 cells, show the morphological shape of migrating neurons. When analyzing the spontaneous motility we found that only GN11 cells express a high capacity of migrating in a matrix of collagen gel. Moreover, in a chemomigratory assay GN11 cells did show a significant response to the chemotactic stimulus represented by the FBS. On the contrary, GT1-7 cells show very low spontaneous motility and appear insensitive to the FBS stimulus. These results suggest that the simultaneous use of the GT1-7/GN11 cells may represent an experimental tool for screening the factors possibly involved in the control of the migratory processes of LHRH neurons in normal and in pathological conditions, such as those due to their impaired migration, like it happens in Kallmann's syndrome.

Antiproliferative action of melatonin on human prostate cancer LNCaP cells

Recent experimental evidence suggests that melatonin, the major pineal hormone, might possess oncostatic properties. The present experiments were performed to verify whether melatonin might modulate the growth of androgen-dependent prostate cancer cells (LNCaP) and to obtain information on its possible mechanism of action. We have shown that melatonin, when given in the nanomolar range, significantly inhibits the proliferation of LNCaP cells; moreover, the pineal gland hormone affects cell cycle distribution by inducing an accumulation of the cells in G0/G1 and a decrease in S phase. To investigate the mechanism of action of melatonin, by RT-PCR analysis we were able to demonstrate the expression, in prostate cancer cells, of a mRNA coding for the membrane Mel1a melatonin receptor. However, by radioreceptor assay, no detectable binding of 2-[125I]iodomelatonin could be observed in membrane preparations from these cells, suggesting that the levels of translation of the mRNA for Mel1a are possibly too low to mediate the antiproliferative action of the hormone. This hypothesis is further supported by the following observations: i) melatonin analogs, specifically acting through membrane receptors (i.e., 2-bromomelatonin), were completely ineffective in modulating prostate cancer cell proliferation; ii) melatonin failed to prevent forskolin-induced cAMP accumulation. These results indicate that melatonin, at nanomolar concentrations, exerts a direct antiproliferative action on androgen-dependent prostate cancer cells, significantly affecting their distribution throughout the cell cycle. Membrane receptors do not seem to be involved in the oncostatic action of the pineal gland hormone.

Factors released by rat type 1 astrocytes exert different effects on the proliferation of human neuroblastoma cells (SH-SY5Y) in vitro

Brain metastases derived from abdominal neuroblastoma are an uncommon complication of this tumour; however, an increase in their occurrence has recently been reported. In the present study, we have investigated the influence of factors derived from central nervous system glial cells on the proliferation of human neuroblastoma cells (SH-SY5Y) in vitro. Co-culture experiments show that a 24-h exposure to factors released by type 1 astrocytes (A1) may induce a significant decrease in [(3)H]thymidine ([(3)H]TdR) incorporation by SH-SY5Y cells. This effect was not duplicated by fresh A1-conditioned medium (A1-CM); A1-CM became active only when it was heated or frozen. In contrast to this short-lived inhibitory effect, long-term treatment (3, 6 and 9 days) with A1-CM produced a significant and dose-dependent increase in SH-SY5Y cell number. Immunoneutralisation of A1-CM with an anti-transforming growth factor-beta antibody eliminated the inhibitory effect on [(3)H]TdR uptake in SH-SY5Y cells, but did not affect the increased number of viable cells observed after long-term treatments. In conclusion, these results showed that factor(s) released by A1 may affect the proliferation/survival of a human neuroblastoma cell line in vitro inducing: (a) a short transient negative effect on DNA synthesis and (b) an overall sustained trophic action. These results are suggestive of a possible role of glial cells in the establishment of brain metastases of neuroblastomas.

Prospective multicenter study on urologic complications after radical surgery with or without radiotherapy in the treatment of stage IB-IIA cervical cancer

A national collaborative group has conducted a multicenter prospective study on the use of a specific glossary for the complications associated with the treatment of cervical cancer, which were analytically described in 1989. This report analyzes the urologic complications with particular reference to radical surgery in stage IB-IIA cancer cases. In the prospective multicenter clinical study 2024 patients with frankly invasive cervical cancer were enrolled (IB = 1041; IIA = 308; IIB = 384; IIIA-B = 237; IV = 54). This report considers 1349 patients with stage IB-IIA disease. Treatment modalities in this group of patients were: type III radical surgery in 21.9%; type III radical surgery followed by radiotherapy in 20.8%; type III radical surgery preceded by radiotherapy in 7.3%; type II radical surgery in 3.1%; type II radical surgery followed by radiotherapy in 8.4%; type II radical surgery preceded by radiotherapy in 18.8%; surgery plus chemotherapy plus radiotherapy in 3.5%; radiotherapy alone in 16%. In this case series 873 complications were registered, and among these 341 (39.1%) were described in the urinary tract. Among 277 bladder complications 47.3% were grade 1; 47.3% grade 2, and 5.4% grade 3. Among 64 ureter complications 59.4% were grade 1; 17.2% grade 2, and 23.4% grade 3. Distribution of severe urinary complications was different according to site (bladder or ureter) and treatment modalities (radical surgery alone: bladder 1.3%, ureter 1.3%; radical surgery followed by radiotherapy: 1.4% bladder, 2.8% ureter; radical surgery preceded by radiotherapy: 3% bladder, 0% ureter). Different distributions of severe urinary complication were also observed in respect to stage (IB vs IIA); treatment: elective vs nonelective. In 673 patients treated with radical surgery plus or minus radiotherapy 123 relapses were registered (18.2%). Incidence of relapse was not different in patients suffering from mild/severe complications vs patients without complications. Disease-free survival, death from tumor, and death from other causes were not different in the group with complications in comparison to the group without complications.

Presence of a reduced opioid response in interleukin-6 knock out mice

Cytokines are known to influence neuronal functions. The purpose of this study was to investigate the putative role of the cytokine interleukin-6 (IL-6) in the pathways involved in opioid-mediated responses, by using IL-6-deficient mice. We reported that with a thermal stimulus IL-6-knock-out (IL-6KO) mice presented nociceptive thresholds similar to those measured in their controls. However, they showed a reduced analgesic response both to the restraint stress and to the administration of low doses of morphine. Hypothalamic levels of the opioid peptide beta-endorphin were significantly higher in IL-6KO mice than they were in their controls. The development of tolerance to the analgesic effect of morphine was more rapid in IL-6-deficient mice than in wild-type controls. Binding experiments showed that the number of opioid receptors in the midbrain, but not in the hypothalamus, decreased in IL-6KO mice. Autoradiographic binding analysis revealed that the density of mu receptors diminished while the delta-opioid receptors did not. These results suggest that IL-6 is necessary for a correct development of neuronal mechanisms involved in the response to both endogenous and exogenous opiates.

Decrease of the number of opioid receptors and of the responsiveness to morphineduring neuronal differentiation induced by 17beta-estradiol in estrogen receptor-transfected neuroblastoma cells (SK-ER3)

Estrogens modulate the density of opioid receptors in selected brain areas; however, it is not clear whether they exert such an effect directly on the cells which express the opioid receptors. Therefore, we analyzed the binding of [3H]-diprenorphine in human neuroblastoma cells stably transfected with the estrogen receptor cDNA (SK-ER3 cell line). A 16-hour exposure of these cells with 1 nM 17beta-estradiol induces a progressive morphological differentiation which appears clearly established 6 days after the suspension of the treatment. The binding of [3H]-diprenorphine was then measured immediately after the exposure to 17beta-estradiol (16 h) as well as 6 days later. The results shows that the number of opioid receptors in SK-ER3 cells is unaffected at 16 h but appears significantly reduced at 6 days. This effect is blocked by the estrogen antagonist ICI-182780, and is coincident to a decrease of the inhibitory effect of morphine on cyclic AMP accumulation. Binding experiments performed using selective ligands suggest that the micro subclass of opioid receptors is down-regulated by estradiol in SK-ER3 cells.

Expression of prostacyclin receptors in luteinizing hormone-releasing hormone immortalized neurons: role in the control of hormone secretion

PGs of the E series are involved in the control of LHRH secretion. The present experiments were conducted to clarify whether PGI2 (prostacyclin) might be also involved in such a control, using multiple methodological approaches on immortalized LHRH-secreting neurons. A RT-PCR procedure to detect mouse PGI2 receptor (IP) messenger RNA was first applied, and the results obtained showed the presence of a specific transcript in two cell lines of immortalized LHRH neurons (GT1-1 and GN11 cell lines). Receptor binding assays on membrane preparations from GT1-1 cells showed the presence of a single specific and saturable class of binding sites (Kd = 4.6 nM; 10,000 sites/cell) for [3H]iloprost, a stable analog of PGI2. Competition experiments showed that the binding sites labeled by [3H]iloprost possess the pharmacological characteristics of IP receptors. In functional studies, PGI2 and its analogs, iloprost and cicaprost, were able to stimulate LHRH release from the GT1-1 cells with elevated potencies (EC50 = 0.6-4.3 nM); PGE1 was only slightly less active (EC50 = 28.5 nM), whereas PGE2, considered the major PG involved in LHRH secretion, was poorly effective (EC50 = 921 nM). The relative potencies (EC50) of these compounds in stimulating the intracellular accumulation of cAMP were in line with their LHRH-releasing activities. In conclusion, these results indicate that immortalized LHRH-secreting neurons express IP receptors through which PGI2 may exert relevant effects on LHRH release.

Scleral Fixation for a Phakic Anterior Chamber Disc Intraocular Lens

BACKGROUND

Angle-supported phakic anterior chamber intraocular lenses (IOLs) require a high degree of anterior vaulting, but this can cause an inadequate distance between the IOL and the cornea, especially during rubbing or squeezing of the eye.

METHODS

A vaultless implant was designed by anchoring 3 supple hepatics through the anterior chamber into the sclera. Thus, a suspended rather than a wedged implant was achieved.

RESULTS

The lens was implanted in 3 eyes of 2 patients in 1990. Good tolerance of the IOL was maintained over 7 years of follow-up.

CONCLUSION

A suspended anterior chamber phakic IOL maintains an adequate position with lack of bowing and shows promising results.

Cholinergic muscarinic mechanisms regulate neuropeptide Y gene expression via protein kinase C in human neuroblastoma cells

Neuropeptide Y (NPY) participates in the control of several functions in the nervous system. NPYergic neurons present in brain areas involved in cognitive processes are linked to ascending projections of the cholinergic system, a finding that suggests a role for acetylcholine in the control of these cells. In the present study, the effect of the activation of cholinergic muscarinic receptors on the expression of the human NPY gene was assessed. The SH-SY5Y neuroblastoma cell line was used as an in vitro model of human neurons; NPY mRNA levels were evaluated by Northern blot analysis. The results indicate that: (a) the expression of the human NPY gene in SH-SY5Y cells is stimulated by the cholinergic muscarinic agonist, carbachol; (b) this effect is mediated by the M3 muscarinic receptor subtype, as indicated by the inhibitory effect of the M3 antagonist 4-DAMP; (c) protein kinase C (PKC) activation plays an important role in the induction of NPY gene expression in this system, as suggested by experiments with the PKC activator, TPA, and the PKC inhibitor, GF 109203X; (d) the stimulation of NPY mRNA levels by TPA and by carbachol in SH-SY5Y cells requires de novo synthesis of RNA and protein. In conclusion, the present study shows that the activation of PKC-coupled muscarinic receptors as the M3 subtype positively modulates the expression of the human NPY gene in SH-SY5Y neuroblastoma cells, via PKC-related mechanisms.