EGFR overexpression and radiation response in glioblastoma multiforme.

PURPOSE: Recent studies have suggested relative radioresistance in glioblastoma multiforme (GM) tumors in older patients, consistent with their shorter survival. Two common molecular genetic abnormalities in GM are age related: epidermal growth factor receptor (EGFR) overexpression in older patients and p53 mutations in younger patients. We tested whether these abnormalities correlated with clinical heterogeneity in GM response to radiation treatment. METHODS AND MATERIALS: Radiographically assessed radiation response (5-level scale) was correlated with EGFR immunoreactivity, p53 immunoreactivity, and p53 exon 5-8 mutation status in 170 GM patients treated using 2 prospective clinical protocols. Spearman rank correlation and proportional-odds ordinal regression were used for univariate and multivariate analysis. RESULTS: Positive EGFR immunoreactivity predicted poor radiographically assessed radiation response (p = 0.046). Thirty-three percent of tumors with no EGFR immunoreactivity had good radiation responses (>50% reduction in tumor size by CT or MRI), compared to 18% of tumors with intermediate EGFR staining and 9% of tumors with strong staining. There was no significant relationship between p53 immunoreactivity or mutation status and radiation response. Significant relationships were noted between EGFR score and older age and between p53 score or mutation status and younger age. CONCLUSION: The observed relative radioresistance of some GMs is associated with overexpression of EGFR.

Analysis of complex relationships between age, p53, epidermal growth factor receptor, and survival in glioblastoma patients.

Glioblastoma multiforme (GBM) carries a dismal prognosis. However, a range of survival times exists, and parameters that define prognostic groups may help to optimize treatment. To identify such prognostic groups, we analyzed tumor tissue from 110 cases of newly diagnosed GBM from two clinical protocols. Similar to other studies, we found no association of epidermal growth factor receptor (EGFR) overexpression (as assessed by immunohistochemistry), p53 immunopositivity, or p53 mutation with survival in the entire sample. However, EGFR overexpression showed trends toward worse prognosis in patients younger than the median age, but better prognosis in patients older than the median age. This interaction of EGFR with age group was statistically significant and led us to focus our further analyses on the younger patients. In this group, a statistically significant association of EGFR overexpression with worse survival was identified in the p53-negative but not p53-positive tumors. We found a similar result after screening these cases for mutations in p53: EGFR overexpression was negatively associated with survival only in the p53 wild-type cases. To confirm this unexpected result, this finding was reproduced in a validation sample of an additional 42 tumors from younger patients on the same two clinical protocols. This complex relationship between EGFR and p53 in younger patients remained in a multivariate analysis that incorporated additional prognostic variables. The results suggest that analysis of prognostic markers in GBM is complex, and maximal information may require analysis of subgroups based on age and the status of specific markers such as p53. In addition, they suggest a specific group of patients on which to focus promising therapies targeting EGFR.

Opioid modulation of recurrent excitation in the hippocampal dentate gyrus.

kappa opioid receptor activation inhibits granule cell-mediated excitatory neurotransmission in the hippocampal formation via a decrease in glutamate release from both perforant path and mossy fiber terminals. We now report a third, anatomically and pharmacologically distinct site of such kappa opioid inhibition within the hippocampus. Granule cell population responses to selective stimulation of an excitatory hilar pathway were decreased by the kappa(1) opioid receptor agonist U69,593, an effect blocked by the kappa(1) antagonist norbinaltorphimine. U69,593 also inhibited hilar path induced long-term potentiation (LTP) of granule cell responses. LTP in this pathway was also blocked by the NMDA receptor antagonist d-2-amino-5-phosphonovalerate, unlike granule cell mossy fiber LTP in CA3. The kappa opioid peptide dynorphin is present in hilar mossy fiber collaterals. Ultrastructural analysis of these collaterals demonstrated dynorphin-containing vesicles in asymmetric synapses formed between axon terminals and granule cell dendrites, suggesting direct granule cell-granule cell connections. Evoked release of endogenous dynorphin within the hilus was effective in reducing hilar excitation of granule cells, although this release, in contrast to the release of dynorphin in the dentate molecular layer, was not dependent on L-type calcium channels. No hilar path excitation was observed in the absence of bicuculline, suggesting a strong GABA(A)-mediated inhibition of this pathway. However, hilar path activity could be seen after LTP, with or without bicuculline. Thus, kappa opioids can inhibit granule cell recurrent excitation, likely via effects on excitatory mossy fiber collaterals. Such collaterals are thought to be important in mediating temporal lobe epilepsy.

Discrepancies in diagnoses of neuroepithelial neoplasms: the San Francisco Bay Area Adult Glioma Study.

BACKGROUND: Valid and reliable diagnoses of disease are key both to meaningful epidemiologic and clinical investigations and to decision-making about appropriate treatment. One previous study highlighted the lack of precision in diagnosing primary brain tumors in a neuropathology referral practice. The current study explores diagnostic discrepancies in a population-based adult glioma series by hospital of origin, specialty training of the original diagnosing pathologist, and clinical significance. METHODS: To confirm patients' eligibility for the San Francisco Adult Glioma Study, the authors obtained participants' pathology specimens and conducted a uniform secondary neuropathology review. Eligible patients were all adults age 20 years or older newly diagnosed with glioma between August 1, 1991, and March 31, 1994, who resided in 1 of 6 San Francisco Bay Area counties. RESULTS: Overall, the original and secondary diagnoses were the same (concordant) for 352 (77%) of the 457 cases available for study. Twenty-six percent of the cases from community hospitals were discordant, compared with 12% of the cases from academic hospitals P= 0.004. Of the 105 discordant diagnoses, 17 (16%) were determined to be clinically significant, defined as a difference that could significantly alter patient management and/or prognosis. Sixteen of these 17 cases originated at community hospitals, and only 1 originated at a hospital with a neuropathologist. Based on the distribution of review diagnoses, subjects presenting at nonacademic hospitals were more likely than those presenting at academic hospitals to have glioblastoma (61% vs. 52%; P = 0.07). CONCLUSIONS: The percentage of cases with discrepant original and review diagnoses was higher among those originally diagnosed at community hospitals without a neuropathologist than among those originally diagnosed at an academic hospital with a neuropathologist. Clinically significant discrepancies were much more likely to have originated at a community hospital without a neuropathologist. These data highlight the importance of review of brain tumors by a neuropathologist prior to decision-making regarding treatment. A separate implication of this study is that glioma cases selected exclusively from academic or nonacademic institutions in a particular geographic area are unlikely to be representative of all cases occurring in that area.

Patient nutrition acuity as a predictor of the time required to perform medical nutrition therapy.

OBJECTIVE: To determine if patient nutrition acuity accurately predicts the time required to perform medical nutrition therapy (MNT). DESIGN: Data detailing demographic characteristics, patient nutrition acuity, and time spent performing MNT were collected for 12 consecutive days. Random systematic sampling was used to select 25%, or a minimum of 20 patients, from daily admissions to the hospital. Nutrition acuity was categorized using a 27-item patient acuity tool. SUBJECTS/SETTING: Analysis included data from 92 acute-care hospitals nationwide; the median census was 271 patients. Of the 7,289 patients in the survey, 3,321 were included in this data analysis. All subjects were assigned an acuity rating and received MNT. Mean age (+/- standard deviation [SD]), was 55 +/- 24 years, and the sample was 48% male and 52% female. Time spent delivering MNT ranged from 5 to 285 minutes (mean +/- SD = 43.3 +/- 34.2 minutes). STATISTICAL ANALYSES PERFORMED: Stepwise multiple regression analysis (P < .05), with independent variables of age, gender, and 27 acuity descriptors, determined time required to perform MNT. RESULTS: The number of acuity descriptors assigned to patients ranged from zero (53 patients) to 20 (1 patient); the mean (+/- SD) for all patients was 5.6 +/- 3.1. Gender and 21 of the 27 acuity descriptors were statistically significant in predicting the time required to perform MNT. APPLICATIONS/CONCLUSIONS: A formula was developed to determine medical nutrition therapy time (MNTT) as minutes per patient sampled. When extrapolated to a facility's patient census, MNTT is the basis for predicting staffing requirements. The MNTT formula is crucial in the present environment of managed care where fiscal accountability challenges staffing rationales.

Adult-onset nemaline myopathy: Another cause of dropped head.

A 59-year-old man with severe neck extensor weakness had findings diagnostic of nemaline myopathy on muscle biopsy. Review of the literature shows that dropped head occurs in nearly half of the patients with adult-onset nemaline myopathy. Other leading causes of dropped head syndrome are amyotrophic lateral sclerosis, myasthenia gravis, and isolated neck extensor myopathy.

Transdermal delivery of nitric oxide from diazeniumdiolates.

Adverse physiological effects can often interfere with the use of nitric oxide (NO) as a therapeutic agent, especially when it is systemically generated from prodrugs. NO which is generated and delivered site-specifically by transdermal donors may be useful in the treatment of parasitic, bacterial or viral skin infections without causing systemic side effects. Three diazeniumdiolates (formerly "NONOate"), including two water soluble compounds, (Z)-1-[N-2-aminoethyl)-N-(2-ammonioethyl)amino]-diazen-1- ium-1,2-diolate (DETA-NO) and (Z)-1-[N-(3-aminopropyl)-N-(3-ammoniopropyl)amino] diazen-1-ium-1,2-diolate (DPTA-NO), and one insoluble compound, DPTA-NO grafted to dextran microspheres (DPTA-NO-g-dextran) were used to transdermally deliver NO to rats. Dextran microspheres were obtained by simultaneously grafting DPTA-NO to dextran and cross-linking dextran with CNBr in an oil-water emulsion. Suspended in hydrogel, DETA-NO, DPTA-NO, and DPTA-NO-g-dextran were applied three times to depilated rats at 4 day intervals. Results show that metabolic urinary nitrate levels increase with time (24-48 h), reach a maximum, and return to baseline by the fourth day. DPTA-NO applications produced an average maximum nitrate level of 94.2 mumol/day +/- 34.2 mumol S.D. compared to the average maximum nitrate level of 39.8 mumol/day +/- 8.6 mumol S.D. obtained from treatment with DETA-NO. These results suggest that DPTA-NO delivered NO more efficiently than DETA-NO. When DPTA-NO-g-dextran microspheres were used as the NO donor, results comparable to DPTA-NO were observed with an average maximum nitrate level of 14.9 mumol/day +/- 3.0 mumol S.D. These and other conclusive data indicate that, via these diazeniumdiolates, NO can be delivered effectively through rat skin.

Non-Hodgkin lymphoma and Kaposi sarcoma in an eyelid of a patient with acquired immunodeficiency syndrome. Multiple viruses in pathogenesis.

A 36-year-old patient with acquired immunodeficiency syndrome sought care because of an upper eyelid lesion that dramatically increased in size. The histopathologic examination revealed a high-grade diffuse large cell non-Hodgkin lymphoma in continuity with a Kaposi sarcoma. In situ hybridization revealed Epstein-Barr virus in the large cell lymphoma and Kaposi sarcoma-associated herpesvirus in the Kaposi sarcoma lesion. This collision tumor is an unusual presentation of 2 malignant neoplasms in a patient with acquired immunodeficiency syndrome, with in situ hybridization evidence of Epstein-Barr virus and Kaposi sarcoma-associated herpesvirus in the lesion.

Spontaneous excitatory currents and kappa-opioid receptor inhibition in dentate gyrus are increased in the rat pilocarpine model of temporal lobe epilepsy.

Temporal lobe epilepsy is associated with a characteristic pattern of synaptic reorganization in the hippocampal formation, consisting of neuronal loss and aberrant growth of mossy fiber collaterals into the dentate gyrus inner molecular layer. We have used the rat pilocarpine model of temporal lobe epilepsy to study the functional consequences of mossy fiber sprouting on excitatory activity and kappa-opioid receptor-mediated inhibition. Using the whole cell voltage-clamp technique, we found that abnormal excitatory activity was evident in granule cells of the dentate gyrus from pilocarpine-treated rats. The frequency of spontaneous excitatory postsynaptic currents (EPSCs) was increased greatly in cells from tissue in which significant mossy fiber sprouting had developed. In the presence of bicuculline, giant spontaneous EPSCs, with large amplitudes and long durations, were seen only in association with mossy fiber sprouting. Giant EPSCs also could be evoked by low-intensity stimulation of the perforant path. Mossy fibers release not only excitatory amino acids, but also opioid peptides. kappa-Opioid receptor-mediated inhibition in normal Sprague-Dawley rats was seen only in hippocampal sections from the ventral pole. In pilocarpine-treated rats, however, kappa receptor-mediated effects were seen in both ventral and more dorsal sections. Thus in this model of temporal lobe epilepsy, several types of abnormal excitatory activity were observed, thereby supporting the idea that mossy fiber sprouting leads to recurrent excitatory connections. At the same time, inhibition of excitatory activity by kappa-opioid receptors was increased, perhaps representing an endogenous anticonvulsant mechanism.

Solitary fibrous tumor involving the renal capsule.

Solitary fibrous tumors are spindle-cell neoplasms that originally were described in the pleura but that can occur in a large variety of sites. We report a well-circumscribed tumor, apparently involving the renal capsule, clinically thought to be a renal-cell carcinoma or oncocytoma. It was composed of bland spindle-shaped cells with a patchy lymphoplasmacytic infiltrate, suggesting sarcomatoid renal-cell carcinoma, inflammatory myofibroblastic tumor, or solitary fibrous tumor; however, immunohistochemical stains were negative for keratin, alpha-smooth-muscle actin, and desmin but strongly positive for CD34. Ultrastructural examination revealed fibroblast-like cells without myofibroblastic or epithelial differentiation. The combined findings favor a diagnosis of a solitary fibrous tumor involving the renal capsule. To our knowledge, this lesion has not been reported in this location.

Kappa opioid receptor-like immunoreactivity in guinea pig brain: ultrastructural localization in presynaptic terminals in hippocampal formation.

Physiological and pharmacological studies have suggested that kappa opioid receptors (KORs) may be located presynaptically in the guinea pig hippocampal formation. In the present study, KOR-like immunoreactivity (-LI) was examined by using a rabbit antibody raised against a synthetic peptide from the carboxyl terminus of a cloned rat kappa receptor (KT). The specificity of affinity-purified KT antibody was confirmed by Western blotting, enzyme-linked immunosorbent assay, immunolabeling of KORs expressed in Xenopus oocytes, and immunocytochemical preadsorption controls. Specificity also was demonstrated by the light microscopic distribution of KT-LI in sections through the forebrain and the pons, which was largely consistent with the distribution of KORs previously reported, and resembled that of immunoreactivity for dynorphin B, an endogenous ligand for KORs. Detailed analysis of the hippocampal formation revealed that KT-LI was located predominantly in thin processes in the granule cell and inner molecular layers of the dentate gyrus. A few KT-labeled processes were also present in stratum lacunosum-moleculare of the CA1 region and all layers of the CA3 region of the hippocampus. By electron microscopy, KT-LI was restricted to unmyelinated axons and axon terminals, and was associated with plasma membranes, large dense-core vesicles, and cytoplasmic surfaces of small vesicles. In the dentate gyrus, immunolabeled terminals formed asymmetric synapses with granule cell perikarya and large unlabeled dendrites. In the CA3 region of hippocampus, KT-LI was present in small unmyelinated axons. The results of this study 1) demonstrate the specificity of the KT antibody, 2) show that the distribution of KT labeling corresponds well with previous KOR and dynorphin localization in many regions, and 3) provide ultrastructural evidence that KORs are located presynaptically in the guinea pig hippocampal formation.

k-Opioid receptor activation of a dendrotoxin-sensitive potassium channel mediates presynaptic inhibition of mossy fiber neurotransmitter release.

Activation of kappa-opioid receptors on mossy fiber terminals in the hippocampus inhibits excitatory amino acid release. The mechanism of presynaptic inhibition at the mossy fiber synapse was investigated through whole-cell voltage-clamp of CA3 pyramidal cells. The application of a kappa-opioid agonist, U69593, reduced the amplitude of the excitatory postsynaptic current response, and this effect was reversed with a k receptor antagonist. Presynaptic potassium channels were blocked by bath application of channel toxins, and the effect of kappa receptor activation was tested. The inhibition caused by U69593 was blocked by low doses of 4-aminopyridine (30 microM) and the selective peptide toxins dendrotoxin and mast cell degranulating peptide. The inhibition was not blocked by low doses of tetraethylammonium chloride (1 mM), barium, or glibenclamide. Thus, we conclude that presynaptic kappa-opioid receptors are coupled to a Shaker-type voltage-dependent potassium channel that is sensitive to dendrotoxin and mast cell degranulating peptide. An increase in presynaptic potassium conductance would enhance the rate of repolarization after action potential invasion, thereby limiting calcium influx and neurotransmitter release. This is the first physiological demonstration of the involvement of a dendrotoxin-sensitive potassium current in presynaptic inhibition mediated by a G protein-coupled receptor.

Nitric oxide-releasing polymers containing the [N(O)NO]- group.

Ions of structure X[N(O)NO]- display broad-spectrum pharmacological activity that correlates with the rate and extent of their spontaneous, first-order decomposition to nitric oxide when dissolved. We report incorporation of this functional group into polymeric matrices that can be used for altering the time course of nitric oxide release and/or targeting it to tissues with which the polymers are in physical contact. Structural types prepared include those in which the [N(O)NO]- group is attached to heteroatoms in low molecular weight species that are noncovalently distributed throughout the polymeric matrix, in groupings pendant to the polymer backbone, and in the polymer backbone itself. They range in physical form from films that can be coated onto other surfaces to microspheres, gels, powders, and moldable resins. Chemiluminescence measurements confirm that polymers to which the [N(O)NO]- group is attached can serve as localized sources of nitric oxide, with one prototype providing sustained NO release for 5 weeks in pH 7.4 buffer at 37 degrees C. The latter composition, a cross-linked poly-(ethylenimine) that had been exposed to NO, inhibited the in vitro proliferation of rat aorta smooth muscle cells when added as a powder to the culture medium and showed potent antiplatelet activity when coated on a normally thrombogenic vascular graft situated in an arteriovenous shunt in a baboon's circulatory system. The results suggest that polymers containing the [N(O)NO]- functional group may hold considerable promise for a variety of biomedical applications in which local delivery of NO is desired.

Endogenous opioid regulation of hippocampal function.

Endogenous opioid peptides modulate neural transmission in the hippocampus. Procnkephalin-derived peptides have been demonstrated to act at mu and delta opioid receptors to inhibit GABA release from inhibitory interneurons, resulting in increased excitability of hippocampal pyramidal cells and dentate gyrus granule cells. Prodynorphin-derived peptides primarily act at presynaptic kappa opioid receptors to inhibit excitatory amino acid release from perforant path and mossy fiber terminals. Opioid receptors reduce membrane excitability by modulating ion conductances, and in this way they may decrease voltage-dependent calcium influx and transmitter release. Synaptic plasticity in the hippocampus also is modulated by endogenous opioids. Enkephalins facilitate long-term potentiation, whereas dynorphins inhibit the induction of this type of neuroplasticity. Further, opioids may play important roles in hippocampal epilepsy. Recurrent seizures induce changes in the expression of opioid peptides and receptors. Also, enkephalins have proconvulsant effects in the epileptic hippocampus, whereas dynorphins may function as endogenous anticonvulsants.

L-type calcium channels mediate dynorphin neuropeptide release from dendrites but not axons of hippocampal granule cells.

Granule cells in the guinea pig dentate gyrus release kappa opioid neuropeptides, dynorphins, from dendrites as well as from axon terminals. We have found that both L- and N-type calcium channel antagonists inhibited dendritic dynorphin release. In contrast, N-type but not L-type calcium channel antagonists inhibited axonal dynorphin release. Neither L- nor N-type channel antagonists directly altered the effects of kappa opioid receptor activation. By inhibiting dynorphin release, L-type channel antagonists also facilitated the induction of long-term potentiation of the perforant path-granule cell synapse. These studies establish that a single cell type can release a transmitter from two different cellular domains and provide new distinction between axonal and dendritic transmitter release mechanisms.

Altered behavior and long-term potentiation in type I adenylyl cyclase mutant mice.

The murine Ca(2+)-stimulated adenylyl cyclase (type I) (EC 4.6.1.1), which is expressed predominantly in brain, was inactivated by targeted mutagenesis. Ca(2+)-stimulated adenylyl cyclase activity was reduced 40-60% in the hippocampus, neocortex, and cerebellum. Long-term potentiation in the CA1 region of the hippocampus from mutants was perturbed relative to controls. Both the initial slope and maximum extent of changes in synaptic response were reduced. Although mutant mice learned to find a hidden platform in the Morris water task normally, they did not display a preference for the region where the platform had been when it was removed. These results indicate that disruption of the gene for the type I adenylyl cyclase produces changes in behavior and that the cAMP signal transduction pathway may play an important role in synaptic plasticity.

Inhibition of glutamate release by presynaptic kappa 1-opioid receptors in the guinea pig dentate gyrus.

1. Activation of kappa 1-opioid receptors inhibits excitatory transmission in the hippocampal dentate gyrus of the guinea pig. The present studies used both anatomic and physiological approaches to distinguish between a pre- and postsynaptic localization of these receptors. 2. The entorhinal cortex was lesioned unilaterally to cause degeneration of perforant path afferents to the dentate molecular layer, and kappa 1-opioid binding sites were measured by labeling with the selective agonist, [3H]-U69593. Binding density was reduced significantly in the dentate gyrus molecular layer ipsilateral to the lesion compared with the contralateral molecular layer and with sham-lesioned controls. 3. Paired-pulse facilitation is a neurophysiologic paradigm that has been used to differentiate pre- and postsynaptic sites of action for agents that inhibit excitatory neurotransmission. U69593 reduced the amplitude of single population spikes and increased the degree of paired pulse facilitation. The potentiation of paired-pulse facilitation was maintained when the stimulation intensity was increased to compensate for the inhibition of excitatory transmission. These effects of kappa 1-receptor activation were similar to those seen after presynaptic inhibition of excitatory neurotransmitter release and support the hypothesis that U69593 presynaptically inhibits excitatory amino acid release in the dentate gyrus. 4. Local application of glutamate by pressure ejection in the dentate molecular layer evoked field excitatory postsynaptic potentials that mimicked those evoked by electrical stimulation of the perforant path. Both responses were sensitive to the non-N-methyl-D-aspartate glutamate receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione. U69593 inhibited responses evoked by perforant path stimulation but had no effect on responses evoked by glutamate application.(ABSTRACT TRUNCATED AT 250 WORDS)

Roles for protein kinases in the induction of nitric oxide synthase in astrocytes.

Lipopolysaccharide (LPS) or a combination of interferon (IFN)-gamma and interleukin (IL)-1 beta can induce a calcium-independent nitric oxide synthase (iNOS) in astrocyte cultures (Simmons and Murphy: J Neurochem 59:897, 1992; Eur J Neurosci 5:825, 1993; Galea et al: Proc Natl Acad Sci USA 89:10945, 1992). This induction can be measured by assaying cyclic GMP levels in the cultures, which correlates with, but is more sensitive than, measurement of nitrite accumulation. To study potential second-messenger systems involved in the induction of iNOS, phorbol 12-myristate 13-acetate (PMA), a protein kinase C (PKC) activator, and various protein kinase inhibitors were employed. PMA induced a time-, dose-, and L-arginine-dependent increase in cyclic GMP, which could be inhibited by dexamethasone or actinomycin D. This induction could be dramatically increased by concurrent treatment with IFN-gamma. The presence of iNOS mRNA could be demonstrated by hybridization with a specific cDNA probe. H7 (a non-specific serine/threonine kinase inhibitor) but not H89 (a more specific PKA inhibitor) prevented induction by all agents. However, downregulation of PKC or pretreatment with the PKC inhibitor calphostin C did not prevent the induction by LPS or cytokines, suggesting that PKC is not necessary for iNOS induction by these mediators. Additionally, genistein (a nonspecific tyrosine kinase inhibitor) could prevent induction by all agents, but the more specific inhibitor, tyrphostin, attenuated only NOS induction by LPS. These results suggest that activation of PKC can lead to, but is not necessary for, the induction of NOS in astrocytes and that there is a potential role for tyrosine kinases in NOS induction by LPS.(ABSTRACT TRUNCATED AT 250 WORDS)

Dynorphin opioids present in dentate granule cells may function as retrograde inhibitory neurotransmitters.

The granule cell population response to perforant path stimulation decreased significantly within seconds following release of endogenous dynorphin from dentate granule cells. The depression was blocked by the opioid receptor antagonists naloxone and norbinaltorphimine, suggesting that the effect was mediated by dynorphin activation of kappa 1 type opioid receptors. Pharmacological application of dynorphin B in the molecular layer was effective at reducing excitatory synaptic transmission from the perforant path, but application in the hilus had no significant effect. These results suggest that endogenous dynorphin peptides may be released from a local source within the dentate molecular layer. By light microscopy, dynorphin-like immunoreactivity (dynorphin-LI) was primarily found in granule cell axons in the hilus and stratum lucidum with only a few scattered fibers evident in the molecular layer. At the extreme ventral pole of the hippocampus, a diffuse band of varicose processes was also seen in the molecular layer, but this band was not present in more dorsal sections similar to those used for the electrophysiological studies. Electron microscopic analysis of the molecular layer midway along the septotemporal axis revealed that dynorphin-LI was present in dense-core vesicles in both spiny dendrites and unmyelinated axons with the majority (74%) of the dynorphin-LI-containing dense-core vesicles found in dendrites. Neuronal processes containing dynorphin-LI were observed throughout the molecular layer. The results suggest that dynorphin release from granule cell processes in the molecular layer regulates excitatory inputs entering the hippocampus from cerebral cortex, thus potentially counteracting such excitation-induced phenomena as epileptogenesis or long-term potentiation.

Bradykinin and capsaicin stimulate cyclic GMP production in cultured rat dorsal root ganglion neurons via a nitrosyl intermediate.

Dorsal root ganglion (DRG) neurons express receptors for bradykinin and capsaicin, both algesic substances. Administration of bradykinin or capsaicin to neurons cultured from embryonic rat DRG stimulated the production of cyclic GMP but did not affect the production of cyclic GMP in nonneuronal DRG cultures. Bradykinin-evoked cyclic GMP production was mediated by B2 receptors and was unaltered by indomethacin. Both bradykinin- and capsaicin-stimulated cyclic GMP production required Ca2+ and was inhibited by methylene blue. Furthermore, methylene blue attenuated basal cyclic GMP production in DRG neurons, suggesting tonic cyclic GMP production in these cells. L-NG-monomethyl arginine inhibited both bradykinin- and capsaicin-stimulated cyclic GMP production as well as basal cyclic GMP production. These findings suggest the involvement of a nitrosyl compound in bradykinin- and capsaicin-stimulated cyclic GMP production and in tonic cyclic GMP production in DRG neurons.