Pharmacologically distinct, pertussis toxin-resistant inward currents evoked by metabotropic glutamate receptor (mGluR) agonists in dorsolateral septal nucleus (DLSN) neurons

We have reported previously that a selective metabotropic glutamate receptor (mGluR) agonist, (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD), caused a slow membrane depolarization in rat dorsolateral septal nucleus (DLSN) neurons. Using single electrode voltage-clamp recording methods, we now investigate the pharmacological properties of the receptor that mediates ACPD-induced membrane currents in DLSN neurons recorded from pertussis toxin (PTX)-treated rats. Two pharmacologically distinct inward currents, that is, the ACPD current and Qm current, have been identified based on their agonist preference and sensitivity to various antagonists. The ACPD current is blocked by L-2-amino-4-phosphonobutyric acid (L-AP4), but is insensitive to L-aspartic acid-beta-hydroxamate (L-AA beta H), (+)-alpha-methyl-4-carboxyphenylglycine (+)-MCPG), or L-2-amino-3-phosphonopropionic acid (L-AP3). The Qm current is blocked by L-AA beta H and (+)-MCPG, but is insensitive to L-AP3 or L-AP4. These two inward currents distribute differentially within subpopulations of DLSN neurons. The ACPD current is the only current observed in most DLSN "burster" neurons, while the Qm current is observed more frequently in DLSN "nonburster" neurons. The pharmacological profiles of these currents suggest that the Qm current is likely mediated by mGluR1 or mGluR5, while the ACPD current is mediated by receptors that are pharmacologically distinct from any of the currently cloned mGluRs.

Immunocytochemical properties of rat renal afferent neurons in dorsal root ganglia: a quantitative study

Immunocytochemical properties of dorsal root ganglion neurons innervating the kidney were studied with retrograde tracing of Fluorogold or Fast Blue dyes applied to the cut renal nerves in the rat. The proportions and sizes of renal afferent neurons labelled with a variety of markers were quantified in T9-L1 dorsal root ganglia from five rats. Compared with the overall size distribution in these ganglia, renal afferent neurons were mainly small with a few medium-sized neurons. The majority (79%) of renal afferent dorsal root ganglion neuronal somata were unlabelled by an anti-neurofilament antibody, RT79, and classified as neurofilament-poor with probable C-fibres. These had an approximately normal distribution of cell sizes. Only 21% were RT79-positive and classified as neurofilament-rich with probable A-fibres, and even these were small to medium sized cells, consistent with them being mostly A delta-fibre neurons. Percentages of renal afferent neurons showing labelling were as follows: peripherin-like immunoreactivity: 69%; calcitonin-gene related peptide: 93%; substance P: 37%; the lectins soybean agglutinin: 57% and peanut agglutinin: 68%; Calbindin D28k-like immunoreactivity: 21% (only weak labelling); carbonic anhydrase like immunoreactivity: 0%. There were differences between probable C-fibre and probable A-fibre neurons, classified according to their labelling with RT97. The percentages of RT97-negative and RT97-positive neurons respectively labelled with the other markers were as follows: peripherin-like immunoreactivity: 82%, 25%; calcitonin gene-related peptide-like immunoreactivity: 99%, 79%; substance P-like immunoreactivity: 43%, 0%; soybean agglutinin: 69%, 24%; peanut agglutinin: 76%, 47%; calbindin-like immunoreactivity: 26%, 0%. Thus, the biggest differences between the probable A- and C-fibre renal afferent neurons were in their peripherin, substance P and calbindin contents. Thus, renal afferent neurons in the dorsal root ganglion are not homogeneous and it is suggested the differences may relate to the known different afferent receptor types within the kidney. It is suggested that the low proportion of neurons with substance P-like immunoreactivity in the renal afferent innervation compared to that of other viscera may relate to the role of the renal vasculature in urine formation.

[Amelioration of aminoglycoside nephrotoxicity by Cordyceps sinensis in old patients]

The protective effect on aminoglycoside nephrotoxicity by Cordyceps sinensis in the old patient was observed. 21 old patients were randomly divided into two groups. Each group received amikacin sulfate for 6 days. In addition, group A was administered Cordyceps sinensis for 7 days and group B was given placebo. The results revealed that group A developed less prominent nephrotoxicity compared with group B as evidenced by less urinary nephro-aminoglycosidase (NAGase) and beta-microglobulin in group A than those in Group B. These results suggested that Cordyceps sinensis exerted a protective effect on aminoglycoside nephrotoxicity in the old patients.

(1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD) induces burst firing via an inositol-1,4,5-triphosphate-independent pathway at rat dorsolateral septal nucleus

We have previously reported that a L-2-amino-3-phosphonopropionate (L-AP3)-sensitive metabotropic glutamate receptor was required for the induction of long-term potentiation (LTP) in rat dorsolateral septal nucleus neurons. (1S,3R)-1-Aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD), a selective agonist for metabotropic glutamate receptors, also causes burst firing of dorsolateral septal nucleus (DLSN) neurons. In this study, we investigated whether this response was mediated by a phospholipase C-(PLC) coupled metabotropic glutamate receptor. The threshold concentration of 1S,3R-ACPD for the induction of burst firing was about 5 microM, while 10 microM 1S,3R-ACPD produced a maximal effect. L-AP3 (50 microM) reduced the burst firing induced by 1S,3R-ACPD (5 microM). Although 1S,3R-ACPD stimulated the formation of inositol-1,4,5-triphosphate [Ins(1,4,5)P3] suggesting the presence of PLC-coupled metabotropic glutamate receptors, it was only effective in a higher (30-100 microM) concentration range. In addition, the 1S,3R-ACPD-stimulated formation of Ins(1,4,5)P3 level was not affected by L-AP3. These observations suggest that the 1S,3R-ACPD induced burst firing is not mediated by PLC-coupled metabotropic glutamate receptors.

[Effect of Rheum officinal on the proliferation of renal tubular cells in vitro]

Rat renal tubules were isolated and grown in culture medium. The effects of rheum officinal (RO) on the proliferation of renal tubular cells were investigated. In culture, the addition of the sera obtained from the rat fed with RO inhibited significantly the proliferation of renal tubular cells, and the effect become even more strong with the increase of the dosage or the long time of administration of RO to the rat. The ingredient RO--emodin added directly to culture medium suppressed the proliferation of renal tubular cells in a dose dependent manner, as measured by the uptake of radiolabeled thymidine. This observation may help explain the beneficial effects of RO in the treatment of chronic renal failure.

[Effect of electrical stimulation of paraventricular nucleus on stress gastric mucosal lesion in rats]

The effect of electrical stimulation of hypothalamic paraventricular nucleus (PVN) on gastric mucosal lesion induced by RWIS (restraint + water-immersion stress) in rats was investigated. The main results were as follows: (1) Electrical stimulation of the PVN could obviously increase the stress gastric mucosal lesion. (2) Microinjection of L-glutamate into PVN could produce similar effect to that of PVN stimulation. (3) PVN lesion could significantly decrease the stress gastric mucosal lesion. (4) The above mentioned effects were attenuated by vagotomy or atropine injected subcutaneously. (5) A further study indicated that the gastric mucosal blood flow was reduced upon PVN stimulation, but no obvious changes of gastric juice volume, total acid output, pepsin activity and gastric barrier mucus were observed. The results mentioned above indicate that the PVN is one of the specific CNS areas capable of increasing the stress-induced gastric mucosal lesion mediated through the cholinergic fibers of the vagal nerve and related to decreased gastric mucosal blood flow, while gastric acid output, pepsin activity and gastric barrier mucus do not seem to play any important role.

Metabotropic glutamate receptor agonists potentiate a slow afterdepolarization in CNS neurons

We have previously reported that, in the rat dorsolateral septal nucleus (DLSN), metabotropic glutamate receptor (met-GluR) agonists evoked a slow depolarization accompanied by an increase in membrane conductance and burst firing. We have speculated that the burst firing elicited by met-GluR agonists may be due to activation or enhancement of a non-specific cation current, which exists in some DLSN neurons. Now we report that a slow afterdepolarization (sADP) mediated by a non-specific cation current was potentiated by both 1S,3R-ACPD and quisqualate. In addition, met-GluR agonists unmask a sADP in DLSN neurons which did not show a sADP under control conditions. Our data suggest that a non-specific cation current can be potentiated by activation of the met-GluR.

Metabotropic glutamate receptors are required for the induction of long-term potentiation

Recent observations have led to the suggestion that the metabotropic glutamate receptor may play a role in the induction or maintenance of long-term potentiation (LTP). However, experimental evidence supporting a role for this receptor in the induction of LTP is still inconclusive and controversial. Here we report that, in rat dorsolateral septal nucleus (DLSN) neurons, which have the highest density of metabotropic receptors and show functional responses, the induction of LTP is not blocked by the NMDA receptor antagonist 2-amino-5-phosphonovalerate, but is blocked by two putative metabotropic glutamate receptor antagonists, L-2-amino-3-phosphonopropionic acid and L-2-amino-4-phosphonobutyrate. Furthermore, superfusion of (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid, a selective metabotropic glutamate agonist, resulted in a long-lasting potentiation of synaptic transmission similar to that induced by tetanic stimuli. Our results demonstrated that activation of postsynaptic metabotropic receptors is both necessary and sufficient for the induction of LTP in the DLSN, and we suggest that such a mechanism may be important at other CNS synapses.

Burst firing of rat septal neurons induced by 1S,3R-ACPD requires influx of extracellular calcium

We have demonstrated that burst firing in rat dorsolateral septal nucleus neurons is a specific response following activation of metabotropic glutamate receptors. Now we report that the burst firing induced by 1S,3R-ACPD (1S,3R-1-aminocyclopentane-1,3-dicarboxylic acid), a selective agonist, is blocked by inorganic calcium channel blockers. Our data suggest that influx of external calcium is required for this metabotropic glutamate response. Intracellular second messenger pathways coupled to the metabotropic glutamate receptor may be more complex than releasing calcium from IP3-sensitive internal stores as is currently hypothesized.

Trans-ACPD (trans-D,L-1-amino-1,3-cyclopentanedicarboxylic acid) elicited oscillation of membrane potentials in rat dorsolateral septal nucleus neurons recorded intracellularly in vitro

Glutamate receptors coupled to phosphoinositol turnover have been identified recently and named 'metabotropic' receptors. However, the exact functional roles of these receptors are still unknown. Trans-ACPD (trans-D,L-1-amino-1,3-cyclopentanedicarboxylic acid) is suggested to be the only selective agonist for metabotropic glutamate receptors. Here we report that trans-ACPD elicits membrane potential depolarization with oscillation of dorsolateral septal nucleus neurons recorded intracellulary in vitro. Our experiments also suggested that there may be multiple interactions between ionotropic quisqualate receptors and metabotropic glutamate receptors. The burst firing induced by high concentrations of trans-ACPD suggests that excessive activation of metabotropic glutamate receptors may lead to cellular toxicity or be associated with clinical disorders such as epilepsy.

Multilocular cystic renal cell carcinoma. Radiological diagnosis

Multilocular cystic renal cell carcinoma (MCRCC), and its pathological characteristics and roentgenological and B-mode ultrasonographic appearances are described. MCRCC, a special renal carcinoma, can be divided into localized and diffused forms.

Role of vagal afferent C fibres in the bradycardiac response to an increase in arterial blood pressure in ferrets

The effects on baroreceptor reflexes of bilateral application of the C fibre neurotoxin, capsaicin, to the cervical vagi have been investigated in decerebrate ferrets. Baroreflex sensitivity was estimated from the relationship between cardiac interval and systolic blood pressure following I.V. infusion of phenylephrine. Control responses to phenylephrine were fitted by two linear slopes with an initial shallow slope, a, followed by a steeper slope, b. Capsaicin abolished slope b and the resulting relationship was best fitted by a single regression with a slope not significantly different from that of the control response a. This suggests that a significant proportion of the baroreflex response induced by phenylephrine is mediated by cardiopulmonary receptors attached to vagal afferent C fibres.

Effect of hyperfiltration, proteinuria and diabetes mellitus on the uptake kinetics of gentamicin in the kidney cortex of rats

The influence of hyperfiltration-hypertrophy, proteinuria and glucosuria on the renal cortical uptake of gentamicin was studied in several experimental models. Two groups of remnant kidney rats, one fed a standard protein diet and one a low protein diet, heavy proteinuric rats (adriamycin) and diabetic rats, each with their own control group, were treated with increasing doses of gentamicin, given as a continuous infusion over 6 hr. The relationship between increasing steady-state serum levels (ranged from 1 to 100 micrograms/ml) and the cortical gentamicin concentrations at the end of the infusions was examined by means of Michaelis-Menten kinetics. The uptake curves were compared to their respective control curves. It was demonstrated that gentamicin uptake was reduced in remnant kidney rats fed standard diet (showing hyperfiltration and heavy proteinuria), in adriamycin rats (showing heavy proteinuria in the absence of hyperfiltration) and in diabetic rats. Uptake of gentamicin in remnant kidney rats fed low protein diet (showing hyperfiltration and slight proteinuria) was comparable to controls. It appeared that among the pathophysiological factors examined, proteinuria is the most important in decreasing the cortical uptake of gentamicin. It is suggested that high levels of proteins in the proximal tubular fluid interfere with the adsorptive endocytic process, involved in the uptake of both proteins and gentamicin.

[Morphometric study on sensitization by hematoporphyrin derivative in Ehrlich ascites tumor cells irradiated by gamma-ray]

In this paper, light and electron micrographs of Ehrlich ascites tumor cells radiated by gamma-ray and influenced by hematoporphyrin derivative (HPD) were analysed by morphometric method. It was found that in these cells, the domain of microfilaments treated by HPD expanded extensively, which enhanced the damage of cells induced by gamma-ray. Twenty five minutes after radiation, the cellular fragments increased, resulting in a decrease in the mean diameter of cells and an increase of nuclear volume density and nucleocytoplasmic ratio. In addition, ribosomes on the rough endoplasmic reticulum surfaces fell off increasingly and the quantity of smooth endoplasmic reticula increased.