Direct effect of nicotine on mesolimbic dopamine release in rat nucleus accumbens shell.

Nicotine stimulates dopamine (DA) cell firing via a local action at somatodendritic sites in the ventral tegmental area (VTA), increasing DA release in the nucleus accumbens (NAcc). Additionally, nicotine may also modulate DA release via a direct effect in the NAcc. This study examined the contribution of the latter mechanism on NAcc DA release by applying nicotine systemically, as well as locally in the VTA and NAcc shell region in rats. Furthermore, the effect of i.v. nicotine on cell firing rate of dopaminergic neurons in the VTA was measured. Systemic administration of nicotine (0.32mg/kg s.c.) increased extracellular DA levels in the NAcc to ∼1.5 fold of baseline, while DA levels in the VTA remained unaffected. A similar DA increase was observed after local NAcc infusion of nicotine (1µM and 10µM). However, 10-1000-fold higher nicotine concentrations were required in the VTA to produce a comparable 150% increase in extracellular DA levels in the ipsilateral NAcc. Additionally, electrophysiological experiments showed that the dopaminergic firing rate in the VTA showed a trend towards an increase after a nicotine dose of 0.1mg/kg i.v. Taken together these data indicate that the effects of nicotine on DA release at the level of the NAcc might be more important for the rewarding effects than originally proposed.

Pre-clinical properties of the alpha4beta2 nicotinic acetylcholine receptor partial agonists varenicline, cytisine and dianicline translate to clinical efficacy for nicotine dependence.

BACKGROUND AND PURPOSE: Smoking cessation trials with three high-affinity partial agonists of alpha4beta2 neuronal nicotinic acetylcholine receptors (nAChRs) have demonstrated differences in their clinical efficacy. This work examines the origin of the differences by taking into account brain exposure and pharmacological effects at human alpha4beta2 nAChRs. EXPERIMENTAL APPROACH: Rat plasma and brain pharmacokinetics were characterized and used to predict human steady-state plasma and brain concentrations following recommended doses of each of the three compounds. The pharmacological characterization included in vitro affinities at different nAChR subtypes, functional efficacies and potencies at the human alpha4beta2 nAChR, as well as in vivo effects on rat mesolimbic dopamine turn-over. KEY RESULTS: A comparison of predicted human brain concentrations following therapeutic doses demonstrated that varenicline and nicotine, but not dianicline and cytisine, can extensively desensitize and, to a lesser extent, activate alpha4beta2 nAChRs. The limited clinical efficacy of dianicline may be accounted for by a combination of weak functional potency at alpha4beta2 nAChRs and moderate brain penetration, while recommended doses of cytisine, despite its high in vitro potency, are predicted to result in brain concentrations that are insufficient to affect alpha4beta2 nAChRs. CONCLUSIONS AND IMPLICATIONS: The data provide a plausible explanation for the higher abstinence rate in smoking cessation trials following treatment with varenicline than with the two other alpha4beta2 nAChR partial agonists. In addition, this retrospective analysis demonstrates the usefulness of combining in vitro and in vivo parameters with estimated therapeutic human brain concentrations for translation to clinical efficacy.

Pharmacological profile of the alpha4beta2 nicotinic acetylcholine receptor partial agonist varenicline, an effective smoking cessation aid.

The preclinical pharmacology of the alpha4beta2 nicotinic acetylcholine receptor (nAChR) partial agonist varenicline, a novel smoking cessation agent is described. Varenicline binds with subnanomolar affinity only to alpha4beta2 nAChRs and in vitro functional patch clamp studies in HEK cells expressing nAChRs show that varenicline is a partial agonist with 45% of nicotine's maximal efficacy at alpha4beta2 nAChRs. In neurochemical models varenicline has significantly lower (40-60%) efficacy than nicotine in stimulating [(3)H]-dopamine release from rat brain slices in vitro and in increasing dopamine release from rat nucleus accumbens in vivo, while it is more potent than nicotine. In addition, when combined with nicotine, varenicline effectively attenuates the nicotine-induced dopamine release to the level of the effect of varenicline alone, consistent with partial agonism. Finally, varenicline reduces nicotine self-administration in rats and supports lower self-administration break points than nicotine. These data suggest that varenicline can reproduce to some extent the subjective effects of smoking by partially activating alpha4beta2 nAChRs, while preventing full activation of these receptors by nicotine. Based on these findings, varenicline was advanced into clinical development and recently shown to be an effective and safe aid for smoking cessation treatment.

Gelation mechanism of milk as influenced by temperature and pH; studied by the use of transglutaminase cross-linked casein micelles.

Casein micelles in milk are colloidal particles consisting of four different caseins and calcium phosphate, each of which can be exchanged with the serum phase. The distribution of caseins and calcium between the serum and micellar phase is pH and temperature dependent. Furthermore, upon acidification casein micelles lose their colloidal stability and start to aggregate and gel. In this paper, we studied two methods of acid-induced gelation, i.e., 1) acidification of milk at temperatures of 20 to 50 degrees C and 2) decreasing the pH at 20 degrees C to just above the gelation pH and subsequently inducing gelation by increasing the temperature. These two routes are called T-pH and pH-T, respectively. The gelation kinetics and the properties of the final gels obtained are affected by the gelation route applied. The pH-T milks gel at higher pH and lower temperature and the gels formed are stronger and show less susceptibility to syneresis. By using intramicellar cross-linked casein micelles, in which release of serum caseins is prevented, we demonstrated that unheated milk serum caseins play a key role in gelation kinetics and characteristics of the final gels formed. This mechanism is presented in a model and is relevant for optimizing and controlling industrial processes in the dairy industry, such as pasteurization of acidified milk products.

Impaired rennetability of heated milk; study of enzymatic hydrolysis and gelation kinetics.

Casein micelles in milk are stable colloidal particles with a stabilizing hairy brush of kappa-casein. During cheese production rennet cleaves kappa-casein into casein macropeptide and para-kappa-casein, thereby destabilizing the casein micelle and resulting in aggregation and gel formation of the micelles. Heat treatment of milk causes impaired clotting properties, which makes heated milk unsuitable for cheese production. In this paper we compared five different techniques, often described in the literature, for their suitability to quantify the enzymatic hydrolysis of kappa-casein. It was found that the technique is crucial for the yield of casein macropeptide and this yield then affects the calculated enzymatic inhibition caused by heat treatment, ranging from 5 to 30%. The technique, which we found to be the most reliable, demonstrates that heat-induced calcium phosphate precipitation does not affect the enzymatic cleavage, while whey protein denaturation causes a very slight reduction of enzyme activity. By using diffusing wave spectroscopy, a very sensitive technique to monitor gelation processes, we demonstrated that heat-induced calcium phosphate precipitation does not affect the clotting. Whey protein denaturation does not affect the start of flocculation but has a clear effect on the clotting process. This work adds to a better understanding of the processes causing the impaired clotting properties of heated milk.

Serotonergic effects and extracellular brain levels of eletriptan, zolmitriptan and sumatriptan in rat brain.

In vivo microdialysis was used to assess the central serotonergic effects and extracellular brain levels of the 5-HT(1B/1D) receptor agonists eletriptan, zolmitriptan and sumatriptan in rats after intravenous and intracerebral administration, while their binding affinities and functional potencies were determined at 5-HT(1B), 5-HT(1D) and 5-HT(1A) receptors. In vitro studies showed that all three triptans are high affinity, full agonists at 5-HT(1B/1D) receptors, but that sumatriptan is functionally less potent as a 5-HT(1B/1D) agonist than zolmitriptan and eletriptan. Local intracortical perfusion with the compounds via the dialysis probe decreased cortical 5-HT (5-hydroxytryptamine, serotonin) release with ED(50) values of approximately 0.1 microM for eletriptan and zolmitriptan and 0.5 microM for sumatriptan. At 3.2 mg/kg i.v., both eletriptan and zolmitriptan decreased 5-HT levels by about 35%, while sumatriptan had no effect, despite the fact that maximal sumatriptan concentrations in cortical dialysates were higher (8.8 nM at 20 min) than those of zolmitriptan (5.9 nM at 20 min) and eletriptan (2.6 nM at 40 min). The observation that eletriptan and zolmitriptan produce almost identical central serotonergic effects, after intracerebral as well as after systemic administration, is in agreement with their comparable functional 5-HT(1B/1D) receptor agonist potencies and their free levels in cortical dialysates after 3.2 mg/kg i.v. On the other hand, the lack of central serotonergic effects of 3.2 mg/kg i.v. sumatriptan is likely due to its weaker functional 5-HT(1B/1D) receptor agonist potency than eletriptan and zolmitriptan, rather than lower brain levels, consistent with sumatriptan's fivefold lower potency after intracerebral administration.

On the structure of kappa/iota-hybrid carrageenans.

The coil-to-helix transition and temperature dependence of the viscosity of commercial kappa/iota-hybrid carrageenans produced by the red algae Sarcothalia crispata, Mazaella laminarioides, and Chondrus crispus were studied using rheometry and optical rotation. The structure of these kappa/iota-hybrid carrageenans was determined by 1H and 13C NMR spectroscopy combined with monosaccharide composition analysis. The coil-to-helix transitions, measured by polarimetry and rheometry, of the kappa/iota-hybrid carrageenans are significantly different from those of pure kappa- and iota-carrageenan, and from hand-made mixtures thereof. This provides evidence that the kappa/iota-hybrid carrageenans are mixed chains, containing both kappa- and iota-repeating units.

Activation of postsynaptic 5-HT(1A) receptors by fluoxetine despite the loss of firing-dependent serotonergic input: electrophysiological and neurochemical studies.

Systemic doses of fluoxetine slow dorsal raphe cell firing by blocking the reuptake carrier located in the cell body region with the surplus 5-HT thus generated activating inhibitory autoreceptors. The concurrent actions of fluoxetine on postsynaptic receptors in raphe projection areas has not been as thoroughly investigated, although it is presumed that a reduction in cell firing should curtail these targeted effects. The goal of the present studies was to assess the degree of postsynaptic receptor activation obtained with fluoxetine and relate it to cell body autoreceptor activation and the level of extracellular 5-HT obtained at the nerve endings. Changes in firing rates of CA3 hippocampal neurons following systemic administration of fluoxetine were used as a marker of SSRI-dependent changes in postsynaptic 5-HT receptor activation; monitoring of unit activity of neurons in the dorsal raphe nucleus served to gauge the degree of serotonergic input in a parallel series of animals. Estimates of the corresponding changes in terminal 5-HT release in the CA3 region were analyzed by microdialysis. The results indicate that fluoxetine inhibits hippocampal cell firing in a dose-dependent manner (ED(50) = 4.4 mg/kg i.v.) and one sensitive to pretreatment with the 5-HT(1A) antagonist WAY-100,635. Within the same dose range, increases in hippocampal extracellular 5-HT approaching 300% above basal levels were achieved. Both the changes in hippocampal neuronal activity and extracellular 5-HT are evident at doses of fluoxetine in excess of that required to inhibit dorsal raphe cell firing (ED(50) = 1.1 mg/kg i.v.). Taken together, these data suggest that increases in extracellular levels of 5-HT on the order of that observed are sufficient to alter postsynaptic excitability and that this accumulation of synaptic 5-HT and the subsequent activation of postsynaptic 5-HT(1A) receptors are achievable despite loss of firing-dependent 5-HT release.

5-HT(1A) receptor activation contributes to ziprasidone-induced dopamine release in the rat prefrontal cortex.

BACKGROUND: Ziprasidone (Zeldox) is a novel antipsychotic with a unique combination of antagonist activities at monoaminergic receptors and transporters and potent agonist activity at serotonin 5-HT(1A) receptors. 5-HT(1A) receptor agonism may be an important feature in ziprasidone's clinical actions because 5-HT(1A) agonists increase cortical dopamine release, which may underlie efficacy against negative symptoms and reduce dopamine D(2) antagonist-induced extrapyramidal side effects. This study investigated the in vivo 5-HT(1A) agonist activity of ziprasidone by measuring the contribution of 5-HT(1A) receptor activation to the ziprasidone-induced cortical dopamine release in rats. METHODS: Effects on dopamine release were measured by microdialysis in prefrontal cortex and striatum. The role of 5-HT(1A) receptor activation was estimated by assessing the sensitivity of the response to pretreatment with the 5-HT(1A) antagonist, WAY-100635. For comparison, the D(2)/5-HT(2A) antagonists clozapine and olanzapine, the D(2) antagonist haloperidol, the 5-HT(2A) antagonist MDL 100,907 and the 5-HT(1A) agonist 8-OHDPAT were included. RESULTS: Low doses (<3.2 mg/kg) of ziprasidone, clozapine, and olanzapine increased dopamine release to approximately the same extent in prefrontal cortex as in striatum, but higher doses (> or =3.2 mg/kg) resulted in an increasingly preferential effect on cortical dopamine release. The 5-HT(1A) agonist 8-OHDPAT produced a robust increase in cortical dopamine (DA) release without affecting striatal DA release. In contrast, the D(2) antagonist haloperidol selectively increased striatal DA release, whereas the 5-HT(2A) antagonist MDL 100,907 had no effect on cortical or striatal DA release. Prior administration of WAY-100635 completely blocked the cortical DA increase produced by 8-OHDPAT and significantly attenuated the ziprasidone- and clozapine-induced cortical DA increase. WAY-100635 pretreatment had no effect on the olanzapine-induced DA increase. CONCLUSIONS: The preferential increase in DA release in rat prefrontal cortex produced by ziprasidone is mediated by 5-HT(1A) receptor activation. This result extends and confirms other in vitro and in vivo data suggesting that ziprasidone, like clozapine, acts as a 5-HT(1A) receptor agonist in vivo, which may contribute to its activity as an antipsychotic with efficacy against negative symptoms and a low extrapyramidal side effect liability.

Engineering a disulfide bond and free thiols in the lantibiotic nisin Z.

The antimicrobial peptide nisin contains the uncommon amino acid residues lanthionine and methyl-lanthionine, which are post-translationally formed from Ser, Thr and Cys residues. To investigate the importance of these uncommon residues for nisin activity, a mutant was designed in which Thr13 was replaced by a Cys residue, which prevents the formation of the thioether bond of ring C. Instead, Cys13 couples with Cys19 via an intramolecular disulfide bridge, a bond that is very unusual in lantibiotics. NMR analysis of this mutant showed a structure very similar to that of wild-type nisin, except for the configuration of ring C. The modification was accompanied by a dramatic reduction in antimicrobial activity to less than 1% of wild-type activity, indicating that the lanthionine of ring C is very important for this activity. The nisin Z mutants S5C and M17C were also isolated and characterized; they are the first lantibiotics known that contain an additional Cys residue that is not involved in bridge formation but is present as a free thiol. Secretion of these peptides by the lactococcal producer cells, as well as their antimicrobial activity, was found to be strongly dependent on a reducing environment. Their ability to permeabilize lipid vesicles was not thiol-dependent. Labeling of M17C nisin Z with iodoacetamide abolished the thiol-dependence of the peptide. These results show that the presence of a reactive Cys residue in nisin has a strong effect on the antimicrobial properties of the peptide, which is probably the result of interaction of these residues with thiol groups on the outside of bacterial cells.

Comparison of the novel antipsychotic ziprasidone with clozapine and olanzapine: inhibition of dorsal raphe cell firing and the role of 5-HT1A receptor activation.

Ziprasidone is a novel antipsychotic agent which binds with high affinity to 5-HT1A receptors (Ki = 3.4 nM), in addition to 5-HT1D, 5-HT2, and D2 sites. While it is an antagonist at these latter receptors, ziprasidone behaves as a 5-HT1A agonist in vitro in adenylate cyclase measurements. The goal of the present study was to examine the 5-HT1A properties of ziprasidone in vivo using as a marker of central 5-HT1A activity the inhibition of firing of serotonin-containing neurons in the dorsal raphe nucleus. In anesthetized rats, ziprasidone dose-dependently slowed raphe unit activity (ED50 = 300 micrograms/kg i.v.) as did the atypical antipsychotics clozapine (ED50 = 250 micrograms/kg i.v.) and olanzapine (ED50 = 1000 micrograms/kg i.v.). Pretreatment with the 5-HT1A antagonist WAY-100,635 (10 micrograms/kg i.v.) prevented the ziprasidone-induced inhibition; the same dose of WAY-100,635 had little effect on the inhibition produced by clozapine and olanzapine. Because all three agents also bind to alpha 1 receptors, antagonists of which inhibit serotonin neuronal firing, this aspect of their pharmacology was assessed with desipramine (DMI), a NE re-uptake blocker previously shown to reverse the effects of alpha 1 antagonists on raphe unit activity. DMI (5 mg/kg i.v.) failed to reverse the inhibitory effect of ziprasidone but produced nearly complete reversal of that of clozapine and olanzapine. These profiles suggest a mechanism of action for each agent, 5-HT1A agonism for ziprasidone and alpha 1 antagonism for clozapine and olanzapine. The 5-HT1A agonist activity reported here clearly distinguishes ziprasidone from currently available antipsychotic agents and suggests that this property may play a significant role in its pharmacologic actions.

Continued improvement in pressure-flow parameters in men receiving finasteride for 2 years. Finasteride Urodynamics Study Group.

OBJECTIVES: To assess the long-term effects of finasteride on pressure-flow parameters in men with urodynamically documented bladder outflow obstruction (BOO). METHODS: One hundred twenty-one men with benign prostatic enlargement (BPE) and lower urinary tract symptoms (LUTS) underwent a pressure-flow study (PFS) at 1 of 11 clinical centers. The PFS technique was standardized, and all tracings were read by a single reader unaware of the treatment group. Patients who were obstructed according to a modified Abrams-Griffiths nomogram were randomized to 5 mg finasteride (n = 81) or placebo (n = 40) for 12 months; all patients continuing into an open extension received finasteride during the second 12 months of therapy. Results of the initial 12-month study demonstrated the benefit of finasteride treatment on PFS parameters. To examine the continuing effects over time, an analysis of the data from 54 patients who completed 24 months of treatment with finasteride is provided. RESULTS: Detrusor pressure at maximum flow (PdetQmax) continued to decrease during the second 12 months of therapy (decreases of 5.3 and 11.7 cm H2O at months 12 and 24, respectively). The percentage of patients obstructed by Abrams-Griffiths classification decreased from 76.2% at baseline to 66.7% at month 12 and 59.6% at month 24. An intention-to-treat analysis yielded similar results. CONCLUSIONS: Finasteride improves urodynamic measures of obstruction in men with BPE and LUTS, with continued improvement during the second 12 months of therapy.

Improvement of pressure flow parameters with finasteride is greater in men with large prostates. Finasteride Urodynamics Study Group.

PURPOSE: We assess the effect of finasteride, a 5alpha-reductase inhibitor, on objective voiding parameters in men with lower urinary tract symptoms and benign prostatic enlargement on digital rectal examination (known as clinical benign prostatic enlargement) in a double-blind placebo controlled multicenter study using strict standard pressure flow study techniques. MATERIALS AND METHODS: A modification of the Abrams-Griffiths nomogram was used by 1 reader to ensure that all patients met objective criteria for bladder outlet obstruction at baseline. After performing a pressure flow study patients with obstruction were randomized 2:1 to receive 5 mg. finasteride (81) or placebo (40) daily. A second pressure flow study was performed at month 12. At baseline and month 12 free urinary flow studies and transrectal ultrasound were performed, and International Prostate Symptom Score questionnaires were completed. Patients were treated between May 1994 and July 1996. RESULTS: Finasteride caused a significant decrease (-8.1 cm. water) in detrusor pressure at maximum flow (p <0.05 versus placebo p = 0.02), increase (+1.1 ml. per second) in maximum flow rate (p <0.05 versus placebo p = 0.02) and decrease (-22.8%) in prostate volume (p <0.05 versus placebo p <0.001). Men with prostates larger than 40 cc had greater improvement in detrusor pressure at maximum flow (between group difference -14.5 cm. water, 95% confidence interval -26.2 to -2.6, p = 0.02) and maximum flow rate (mean treatment effect +1.6 ml. per second, 95% confidence interval -0.2 to 3.0, p = 0.02) compared to those with prostates 40 cc or less (between group differences not significant). CONCLUSIONS: Finasteride treatment resulted in improvements in urodynamic parameters, which were greater in men with large prostates.

Repeated pressure-flow studies in the evaluation of bladder outlet obstruction due to benign prostatic enlargement. Finasteride Urodynamics Study Group.

Test-retest reliability of repeated voids in pressure-flow studies and the influence on maximum flow rate (Q(max)pQ), detrusor pressure at maximum flow rate (p(det)Qmax), voided volume, and residual urine were studied. Also the agreement in interpretation of pressure-flow tracings between investigators and a single blinded central reader acting as a quality control center (QCC) were assessed. In addition, correlations between p(det)Qmax and patient age, International Prostate Symptom Score (IPSS), free maximum flow rate (Qmax), and prostate volume were calculated. Using suprapubic pressure recording, 216 men with lower urinary tract symptoms (LUTS) due to benign prostatic enlargement (BPE) were investigated in 11 centers. In each pressure-flow study, three sequential voids were performed, and quality controlled recordings were analyzed for Q(max)pQ and p(det)Qmax by the QCC. Trans rectal ultrasound was used to measure the prostate volume. Mean Q(max)pQ did not change, but p(det)Qmax decreased significantly in the second and third sequential voids. Using the Abrams-Griffiths nomogram definition of obstruction, 125 patients (67%) were classified as obstructed from the first void, but only 111 patients (59%) from the third void. The agreement between the investigator assessment and that of a single blinded reader was good. There was no significant correlation between p(det)Qmax and patient age, IPSS, and Qmax, whereas a modest correlation was found between p(det)Qmax and prostate volume. In summary, there was no significant change in Q(max)pQ, but p(det)Qmax decreased for the three consecutive voids, which can be explained by a decrease in outlet resistance. The agreement between the investigator and QCC interpretations shows the value of a standardized technique, supporting the feasibility of multicenter urodynamic studies. There is a modest, but statistically significant, correlation between detrusor pressure and prostate size, supporting the hypothesis that prostate size is a contributing factor in symptomatic BPH.

Structural features of the final intermediate in the biosynthesis of the lantibiotic nisin. Influence of the leader peptide.

The antimicrobial membrane-interacting polypeptide nisin is a prominent member of the lantibiotic family, the members of which contain thioether-bridged residues called lanthionines. To gain insight into the complex biosynthesis and the structure/function relationship of lantibiotics, the final intermediate in the biosynthesis of nisin A was studied by nuclear magnetic resonance spectroscopy. In aqueous solution the leader peptide part of this precursor adopts predominantly a random coil structure, as does the synthetic leader peptide itself. The spatial structure of the fully modified nisin part of the precursor is similar to that of nisin in water. The leader peptide part does not interact with the nisin part of the precursor molecule. Thus, these two parts of the precursor do not influence each other's conformation significantly. The conformation of the precursor was also studied while complexed to micelles of dodecylphosphocholine, mimicking the primary target of the antimicrobial activity of nisin, i.e. the cytoplasmic membrane. The location of the molecule relative to the micelles was investigated by using micelle-inserted spin-labeled 5-doxylstearic acid. It was observed that the N-terminal half of the nisin part of the precursor interacts in a different way with micelles than does the corresponding part of mature nisin, whereas no significant differences were found for the C-terminal half of the nisin part. In this model system the leader peptide is in contact with the micelles. It is concluded that the strongly reduced in vivo activity of the precursor molecule relative to that of nisin is not caused by a difference in the spatial structure of nisin and of the corresponding part of precursor nisin in water or by a shielding of the membrane interaction surface of the nisin part of the precursor by the leader peptide. Probably a different interaction of the N-terminal part of the nisin region with membranes contributes to the low activity by preventing productive insertion. The residues of the leader peptide part just next to the nisin part are likely to contribute most to the low activity of the precursor.

Influence of charge differences in the C-terminal part of nisin on antimicrobial activity and signaling capacity.

Three mutants of the antibiotic nisin Z, in which the Val32 residue was replaced by a Glu, Lys or Trp residue, were produced and characterized for the purpose of establishing the role of charge differences in the C-terminal part of nisin on antimicrobial activity and signaling properties. 1H-NMR analyses showed that all three mutants harbor an unmodified serine residue at position 33, instead of the usual dehydroalanine. Apparently, the nature of the residue preceding the serine to be dehydrated, strongly affects the efficiency of modification. Cleavage of [Glu32,Ser33]nisin Z by endoproteinase Glu-C yielded [Glu32]nisin Z(1-32)-peptide, which has a net charge difference of -2 relative to wild-type nisin Z. The activity of [Lys32,Ser33]nisin Z against Micrococcus flavus was similar to that of wild-type nisin, while [Trp32,Ser33]nisin Z, [Glu32,Ser33]nisin Z and [Glu32]nisin Z(1-32)-peptide exhibited 3-5-fold reduced activity, indicating that negative charges in the C-terminal part of nisin Z are detrimental for activity. All variants showed significant loss of activity against Streptococcus thermophilus. The potency of the nisin variants to act as signaling molecules for auto-induction of biosynthesis was significantly reduced. To obtain mutant production, extracellular addition of (mutant) nisin Z to the lactococcal expression strains was essential.

Do 5-HT1B/1D autoreceptors modulate dorsal raphe cell firing? In vivo electrophysiological studies in guinea pigs with GR127935.

GR127935 is a selective antagonist of release-modulating 5-HT1B/1D autoreceptors on serotonergic terminals and, as such, would be expected to produce increases in extracellular 5-HT. The changes in 5-HT observed are mixed, however, possibly due to the presence of somatodendritic 5-HT1a/1D autoreceptors. Theoretically, blockade of these autoreceptors would elevate intra-raphe 5-HT which, in turn, would activate somatodendritic 5-HT1A autoreceptors and slow firing rate. As recorded in anesthetized guinea pigs, dorsal raphe cell firing was unaffected by doses of GR127935 ranging from 20 to 20000 micrograms/kg i.v. Lower doses of GR127935 (0.002-2 micrograms/kg i.v.) yielded highly variable responses, although these were not significantly different from baseline. 8-OH-DPAT in these and similar neurons produced the robust dose-dependent inhibitory response expected of a 5-HT1A agonist; increases in extracellular 5-HT resulting from re-uptake blockade by fluoxetine also suppressed unit activity. Doses of CP-135,807, a centrally-acting 5-HT1B/1D agonist, to increase tone on the somatodendritic 5-HT1B/1D autoreceptor produced only a trend toward decreases in dorsal raphe neuronal firing. The overall weak effect of GR127935 on raphe unit activity suggests that the mechanism described previously must take into account factors such as the degree of intra-raphe 5-HT release, the endogenous tone on the autoreceptors, receptor selectivity and intrinsic activity of GR127935 and/or heterogeneity within the subtype.

[Determination of infravesical obstruction in men with benign prostatic hyperplasia using pressure-flow measurement and analysis with the Dx/CLIM software program]. / Stanovenie infravezikálnej obstrukcie u muzov s benígnou hyperpláziou prostaty pomocou tlakovo-prietokových meraní a analýzy Dx/CLIM.

BACKGROUND: Quantification of infravesical obstruction is important in the management of clinical benign prostatic hyperplasia (BPH). OBJECTIVES: The assessment of obstruction degree according to the urethral resistance parameter (URA) and bladder contractility (W) with software Dx/CLIM. METHODS: The study retrospectively analysed a group of 61 patients with BPH in order to assess the degree of obstruction and bladder contractility. Each of the patients underwent pressure/flow studies with Dx/CLIM analysis (URA < 29 cm H2O-unobstructed, Wmax > 12.8 W/m2-normal bladder contractility) and symptom score evaluation (maximum 15 points). In a dose-finding, placebo-controlled study 12 patients received 2 mg of doxazosin (alpha-1 blocker) and 11 patients received placebo during 4 weeks of treatment. RESULTS: 15 patients were unobstructed (25%) out of whom 10 had poor bladder contractility. Obstruction was present in 46 patients (75%) out of whom 18 had impaired contractility. During treatment, the symptom score decreased statistically significantly in both groups (p < 0.05). URA decreased significantly only in the 2 mg group (2 mg group: baseline URA = 53.9, final mean URA = 40.1, p < 0.05; placebo group: baseline URA = 52.9, final mean URA = 56.1). Detrusor contractility was not significantly affected. CONCLUSIONS: Pressure/flow studies with Dx/CLIM analysis are very useful in the selection of BPH patients for treatment modalities and in the assessment of efficacy. Doxazosín decreases urethral resistance effectively. (Tab. 3, Fig. 3, Ref. 12.)