Stoichiometry of cholesterol-sphingomyelin condensed complexes in monolayers

Some binary mixtures of cholesterol and phospholipids in monolayers have thermodynamic phase diagrams with two upper miscibility critical points. This feature has been interpreted in terms of 'condensed complexes' between the phospholipid and cholesterol. The present work gives evidence for the formation of complexes with a common simple integral stoichiometry in binary mixtures of cholesterol and a series of five sphingomyelins where the amide-linked acyl chain length is varied. This indicates that these complexes have a distinct geometry even though they form a liquid phase.

Orexin A excites serotonergic neurons in the dorsal raphe nucleus of the rat

Orexin A (10-300 nM) strongly excited dorsal raphe serotonergic neurons maintained in vitro. The depolarization persisted in the presence of tetrodotoxin (TTX, 0.5 microM) and was associated with an increase in input resistance. These results have relevance in the context of food intake regulation and the disease, narcolepsy.

Of mice and men: virtual Hebb-Williams mazes permit comparison of spatial learning across species

We developed a computer-generated virtual environment to test humans, for the first time, on the Hebb-Williams mazes. The goal was to provide a standardized test that could be used to directly compare human performance with that of C57BL/6J mice performing in real versions of the mazes. Such a comparison seems crucial if conclusions regarding genetic manipulations of rodents are to be mapped onto human cognitive disorders. The learning curves across species were strikingly similar, lending support to the rodent model of human spatial memory. Humans learned faster than rodents in both the acquisition and the test portions of the protocol, and females of both species were less efficient in solving these problems than males. These results represent the first modern comparison of human and rodent learning that uses the same test of spatial problem solving.

Histamine H(3) receptors depress synaptic transmission in the corticostriatal pathway

The effect of histamine on the main input to the striatum - the corticostriatal pathway - was studied using electrophysiological techniques in brain slices from rats and mice. Field potentials (FPs) were recorded in the striatum following stimulation at the border of the striatum and the cortex. Bath application of histamine caused a pronounced and long-lasting depression of FPs in rat slices with an IC(50) of 1.6 microM and a maximal depression of around 40%. In mouse slices histamine also depressed FPs, but to a lesser extent and more transiently. Further experiments in rat slices showed that histamine H(3) receptors were responsible for this depression since the selective H(3) receptor agonist R-alpha-methylhistamine (1 microM) mimicked the action of histamine whilst the selective H(3) receptor antagonist, thioperamide (10 microM) blocked the depression caused by histamine application. The histaminergic depression was probably not mediated indirectly through interneurons since blockade of GABA(A), GABA(B), nicotinic and muscarinic receptors or nitric oxide synthase did not prevent the histamine effect. Intracellular recordings from medium spiny neurons in the striatum revealed that histamine did not affect postsynaptic membrane properties but increased paired-pulse facilitation of excitatory synaptic responses indicating a presynaptic locus of action.

Interfacial interactions of ceramide with dimyristoylphosphatidylcholine: impact of the N-acyl chain

The mixing behavior of dimyristoylphosphatidylcholine (DMPC) with either N-palmitoyl-sphingosine (C16:0-ceramide) or N-nervonoyl-sphingosine (C24:1-ceramide) was examined using monomolecular films. While DMPC forms highly elastic liquid-expanded monolayers, both neat C16:0-ceramide and C24:1-ceramide yield stable solid condensed monomolecular films with small areas and low interfacial elasticity. Compression isotherms of mixed C16:0-ceramide/DMPC films exhibit an apparent condensation upon increasing X(cer16:0) at all surface pressures. The average area isobars, coupled with the lack of a liquid-expanded to condensed phase transition as X(cer16:0) is increased, are indicative of immiscibility of the lipids at all surface pressures. In contrast, isobars for C24:1-ceramide/DMPC mixtures show surface pressure-dependent apparent condensation or expansion and surface pressure-area isotherms show a composition and surface pressure-dependent phase transition. This suggests miscibility, albeit non-ideal, of C24:1-ceramide and DMPC in both liquid and condensed surface phases. The above could be verified by fluorescence microscopy of the monolayers and measurements of surface potential, which revealed distinctly different domain morphologies and surface potential values for the DMPC/C16:0- and DMPC/C24:1-ceramide monolayers. Taken together, whereas C16:0-ceramide and DMPC form immiscible pseudo-compounds, C24:1-ceramide and DMPC are partially miscible in both the liquid-expanded and condensed phases, and a composition and lateral pressure-dependent two-phase region is evident between the liquid-expanded and condensed regimes. Our results provide novel understanding of the regulation of membrane properties by ceramides and raise the possibility that ceramides with different acyl groups could serve very different functions in cells, relating to their different physicochemical properties.

Basic fibroblast growth factor induced angiogenesis and prefabricated flap survival

Prefabrication of a latissimus dorsi myocutaneous flap was performed in adult male Landrace pigs. Gelfoam sponges were used as a delivery system for basic fibroblast growth factor (bFGF) at the muscle-subcutaneous tissue interface. Skin survival and angiogenesis were augmented in the growth-factor-treated animals. These data support the use of basic fibroblast growth factor to enhance flap prefabrication.

Cost effectiveness of treatment options in advanced breast cancer in the UK

OBJECTIVE

To compare clinical and economic study data for docetaxel, paclitaxel and vinorelbine in the treatment of anthracycline-resistant advanced breast cancer.

STUDY DESIGN AND METHODS

A Markov decision-analysis model to simulate the clinical course of a 'typical' patient with advanced breast cancer during salvage chemotherapy was updated with response rates and adverse effect rates from phase III clinical trial data for docetaxel, paclitaxel and vinorelbine. Costs were taken from UK national databases and hospitals. Utilities were estimated from 30 oncology nurses in the UK using the standard gamble method.

PERSPECTIVE

National Health Service.

RESULTS

When compared with other chemotherapeutic agents, docetaxel has been shown to increase response rate, time to progression and survival in patients with advanced breast cancer. In the base-case analysis, the incremental cost-utility ratio for docetaxel versus paclitaxel was pound1995 per quality-adjusted life year (QALY) gained (1998 values). The incremental cost-utility ratio for docetaxel versus vinorelbine was pound14 055 per QALY gained. In the comparison with vinorelbine, docetaxel provided the equivalent of an additional 92 days of perfect health. Sensitivity analyses confirmed the robustness of the model and the validity of the base-case analysis results. Even in the worst case scenarios, docetaxel remained cost effective compared with paclitaxel and vinorelbine.

CONCLUSIONS

These findings support the use of the taxoids, notably docetaxel, in the management of advanced breast cancer.

Interactions between N-methyl-D-aspartate and nitric oxide in the modulation of ultrasonic vocalizations of infant rats

The effects of interactions between N-methyl-D-aspartate (NMDA) and nitric oxide on ultrasonic vocalizations, motor activity and body temperature was investigated in 9-10-day-old rat pups. The competitive NMDA receptor antagonist, 3-((+/-)-2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP), and the nitric oxide synthase inhibitor, nitro-L-arginine-methyl ester (L-NAME), decreased the emission of ultrasonic vocalizations while NMDA and the nitric oxide precursor, L-arginine, produced a trend toward increased emission of ultrasonic vocalizations. CCP also attenuated the geotaxic response. Co-administration of CPP with L-NAME virtually abolished the emission of ultrasonic vocalizations and the ability to show the geotaxic response while co-administration of NMDA with L-arginine increased the emission of ultrasonic vocalizations and decreased body temperature with no effect on the geotaxic response. NMDA and L-arginine reversed the effects of L-NAME, but not of CPP, on ultrasonic vocalizations. L-arginine but not NMDA antagonized the effect of CPP on the geotaxic response. Our results confirmed the functional coupling between NMDA receptor activation and nitric oxide in modulating anxiety-like behavior and motor coordination in infant rats.

A randomized prospective study of polyglycolic acid conduits for digital nerve reconstruction in humans

This article reports the first randomized prospective multicenter evaluation of a bioabsorbable conduit for nerve repair. The study enrolled 98 subjects with 136 nerve transections in the hand and prospectively randomized the repair to two groups: standard repair, either end-to-end or with a nerve graft, or repair using a polyglycolic acid conduit. Two-point discrimination was measured by a blinded observer at 3, 6, 9, and 12 months after repair. There were 56 nerves repaired in the control group and 46 nerves repaired with a conduit available for follow-up. Three patients had a partial conduit extrusion as a result of loss of the initially crushed skin flap. The overall results showed no significant difference between the two groups as a whole. In the control group, excellent results were obtained in 43 percent of repairs, good results in 43 percent, and poor results in 14 percent. In those nerves repaired with a conduit, excellent results were obtained in 44 percent, good results in 30 percent, and poor results in 26 percent (p = 0.46). When the sensory recovery was examined with regard to length of nerve gap, however, nerves with gaps of 4 mm or less had better sensation when repaired with a conduit; the mean moving two-point discrimination was 3.7 +/- 1.4 mm for polyglycolic acid tube repair and 6.1 +/- 3.3 mm for end-to-end repairs (p = 0.03). All injured nerves with deficits of 8 mm or greater were reconstructed with either a nerve graft or a conduit. This subgroup also demonstrated a significant difference in favor of the polyglycolic acid tube. The mean moving two-point discrimination for the conduit was 6.8 +/- 3.8 mm, with excellent results obtained in 7 of 17 nerves, whereas the mean moving two-point discrimination for the graft repair was 12.9 +/- 2.4 mm, with excellent results obtained in none of the eight nerves (p < 0.001 and p = 0.06, respectively). This investigation demonstrates improved sensation when a conduit repair is used for nerve gaps of 4 mm or less, compared with end-to-end repair of digital nerves. Polyglycolic acid conduit repair also produces results superior to those of a nerve graft for larger nerve gaps and eliminates the donor-site morbidity associated with nerve-graft harvesting.

Influence of lung volume on pulmonary microvascular pressure-volume characteristics

The pressure-volume (P-V) characteristics of the lung microcirculation are important determinants of the pattern of pulmonary perfusion and of red and white cell transit times. Using diffuse light scattering, we measured capillary P-V loops in seven excised perfused dog lobes at four lung volumes, from functional residual capacity (FRC) to total lung capacity (TLC), over a wide range of vascular transmural pressures (Ptm). At Ptm 5 cmH(2)O, specific compliance of the microvasculature was 8.6%/cmH(2)O near FRC, decreasing to 2.7%/cmH(2)O as lung volume increased to TLC. At low lung volumes, the vasculature showed signs of strain stiffening (specific compliance fell as Ptm rose), but stiffening decreased as lung volume increased and was essentially absent at TLC. The P-V loops were smooth without sharp transitions, consistent with vascular distension as the primary mode of changes in vascular volume with changes in Ptm. Hysteresis was small (0.013) at all lung volumes, suggesting that, although surface tension may set basal capillary shape, it does not strongly affect capillary compliance.

Angiotensin-converting enzyme, transforming growth factor beta(1), and interleukin 11 in the osteolytic lesions of Langerhans cell histiocytosis

OBJECTIVE

To assess the expression of potential osteoclastogenic and osteolytic factors in osteolytic lesions from patients with Langerhans cell histiocytosis.

DESIGN

Paraffin-embedded biopsy sections from 5 such archival cases underwent immunohistochemical procedures with antibodies to detect the following antigens: CD(1a), S100 protein, interleukin 11, the latency-associated peptide of transforming growth factor beta(1), and angiotensin-converting enzyme.

RESULTS

Commonalities noted include (1) the presence of multinucleated osteoclast-like giant cells, (2) the expression of interleukin 11 and latency-associated peptide antigens in lesional Langerhans cells, and (3) plasmalemmal immunoreactivity for angiotensin-converting enzyme antigen on non-Langerhans cell histiocytes and, on occasion, osteoclast-like giant cells and endothelial cells.

CONCLUSIONS

These observations suggest a possible pathogenetic sequence for osteolysis in Langerhans cell histiocytosis that involves angiotensin II formation, leading to the activation of latent transforming growth factor beta(1) and, in turn, to the enhanced production of interleukin 11, resulting in both osteoclastogenesis and impaired remodeling of bone.

Morphodensitometric analysis of protein kinase C beta(II) expression in rat colon: modulation by diet and relation to in situ cell proliferation and apoptosis

We have recently demonstrated that overexpression of PKC beta(II) renders transgenic mice more susceptible to carcinogen-induced colonic hyperproliferation and aberrant crypt foci formation. In order to further investigate the ability of PKC beta(II) to modulate colonocyte cytokinetics, we determined the localization of PKC beta(II) with respect to cell proliferation and apoptosis along the entire colonic crypt axis following carcinogen and diet manipulation. Rats were provided diets containing either corn oil [containing n-6 polyunsaturated fatty acids (PUFA)] or fish oil (containing n-3 PUFA), cellulose (non-fermentable fiber) or pectin (fermentable fiber) and injected with azoxymethane (AOM) or saline. After 16 weeks, an intermediate time point when no macroscopic tumors are detected, colonic sections were utilized for immunohistochemical image analysis and immunoblotting. Cell proliferation was measured by incorporation of bromodeoxyuridine into DNA and apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling. In the distal colon, PKC beta(II) staining was localized to the upper portion of the crypt. In comparison, proximal crypts had more (P < 0.05) staining in the lower tertile. AOM enhanced (P < 0.05) PKC beta(II) expression in all regions of the distal colonic crypt (upper, middle and lower tertiles). There was also an interaction (P < 0.05) between dietary fat and fiber on PKC beta(II) expression (corn/pectin > fish/cellulose, fish/pectin > corn/cellulose) in all regions of the distal colonic crypt. With respect to colonic cell kinetics, proliferation paralleled the increase in PKC beta(II) expression in carcinogen-treated animals. In contrast, apoptosis at the lumenal surface was inversely proportional to PKC beta(II) expression in the upper tertile. These results suggest that an elevation in PKC beta(II) expression along the crypt axis in the distal colon is linked to enhancement of cell proliferation and suppression of apoptosis, predictive intermediate biomarkers of tumor development. Therefore, select dietary factors may confer protection against colon carcinogenesis in part by blocking carcinogen-induced PKC beta(II) expression.

Selective depletion of bacteria alters but does not eliminate odors of individuality in Rattus norvegicus

To determine if odors of individuality are influenced by the removal of Gram-negative or Gram-positive gut bacteria, Long-Evans rats were trained in an operant olfactometer to discriminate between the odors of two individual conspecifics and their operant responses to three different odors in randomly presented probe trials were analyzed. Significantly more responses were made to the probe odors from two known individuals than to the probe odors from known individuals with their Gram-negative bacteria eliminated (Experiment 1) or their Gram-positive bacteria eliminated (Experiment 2). Responses to the probe odors from known rats with bacterial selectively depleted did not differ significantly from responses to probe odors from unknown rats. These results support the hypothesis that the urinary odor of an individual rat is altered by the removal of specific gut bacteria. In Experiments 3 and 4, subjects made fewer errors in learning to discriminate between the odors of the familiar rats whose bacteria had been selectively depleted than between the odors of unknown rats. This "savings effect" indicates that some components of the individual urinary odors were retained after the removal of specific gut bacteria. Thus, the eliminated bacteria were not totally responsible for the odors of individuality. The outcome of Experiments 3 and 4 also indicates that conclusions regarding the recognition of odors by rats should not be made on the outcome of probe trial experiments alone.

HER-2/neu protein-receptor-positive breast carcinoma: an immunologic perspective

Immunotherapy using a monoclonal antibody against the human epidermal growth factor receptor 2 protein, HER-2/neu, has proven to be clinically efficacious in about one-half of breast cancer patients who exhibit strong (3+) plasmalemmal immunoreactivity for this protein. The tumoricidal effect of this antibody relies in part upon antibody-dependent cell-mediated cytotoxicity. This report provides observations on certain factors or circumstances which could have an impact on this aspect of the therapeutic approach. These include: (1) concurrent medications; (2) the composition (immunophenotype) of peritumoral lymphocytes and the generally limited numbers of intratumoral T-lymphocytes/natural killer (NK) cells, monocytes, and neutrophilic granulocytes; (3) the presence of circulating HER-2/neu antigens which might bind the exogenous antibody and lead to immune complex formation; (4) the variable co-expression in the tumor of cytokines known to downregulate NK cell function (ie, transforming growth factor-beta1 [TGF-beta1] and platelet-derived growth factor [PDGF]-AB); and (5) the tumoral and/or stromal immunoreactivity for angiotensin-converting enzyme, which forms a part of one of the pathways for the activation of latent TGF-beta1 and for the biosynthesis of PDGF-AB. These observations provide an immunologic perspective for the use of monoclonal antibody therapy in HER-2/neu protein-receptor-positive breast carcinoma and suggest a role for the clinical laboratory in identifying potential avenues for additional manipulations of the immune system in individual cases in order to enhance the therapeutic response.

Flibanserin has anxiolytic effects without locomotor side effects in the infant rat ultrasonic vocalization model of anxiety

This study compared the effects of flibanserin, a novel 5-HT(1A) agonist/5-HT(2A) antagonist; diazepam, a traditional anxiolytic; and imipramine, a traditional antidepressant, on separation-induced ultrasonic vocalizations (USVs), locomotor behaviour, negative geotaxis and body temperature of 7 - 8-day-old rat pups. Flibanserin (5, 10, 25 and 50 mg kg(-1) s.c.) reduced USVs but had no effects on locomotor behaviour or negative geotaxis. Lower doses of flibanserin (0.5, 1, 2 and 4 mg kg(-1) s.c.) had no effect on any behaviour. Diazepam (0.25, 0.5, 1 and 2 mg kg(-1) s.c.) not only reduced the USVs but also increased rolling and increased the latency of the negative geotaxic response. Imipramine (10, 15, 20 and 30 mg kg(-1) s.c.) reduced USVs, increased total locomotor activity and rolling but had no effect on negative geotaxis. None of the drugs altered body temperature. Our data showed that flibanserin is as effective in reducing the USVs as diazepam and imipramine but has a lower incidence of motor side effects. This suggests that flibanserin might be effective for the treatment of mood disturbances such as anxiety.

Free nonvascularized composite nail grafts: an institutional experience

Free, nonvascularized composite nail grafts have been reported as a successful method to reconstruct nail deformities due to congenital anomalies or traumatic defects. The authors performed a decade review of their experience with nine patients who had had 10 free, nonvascularized composite nail grafts. Patient demographics, mechanism of injury, timing, site of reconstruction, and amount of nail to be replaced were all recorded. Results of nail growth in reconstructed nails were judged as excellent, good, fair, or poor on the basis of the appearance of the nail. The majority of reconstructed nails had half or more of the nail bed replaced. The 10 cases (mean follow-up of 1.8 years) that were reported had two excellent, three good, two fair, and three poor outcomes. There was no apparent relation between the successful outcome of the procedure and patient age, timing of reconstruction, or amount of nail bed replaced. Although the authors' experience suggests the unpredictable nature of this type of graft, it should be considered for patients who desire nail reconstruction and are not candidates for ablative or vascularized nail complex transfer procedures.

Continuous postoperative catheter irrigation is not necessary for the treatment of suppurative flexor tenosynovitis

The records of 75 patients admitted with pyogenic flexor tenosynovitis at two academic centers were reviewed. The functional outcomes of patients who received intraoperative irrigation only (n = 20) and those that had both intraoperative irrigation and continuous postoperative irrigation (n = 55) were compared. There were no statistically significant differences between the outcomes in the two groups.

Correction of pincer-nail deformity using dermal grafting

Pincer-nail syndrome has been described as distortion in the shape of the nails with excessive transverse curvature of the plate that increases from proximal to distal, leading to pinching and loss of soft tissue in the affected digit, resulting in severe pain. Many treatments have been recommended, but an effective long-term method that preserves the nail matrix has not been described. A method of dermal grafting under the nail matrix is described, and the results of treatment of six digits are reported. Five women and one man with an average age of 52 were treated. The affected digit was the thumb in four patients and the great toe in two patients. Follow-up averaged 25 1/2 months. The results were good in all cases with only one side of one nail remaining slightly curved. Pain was relieved in all cases, and complete adherence of the new nail plate occurred. Dermal grafting seems to provide excellent long-term treatment of the pincer-nail deformity with preservation of the nail matrix.

Sphingomyelin interfacial behavior: the impact of changing acyl chain composition

Sphingomyelins (SMs) containing homogeneous acyl chains with 12, 14, 16, 18, 24, or 26 carbons were synthesized and characterized using an automated Langmuir-type film balance. Surface pressure was monitored as a function of lipid molecular area at constant temperatures between 10 degrees C and 30 degrees C. SM containing lauroyl (12:0) acyl chains displayed only liquid-expanded behavior. Increasing the length of the saturated acyl chain (e.g., 14:0, 16:0, or 18:0) resulted in liquid-expanded to condensed two-dimensional phase transitions at many temperatures in the 10-30 degrees C range. Similar behavior was observed for SMs with lignoceroyl (24:0) or (cerotoyl) 26:0 acyl chains, but isotherms showed only condensed behavior at 10 and 15 degrees C. Insights into the physico-mechanical in-plane interactions occurring within the different SM phases and accompanying changes in SM phase state were provided by analyzing the interfacial area compressibility moduli. At similar surface pressures, SM fluid phases were less compressible than those of phosphatidylcholines with similar chain structures. The area per molecule and compressibility of SM condensed phases depended upon the length of the saturated acyl chain and upon spreading temperature. Spreading of SMs with very long saturated acyl chains at temperatures 30-35 degrees below T(m) resulted in condensed films with lower in-plane compressibilities, but consistently larger cross-sectional molecular areas than the condensed phases achieved by spreading at temperatures only 10-20 degrees below T(m). This behavior is discussed in terms of the enhancement of SM lateral aggregation by temperature reduction, a common approach used during domain isolation from biomembranes.

Cloning and expression of glycolipid transfer protein from bovine and porcine brain

Glycolipid transfer protein (GLTP) is a small (23-24 kDa), basic protein (pI congruent with 9.0) that accelerates the intermembrane transfer of various glycolipids. Here, we report the first cloning of cDNAs that encode the bovine and porcine GLTPs. The cDNA open reading frame for bovine GLTP was constructed by bridge-overlapping extension polymerase chain reaction (PCR) after obtaining partial coding cDNA clones by hot start, seminested, and rapid amplification of cDNA ends-PCR. The cDNA open reading frame for porcine GLTP was constructed by reverse transcriptase-PCR. The encoded amino acid sequences in the full-length bovine and porcine cDNAs were identical, consisting of 209 amino acid residues, and were nearly the same as the published sequence determined by Edman degradation. The cDNA encoded one additional amino acid at the N terminus (methionine), arginine at positions 10 and 200 instead of lysine, and threonine at position 65 instead of alanine. Expression of GLTP-cDNA in Escherichia coli using pGEX-6P-1 vector resulted in glutathione S-transferase (GST)-GLTP fusion protein. Regulation of growth and induction conditions led to approximately 50% of expressed fusion protein being soluble and active. Proteolytic cleavage of GST-GLTP fusion protein (bound to GST-Sepharose) and affinity purification resulted in fully active GLTP. Northern blot analyses of bovine tissues showed a single transcript of approximately 2.2 kilobases and the following hierarchy of mRNA levels: cerebrum > kidney > spleen congruent with lung congruent with cerebellum > liver > heart muscle. Reverse transcriptase-PCR analyses of mRNA levels supported the Northern blot results.

Cholinergic medial septum neurons do not degenerate in aged 129/Sv control or p75(NGFR)-/-mice

Cholinergic medial septum neurons express TrkA and p75 nerve growth factor receptor (p75(NGFR)) and interactions between TrkA and p75(NGFR) are necessary for high-affinity binding and signaling of nerve growth factor (NGF) through TrkA. In adult p75(NGFR)-deficient (-/-) mice, retrograde transport of NGF and other neurotrophins by these neurons is greatly reduced, however, these neurons maintain their cholinergic phenotype and size. Reduced transport of NGF has been proposed to play a role in Alzheimer's disease. Here, we investigated whether chronic and long-term absence of p75(NGFR) (and possibly reduced NGF transport and TrkA binding) would affect the cholinergic septohippocampal system during aging in mice. In young (6-8 months), middle aged (12-18 months), and aged (19-23 months) 129/Sv control mice the total number of choline acetyltransferase-positive medial septum neurons and the mean diameter and cross sectional area of the cholinergic cell bodies were similar. The cholinergic hippocampal innervation, as measured by the density of acetylcholinesterase-positive fibers in the outer molecular layer of the dentate gyrus was also similar across all ages. These parameters also did not change during aging in p75(NGFR) -/- mice and the number and size of the choline acetyltransferase-positive neurons and the cholinergic innervation density were largely similar as in control mice at all ages. These results suggest that p75(NGFR) does not play a major role in the maintenance of the number or morphology of the cholinergic basal forebrain neurons during aging of these mice. Alternatively, p75(NGFR) -/- mice may have developed compensatory mechanisms in response to the absence of p75(NGFR).

Inhibition of nitric oxide synthase reduces ultrasonic vocalizations of rat pups

The present study investigated the effects of drugs acting on the brain nitric oxide pathway on ultrasonic vocalizations, body temperature and locomotion in 7-8-day-old rat pups. Both a selective neuronal nitric oxide synthase (NOS) inhibitor (7-nitroindazole) and a non-selective NOS inhibitor (nitro-L-arginine-methyl ester, L-NAME) decreased the number of ultrasonic vocalizations in a dose-dependent manner. The non-selective NOS inhibitor, L-NAME, suppressed not only ultrasonic vocalizations but also locomotion. The inactive isomer of the NOS inhibitor, nitro-D-arginine-methyl ester (D-NAME), and the biological precursor of nitric oxide, L-arginine, had no effect on ultrasonic vocalizations or locomotion. These data indicate that drugs suppressing nitric oxide synthesis produced an anxiolytic effect in rat pups. However, only the selective NOS inhibitor, 7-nitroindazole, was 'anxioselective', i.e., reduced ultrasonic vocalizations without causing sedation. Increased synthesis of nitric oxide in the brain had no apparent behavioral effect in this model.

Dopaminergic modulation of rat pup ultrasonic vocalizations

The dopamine D(1) receptor agonist, R(+)-6-chloro-7, 8-dihydroxy-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrobromide (SKF 81297), the dopamine D(2)/D(3) receptor agonist, trans-(-)-4aR-4,4a,5,6,7,8,8a,9-octahydro-5-propyl-1H-pyrazolo[3, 4-g]quinoline hydrochloride (quinpirole), and the dopamine D(3) receptor agonist, (+/-)-7-hydroxy-dipropylaminotetralin hydrobromide (7-OH-DPAT) all reduced the frequency of isolation-induced infant rat ultrasonic vocalizations and lowered body temperature when compared to saline-injected controls. Ultrasonic vocalization rate was not affected by either the dopamine D(1) receptor antagonist, R(+)-2,3,4, 5-tetrahydro-8-iodo-3-methyl-5-phenyl-1H-3-benzazepin-7-ol hydrochloride (SCH 23390) or the dopamine D(2)/D(3) receptor antagonist, S(-)-raclopride-L-tartrate (raclopride) when given alone, nor did these antagonists block the ultrasonic vocalization reductions caused by the dopamine D(1) receptor agonist or the dopamine D(2)/D(3) receptor agonist. The dopamine D(2)/D(3) receptor antagonist but not the dopamine D(1) receptor antagonist blocked the dopamine D(3) receptor agonist's ultrasonic vocalization reduction. SKF 81297 reduced general activity while quinpirole and 7-OH-DPAT increased activity. Raclopride reversed quinpirole's reduction in body temperature, as well as 7-OH-DPAT's effects on body temperature, ultrasonic vocalizations, and activity. These results indicate that dopamine D(1), D(2)/D(3), and D(3) receptor agonists all reduce ultrasonic vocalizations by as yet undetermined mechanisms.