HCV RNA Genomic sequences and HCV-E2 glycoprotein in sural nerve biopsies from HCV-infected patients with peripheral neuropathy

AIMS

Peripheral neuropathy (PN), the major neurological complication of chronic HCV infection, is frequently associated with mixed cryoglobulinaemia (MC) and small-vessel systemic vasculitis. While humoral and cell-mediated immune mechanisms are suspected to act together in an aberrant immune response that results in peripheral nerve damage, the role of HCV remains largely speculative. The possible demonstration of HCV in peripheral nerve tissue would obviously assume important pathogenic implications.

METHODS

We studied sural nerve biopsies from 11 HCV-positive patients with neuropathic symptoms: five with and six without MC. In situ hybridization (ISH) and immunofluorescence studies were carried out to detect genomic and antigenomic HCV RNA sequences and HCV-encoded E2-glycoprotein, respectively.

RESULTS

Epineurial vascular deposits of E2-glycoprotein were found in four (80%) MC and in two (33.3%) non-MC patients, respectively. These findings were enhanced by the perivascular deposition of positive-, though not negative-strand replicative RNA, as also found in the nerve extracts of all patients. Mild inflammatory cell infiltrates with no deposits of immunoglobulins and/or complement proteins were revealed around small vessels, without distinct vasculitis changes between MC and non-MC patients.

CONCLUSIONS

These results indicate that nerve vascular HCV RNA/E2 deposits associated to perivascular inflammatory infiltrates were similar in chronically HCV-infected patients, regardless of cryoglobulin occurrence. Given the failure to demonstrate HCV productive infection in the examined sural nerve biopsies, nerve damage is likely to result from virus-triggered immune-mediated mechanisms.

Activation-induced cytidine deaminase in B cells of hepatits C virus-related cryoglobulinaemic vasculitis

Immunoglobulin variable region heavy chain (IgVH ) somatic gene diversification is instrumental in the transformation process that characterizes hepatitis C virus (HCV)-related B cell lymphoproliferative disorders. However, the extent to which activation-induced cytidine deaminase (AID), an enzyme essential for IgV gene somatic hypermutation (SHM), is active in cryoglobulinaemic vasculitis (CV) remains unclear. AID mRNA expression in the peripheral blood of 102 chronically hepatitis C virus (HCV)-infected patients (58 with and 44 without CV) and 26 healthy subjects was investigated using real-time reverse transcription-polymerase chain reaction (RT-PCR). The features of activation-induced cytidine deaminase (AID) protein and mRNA transcripts were explored in liver tissue biopsies and portal tracts isolated using laser capture microdissection. In chronically HCV-infected patients, AID mRNA expression was almost threefold higher in those with than in those without CV and sevenfold higher than in healthy subjects (median-fold: 6.68 versus 2.54, P = 0.03 and versus 0.95, P = 0.0003). AID transcript levels were significantly higher in polyclonal than in clonally restricted B cell preparations in either CV or non-CV patients (median-fold, 15.0 versus 2.70, P = 0.009 and 3.46 versus 1.58, P = 0.02, respectively). AID gene expression was found to be related negatively to age and virological parameters. AID protein was found in portal tracts containing inflammatory cells that, in several instances, expressed AID mRNA transcripts. Our data indicate that the aberrant expression of AID may reflect continuous B cell activation and sustained survival signals in HCV-related CV patients.

ProNGF\NGF imbalance triggers learning and memory deficits, neurodegeneration and spontaneous epileptic-like discharges in transgenic mice

ProNGF, the precursor of mature nerve growth factor (NGF), is the most abundant form of NGF in the brain. ProNGF and mature NGF differ significantly in their receptor interaction properties and in their bioactivity. ProNGF increases markedly in the cortex of Alzheimer's disease (AD) brains and proNGF\NGF imbalance has been postulated to play a role in neurodegeneration. However, a direct proof for a causal link between increased proNGF and AD neurodegeneration is lacking. In order to evaluate the consequences of increased levels of proNGF in the postnatal brain, transgenic mice expressing a furin cleavage-resistant form of proNGF, under the control of the neuron-specific mouse Thy1.2 promoter, were derived and characterized. Different transgenic lines displayed a phenotypic gradient of neurodegenerative severity features. We focused the analysis on the two lines TgproNGF#3 and TgproNGF#72, which shared learning and memory impairments in behavioral tests, cholinergic deficit and increased Aβ-peptide immunoreactivity. In addition, TgproNGF#3 mice developed Aβ oligomer immunoreactivity, as well as late diffuse astrocytosis. Both TgproNGF lines also display electrophysiological alterations related to spontaneous epileptic-like events. The results provide direct evidence that alterations in the proNGF/NGF balance in the adult brain can be an upstream driver of neurodegeneration, contributing to a circular loop linking alterations of proNGF/NGF equilibrium to excitatory/inhibitory synaptic imbalance and amyloid precursor protein (APP) dysmetabolism.

Nifedipine-morphine interaction: a further investigation on nociception and locomotor activity in mice

Nociception and locomotor activity were tested in mice (C57BL/6 and DBA/2 strains), receiving the dihydropyridine calcium-channel blocker nifedipine, alone or combined with morphine. The calcium antagonist did not change the reaction time to thermal stimulation (tail-flick test), when administered alone, but combinations of nifedipine and morphine prolonged tail-flick latencies less than did the opiate alone. Nifedipine decreased locomotion in both strains, reduced the hypermotility induced by morphine in C57 mice, and enhanced the locomotor depression induced by the opiate in DBA mice. A comparison of the effects of nifedipine with those of the non-calcium antagonist vasodilator, hydralazine, suggests that the interactions with morphine were not exclusively related to neuronal changes produced by calcium channel blockade, but also to haemodynamic factors. In fact, except for the lack of interference with morphine-induced hypermotility in C57 mice, hydralazine, given alone or in combination with morphine, produced effects similar to those of nifedipine.

Similar effects of nifedipine and hydralazine on anaesthesia and hypermotility induced by pentobarbitone in mice

Nifedipine, a dihydropyridine calcium channel blocker, and hydralazine, a non-calcium channel antagonist vasodilatator, enhanced pentobarbitone-induced sleeping time and reversed locomotor hyperactivity induced by a subhypnotic dose of the barbiturate in mice. The similarity of the behavioural effects, exerted by nifedipine and hydralazine, suggest that haemodynamic factors may play an important role in the interaction of calcium channel antagonists with barbiturates.

Chronic intracerebroventricular TLQP-21 delivery does not modulate the GH/IGF-1-axis and muscle strength in mice

OBJECTIVE

Biallelic ablation of VGF determines a dwarf phenotype. VGF precursor protein encodes for different biologically active peptides none of which has been related to growth or muscular abnormalities. Here we present the first attempt to fill this gap. We tested the hypothesis that a recently identified VGF-derived peptide, TLQP-21, shown to centrally modulate metabolic functions, could also modulate growth hormone (GH)-axis and muscle strength.

DESIGN

Adult male mice were chronically icv injected with TLQP-21 (15 microg/day for 14 days). Physiological, molecular and behavioral parameters related to the GH/IGF-1-axis were investigated.

RESULTS

Except for a reduction in the soleus weight, TLQP-21 did not affect GH/IGF-1-axis mediators, muscle strength and muscle weight.

CONCLUSIONS

Results collected exclude a role for TLQP-21 in modulating the GH/IGF1-axis and muscle functions. VGF-derived peptides involved in the dwarf phenotype of VGF-/- mice have to be identified yet.

Anti-allodynic efficacy of botulinum neurotoxin A in a model of neuropathic pain

Neuropathic pain is typified by injuries to the peripheral and central nervous system and derives from such causes as cancer, diabetes, multiple sclerosis, post-herpetic neuralgia, physical trauma or surgery, and many others. Patients suffering neuropathic pain do not respond to conventional treatment with non-steroidal anti-inflammatory drugs and show a reduced sensitivity to opiates often associated with serious side effects. Recently, it has been demonstrated that botulinum neurotoxin serotype-A (BoNT/A) is able to induce analgesia in inflammatory pain conditions. The goal of this research was to test if BoNT/A was able to relieve also neuropathic pain symptoms. By using chronic constriction injury of the sciatic nerve, a mouse model of neuropathic pain, we observed that peripheral administration of BoNT/A strongly reduced the mechanical allodynia associated with this neuropathy. Remarkably, a single non-toxic dose of BoNT/A was sufficient to induce anti-allodynic effects, which lasted for at least 3 weeks. This result is particularly relevant since neuropathic pain is poorly treated by current drug therapies. This communication enlarges our knowledge on potentially new medical uses of BoNT/A in efforts to ameliorate human health conditions, with very important implications in the development of new pharmacotherapeutic approaches against neuropathic pain.

TLQP-21, a VGF-derived peptide, increases energy expenditure and prevents the early phase of diet-induced obesity

The vgf gene has been identified as an energy homeostasis regulator. Vgf encodes a 617-aa precursor protein that is processed to yield an incompletely characterized panel of neuropeptides. Until now, it was an unproved assumption that VGF-derived peptides could regulate metabolism. Here, a VGF peptide designated TLQP-21 was identified in rat brain extracts by means of immunoprecipitation, microcapillary liquid chromatography-tandem MS, and database searching algorithms. Chronic intracerebroventricular (i.c.v.) injection of TLQP-21 (15 mug/day for 14 days) increased resting energy expenditure (EE) and rectal temperature in mice. These effects were paralleled by increased epinephrine and up-regulation of brown adipose tissue beta2-AR (beta2 adrenergic receptor) and white adipose tissue (WAT) PPAR-delta (peroxisome proliferator-activated receptor delta), beta3-AR, and UCP1 (uncoupling protein 1) mRNAs and were independent of locomotor activity and thyroid hormones. Hypothalamic gene expression of orexigenic and anorexigenic neuropeptides was unchanged. Furthermore, in mice that were fed a high-fat diet for 14 days, TLQP-21 prevented the increase in body and WAT weight as well as hormonal changes that are associated with a high-fat regimen. Biochemical and molecular analyses suggest that TLQP-21 exerts its effects by stimulating autonomic activation of adrenal medulla and adipose tissues. In conclusion, we present here the identification in the CNS of a previously uncharacterized VGF-derived peptide and prove that its chronic i.c.v. infusion effected an increase in EE and limited the early phase of diet-induced obesity.

[Obesity and lifestyles among teenagers in Apulia. Survey run by a team of general practitioners]

Obesity represents one of the most worrying public health concern of the last decades. The objective of the present work was to find out more about the real risky habits of teenagers, in order to think of specific educational programs. The research sample was composed of 721 respondents (aged 11-13 years old) attending the primary schools located in Martina Franca (TA). More than 70% of the sample was formed by normal weight individuals, 24.5% was composed of overweight individuals, 5.5% were obese. The relevant differences existing between normal weight and overweight individuals are basically due to the different daily meals organization and to the specific vegetable consumption habits. More than 83% of normal weight individuals have breakfast in the morning, while among the overweight only 75% do it (OR = 0.6; 95% IC: 0.4-0.9; p < 0.01); more than 94% of normal weight kids have snack breaks between the main meals, while only 82% of overweight respondents are used to do it (OR = 0.2; 95% IC: 0.15-0.43; p < 0.01). 36% of the overweight eat vegetables everyday, among the normal weight 45% eat them (chi2 = 12.5, p < 0.05). No relevant differences in the extra school time management. The main outcome of the present study is that kids basically follow a common eating behavior: high carbohydrates and proteins consumption, low fruit and vegetables consumption, few time spent in physical activities. This is why it is strongly recommended to develop educational programs targeted to individuals in this age range.

Pain sensitivity in mice lacking the Ca(v)2.1alpha1 subunit of P/Q-type Ca2+ channels

The role of voltage-gated Ca(2+) (Ca(V)) channels in pain mechanisms has been the object of intense investigation using pharmacological approaches and, more recently, using mutant mouse models lacking the Ca(V)alpha(l) pore-forming subunit of N-, R- and T-type channels. The role of P/Q-type channels in nociception and pain transmission has been investigated by pharmacological approaches but remains to be fully elucidated. To address this issue, we have analyzed pain-related behavioral responses of null mutant mice for the Ca(V)2.1alpha(1) subunit of P/Q-type channels. Homozygous null mutant Ca(V)2.1alpha(1)-/- mice developed dystonia at 10-12 days after birth and did not survive past weaning. Tested at ages where motor deficit was either absent or very mild, Ca(V)2.1alpha(1)-/- mice showed reduced tail withdrawal latencies in the tail-flick test and reduced abdominal writhes in the acetic acid writhing test. Adult heterozygous Ca(V)2.1alpha(1)+/- mice did not show motor deficits in the rotarod and activity cage tests and did not show alterations in pain responses in the tail-flick test and the acetic acid writhing test. Strikingly, they showed a reduced licking response during the second phase of formalin-induced inflammatory pain and a reduced mechanical allodynia in the chronic constriction injury model of neuropathic pain. Our findings show that P/Q-type channels play an antinociceptive role in sensitivity to non-injurious noxious thermal stimuli and a pronociceptive role in inflammatory and neuropathic pain states, pointing to an important role of Ca(V)2.1 channels in central sensitization.

Substituted tetraazaacenaphthylenes as potent CRF1 receptor antagonists for the treatment of depression and anxiety

Two isomers of the hexahydro-tetraazaacenaphthylene templates (1 and 2) are presented as novel, potent, and selective corticotropin releasing factor-1 (CRF1) receptor antagonists. In this paper, we report the affinity and SAR of a series of compounds, as well as pharmacokinetic characterization of a chosen set. The anxiolitic activity of a selected example (2ba) in the rat pup vocalization model is also presented.

Contrast and depth enhancement in two-photon microscopy of human skin ex vivo by use of optical clearing agents

We investigate the application of hyperosmotic optical clearing agents to improve the image contrast and penetration depth in two-photon microscopy of human dermis ex vivo. We show that the agents glycerol, propylene glycol, and glucose all convey significant improvements and we provide results on their dynamic behaviour and the reversibility of the effect. At suitable concentrations, such agents have the potential to be compatible with living tissue and may possibly enhance in-vivo deep-tissue imaging.

Formalin hindpaw injection induces changes in the [3H]prazosin binding to alpha1-adrenoceptors in specific regions of the mouse brain and spinal cord

Involvement of the alpha1-adrenoceptor subtypes in early and late phases of formalin pain was investigated by quantitative in vitro autoradiography in the spinal cord and brain structures of CD-1 mice. Total alpha1-adrenoceptors binding (including all alpha1-adrenoceptor subtypes) was assessed with [3H]prazosin; alpha(1B)-adrenoceptor was assessed with [3H]prazosin in the presence of 10 nM WB4101 to mask remaining alpha1-adrenoceptor subtypes. Early after formalin injection the alpha1-adrenoceptors (mainly alpha1B receptor) binding was reduced in the contralateral hind limb area of the somatosensory cortex and in the secondary motor cortex. A reduction occurred also in the ipsilateral laminae I-III of the spinal cord (both alpha1B- and non-alpha1B-adrenoceptors). Lately an increase of alpha1-adrenoceptors binding (mostly subtypes other than alpha1B) appeared in discrete amygdaloid and thalamic nuclei. These results provide the first description of changes at the level of central alpha1-adrenoceptors' binding during the formalin-induced pain in mice. Their distribution suggests that they may have a functional meaning.

Central injection of botulinum neurotoxins: behavioural effects in mice

Strains of Clostridium botulinum produce seven antigenically distinct botulinum neurotoxins (BoNTs) designated as serotypes A-G. All serotypes interfere with neural transmission by blocking the release of acetylcholine in cholinergic neurons. They cleave specific sites on proteins of the SNARE [soluble n-ethylmaleimide-sensitive factor (NSF) attachment protein receptor] complex, which play a key role in neuroexocytosis. This study assessed the behavioural effects due to central administration of BoNTs in mice. CD1 mice were injected intracerebroventricularly (icv) with sub-lethal doses of BoNT/A or /B and their behavioural responses in conditioning of active avoidance, object recognition test and pharmacologically induced locomotor activity were tested. Compared to control mice, BoNT-treated mice showed: (1) a reduced capacity to discriminate a novel object within a familiar environment; (2) an enhanced stimulant effect by scopolamine and a depressant effect by oxotremorine on locomotor activity. In contrast, central injection of BoNTs did not alter active avoidance acquisition. These results suggest an in vivo functional alteration due to the action of BoNTs directly administered into the central nervous system. The present data demonstrate that BoNTs may represent an analytical tool for studying the functional role of cholinergic neurons.

The interaction of tetrahydroisoquinoline derivatives with antinociceptive action of morphine and oxotremorine in mice

To extend our earlier data on synergistic action of tetrahydroisoquinolines and morphine, we have investigated the analgesic effects of 1,2,3,4-tetrahydroisoquinoline (TIQ) and its 1-methyl-(1-MeTIQ) and N-methyl (N-MeTIQ) analogs on analgesia induced by morphine and oxotremorine. 1-MeTIQ and N-MeTIQ induced a moderate, delayed and prolonged analgesic action measured in the tail-flick test in CD-1 mice; 1-MeTIQ and TIQ prolonged the opiate (morphine, 2.5 mg/kg i.p.) analgesia while TIQ and N-TIQ potentiated cholinergic (oxotremorine, 0.02 mg/kg i.p.) analgesia. The involvement of the opioid and noradrenergic systems in this effect is discussed.

'Tissue' transglutaminase ablation reduces neuronal death and prolongs survival in a mouse model of Huntington's disease

By crossing Huntington's disease (HD) R6/1 transgenic mice with 'tissue' transglutaminase (TG2) knock-out mice, we have demonstrated that this multifunctional enzyme plays an important role in the neuronal death characterising this disorder in vivo. In fact, a large reduction in cell death is observed in R6/1, TG2(-/-) compared with R6/1 transgenic mice. In addition, we have shown that the formation of neuronal intranuclear inclusions (NII) is potentiated in absence of the 'tissue' transglutaminase. These phenomena are paralleled by a significant improvement both in motor performances and survival of R6/1, TG2(-/-) versus R6/1 mice. Taken together these findings suggest an important role for tissue transglutaminase in the regulation of neuronal cell death occurring in Huntington's disease.

In vitro evaluation of antioxidant activity by electrophoresis and high performance liquid chromatography

Two methods for the analysis of antioxidants, based on polyacrylamide gel electrophoresis (PAGE) and gel permeation high performance liquid chromatography (HPLC) were developed. Both of them exploit the variations of the signal (band or peak) given by human serum albumin (0.2% w/v in 100 mM sodium phosphate pH 7) upon oxidation with hypochlorite (1% of a solution containing 4% active Cl), quantitatively determined by densitometric analysis or peak integration. Based on such changes, two formulas were defined which allowed the determination of the antioxidant activity of ascorbic acid (EC(50,PAGE)=4.8x10(-4) M, EC(50,HPLC)=3.6x10(-4) M), glutathione (EC(50,PAGE)=1.5x10(-4) M, EC(50,HPLC)=2.0x10(-4) M) and melatonin (EC(50,PAGE)=5.2x10(-4) M, EC(50,HPLC)=3.2x10(-4) M), chosen as reference compounds. A good correlation was found between the activities of these substances in the two assays, which are also in good agreement with literature data, indicating that the two methods are essentially equivalent. These assays could be useful for the screening of new antioxidant drugs for pathological conditions such as cataract, rheumatic diseases, atherosclerosis and Alzheimer's disease.

Shuttle-box avoidance learning in mice: improvement by glucose combined with stimulant drugs

Glucose was tested alone or in combination with two stimulant drugs, amphetamine and nicotine, in mice of the CD-1 strain subjected to five daily shuttle-box training sessions. Pretraining intraperitoneal administration of glucose (50 or 100 mg/kg) had no effect, while amphetamine and nicotine, given alone, significantly improved avoidance acquisition at a dose of 0.5 mg/kg, but not 0.025 mg/kg. Significant improvement of avoidance learning was also produced by a combination of glucose with the lower dose of amphetamine or nicotine. This enhancing action, produced by a combination of glucose and stimulant drugs, at doses ineffective by themselves, might be due to a concomitant cholinergic and dopaminergic activation, induced by glucose and stimulant drugs, respectively.

MK-801-induced disruptions of one-trial inhibitory avoidance are potentiated by stress and reversed by naltrexone

Five experiments were carried out to investigate opioid and NMDA receptor-mediated responses to one-trial inhibitory avoidance training in CD1 mice. In the first experiment immediate posttraining intraperitoneal administration of the noncompetitive N-methyl-d-aspartate (NMDA) receptor antagonist MK-801 impaired the performance of mice. The effects of MK-801 were time-dependent (they were absent in mice injected with the drug starting 120 min after training). No effect was evident in no-foot-shock groups, showing lack of proactive influence of the treatment on performance. In the second experiment preexposure of the mice to the testing apparatus decreased the effects of MK-801. In the the third experiment naltrexone antagonized the effects of MK-801, suggesting an involvement of opioid neurons. In the fourth experiment immediate posttraining immobilization stress exerted a potentiating effect on the performance of MK-801-injected animals. In the fifth experiment the potentiation of the impairing effect of MK-801 induced by immobilization stress was antagonized by naltrexone.

Effects of postnatal manipulation on nociception and morphine sensitivity in adult mice

The long-term effects of postnatal manipulation on nociception were studied in NMRI albino male mice. During the first two weeks of life, pups were removed from their cage and deprived of maternal/nest odour for 15 min/day. To evaluate pain sensitivity, adult mice exposed to this postnatal manipulation (CB group) were tail flick and formalin tested for acute and tonic pain, respectively. CB mice showed a reduced pain sensitivity both in tail-flick and in formalin tests in comparison with control animals. Moreover, responsiveness to morphine (MO 1.0, 2.5, and 5.0 mg/kg, i.p.) in young (35 days old) and adult (90 days old) postnatally manipulated animals was evaluated with the tail-flick test: a decrease of the antinociceptive effects induced by morphine both in young and adult males was observed in postnatally manipulated animals. Morphine induced significant analgesic effects in control mice at doses lower than those affecting nociceptive thresholds both in young and adult CB mice. In addition, young animals showed a higher sensitivity to morphine than adults, independently of postnatal manipulation. The long-term effects of postnatal manipulation on nociception are discussed in terms of involvement of the opioid system and of the characteristics of pup manipulation.

Oxotremorine-induced modifications of the behavioral and neuroendocrine responses to formalin pain in male rats

In the present investigation, the antinociceptive effects of the muscarinic cholinergic agonist, oxotremorine, were evaluated in rats using the formalin test. In Expt. 1, two oxotremorine concentrations (0.1 and 0.2 mg/kg) and two administration times (15 and 1 min before formalin injection) were chosen. All spontaneous and formalin-evoked behavioral responses were considered. In Expt. 2, only the higher concentration of oxotremorine (0.2 mg/kg) was administered 15 or 1 min before the formalin test. The animals were killed 15, 30 or 60 min after formalin treatment. Blood was collected from the trunk to determine corticosterone plasma levels. Some brain areas (hypothalamus, septum and periaqueductal gray matter) were dissected for determination of the beta-endorphin content. Oxotremorine induced a dose- and time-dependent reduction of all formalin-evoked responses: licking was decreased during both the first and second phases of the formalin test, flexing was decreased during the second phase by the higher concentration only and paw-jerk was decreased during the first phase by both concentrations. Rearing and line-crossing were significantly decreased by oxotremorine while exploratory activity was only partially reduced; self-grooming was increased. These effects on exploratory activity and self-grooming were abolished by formalin treatment. beta-endorphin content in the septum was increased by oxotremorine administered 15 min, but not 1 min, before formalin-treatment. beta-endorphin in the hypothalamus increased in all formalin-treated groups independently of oxotremorine administration. These results confirm, and extend to tonic pain, the analgesic effect exerted by oxotremorine on phasic responses. Because of the different effects on each formalin-induced response, they also indicate both spinal and supraspinal CNS sites of action.

Effects of the novel acetylcholinesterase inhibitor N-octyl-1,2,3, 4-tetrahydro-9-aminoacridine on locomotor activity and avoidance learning in mice

The acetylcholinesterase reversible inhibitor N-octyl-1,2,3, 4-tetrahydro-9-aminoacridine (THA-C8) is a new synthesized derivative of tacrine (THA) characterized by an alkyl chain in the molecular structure which ameliorates the penetrability of the compound into the central nervous system. THA-C8 (0.1-5 mg/kg) significantly reduced spontaneous locomotor activity in CD1 mice at a dose of 3 mg/kg. Moreover, THA-C8 (0.2-2 mg/kg) significantly improved shuttle-box avoidance acquisition at doses (0.25, 0.3, 1 mg/kg) not affecting locomotion and that are much lower than the doses reported to be effective for THA in animal models. From the data reported it seems that the new compound could be interesting for therapeutic purposes.

Attenuation by nimodipine of amitriptyline-induced avoidance impairment in mice

The effects of the dihydropyridine calcium channel blocker nimodipine on avoidance impairment induced by the tricyclic antidepressant amitriptyline were assessed during shuttle-box training and in previously trained mice of the DBA/2 strain. Nimodipine (0, 0.5, 1, 2.5, or 5 mg/kg) had no effect alone, but attenuated the avoidance impairment induced by 5 mg/kg amitriptyline on avoidance acquisition, as well as on a previously learned avoidance response. The avoidance improving action of the calcium channel blocker was less evident in mice receiving a larger dose (7.5 mg/kg) of the antidepressant drug. The effect of nimodipine did not appear to be specifically related to the avoidance impairment induced by amitriptyline, because the calcium antagonist also attenuated the avoidance impairing action of the neuroleptic chlorpromazine. The avoidance impairment induced by amitriptyline and chlorpromazine, and the related ameliorating action of nimodipine, seem imputable to drug effects on the performance of the avoidance response, rather than to interferences with learning processes. The results suggest that, in the case of concomitant administration, nimodipine could alleviate adverse side effects of tricyclic antidepressant, i.e., psychomotor disturbances.

Intrathecal oxotremorine affects formalin-induced behavior and spinal nitric oxide synthase immunoreactivity in rats

The present research was undertaken to investigate, by behavioral and immunohistochemical methods, the effects of intrathecal (i.th.) injection of the muscarinic agonist oxotremorine on the response to the long-lasting nociceptive stimulus induced by injection of formalin into the rat hind paw. Formalin injection induced a biphasic, pain-induced behavioral response (paw jerks), as well as an increase in the number of nitric oxide (NO) synthase-labeled neurons in laminae I-III, IV, and X, but not in laminae V-VI. Oxotremorine (0.1-10 ng, i.th.) inhibited paw-jerk frequency in both phases of formalin-induced behavior. The immunohistochemical results showed that i.th.-injected oxotremorine differently affected the level of NO synthase in lumbar part of the spinal cord: no change or increase after the dose of 1 ng, and a significant reduction of nitric oxide synthase neurons after the higher dose (10 ng). These results evidenced a role of cholinergic system in the modulation of tonic pain and in nitric oxide synthase expression at the spinal cord level, which further suggests that these two systems could be involved in phenomena induced by long-lasting nociceptive stimulation.

Antinociception after both peripheral and intrathecal injection of oxotremorine is modulated by spinal nitric oxide

The present study investigated the role of spinal nitric oxide (NO) in the antinociception induced by intraperitoneal (i.p.) and intrathecal (i.th.) injection of oxotremorine. The experiments were carried out on male Wistar rats, which had cannulas chronically implanted in the lumbar enlargement of the spinal cord. Antinociceptive effects were evaluated using a tail-flick and a paw pressure test. To raise the spinal NO level, the rats received the NO donor, 3-morpholino-sydnonimine (SIN-1, 10 and 100 microg/5 microl); to lower the NO level, the inhibitor of NO synthase, N-nitro-L-arginine methyl ester (L-NAME, 50 and 400 microg/5 microl), was administered. Both those substances were injected i.th. Systemic injections of oxotremorine (0.02 and 0.1 mg/kg) produced a significant increase in the thermal nociceptive threshold, while the mechanical threshold was affected only by the higher dose (0.1 mg/kg) of the muscarinic agonist. I.th. injections of oxotremorine (0.1 ng, 1 ng, 1 microg/5 microl) produced significant antinociception in both those tests. I.th. administration of SIN-1 in doses which themselves did not affect the nociceptive threshold antagonized both the peripheral and central oxotremorine antinociception. I.th. administration of L-NAME (50 and 400 microg/5 microl) did not change the nociceptive threshold, but dose-dependently potentiated the effects of oxotremorine injected i.p. in both tests; however, the effect of i.th. administration of oxotremorine was potentiated only in the tail-flick test. Our results demonstrate that irrespective of the way of its injection, the antinociceptive effect of oxotremorine is modulated by activity of the spinal NO. Moreover, our results further support the hypothesis that NO present in the spinal cord exerts pronociceptive effects.

Shuttle-box avoidance learning in mice: improvement by combined glucose and tacrine

Glucose and the acetylcholinesterase inhibitor tacrine were tested, alone and in combination, in mice of the CD-1 strain subjected to five daily shuttle-box training sessions. Pretraining intraperitoneal administration of glucose alone (50-400 mg/kg) had no significant effect, while tacrine alone (0.5-3 mg/kg) improved avoidance acquisition at the dose of 2 mg/kg only. Significant avoidance learning improvements were instead produced by 50 or 100 mg/kg glucose combined with 0.5 or 1 mg/kg tacrine. The effects on shuttle-box avoidance acquisition produced by glucose combined with a cholinomimetic agent support the hypothesis that cholinergic mechanisms may be involved in the action of glucose on learning and memory. However, the main finding of the present study is related to the enhancement by glucose of the learning improving action of a drug clinically used as cognitive enhancer.

Prevention of amitriptyline-induced avoidance impairment by tacrine in mice

The effects of two cognition enhancers on avoidance impairment induced by the tricyclic antidepressant amitriptyline were assessed during shuttle-box avoidance acquisition and in previously trained mice of the DBA/2 strain. The nootropic agent piracetam (50, 100 or 200 mg/kg, i.p.) had slight or no effect in mice receiving amitriptyline (5 or 10 mg/kg, i.p.). Conversely, the acetylcholinesterase inhibitor tacrine (0.5, 1, 2 or 3 mg/kg, i.p.) prevented the avoidance impairment induced by 5 mg/kg amitriptyline on shuttle-box avoidance acquisition as well as on a previously learned avoidance response. The avoidance disrupting action produced by 10 mg/kg of the antidepressant drug was not affected by the anticholinesterase drug. The preventing action of tacrine seems specifically related to the avoidance impairment induced by amitriptyline, since the acetylcholinesterase inhibitor did not reduce, but enhanced the avoidance impairing action of the neuroleptic chlorpromazine. Taken together, the results indicate that amitriptyline-induced avoidance impairment, and the related preventing action of tacrine, may be ascribed to drug effects on the performance of the avoidance response, rather than to interferences with learning processes.

Studies on a new series of THA analogues: effects of the aromatic residues that line the gorge of AChE

A series of N-monoalkylsubstituted 1,2,3,4-tetrahydro-9-aminoacridines have been prepared after modelling simulation of the AChE-inhibitor complex. Molecular modelling has predicted a number of hydrophobic residues to be involved in the catalytic mechanism of this interaction between the binding sites of AChE and this series of aminoacridines. In these compounds the acridine moiety becomes sandwiched between the rings of PHE330 and TRP84. In particular, the alkyl chain shows the important role of aromatic groups as binding sites. Their in vitro inhibitory properties (enzyme from Electrophorus electricus) confirm the aromatic groups as a general and significant characteristic of the mechanism of AChE inhibition.

Nitric oxide synthase inhibitors enhance the antinociceptive effects of oxotremorine in mice

Recent studies suggested that the L-arginine/nitric oxide (NO)/cyclic GMP pathway is involved in the modulation of pain perception. The present experiments were undertaken to find out the role of this pathway in the antinociception induced by oxotremorine administration. Male mice of the CD-1 strain were injected with different doses of the muscarinic agonist oxotremorine (0.005, 0.01, 0.02, 0.03 mg/kg i.p.) 5 min after the administration of saline solution or the inhibitors of NO synthase NG-nitro-L-arginine methyl ester (L-NAME: 10 and 20 mg/kg, i.p.) or NG-nitro-L-arginine (N-ARG: 10 and 20 mg/kg i.p.). Oxotremorine induced a dose- and time-dependent analgesic effect in mice, which was significantly increased by L-NAME and N-ARG administration. Either doses of the NO inhibitors given alone had no effect on the nociceptive threshold. The present results show a role of NO in the antinociception mediated by the muscarinic receptor stimulation and suggest that it exerts an inhibitory action on cholinergic analgesia.

Time-related effects of stress on cholinergic sensitivity

The effect of the administration of the muscarinic cholinergic agonist oxotremorine on locomotor activity was investigated in DBA/2 mice subjected to chronic restraint stress of different durations (120 min daily for 10, 14 or 18 days). Oxotremorine induced a depressant effect on locomotion, which was reduced after 10 and 14 days of restraint, but not after a 18-day restraint stress. Acetylcholine (ACh) content was significantly reduced in prefrontal cortex after 10 and 14 days of stress but returned to control values after 18 days of restraint. No changes in ACh content were observed in nucleus accumbens and striatum. These results are discussed in terms of possible changes in muscarinic receptor sensitivity.

Reunion of separated sibling mice: neurobiological and behavioral aspects

Outbred albino NMRI male mice encountering a brother in adulthood, after a long period of separation, show an opioid-dependent increase in pain threshold. Unrelated and unfamiliar males show no similar changes in pain sensitivity. This study investigates which kind of stimuli from the partner may be responsible for such a modification at the neural level. The tail-flick test is used as a measure of pain sensitivity. Exposure to the scent of the brother's home cage, as well as exposure to visual, olfactory and auditory stimuli and partial physical contact with the related male, are not sufficient to induce changes in nociception. Physical affiliative contact between males is higher in sib than in nonsib pairs, and a positive correlation exists in sib pairs between huddling behavior and pain sensitivity at the end of a 2-h social session. Siblings injected with naloxone, an opioid receptor blocker, show a decrease in social behaviors involving physical contact. These results suggest that physical affiliative contact between sibling mice may be responsible for the enhancement of nociceptive threshold.

Locomotor activity pattern induced by diazepam in control and caffeine-treated mice

The effect of diazepam on locomotor activity was tested by measuring the number of crossings between two compartments of a toggle-floor box, in control mice (water drinking) and in mice receiving caffeine solution (0.5 g/I) instead of drinking water. In control mice, diazepam did not produce any significant change in total activity measured on the whole 60-min test, but animals showed phases of increased activity broken by periods of immobility. After chronic ingestion (18 days) of caffeine, doses of 0.5, 1 and 2 mg/kg ip diazepam significantly increased total locomotor activity. Caffeine slightly reduced diazepam-induced immobility and increased the frequency of crossings in active periods. Taken together, these two effects may explain the significant increase in total activity induced by diazepam in caffeine-treated mice. Mixed stimulatory-depressant action was also produced by 3 mg/kg diazepam, a dose that slightly decreased the total activity.

Enhancement by nifedipine of cholinergic-induced depression of locomotor activity in mice

The dihydropyridine calcium channel blocker nifedipine did not affect spontaneous locomotor activity in mice when given alone but enhanced the depressant effects of the muscarinic receptor agonist oxotremorine and of the acetylcholinesterase inhibitor physostigmine. Such a behavioral depression might be due to neuronal changes induced by central calcium channel blockade combined with cholinergic activation. However, an involvement of hemodynamic factors, related to peripheral vasodilatation, cannot be excluded as locomotor depressant effects were also exerted by combinations of the two cholinomimetic agents with hydralazine, a non-calcium antagonist vasodilator.

Attenuation of cholinergic analgesia by nifedipine

Nociception was tested in mice receiving oxotremorine or physostigmine either after the dihydropyridine calcium channel blocker nifedipine or the non-calcium antagonist vasodilator hydralazine. Nifedipine did not change the reaction time to thermal stimulation (tail-flick test), but attenuated the prolonging action on tail-flick latencies exerted by the two cholinomimetic agents. Hydralazine had no effect alone nor modified the action of cholinomimetics. The results suggest that attenuation of cholinergic analgesia by nifedipine might be related to not yet defined neuronal changes produced by calcium channel blockade, but changes in the pharmacokinetics of oxotremorine and physostigmine cannot be ruled out.

Endogenous opioids: a proximate reward mechanism for kin selection?

The kin selection theory predicts that individuals would behave differently toward one another, depending on their genetic relatedness. Proximate mechanisms have been postulated to exist helping the individual to discriminate what is good or bad for him. Opioids have been discovered to be involved in the mediation of reinforcement, in particular they underlay social emotion. In this study it is shown that pain sensitivity decreased in male mice interacting with siblings following 2 months of separation; this analgesic response was antagonized by naloxone administration. Interaction with unknown and unrelated subjects did not change the nociceptive threshold. These results suggest that interacting with kin is an adaptive situation reinforced, at the neural level, by the release of endogenous opioids.

Effects of oxotremorine on inhibitory avoidance behaviour in two inbred strains of mice: interaction with 5-methoxy-NN-dimethyltriptamine

The effects of the cholinergic muscarinic agonist, oxotremorine (0.005, 0.01, 0.02 and 0.04 mg/kg), the serotonergic agonist, 5-methoxy-NN-dimethyltriptamine (5-MeODMT) (0.5, 1 and 2 mg/kg), and their combination, were investigated in C57BL/6 and DBA/2 mice using a one-trial inhibitory avoidance task, drug treatment being given immediately after the acquisition trial. Post-trial administration of oxotremorine facilitated, while post-trial administration of 5-MeODMT inhibited memory retention of both strains in a dose-dependent fashion. The DBA/2 strain was more affected by oxotremorine than the C57BL/6 mice; no strain-dependent sensitivity to serotonergic agonist administration was observed. In both strains, the combination of oxotremorine plus 5-MeODMT inhibited the performance improvement shown by the administration of the cholinergic agonist alone. The facilitatory role of cholinergic stimulation on retention performance was confirmed and an inhibitory action of the serotonergic system on memory processes was suggested. Moreover, the present results support a functional interaction between cholinergic and serotonergic systems on memory consolidation.

Role of anxiety in subordinate male mice sexual behavior

Dominant and subordinate male mice behave differently when exposed to a female, with subordinates showing impairment of their sexual performance in the presence of the male antagonist. In the present study, we investigate whether these rank-related behavioral differences can be modified by an anxiolytic treatment. In a first experiment, diazepam (0.25 mg/kg) improves the performance of subordinate mice toward the female, as shown by the increase of proxemic behavior, anogenital sniffing, and social grooming of the female. Social grooming of the female is the only behavior modified by a higher dose of the anxiolytic drug (0.5 mg/kg). A second experiment, in which dominant and isolated mice are subjected to the same experimental procedure, demonstrates that social behavior of these two classes of males is not affected by the pharmacological treatment. The results are discussed in terms of the advantages of using subordinate males in such a sexual context as a model for the study of anxiolytic drugs.

Length of social deprivation differently affects free-choice morphine consumption in C57BL/6J mice

The effects of social deprivation on morphine consumption in C57BL/6J mice were investigated. Social or isolated animals (length of isolation: 7, 12, 17 days) were submitted to a free-choice between water and morphine hydrochloride solution (0.5 mg/ml). Isolation affects morphine consumption, with solitary housed mice drinking more morphine solution than socially housed animals. Moreover the amount of morphine intake depends on the duration of the isolation period to which mice are subjected. The importance of environmental factors on opiate consumption may be considered in terms of the possible implications of drug addiction in humans.

Serotonergic influence on cholinergic-induced analgesia: differences in two inbred strains of mice

C57BL/6 (C57) and DBA/2 (DBA) inbred mice showed different analgesic responses to cholinergic stimulation. The simultaneous administration of muscarinic and serotonergic agonists, oxotremorine and 5-methoxy-NN-dimethyltryptamine (5-MeODMT), lowered the antinociceptive effect of the cholinergic drug in DBA mice, while no effects were detectable in the C57 strain. These results suggest a strain-dependent behavioural effect of the interaction of cholinergic and serotonergic neuronal systems.

Amygdala and dorsal hippocampus lesions block the effects of GABAergic drugs on memory storage

These experiments examined the effects of posttraining systemic administration of the GABAergic agonist muscimol and the GABAergic antagonist bicuculline on retention in mice with bilateral lesions of the amygdala, dorsal hippocampus or caudate nucleus. Unoperated male CD1 mice and mice with either sham lesions or electrolytically induced lesions of these 3 brain regions were trained in a one-trial inhibitory avoidance task and, immediately after training, received i.p. injections of either muscimol, (1.0, 2.0 or 3.0 mg/kg), bicuculline, (0.25, 0.5 or 1.0 mg/kg), or control solutions. Retention was tested 24 h after training. Lesions of the 3 brain regions produced comparable impairment of retention. In the unoperated controls and sham controls muscimol and bicuculline produced dose-dependent impairment and enhancement, respectively, of retention. The drug effects on retention were blocked by lesions of the amygdala and hippocampus, but were not blocked by lesions of the caudate nucleus. These findings are consistent with other recent evidence suggesting that the amygdala and hippocampus are involved in mediating posttraining neuromodulatory influences on memory storage.

Reduction of oxotremorine-induced analgesia after chronic but not acute restraint stress

The analgesic response (tail-flick latency) induced by the muscarinic cholinergic agonist oxotremorine was investigated in DBA/2 mice exposed to acute (a single 2 h session) and chronic (2 h once daily for 10 days) restraint stress. While a single exposure to stress did not influence the antinociceptive effects of the cholinergic agonist, chronic stress induced a clear-cut reduction of the oxotremorine-induced analgesia. The results show an involvement of cholinergic mechanisms in the adaptive modulation of nociception after chronic stressful events.

Deltorphin, a naturally occurring peptide with high selectivity for delta opioid receptors, improves memory consolidation in two inbred strains of mice

Deltorphin, a heptapeptide that selectively binds to delta receptors, was intracerebroventricularly administered to mice belonging to the strains C57BL/6 and DBA/2 immediately after training in a one-trial inhibitory avoidance task. The retention performance of both strains was improved by the peptide administration, with DBA mice being more sensitive to this effect. The results show different effects of delta and mu receptor agonists on memory consolidation and of strain differences in number and/or distribution of delta opioid receptors in the brain.

Chronic administration of phosphatidylserine during ontogeny enhances subject-environment interactions and radial maze performance in C57BL/6 mice

A longitudinal behavioral study was performed in mice exposed to the bovine brain phospholipid phosphatidylserine (BC-PS) from birth until sixty days. Examination of treated and control pups revealed no effect of the treatment on body weight nor on sensorimotor reflexes. At one and two months of age, when placed in an open field and, particularly, in the presence of a novel object, treated mice were found more interactive with their environment than control mice. Finally, when submitted to a radial eight-arm maze problem, choice accuracy was higher and maze-running strategies more adaptive in treated than in control adult mice. These results suggest a stimulating effect of the treatment on subject-environment interactions during ontogeny underlying improved cognitive abilities in adulthood.

Age-related cholinergic drug effects on analgesia in two inbred strains of mice

The two inbred strains of mice C57BL/6 and DBA/2 are characterized by a different behavioral reactivity to cholinergic agents during development. The present experiment revealed that the strain-dependent differences in cholinergic-mediated analgesia during development disappeared during adult life. In fact, oxotremorine administration (0.0025 and 0.005 mg/kg) exerted the same analgesic effect in both strains at 6 months of age, in contrast with the finding of the lack of any effect of the drug in C57 mice at two months of age in comparison with DBA.