A single subanesthetic dose of ketamine relieves depression-like behaviors induced by neuropathic pain in rats.

BACKGROUND: Chronic pain is associated with depression. In rodents, pain is often assessed by sensory hypersensitivity, which does not sufficiently measure affective responses. Low-dose ketamine has been used to treat both pain and depression, but it is not clear whether ketamine can relieve depression associated with chronic pain and whether this antidepressant effect depends on its antinociceptive properties. METHODS: The authors examined whether the spared nerve injury model of neuropathic pain induces depressive behavior in rats, using sucrose preference test and forced swim test, and tested whether a subanesthetic dose of ketamine treats spared nerve injury-induced depression. RESULTS: Spared nerve injury-treated rats, compared with control rats, showed decreased sucrose preference (0.719 ± 0.068 (mean ± SEM) vs. 0.946 ± 0.010) and enhanced immobility in the forced swim test (107.3 ± 14.6s vs. 56.2 ± 12.5s). Further, sham-operated rats demonstrated depressive behaviors in the acute postoperative period (0.790 ± 0.062 on postoperative day 2). A single subanesthetic dose of ketamine (10 mg/kg) did not alter spared nerve injury-induced hypersensitivity; however, it treated spared nerve injury-associated depression-like behaviors (0.896 ± 0.020 for ketamine vs. 0.663 ± 0.080 for control rats 1 day after administration; 0.858 ± 0.017 for ketamine vs. 0.683 ± 0.077 for control rats 5 days after administration). CONCLUSIONS: Chronic neuropathic pain leads to depression-like behaviors. The postoperative period also confers vulnerability to depression, possibly due to acute pain. Sucrose preference test and forced swim test may be used to compliment sensory tests for assessment of pain in animal studies. Low-dose ketamine can treat depression-like behaviors induced by chronic neuropathic pain.

Prostaglandin E2 (PGE2) increases the number of rat bone marrow osteogenic stromal cells (BMSC) via binding the EP4 receptor, activating sphingosine kinase and inhibiting caspase activity.

Prostaglandin E(2) (PGE(2)) is bone-anabolic, i.e. stimulates bone formation and increases bone mass. In this study, we explored possible intracellular mechanisms of its increase of osteogenic cells in rat bone marrow. Adherent rat bone marrow cells were counted after 12-48 h or cultured for 21 days and mineralized nodules were counted. Also, apoptosis of marrow cells was measured after in vivo PGE(2) injection. PGE(2) (100 nM) increased 2-3 fold the number of adherent BMSC, an effect which was mediated via binding the EP(4) receptor since it was mimicked by forskolin and 11-deoxy-prostaglandin E(1) (PGE(1)) and was blocked by DDA and L-161982 (EP(4) antagonist). PGE(2) stimulated sphingosine kinase (SPK) activity since its effects were blocked by DMS (SPK inhibitor) and mimicked by SPP (SPK product). PGE(2) reduced the activity of caspase-3 and -8 in BMSC and their inhibitors increased BMSC number and nodule formation. In vivo, PGE(2) prevented the increase in the apoptosis of bone marrow cells caused by indomethacin. We propose that PGE(2) exerts an anti-apoptotic effect on BMSC, thereby increasing their number and subsequent osteoblastic differentiation. Such an effect could explain how PGE(2) stimulates bone formation in vivo.

The effect of mianserin add-on, on the intensity of opioid withdrawal symptoms during detoxification program--a randomized, double blind, placebo controlled, prospective study.

BACKGROUND: Based on pre-clinical studies regarding the interaction of various antidepressant drugs with the opioid system, we designed a clinical study to be carried out in the 'in-patient detoxification unit' within a large community centre for treatment of drugs dependent people. We evaluated the effect of mianserin add-on, on the intensity of opioid withdrawal symptoms in opiate dependent subjects undergoing medication-supported physical detoxification and integrated psychosocial and psychotherapeutic intervention for the treatment of dependence. METHODS: Mianserin (or placebo) was added to the routine medication protocol, during the 3-week in-patient phase of detoxification in a prospective, randomized, double blind, placebo controlled study. Mianserin (or placebo) was continued after discharge and patients were followed up for 3 months in order to evaluate relapse rates. Opiate withdrawal symptoms were assessed during the first 10 days, while depression and anxiety were assessed throughout the 3 months of study. RESULTS: From day 2 onward, patients in the study group showed significantly lower withdrawal symptoms than the control group patients and reached this peak faster (study group 2.8 days, control group 3.2 days, p<0.001). However, drop out rates were higher in the study group throughout the study period and only 13% of the study group patients, compared to 30% of the control group patients reached the end point. CONCLUSION: Though adding mianserin to the medication treatment during detoxification of opiate-dependent persons attenuated significantly both the intensity and the duration of withdrawal symptoms, the overall drop out rate was negatively influenced in the study group compared to the control group and fewer patients completed the study. Further study is needed in order to establish the origin of the paradox of higher drop out rates in the presence of attenuated intensity and duration of opiate withdrawal symptoms in the study group, and the clinical implications that should be drown.

A selective EP4 receptor antagonist abrogates the stimulation of osteoblast recruitment from bone marrow stromal cells by prostaglandin E2 in vivo and in vitro.

Recent evidence indicates that systemic administration of PGE2 increases bone formation and bone mass via activation of the EP4 receptor. Previously, we demonstrated that osteoblastic recruitment from rat bone marrow stromal cells (BMSC) is a major mechanism for the anabolic effect of PGE2. In this study, we used a selective EP4 antagonist to test if the stimulation of osteoblast differentiation from rat BMSC in vitro and in vivo involves the EP4 receptor. In vitro, PGE2 (100 nM) increased nodule formation and alkaline phosphatase (ALP) activity in cultures of rat BMSC 1.5- to 2-fold. These effects were abolished by the EP4 antagonist at 10(-6) M but not 10(-9) M. Furthermore, PGE2 increased the number of surviving adherent BMSC by approximately 225% and the EP4 antagonist prevented this effect as well. The antagonist had no effect on basal levels of nodule formation and adherent cell number. In vivo, daily systemic administration of PGE2 at 6 mg/kg for 2 weeks increased cancellous bone area (by approximately 50%) and increased nodule formation (measured as mineralized area) in ex vivo stromal cultures by approximately 50%. Pre-administration of the EP4 antagonist at 10 mg/kg abrogated both the increase in bone mass as well as the increase in nodule formation. These data indicate that PGE2 stimulates osteoblastic commitment of BMSC via activation of the EP4 receptor.

Mianserin and trazodone significantly attenuate the intensity of opioid withdrawal symptoms in mice.

The aims of this study were to evaluate the effects of trazodone and mianserin on opioid-withdrawal symptoms in morphine-dependent mice. We used a comparative study of the effect of each drug on withdrawal symptoms in one model of acutely high-dose morphine-dependent mice, and two models (high-dose and lu-dose) of chronically morphine-dependent mice at the Tel Aviv University Sackler School of Medicine's laboratory.Trazodone, mianserin or both were given to the morphine-dependent mice together with a high dose of naloxone. Intensity of withdrawal symptoms was evaluated by tail-flick assay latencies and three behavioural measurements (rearing, jumping and grooming) in each group. Trazodone and mianserin, each separately,significantly attenuated withdrawal symptoms in all three models. However, the combined treatment of trazodone together with mianserin was not superior to each drug alone. The combination of trazodone and mianserin has no additive value to each drug alone in the control of withdrawal symptoms in opiate-dependent mice undergoing detoxification. When used in clinical settings, caution is needed in order to prevent the unknown influence of opioid-like drugs in medication-assisted detoxification programmes if complete opiate detoxification is the aim.

The antinociceptive effect of trazodone in mice is mediated through both mu-opioid and serotonergic mechanisms.

The antinociceptive effects of trazodone (a triazolopyridine derivative with antidepressant activity) and its interaction with various opioid, noradrenaline and serotonin receptor subtypes were evaluated. Mice were tested with a hotplate analgesia meter. Trazodone induced a dose-dependent antinociceptive effect following i.p. administration. The ED(50) for mice in the hotplate assay for trazodone was 24.8 mg/kg (9.8; 67.4; 95% CL). The effect of opioid, adrenergic and serotonergic receptor antagonists was examined as to their ability to block trazodone antinociception. Trazodone-induced antinociception was significantly inhibited by naloxone, beta-FNA and naloxonazine, but not by nor-BNI or naltrindole, implying involvement of mu1- and mu2-opioid mechanisms. When adrenergic and serotonergic antagonists were used, metergoline (p<0.05) but not phentolamine or yohimbine, decreased antinociception elicited by trazodone, implying a clear 5-HT mechanism of antinociception. When trazodone was administered together with various agonists of the opioid receptor subtypes, it significantly potentiated antinociception mediated by mu1- and mu2- opioid receptor subtypes. Summing up these results, we conclude that the antinociceptive effect of trazodone is mainly influenced by the mu1- +mu2-opioid receptor subtype combined with the serotonergic receptor. These results explain the diffuse clinical use of trazodone in the management of some pain syndromes, and in opioid- and alcohol-detoxification programs, but raise questions regarding a possible 'indirect' opioid-dependence induced by trazodone itself.

An avian model for the reversal of 6-hydroxydopamine induced rotating behaviour by neural grafting.

A new animal model of parkinsonism was established in 'Black Silkie' chickens by means of unilateral injections of 6-hydroxy-dopamine into the substantia nigra. Apomorphine produced a strong contralateral turning pattern in the lesioned chickens, amphetamine had no effect. 6-OHDA treated animals received embryonic transplants of substantia nigra cell suspensions which caused them to cease rotating (P < 0.01). This finding allows us to add an avian model, which offers unique methodological advantages, for reversal of 6-OHDA-induced rotating behavior by transplantation.

Effect of loading on the migration of periodontal fibroblasts in the rat incisor.

The influence of occlusal loading on periodontal fibroblasts was investigated in hypoloaded (shortened out of occlusion), functionally loaded and hyperloaded (constant linguointrusive mechanical loads of 9.4 +/- 0.06 g) lower left rat incisors. One hour following injection of 3H-thymidine, half of the animals in each group were killed, while the remaining rats were killed 2 weeks later. The decalcified incisors were embedded in glycolmethacrylate and sectioned (2 microns) serially, perpendicularly to the long tooth axis. Labeled and unlabeled fibroblasts in the tooth-related periodontal ligament were counted in 8 x 80 microns consecutive layers. Cell density (CD) and labeling index (LI) were plotted according to their location on the apico-incisal and cementum-bone axes. Loading caused a decrease in CD and a shift of cells from the cementum towards the middle of the ligament, proportionally to load intensity and duration. The average tooth-to-bone movement of the cells was 2 microns/day in the hypoloaded and 4 microns/day in the two loaded groups. The mean daily tooth eruption rate was 975 +/- 60 microns, 499 +/- 18 microns and 103 +/- 27 microns in the hypo-, functionally- and hyperloaded teeth, respectively. The respective concomitant average daily cell migration rates in the incisal direction were 786 microns, 500 microns, and 500 microns, i.e. 80%, 100% and 485% of the tooth eruption rates. The gross disparity between cell velocity and tooth movement under conditions of restrained eruption indicates active motility of the fibroblasts, rather than their passive tooth-eruption dependent translation.

Amplitude of M responses. Side to side comparability.

The peak amplitude of the M response from the extensor digitorum longus muscle (EDL) was measured in 26 healthy subjects (12 women and 14 men, aged 19 to 45 years) using conventional peroneal nerve stimulation at the fibular head. The mean amplitude of the EDL was 6.5 mV (+/- 1.3 mV) and 6.1 mV (+/- 1.2 mV) for the right and left sides, respectively. The side to side difference in amplitude of the M response was 0.4 mV (+/- 1.1 mV). Twenty-five of the twenty-six subjects had side to side amplitude differences within two standard deviations of the mean. None of the subjects had an EDL amplitude from the right lower limb over 1.8 mV less than that of the left, nor an EDL amplitude from the left lower limb over 2.8 mV less than that of the right. The technique used in the present study allows an accurate assessment of the M response amplitude from the EDL muscle. These reference data should prove useful in the evaluation of early focal nerve root injury (e.g. after 4 days, within 3 weeks) and in establishing prognosis for recovery in such conditions.