Dynamic regulation of striatal dopaminergic grafts during locomotor activity

In addition to CD4+ T lymphocytes, cells of monocyte/macrophage lineage are a major target for human immunodeficiency virus type 1 (HIV-1) infection. In vitro studies of HIV-1 infection in human monocyte-derived macrophages can be undertaken by a reproducible cell-based assay. A macrophage-based infectivity assay was developed based on the semi-quantitative scoring of HIV-1 induced cytopathology in monolayer macrophage cultures. The assay exhibited dilution-dependent linearity with all three primary macrophage-tropic isolates tested. The end-point infectivity titers determined by this assay correlated with the results obtained by detecting viral p24 antigen in the culture supernatant. The applications of the assay in both neutralization and anti-viral protocols yielded identical results with the more time-consuming and costly p24 formats. Since the assay offers a simple and low-cost method of measuring HIV-1 infectivity in human primary macrophages, it can be used quite easily for large-scale screening or evaluation of candidate vaccines and anti-viral agents.     

Glial cell line-derived neurotrophic factor increases survival, growth and function of intrastriatal fetal nigral dopaminergic grafts

The ability of transplants of fetal nigral neurons to reverse symptoms in patients with Parkinson's disease is, at least in part, limited by the poor survival of the grafted dopaminergic neurons and the restricted host reinnervation from the graft. Here, we report that glial cell line-derived neurotrophic factor, a novel trophic factor for developing dopaminergic neurons, can increase survival and fibre outgrowth of fetal nigral dopaminergic neurons, and stimulate graft-induced functional recovery after transplantation in a rat model of Parkinson's disease. Injections of rat glial cell line-derived neurotrophic factor adjacent to the graft enhanced graft function, resulting in complete compensation of amphetamine-induced turning behaviour already by two weeks postgrafting as opposed to four weeks in the control group. The total number of surviving tyrosine hydroxylase-positive neurons was about two-fold greater in the glial cell line-derived neurotrophic factor-treated animals compared to the vehicle-injected controls, and the density of tyrosine hydroxylase-positive fibres was found to be increased both in the host striatum (from 37.6 +/- 8.3% to 105.5 +/- 9.7% of intact striatum) as well as inside the graft (55% increase). Moreover, in animals treated with glial cell line-derived neurotrophic factor, the outgrowth of tyrosine hydroxylase-positive fibres was mostly directed towards the injection site. These findings show that supply of exogenous glial cell line-derived neurotrophic factor to the transplantation site improves survival, growth and function of transplanted fetal nigral dopaminergic neurons in the rat Parkinson model.     

Reduced striatal tyrosine hydroxylase activity is not accompanied by change in responsiveness of dopaminergic receptors following chronic treatment with deprenyl

Deprenyl is the only selective monoamine oxidase B (MAO-B) inhibitor that is in clinical use for the treatment of Parkinson's disease. Our previous studies showed that chronic treatment of rats with low (MAO-B selective) doses of deprenyl inhibited dopamine (DA) re-uptake and enhanced DA release in the striatum. These changes could affect DA synthesis rate by activation of negative feedback loops. Chronic deprenyl treatment has also been suggested to cause down-regulation of release-modulating DA receptors. The effects of chronic and acute treatment with deprenyl on ex vivo striatal tyrosine hydroxylase activity were therefore studied, by determination of steady-state tissue level of DOPA following administration of NSD-1015 (100 mg/kg i.p.). In addition, we assessed changes in the in vivo sensitivity of dopaminergic receptors from the reduction in DOPA extracellular level after systemic apomorphine administration (2.5 mg/kg s.c.), following elevation of microdialysate DOPA by systemic or local aromatic amino acid decarboxylase inhibition with NSD-1015. Chronic treatment with deprenyl (0.25 mg/kg s.c. daily for 21 days) caused a significant reduction in tyrosine hydroxylase activity to 60% of control, with no change in the apomorphine-induced reduction of microdialysate DOPA and DOPAC. The reduction in tyrosine hydroxylase activity is compatible with our previous results showing an increase in striatal DA extracellular level following chronic treatment with deprenyl. The increased extracellular striatal DA level could reduce tyrosine hydroxylase activity through activation of a negative feedback loop, by activation of either presynaptic or postsynaptic DA receptors.     

Altered responding to cholecystokinins and dopaminergic agonists following 6-hydroxydopamine treatment in rats.

In 5 experiments with 265 male Wistar albino rats, production of lesions in the brain dopamine (DA) system by intraventricular injection of 6-hydroxydopamine (6-OHDA) resulted in increased responses to subcutaneous apomorphine (0.5 mg/kg) and reduced responses to methamphetamine (0.15 mg/kg). It also made Ss increase responding to intracerebroventricular (icv) cholecystokinin octapeptide (CCK-8; 0.5–2 μg) and reduce responding to cholecystokinin tetrapeptide (CCK-4; 0.5–2 μg). Response changes were quantified by measuring the level of general activity. Results indicate that DA dysfunction not only affected DA receptor sensitivity but also the sensitivity of the CCK system. The response to CCK-8 was partially blocked by a selective CCK-8 antagonist, proglumide (5 μg, icv), a result suggesting the involvement of the CCK-8 receptor system. Results indicate that manipulation of 1 neuronal system could induce sensitivity changes in another closely related system. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Unilateral striatal grafts induce behavioral and electrophysiological asymmetry in rats with bilateral kainate lesions of the caudate nucleus.

Rats (n?=?11) with bilateral kainate lesions of the caudate nucleus and subsequent unilateral transplantation of embryonic striatal tissue into the damaged area preferred 4 months later to reach for food with the forepaw contralateral to the graft. No such asymmetry was observed in lesioned, nontransplanted (n?=?8) or unoperated (n?=?5) control rats. Good integration of the graft with the host brain was indicated by the finding that cortical spreading depression did not enter the lesioned caudate nucleus but did penetrate into the lesioned caudate with the graft almost as regularly as in intact rats. Behavioral asymmetry produced by unilateral grafts in bilaterally lesioned animals reveals the effects of transplantation with more sensitivity than the graft-induced compensation of the asymmetries caused by unilateral lesions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Joint effect of dopaminergic genes on likelihood of smoking following treatment with bupropion SR.

Objective: To determine the relationship between joint variation in 2 dopaminergic genes and the likelihood of nonsmoking following treatment with bupropion sustained release (SR). Design: Three hundred twenty-three participants in a bupropion SR smoking cessation effectiveness trial with 12-month follow-up were genotyped for variants of dopamine receptor gene DRD2 and dopamine transporter SLC6A3. Main Outcome Measures: Self-reported 7-day point prevalence of nonsmoking. Results: Neither genotype alone was associated with 7-day point-prevalent nonsmoking at the 12-month follow-up. However, in the presence of the DRD2 A1 allele, SLC6A3 status was significantly associated with the likelihood of nonsmoking at the 12-month follow-up (individuals with DRD2 A1+ and SLC6A3 9- were more likely to be smoking). In the absence of the DRD2 A1 allele, the association between SLC6A3 status and nonsmoking was nonsignificant. Conclusion: Although these results are suggestive, a more compelling test is needed of the hypothesis that dopaminergic gene interaction underlies, in part, the likelihood of smoking following treatment with bupropion SR. Most likely this will come from larger studies involving prospective randomization to treatment based on genotype. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral sensitization to amphetamine is not accompanied by a decrease in the number of c-Fos containing cells in the striatum

The expression of c-Fos-like immunoreactivity (FLI) and chronic Fos-related antigen-like immunoreactivity (FRALI) accompanying behavioral sensitization to amphetamine was assessed in male rat striatum. Animals were treated for four days with amphetamine (A; 5 mg/kg) or vehicle (V) and challenged with A or V on the fifth day. The number of FLI-positive cells in the striatum was enhanced in V-A and A-A groups as compared to control (V-V), while the number of FRALI-positive cells in the striatum was enhanced in the A-V and A-A groups as compared to control. These results suggest that the absence of a decrease in the number of striatal FLI-positive cells accompanying chronic amphetamine treatment is not due to antibody cross-reactivity with chronic FRAs, and that behavioral sensitization to amphetamine is not accompanied by a change in the number of striatal cells expressing c-Fos.     

Behavioral effects of GM1 ganglioside treatment and intrahippocampal septal grafts in rats with fimbria-fornix lesions

The monosialoganglioside GM1 is a compound with neurotrophic properties found to foster functional recovery in various paradigms of brain damage. The present experiment examined whether systemic treatment with GM1 may facilitate behavioral recovery in rats with fimbria-fornix lesions and intrahippocampal grafts rich in cholinergic neurons. Among 68 Long-Evans female rats, 46 sustained a bilateral electrolytic lesion of the fimbria and the dorsal fornix and 22 were sham-operated. Fourteen days later, half the lesioned rats were subjected to intrahippocampal grafts of a fetal septal cell suspension. Starting a few hours after lesion surgery and over a 2-month period, half the rats of each surgical treatment group received a daily injection of GM1 (30 mg/kg i.p.), the other half being injected with saline as a control. All rats were subsequently tested for locomotor activity and radial maze learning. The lesions induced locomotor hyperactivity and impaired learning performances in both an uninterrupted and an interrupted radial maze testing procedure. In all rats with surviving grafts, the grafts had provided the hippocampus with a new and dense organotypic acetylcholinesterase-positive innervation pattern which did not differ between saline- and GM1-treated subjects. The scores/performances of the rats that had received only the grafts or only the GM1 treatment did not differ significantly from those of their respective lesion-only counterparts. However, in the radial-arm maze task, the grafted rats given GM1 showed improved learning performances as compared with their saline-treated counterparts: they used more efficient visit patterns under the uninterrupted testing conditions and made fewer errors under the interrupted ones. The results suggest that GM1 treatment or intrahippocampal grafts used separately do not attenuate the lesion-induced behavioral deficits measured in this experiment. However, when GM1 treatment and grafts are used conjointly, both may interact in a manner allowing part of these deficits to be attenuated.     

Precocious mating in male rats following treatment with androgen or estrogen.

Conducted 5 experiments with 179 male Royal Victoria Hospital hooded rats. Daily subcutaneous injections of 1,000 MUg/100gm testosterone propionate of 5 MUg/100gm estradiol benzoate (EB) after postnatal Day 10 accelerated initial intromission and ejaculation in intact Ss. Precocious Ss continued to copulate after treatments were stopped. Age at the 1st display of intromission was unrelated to age at the 1st injection of EB. However, initiation of EB treatments before Day 11 was associated with rapid loss of intromission following cessation of treatment in adulthood. EB activated the 1st mating of prepuberally castrated and sham-operated Ss with nearly equal facility. Also, prepuberal castrates primed with EB subsequently intromitted after receiving fewer androgen replacement injections than control Ss. (24 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral effects of amphetamine in rats with lesions in the corpus striatum.

Conducted 5 experiments, using a total of 132 male albino Sprague-Dawley rats. Lesions in the ventral striatum lowered forebrain dopamine and impaired avoidance behavior more severely than comparable lesions in the dorsal striatum. Ventral striatal damage also antagonized the effects of amphetamine on stereotyped behavior and on intertrial activity. Lesions in the dorsal striatum did not modify the effect of amphetamine in these tests. Neither dorsal nor ventral striatal lesions significantly depleted forebrain norepinephrine, and both failed to affect the facilitatory effects of amphetamine on exploratory activity in an open field. These observations support the hypothesis that some but not all of the behavioral effects of amphetamine may be due to the drug's action on dopaminergic components of the striatum. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Delayed treatment with rolipram protects against neuronal damage following global ischemia in rats

In this study the effect of post-treatment with rolipram, an inhibitor of cAMP phosphodiesterase, on neuronal damage following global ischemia was evaluated. Global cerebral ischemia was induced in male Wistar rats by four-vessel occlusion for 20 minutes. Rolipram was administered 6 hours after onset of ischemia and thereafter the following 7 days daily once at a dose of 0.3 or 3.0 mg/kg intraperitoneally. Four weeks after ischemia the amount of intact neurons in the hippocampus and in the striatum was assessed following perfusion fixation. The ischemia-induced neuronal damage in the CA1 sector of the hippocampus and in the striatum was reduced by rolipram at either dose. The present results show that treatment with rolipram reduces ischemic neuronal damage at a therapeutic window of 6 hours.     

Release of DNA from the nuclei of hepatocytes of rats following their treatment with heparin

The influence of heparin on the protein fractions and DNA of the isolated nuclei of hepatocytes was studied by biochemical and cytospectrophotometrical methods on Wistar rats. It was found that 0.05% sodium heparinate solution blocked 95% of the histones, not influencing the non-histone proteins of the cell nucleus. Histone blocking was connected with the DNA release into the incubation medium in the amounts proportional to the incubation period.     

Hippocampal grafts of acetylcholine-producing cells are sufficient to improve behavioural performance following a unilateral fimbria-fornix lesion

Lesions of the septohippocampal pathway produce cognitive deficits that are partially attenuated by grafts of cholinergic-rich tissue into denervated target regions or by systemic administration of cholinomimetic drugs. In the present study, fibroblasts engineered to produce acetylcholine were used to test the hypothesis that restoration of hippocampal acetylcholine in rats with septohippocampal lesions is sufficient to improve cognitive processing post-damage. Rats received unilateral grafts of acetylcholine-producing or control fibroblasts into the hippocampus immediately prior to an aspirative lesion of the ipsilateral fimbria-fornix. Some rats with fimbria-fornix lesions were implanted with acetylcholine-producing or control fibroblasts into the neocortex, another major target of the basal forebrain cholinergic system, to determine if the site of acetylcholine delivery to the damaged brain is critical for functional recovery. Rats were tested in a hidden platform water maze task, a cued water maze task and activity chambers between one and three weeks post-grafting. Compared to unoperated controls, rats with fimbria fornix lesions only were significantly impaired in hidden platform water maze performance. Hippocampal grafts of acetylcholine-producing cells reduced lesion-induced deficits in the water maze, whereas hippocampal control grafts and cortical grafts of either cell type were without effect. Locomotor activity and cued water maze performance were unaffected by the lesion or the implants. Taken together, these data indicate that water maze deficits produced by fimbria fornix lesions, which disrupt a number of hippocampal neurotransmitter systems, can be attenuated by target specific replacement of acetylcholine in the hippocampus and that this recovery occurs in the absence of circuitry repair.     

Differential cerebrovascular responsiveness in spontaneously hypertensive rats following antihypertensive treatment with clonidine and verapamil

Numerous studies have been reported examining the effects of antihypertensive treatment on peripheral vascular responsiveness in spontaneously hypertensive rats (SHR). This study was conducted to determine the effects of chronic treatment with 2 antihypertensive agents on cerebrovascular responsiveness in male SHR and Wistar-Kyoto (WKY) rats. SHR and WKY (3-4 weeks old) received either placebo, clonidine (CLON, 10 mg pellet) or verapamil (VER, 5 mg pellet). Vascular reactivity studies on the basilar artery, using standard smooth muscle bath techniques, were conducted following 6 weeks of treatment. Both CLON and VER significantly attenuated the rise in blood pressure in SHR. Basilar artery responsiveness to KCl, serotonin (5-HT), and calcium were significantly increased whereas responses to acetylcholine (ACH), isoproterenol (ISO) and sodium nitroprusside (SNP) were significantly reduced in SHR compared to WKY. CLON had no effect on basilar artery responsiveness to either the contractile or relaxation agents in SHR. However, although responses to KCl, 5-HT and calcium were not affected by VER in SHR, VER significantly increased the responses to ACH, ISO and SNP. Neither CLON nor VER treatment affected basilar artery responsiveness to any of the agents in WKY. These data demonstrate that, even though CLON and VER have similar antihypertensive effects, differential effects of the 2 agents on cerebrovascular responsiveness in the SHR are apparent. This would suggest that the vascular effects of VER and CLON are dependent upon the mechanism of action of the agents and not simply due to prevention of the elevation in blood pressure.     

Olivocerebellar axon regeneration and target reinnervation following dissociated Schwann cell grafts in surgically injured cerebella of adult rats

The ability of Schwann cells to induce the regeneration of severed olivocerebellar and Purkinje cell axons across an injury up to their deafferented targets was tested by transplanting freshly dissociated cells from newborn rat sciatic nerves into surgically lesioned adult cerebella. The grafted glial cells consistently filled the lesion gap and migrated into the host parenchyma. Transected olivocerebellar axons vigorously regenerated into the graft, where their growth pattern and direction followed the arrangement of Schwann cell bundles. Although some of these axons terminated within the transplant, many of them rejoined the cerebellar parenchyma beyond the lesion. Here, their fate depended on the territory encountered. No growth occurred in the white matter. Numerous fibres penetrated into the granular layer and formed terminal branches that remained confined within this layer. A few of them, however, regenerated up to the molecular layer and formed climbing fibres on Purkinje cell dendrites. By contrast, the growth of transected Purkinje cell axons into the grafts was very poor. These results underscore the different intrinsic responsiveness of Purkinje cell and olivocerebellar axons to the growth-promoting action of Schwann cells, and show that the development and outcome of the regenerative phenomena is strongly conditioned by the spatial organization and specific features of the environmental cues encountered by the outgrowing axons along the course they follow. However, Schwann cells effectively bridge the lesion gap, induce the regeneration of olivocerebellar axons, and direct their growth up to the deafferented host cortex, where some of them succeed in reinnervating their natural targets.