Chemical cardiac sympathetic denervation hampers defibrillation in the dog

Generation of Mitochondrial Toxin Rodent Models of Parkinson's Disease Using 6-OHDA , MPTP , and Rotenone

Several animal models are employed to discover novel treatments for the symptoms of Parkinson's disease (PD). PD models can be divided into two models: neurotoxin models and genetic models. Among neurotoxins to produce PD models, 6-hydroxydopamine (6-OHDA), 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), and rotenone, which inhibit the mitochondrial complex I, are widely used. Animal models of PD using these neurotoxins are also known as mitochondrial toxin models. Here this chapter describes the preparation of these mitochondrial toxin models.

In vivo, in vitro and pharmacologic models of Parkinson's disease

Parkinson's disease (PD), which is the second most common neurodegenerative disorder after Alzheimer's disease, is firstly defined after James Parkinson's report. It carries motor symptoms such as resting tremor, bradykinesia and rigidity of skeletal muscle and freezing of gait. Furthermore, non-motor symptoms such as cognitive and behavioral problems, besides sensory impairments are seen in the patients. However, they may also suffer from sleep disorders or autonomic dysfunction. Although there are some medications in order to symptomatic management, but unfortunately, scientist could not have found exact approaches to cure this disease. Hence, producing a model which can express the most pathophysiologic and behavioral aspects of the disease is a desire. In this paper, we aimed to describe the different models of Parkinson's disease in brief.

Classic and new animal models of Parkinson's disease

Neurological disorders can be modeled in animals so as to recreate specific pathogenic events and behavioral outcomes. Parkinson's Disease (PD) is the second most common neurodegenerative disease of an aging population, and although there have been several significant findings about the PD disease process, much of this process still remains a mystery. Breakthroughs in the last two decades using animal models have offered insights into the understanding of the PD disease process, its etiology, pathology, and molecular mechanisms. Furthermore, while cellular models have helped to identify specific events, animal models, both toxic and genetic, have replicated almost all of the hallmarks of PD and are useful for testing new neuroprotective or neurorestorative strategies. Moreover, significant advances in the modeling of additional PD features have come to light in both classic and newer models. In this review, we try to provide an updated summary of the main characteristics of these models as well as the strengths and weaknesses of what we believe to be the most popular PD animal models. These models include those produced by 6-hydroxydopamine (6-OHDA), 1-methyl-1,2,3,6-tetrahydropiridine (MPTP), rotenone, and paraquat, as well as several genetic models like those related to alpha-synuclein, PINK1, Parkin and LRRK2 alterations.

Dual-isotope single-photon emission computed tomography for dopamine and serotonin transporters in normal and Parkinsonian monkey brains

INTRODUCTION

Parkinson's disease (PD) affects both dopaminergic and serotonergic systems. In this study, we simultaneously evaluated dopamine and serotonin transporters in primates using dual-isotope single-photon emission computed tomography (SPECT) imaging and compared the results with traditional single-isotope imaging.

METHODS

Four healthy and one 6-OHDA-induced PD monkeys were used for this study. SPECT was performed over 4 h after individual or simultaneous injection of [(99m)Tc]TRODAT-1 (a dopamine transporter imaging agent) and [(123)I]ADAM (a serotonin transporter imaging agent).

RESULTS

The results showed that the image quality and uptake ratios in different brain regions were comparable between single- and dual-isotope studies. The striatal [(99m)Tc]TRODAT-1 uptake in the PD monkey was markedly lower than that in normal monkeys. The uptake of [(123)I]ADAM in the midbrain of the PD monkey was comparable to that in the normal monkeys, but there were decreased uptakes in the thalamus and striatum of the PD monkey.

CONCLUSIONS

Our results suggest that dual-isotope SPECT using [(99m)Tc]TRODAT-1 and [(123)I]ADAM can simultaneously evaluate changes in dopaminergic and serotonergic systems in a PD model.

Modulation of the sinus rate during ventricular fibrillation

BACKGROUND

During supraventricular and ventricular tachycardia, the arterial baroreflex predominates with minimal contribution from the cardiopulmonary reflex. To our knowledge, the role of the arterial baroreflex gain (BRG) during and immediately following termination of ventricular fibrillation (VF) has not been characterized.

OBJECTIVE

We hypothesized that (1) arterial BRG correlated with sinus node cycle length (SNCL) changes during VF, and that (2) the greater the arterial BRG, the greater the blood pressure (BP) recovery following successful defibrillation.

METHODS

Arterial BRG was assessed in 18 patients referred for the implantation of a defibrillator incorporating an atrial lead. The average SNCL was measured during the 5 seconds prior to VF induction and the last 5 seconds during VF before defibrillation. Percent SNCL change (%DeltaSNCL) was determined. Arterial BP recovery was calculated as the difference in mean BP following defibrillation compared to during VF.

RESULTS

Arterial BRG ranged between -3 and 18 ms/mmHg. During VF, SNCL shortened in 11 patients (group A, mean %DeltaSNCL =-15%), and surprisingly lengthened in seven patients (group B, mean %DeltaSNCL = 5%). There was no correlation between %DeltaSNCL and arterial BRG. In fact, arterial BRG in group A was lower when compared with group B (P = 0.075). Similarly, there was no correlation between arterial BRG and BP recovery.

CONCLUSIONS

We found no correlation between arterial BRG and %DeltaSNCL during VF, or BP recovery following defibrillation. Our findings of SNCL lengthening in 7 of 18 patients suggest that in some patients, arterial BRG plays a minor role during VF with a greater contribution from the cardiopulmonary BRG.

Toxin-induced models of Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative disease that appears essentially as a sporadic condition. It results mainly from the death of dopaminergic neurons in the substantia nigra. PD etiology remains mysterious, whereas its pathogenesis begins to be understood as a multifactorial cascade of deleterious factors. Most insights into PD pathogenesis come from investigations performed in experimental models of PD, especially those produced by neurotoxins. Although a host of natural and synthetic molecules do exert deleterious effects on dopaminergic neurons, only a handful are used in living laboratory animals to recapitulate some of the hallmarks of PD. In this review, we discuss what we believe are the four most popular parkinsonian neurotoxins, namely 6-hydroxydopamine (6-OHDA), 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), rotenone, and paraquat. The main goal is to provide an updated summary of the main characteristics of each of these four neurotoxins. However, we also try to provide the reader with an idea about the various strengths and the weaknesses of these neurotoxic models.