Time to Abolish the Forced Swim Test in Rats for Depression Research?

The forced swim test (FST) is a controversial rodent test that has been used for decades, mainly in depression studies. The severity of the procedure makes it ethically questionable and its validity has also been questioned. In this paper we contribute new data to this debate. We identified original research papers related to Major Depressive Disorder (MDD), using rats as models. We compared the citations received by studies that used the FST and by studies that did not, within subsequent human medical papers. The results show that the number of citations received by both groups was very low, but in the papers describing the FST data the median citation number was zero. Citation analysis indicates that the FST is not contributing significantly to the understanding or cure of MDD. We briefly review other approaches that overcome the ethical limitations of the FST, and which might also surpass its efficacy.

Exploring the side effect profile of 16-Ethynyl Salvinorin A

<p>Introduction: Drug addiction is a chronic and relapsing disorder that has widespread socioeconomic and health consequences. Globally, there are over 29.5 million people who are drug dependent, and New Zealand has one of the highest rates of drug use rates in the developed world. Currently, there are no Food and Drug Administration (FDA) approved pharmacotherapies that target psychostimulant addiction. Kappa opioid receptor (KOPr) agonists are being studied as a potential pharmacotherapy as it utilizes the brain’s own mechanism for controlling reward, however, KOPr agonists have unwanted side effects such as dysphoria and sedation. This thesis explores the KOPr agonists Salvinorin A (Sal A), a naturally-occurring, highly potent and short-acting non-nitrogenous KOPr agonist and a structural analogue, 16-Ethynyl Salvinorin A (16-Ethy). KOPr agonists, such as Sal A have known preclinical anti-addictive and anti-reward effects, therefore, this thesis focuses on evaluating Sal A and 16-Ethy in preclinical tests of reward and side effects. Methods: Male Sprague-Dawley rats were used in preclinical tests to evaluate common KOPr-mediated side-effects including anxiety (elevated plus maze), depression (forced swim test) sedation (locomotor activity) and aversion (conditioned place aversion). The anti-cocaine effects were also examined using self-administration, dose-response and drug-behavioural sensitisation tests. 16-Ethy was tested at 2 mg/kg in all experiments. Results: Acute pre-treatment of 16-Ethy induced sedative effects in non-habituated locomotor activity but when rats were habituated prior to administration, no sedation was observed. In contrast, Sal A (2 mg/kg) had sedative effects in habituated, but not in non-habituated locomotor activity (p = 0.0037). Compared to vehicle-treated rats, 16-Ethy and Sal A did not display pro-depressive effects in the forced swim test, show anxiogenic or aversive properties or modulate behavioural sensitisation to cocaine. Cocaine self-administration and dose-response tests were not successfully completed. Conclusion: At 2 mg/kg, 16-Ethy was found to display sedative effects in non-habituated locomotor activity but not in a habituated paradigm. Compared to vehicle-treated rats, 16-Ethy did not display pro-depressive effects in the forced swim test, or display anxiogenic or aversive properties and did not show significant cocaine sensitisation. Cocaine self-administration and dose-response tests were not successfully completed and will need to be repeated to ascertain the effects of 16-Ethy on them. However, 16-Ethy has shown glimpses of promise as a potential pharmacotherapy against addiction.</p>

Exploring the side effect profile of 16-Ethynyl Salvinorin A

<p>Introduction: Drug addiction is a chronic and relapsing disorder that has widespread socioeconomic and health consequences. Globally, there are over 29.5 million people who are drug dependent, and New Zealand has one of the highest rates of drug use rates in the developed world. Currently, there are no Food and Drug Administration (FDA) approved pharmacotherapies that target psychostimulant addiction. Kappa opioid receptor (KOPr) agonists are being studied as a potential pharmacotherapy as it utilizes the brain’s own mechanism for controlling reward, however, KOPr agonists have unwanted side effects such as dysphoria and sedation. This thesis explores the KOPr agonists Salvinorin A (Sal A), a naturally-occurring, highly potent and short-acting non-nitrogenous KOPr agonist and a structural analogue, 16-Ethynyl Salvinorin A (16-Ethy). KOPr agonists, such as Sal A have known preclinical anti-addictive and anti-reward effects, therefore, this thesis focuses on evaluating Sal A and 16-Ethy in preclinical tests of reward and side effects. Methods: Male Sprague-Dawley rats were used in preclinical tests to evaluate common KOPr-mediated side-effects including anxiety (elevated plus maze), depression (forced swim test) sedation (locomotor activity) and aversion (conditioned place aversion). The anti-cocaine effects were also examined using self-administration, dose-response and drug-behavioural sensitisation tests. 16-Ethy was tested at 2 mg/kg in all experiments. Results: Acute pre-treatment of 16-Ethy induced sedative effects in non-habituated locomotor activity but when rats were habituated prior to administration, no sedation was observed. In contrast, Sal A (2 mg/kg) had sedative effects in habituated, but not in non-habituated locomotor activity (p = 0.0037). Compared to vehicle-treated rats, 16-Ethy and Sal A did not display pro-depressive effects in the forced swim test, show anxiogenic or aversive properties or modulate behavioural sensitisation to cocaine. Cocaine self-administration and dose-response tests were not successfully completed. Conclusion: At 2 mg/kg, 16-Ethy was found to display sedative effects in non-habituated locomotor activity but not in a habituated paradigm. Compared to vehicle-treated rats, 16-Ethy did not display pro-depressive effects in the forced swim test, or display anxiogenic or aversive properties and did not show significant cocaine sensitisation. Cocaine self-administration and dose-response tests were not successfully completed and will need to be repeated to ascertain the effects of 16-Ethy on them. However, 16-Ethy has shown glimpses of promise as a potential pharmacotherapy against addiction.</p>

Evaluation of Additive or Synergistic Effect of Piper nigram and Ocimum sanctum Extracts for their Antidepressant Activity

Depression is a state of excessive sensitivity to criticism, fear of rejections, lack of self-interest, loss of pleasure. In the traditional systems of medicine, many plants and formulations have been used to treat depression for thousands of years. In recent times, research on the plants increased globally and so many plants provide the evidence to cure diseases. Ocimum sanctum, popularly known as Tulsi is one of the sacred herbs for Hindus in the Indian subcontinent. It has a versatile role in traditional medicine. The fruits of Piper nigrum are used to make black pepper. This hotly pungent spice is one of the earliest known and most widely used spices in the world today. Wide range of animal tests for antidepressant agents are commonly used. The Forced swim test and Tail suspension test in mice were mostly used. Hence in the present study Forced swim test was used as animal model of depression. In present study immobility time in Forced swim test was significantly decreased by a combination of Piper nigrum fruit extract and Ocimum sanctum extract treated groups compared to control group. The combination of extracts (50 mg/kg each) activity was comparable to standard drug Fluoxetine. Treatment with extracts does not modify the locomotor activity of mice, which indicates that they exert antidepressant effects without modifying significantly locomotor activity. Therefore, the present study confirms the combination of alcoholic extract of Piper nigrum (AEPN) fruit and aqueous extract of Ocimum sanctum (AEOS) possessing additive/synergistic antidepressant activity.

Alpha-lipoic acid enhances short-term spatial memory of mice in open-space forced swim-induced depression mouse model

Depression affects over 264 million people of all ages globally. Major depressive disorder significantly and chronically reduced quality of life by its association with functional impairment both at home and in the workplace. Depressive patients consistently complain about cognitive disturbances, significantly exacerbating the burden of this illness. Several studies have shown that alpha-lipoic acid (ALA) possesses mitochondrial, antioxidant, anti-inflammatory and anti-diabetic properties, indicating a basis for evaluating the efficacy of ALA in depression. Hence, this research aimed to assess the possible anti-depressant effect of ALA in mice exposed to the open space forced swim test (OSFST) model of depression. Twenty-five (25) Swiss albino mice were grouped into five groups (n=5). Group 1: [Normal saline (NS)], Groups 2, 3 and 4 received graded doses of ALA 100, 200 and 400 mg/kg, respectively, Group 5 received fluoxetine 20 mg/kg orally. The animals were subjected to OSFST, novel object recognition test (NORT) and Y-maze test. Serotonin, brain-derived neurotrophic factor (BDNF), superoxide dismutase (SOD), malondialdehyde (MDA) and catalase levels of the mice were assessed. Treatment with ALA and fluoxetine significantly decreased immobility time compared to NS group in OSFST (p<0.05). Also, ALA at doses of 200 & 400 mg/kg and fluoxetine 20 mg/kg significantly increased spontaneous alternation ratio in the Y-maze test compared to the normal saline group (p<0.05), however, no significant difference was observed in novel object recognition using NORT between NS, ALA and fluoxetine treated groups. Similarly, the level of serotonin, SOD and catalase were not altered between the ALA and fluoxetine treated groups and NS group. In contrast, fluoxetine 20 mg/kg increased the brain BDNF level of the mice (p<0.05). Alpha-lipoic acid ameliorated depression in the OSFST murine model of depression and improved their cognition. Thus ALA can be a promising candidate in the development of novel anti-depressant medication.