Preclinical Screening of Antidepressant Activity of Formulated Sertraline Hydrochloride-Loaded Solid Lipid Nanoparticles in Rats

_____________________________________________________________________________________________________ ABSTRACT Objective: The main goal of our study was to investigate the antidepressant activity of Formulated Sertraline hydrochloride-loaded Solid Lipid Nanoparticles (SLNPs) by using a rat forced swimming test (FST) and tail suspension test (TST). Materials and Methods: Animals were divided into three groups, consisting of six rats in each group. Out of these, one group served as control that received distilled water, second group was standard received Sertraline HCl (20 mg/kg intranasal) and third group was received test formulation (SLNPs 50 mg/kg intranasal). To assess the effect of SLNPs on immobility activity through FST and TST were used to take as a measure of antidepressant activity. Results: SLNPs reduced the immobility duration in TST as well as in FST. In both methods, there was a statistical significant decrease in immobility of SLNPs group when compared to the control group. Conclusion: The results suggested that SLNPs produced significant antidepressant effect in rats which was comparable with control group and standard Sertraline HCl group animals.


INTRODUCTION
Depression is a life-threatening psychiatric disorder and a major public health concern worldwide with an incidence of 5% and lifetime prevalence of 15-20%. Moreover, it is estimated that by 2021 depression will be in the top three contributors to the burden of disease [1,2]. Depression is associated with disability, decreased quality of life, increased health-related costs and is considered main risk factor for many diseases, including cardiovascular, metabolic and neuropsychiatric disorders [3,4]. Current pharmaco-therapeutic treatments have limited efficacy and are associated with many deleterious side effects [5,6]. Therefore, the development of innovative and improved treatments remains crucial. Hence, animal models are essential for advance research in this field. In this view, the present study was designed to preclinical screening the ability of SLNPs as antidepressants in rats.

Chemicals and Reagents
Sertraline HCl was obtained from Wockhardt, Aurangabad, India.

SLNPs Preparation
The hot homogenization method was used for the preparation of sertraline hydrochlorideloaded SLNs [7].

Animals
The experiments were performed on healthy albino Wistar rats (150-220 g) of both sex that were procured from Laxmi Biofarms Pvt Ltd, Pune. The animals were freely accessible to water and foods, and further acclimatized for at least one week before use. The rat experiment was approved by the IAEC (approval ref no.1554/PO/Re/S/11/ CPCSEA).

Group I: Group control given Distilled water.
Group II: Standard Group animals received Sertraline HCL (20 mg/kg) by nasal route Group III: Test Group animals received SLNPs-(50 mg/kg) by nasal route All the drugs were given 1 hour before the experiment.
Tail suspension test was performed by suspending the rat by its tail using adhesive tape placed ∼1cm from tip of the tail thereby holding it 50 cm above the ground. The immobility time, was recorded on the basis of absence of escape behavior, in each rat for 6 mins.

Forced Swimming Test
The Forced Swim test (FST) was performed according to the method described by Porsolt et al. [9]. Forced swim test was performed in a glass cylinder (21 × 21 × 50 cm) filled with water up to 35 cm and maintained at 24 ± 1˚C. Individual rat had undergone pretest by placing them in cylinder for 15 mins and later at room temperature. On the next day, each rat was placed again in the cylinder for 6 mins under the same conditions and immobility time was measured. Immobility was marked by the absence of movement to escape and float in water or making efforts other than those to keep its head above water level. To avoid any behavioral changes, due to contamination, water was changed frequently, and after the test period of 6 mins, animals were dried with help of drying paper.
Immobility time for 4 min and 6 mins were recorded. After 2 mins of vigorous activity, every one animal implicated immobile posture. The overall duration of immobility was determined and accordingly graded. The reduction in immobility duration was used as antidepressant activity for all the groups.

Statistical Analysis
Results were articulated in terms of mean ± SEM (n=6), with use of statistical analysis by one way ANOVA along with Turkey-Kramer test by using Graph Pad Instat Software. p-values less than 0.05 was considered to be statistically significant (P<0.05).

Tail Suspension Test
Administered standard Sertraline HCL (20 mg/kg, Intranasal) produced significantly (P<0.01) reduction in the duration of immobility (72.5±7.22) in rats as compared to the control group animals. The SLNPs at doses of 50 mg/kg by nasal route significantly (P<0.05) decreased the duration of immobility (77.3±12.04).

Forced Swimming Test
There was a statistically significant (P<0.05) decrease in the immobility in standard and test group when compared to the control group. Administered Standard Sertraline HCL (20 mg/kg, Intranasal) exhibited significant (P<0.05) decrease in the Immobility period to 48.83±1.96.The SLNPs at doses of 50 mg/kg intranasal showed significant (P<0.05) decrease in duration of immobility to 46.3±2.376.

DISCUSSION
Depression is a type of mood illness characterized by a continuous sense of sadness and a loss of interest. It affects behavioral characteristics which lead to mental and physical difficulties. It's also known as major depressive disorder or clinical depression [10]. Depression occurs due to deficiency in the biogenic monoamine such as serotonin (5HT), dopamine (DA) and noradrenaline (NA) [11]. The treatment with antidepressants was done on the basis of their ability to improve monoaminergic transmission. The screening models help to find the efficacy of SLNPs with respect to a standard drug [12].
SLNPs are made up of biocompatible, biodegradable, non-toxic lipids and they are small in particle size and lipophilic nature. So, SLNs have an innate ability to traverse the Blood brain barrier, making them a suitable carrier for medication delivery into the brain [13].
Forced swimming test (FST) and tail suspension tests (TST) act as the behavioral despair model, claim to mimic a condition like to that of human depression. The experiments were based on the finding that when animals were placed in an inescapable chamber, they establish an immobile posture after making initial escape-oriented movements. The immobility was assumed to be due to either a lack of consistency in escapedirected behavior or a lack of motivation (i.e. behavioral despair) or the emergence of passive behavior that prevents the animal from engaging in active means of coping with stressful circumstances.

Fig. 2. Effect of SLNPs on the duration of immobility (s) in the rat of forced swimming test
In the FST and TST, pre-treatment with SLNPs-F6 (50 mg/kg) and Sertraline HCL (20 mg/kg) significantly reduced immobility time [Figs. 1 & 2]. The attenuating effect of SLNPs-F6 on endogenous depression may be explained to escape-directed behaviors with minimal immobility posture shown by SLNPs-F6 treated rats. TST reveals anti-immobility effects from a wide range of antidepressants, including tricyclic antidepressants (TCA), electro-convulsive shock (ECS), monoamine oxidase inhibitors (MAOI), selective serotonin uptake inhibitors (SSRI), and even atypical antidepressants. As a result, SLNPs-activity F6's could be interpreted by anyone established mechanism [11].
The forced swimming test in rodents thus is a well-known behavioral test that predicts the clinical efficacy of various types of antidepressants and explores the mechanism of action [14]. Monoamines (5-HT, noradrenaline, and dopamine) play a critical role in the development of the depression syndrome [11]. The FST stress dramatically enhanced MAO-A and MAO-B activity, lowering neurotransmitter levels in the mouse brain, according to the findings. MAO-A decreased neurotransmitters like 5-HT and NE particularly, while MAO-A and MAO-B jointly decreased DA [12]. Depression is thought to be a condition caused by malfunctions in neurotransmitters such as serotonin, dopamine, and noradrenaline [15].

CONCLUSION
The present study has shown antidepressant activity of SLNP-F6 in all classic models such as forced swimming test (FST) and tail suspension test (TST) comparable to the control group animals and standard drug Sertraline hydrochloride.
However, further studies are needed to elicit its exact mechanism of action and to identify the active ingredient as a potent and effective antidepressant agent.

CONSENT
It is not applicable.

ETHICAL APPROVAL
The experimental protocol was approved by the Institutional Animal Ethical Committee (approval ref no.1554/PO/Re/S/11/CPCSEA).