Pentobarbitone Induced Sleeping Time - A animal model for evaluate CNS depressant Activity of unknown drug.
Barbiturates induce sleep in man and animals by depressing the central nervous system. Barbiturate is a GABA receptor agonist, probably binds picrotoxin-binding site of GABA receptor, and results in increase in duration of opening of chloride channel thus reduced membrane excitability. They also inhibit excitatory AMPA glutamate receptor. The barbiturate-induced hypnosis can be easily studied in experimental animals. For this purpose generally Pentobarbitone Sodium a short to mediate acting barbiturate, is used Pentobarbitone produces quick onset of sleep is indicated by loss of righting reflex and the recovery is easily detected as the animal regain their righting reflex. Righting reflex is referred as inability to maintain posture. This can be elicited by lifting the animal at a time up to the height and dropped the animal from that height gently on table covered with soft cushion. Animals that is dropped from height immediately restores the posture and behaves normally. This immediate regaining of posture is termed as righting reflex. The time between losses of recovery of righting reflex is recorded as sleeping time. Depressant action of an extract on CNS is indicated by increase of the barbiturate induced sleeping time.
Healthy young 8 to 12 weeks old Albino Wistar rats of laboratory strains of either sex weighing 200 -250 g should be employed. Females should be nulliparous and non-pregnant. The temperature in the experimental animal room was should be at 22°C (± 3°C) with the relative humidity was at 50 % to 60 %. Lighting should be provided artificial, the sequence being 12 hours light and 12 hours dark. The animals should be housed individually. For feeding conventional rodent laboratory diets should be used with an unlimited supply of drinking water. The animals should be kept in their cages for at least 5 days prior to dosing to allow for acclimatization to the laboratory conditions and should be fasted overnight ad libitum prier to dosing extract/ standard drug/ vehicle.
Selection of doses of drug/ extract (As per OECD Guidelines 425):
For the assessment of Antidepressant activity, three dose levels should be chosen in such a way that, middle dose should be approximately one tenth of the maximum dose during acute toxicity studies, and a high dose should be twice that of one tenth dose and a low dose should be 50% of one tenth dose
Divide overnight fasted animals in to four groups comprising of six animals each. Administer Phenobarbitone (40 mg /Kg body weight, i.p) one hour after oral administration of extracts or drug orally (2 mL/100g body weight, extract / drug should be suspended in 0.6% Sodium Carboxy Methyl Cellulose) to animals of group II and IV, and record the sleeping time as the period starting with loss and regaining righting reflex. Serve Group I as control should receive vehicle (2mL/100g body weight, 0.6% Sodium Carboxy Methyl Cellulose) and Pentobarbitone.
The data should be presented as mean ± SEM. The data should be analyzed by one-way analysis of variance (ANOVA) followed by Dunnett’s test.