Guided By Mr.Rupesh GautamSr.Lecturer in Pharmacology

Jaipur College of PharmacyRajasthan, India

Hypnotics Screening MethodsBy Tarun BiswasM.Pharm Sem.IIDept. of Pharmacology

• Hypnotic:- Hypnotic drug are that which induce and / or maintain sleep, similar to normal arousable sleep.

Screening Methods

1. Potentiation of hexobarbital sleeping time

2. Experimental insomnia in rats3. EEG registration in conscious cats4. Automated rat sleep analysis

system

1.Pontentiation of hexobarbital sleeping timeprinciple:-. The test is used to elucidate CNS activity

of drugs . Not only hypnotics, sedative,

tranquilizers but also antidepressants . The loss of righting reflex is measured

for the duration of hexobarbital sleeping time

. Mice are used in this test.

Procedure cont ….

• NMRI mice(male) in group of 10• Average weight - 18-22gm• Orally, i.p. or s.c. dosage of test or

standard compound (e.g. Diazepam 3 mg/kg) or the vehicle.

• After 30 min i.p. or s.c injection or 60 min after oral dosing 60 mg/kg hexobarbital is injected i.v route

• The animals are placed on their backs on a warmed (37 C) pad and the duration of loss of righting reflex( starting time of hexobarbital injection) is measured.

• Injection of hexobarbital usually cause anesthesia for about 15 min.

Procedure cont ….

Evaluation:-

• Mean value of duration of anesthesia are recorded in control and experimental group

• % change in duration of anesthesia is calculated

2.Experimental insomnia in rats• Developed by james and piper 1978• The compounds are tested in normal

animals where they do not significantly decrease weakfulness.

Procedure:-• Male wistar rate 200-275gm prepared

for chronic electroencephalographic and electomyographic recording.

2.Experimental insomnia in rats Cont.

• Four silver/silver chloride electrode and two disc nuchal electrode are implanted

• Minimum10days allowed for recovery from surgery

• Animals are placed into sound-attenuated recording chamber with grid floor.

Procedure cont….

• On the control day, the animals are dosed with the vehicle and control nonstress recording is obtained for 8hrs.

• Next day the animals are again injected and then exposed to electric footshock for 8hrs

• The footshock is delivered through grid floor of the recording chamber

Cont….• During the footshock the EEG and

EMG recording circuits are automatically interrupted

• On the next day the rats are dosed with the test compound or the standard and recording are obtained during a shock session of 8hrs

Evaluation• The sleep wake cycle is definitely

altered by the stress procedure .• The amount of arousal and of slow

wave sleep 1 are increased .• Slow wave 2nd and paradoxical sleep

decreased.• Phenobarbitone and benzodiazepines

antagonize these change at least partially.

3. EEG REGISTRATION IN CONSCIOUS CATS

Principle The effect of hypnotics on sleep

pattern of EEG tracings can be studied in conscious, freely moving cats with chronically implanted electrode

Procedure

• Female cats weighing 2.5-3.5 kg are anesthetized and prepared with bipolar subcortical electrodes in the reticular formation,dorsal hippocampus,and either amygdala,caudate necleus

Procedure cont….

• Cortical screw electrode are placed over the anterior suprasylvian,lateral,medial suprasylvian ectosylvian gyri

• Two teflon coated steel wires are placed in the cervical neck muscles

All wires are connected to a subminiature

socket and implanted in dental acrylic

Cont….

• Cats of this chronic colony are then intermittently utilized for drug experiments at interdrug intervals of at least two weeks

• Cats are taken into an experimental chamber 70, 80 cm high

• The box is lighted and ventilated with room air at 21 c

Cont….

• The cat is immediately connected to a cable which exits through the top center of the cage into a mercury swivel

• Recording of the cortical EEG, cervical neck muscle tone and reticular formation multiple unit activity

Evaluation

• The data are analyzed by analysis of variance with subjects, days , and drug as factors

References

• Vogel. H. G, “Drug Discovery and Evaluation” second edition, page no.495-499