Chemical transmission and drug action in CNS
-
Upload
arslan-tahir -
Category
Health & Medicine
-
view
156 -
download
0
Transcript of Chemical transmission and drug action in CNS
CHEMICAL TRANSMISSION AND DRUG ACTION IN THE CNS
INTRODUCTION
•Drugs acting on CNS are of special significance and of major therapeutic use but also the drugs which are commonly administered for non-medical reasons like coffee, tea and nicotine•CNS is functionally more complex. Behavior of drug on the individual cell of brain is different from the whole brain unlike the other organs
Two reasons for
understanding the action of drugs on
CNS is difficult:
CHEMICAL SIGNALING IN THE CNS
CNS produce neurotransmitter
which start processes in the body and control the biological functions
It is important to study the physiology of brain and to study chemical
signaling because whole body is linked with it.
Drug acting upon CNS will also
produce effects on the body.
For Example,
Adrenaline, controls the eyes and little bit dryness
of mouth
CHEMICAL SIGNALING IN THE CNS
CHEMICAL SIGNALING IN THE CNSNeurotransmitters control various process in the body in a range of different time scales. The time scale
may be in
Miliseconds
Minutes
Hours
Days
Months
Year
Brain system works like a candy floss into the grand canyon
Candy floss mean number of threads that are placed on a stick and enter into a grand canyon
TARGETS FOR DRUG ACTION
Targets for drug action
Receptors Enzymes Ion channels Carrier Molecules
Receptors •A protein that recognizes the body’s natural mediator or the drug•When ligand will bind, it transmits signal and elicits a biological effect
Ion channels •Ion channels are proteins in membrane that allow passage of specific ions only when activated•Upon receiving signals, it will open and allows the ions to pass
Enzymes • Biological catalysts that speed up chemical reaction without being changed•Many drugs act by inhibiting the action of enzymes
Carrier molecules •Membrane bounded proteins that transport specific molecules•Molecule to be transported binds to specific protein for recognition site on the carrier and then molecule is transferred to other side of membrane
TARGETS FOR DRUG ACTION
DRUG ACTION IN CNSStudy action of drug on brain is difficult
due to complexity of neuronal interconnections in the brain
Difficult to predict effects of blocking or enhancing release or action of one or other
neurotransmitters greatly depend upon
External inputsInfluence of glial cells
Range of secondary adaptive responses
Blood brain barrier
Drug transport to specific target in brain Direct penetration
Small non-polar molecules diffuse passively across
cell membrane
Penetration via transporters
Transporters facilitate entry into
brain
DRUG ACTION IN CNS
CLASSIFICATION OF PSYCHOTROPIC DRUGS
Anaesthetic agents •Used to produce surgical anesthesia•For example, halothane, propofol
Anxiolytic and Sedatives •Used to induce sleep and reduce anxiety•Hypnotics, sedatives, minor tranquilizers•For example, barbiturates, benzodiazepines
Antipyschotics drugs •Used to relieve schizophrenic illness•Neuroleptics, major tranquilizers•Clozapine, chlorpronazine
Antidepressant drugs •Used to relieve depressive illness•Thymoleptics•Escitalopram
Analgesic drugs •Used to relieve from pain •For example, opiates and carbamazepine
Psychomotor stimulants •Used to induce wakefulness and euphoria•Psychostimulants•For example, amphetamine, cocaine, caffeine
Psychotomimetic drugs •Used to cause disturbance of perception •Hallucinogens, psychodysleptics•For example, mesacline, phencyclidine
Cognition enhancers •Used to improve memory and cognitive performance •Nootropic drugs•For example, tacrine, donepezil
CLASSIFICATION OF PSYCHOTROPIC DRUGS
Some drugs defy this classification
For example, lithium, dissociative anesthetic, used in the treatment of manic depressive psychosis and ketamine
It produces psychotropic effect rather similar to those produced by phecyclidine
CLASSIFICATION OF PSYCHOTROPIC DRUGS
END