Gaba receptors

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GABA RECEPTORS:

GABA RECEPTORS BY MOHD. SHARIQ ANSARI DEPARTMENT OF PHARMACOLOGY H.S.K. COLLEGE OF PHARMACY BAGALKOT KARNATAKA SEMINAR ON

CONTENTS:

CONTENTS HISTORY INTRODUCTION SYNTHESIS AND METABOLISM FUNCTIONS GABA RECEPTORS CLASSIFICATION AGONIST AND ANTAGONIST PHARMACOLOGICAL EFFECTS REFERENCE

HISTORY:

HISTORY Before 1883 known as a metabolite of plants and microorganisms. 1949 identified in animal tissue,not incorporated in proteins. 1956 first indications on an inhibitory activity on nervous tissue. In 1950, further, GABA was discovered to be an integral part of the mammalian central nervous system.

INTRODUCTION:

INTRODUCTION GABA (gamma- amino butyric acid) is the major inhibitory amino acid transmitter of the mammalian central nervous system and it is present in some 40% of all neurons of cortex. GABA contributes to motor control, vision, and many other cortical functions. It also regulates anxiety. It is abundant in nigrostraital system, and also occur in lower conc. n throughout the grey matter. This channel mainly allows chloride influx against gradient neurons to enter the neuron, thus reducing its excitability, and thus classified as an inhibitory neurotransmitter.

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Vigabatrine - SYNTHESIS AND METABOLISM

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SYNTHESIS AND METABOLISM Guvacine, nipecotic acid - - Vigabatrine -

FUNCTION OF GABA:

FUNCTION OF GABA Inhibitory transmitter Servers as a transmitter at about 30% of all synapses in the CNS. In short it is obiquitous in the brain.

RECEPTORS:

RECEPTORS GABA receptors are channels receptors . This means that when GABA binds to them, they change shape slightly to allow ions to pass through their central channel. GABA acts on two distinct types of receptor the GABA A receptor ( ligand-gated channel ) - pentameric in structure (α, β, and γ ) the GABA B ( G-protein coupled receptor ) - functional receptor is dimer consisting of 2 different subunits GABA A receptors located perisynaptically are responsible for slow inhibitory, effects produced by GABA diffusing further from its site of release. Thus GABA produces inhibition by acting both as a fast 'point-to-point' transmitter and as an 'action-at-a-distance' neuromodulator

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GABA A receptor GABA A receptors resemble NMDA receptors in that drugs may act at several different sites. These include the GABA-binding site several modulatory sites the ion channel.

GABAB receptor:

GABA B receptor G-protein coupled receptor, hyperpolarises neurons by increasing K + conductance and altering Ca 2+ flux. Insensitive bicuculline. Widespread pre- and postsynaptically. Selectively activated by the antispastic drug baclofen, are coupled to G proteins that either inhibit calcium channels or activate potassium channels.

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GABA C RECEPTOR A 3 rd class receptor has recently been proposed which closely resembling GABA A receptors in their structure and function. The GABA C receptor is a transmitter-gated Cl – channel. The GABA C receptor is less widely distributed than the A and B subtypes. GABA is more potent by an order of magnitude at GABA C than at GABA A GABA C receptor are constructed from a different family of subunits and have slightly different pharmacological properties. Their functional significance remains unknown. GABA C receptors are found in the retina, spinal cord, superior colliculus , and pituitary.

γ-HYDROXYBUTYRATE:

γ -HYDROXYBUTYRATE Side product Occurs in brain As a synthetic drug from 1960 onwards, It has found favour with bodybuilders, based on its ability to evoke the release of growth hormone, and with party-goers, based on its euphoric and disinhibitory effects. The pharmacological properties of GHB are not well understood, although it is believed to activate GABA B receptors, partly through conversion to GABA, and may also bind to specific GHB receptor sites, of which little is known.

DRUGS ACTING ON GABA RECEPTORS:

DRUGS ACTING ON GABA RECEPTORS

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Reduction of anxiety & aggression Sedation & induction of sleep Reduction of muscle tone & coordination Anticonvulsant effect PHARMACOLOGICAL EFFECTS

REFERENCES:

‘‘ Pharmacology’’ by Rang and Dale , 6 th edition , ELSEVIER Publications ‘‘ Essentials of medical pharmacology’’ by KD Tripathi, 6 th edition, JAYPEE Publications. Basic and clinical pharmacology by G. katzung , 9 th edition. www.nature.com www.google.co.in REFERENCES

THANKS:

THANKS

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