🔴 Mechanism of Action 🔴

🔺General Anaesthetics :-

General anesthesia is defined by reversible unconsciousness, lack of response to noxious stimuli, and amnesia, induced by chemical agents.

Mechanisms underlying the anaesthetic effect are not known.
The most prevalent belief was that anaesthetic drugs acted on the lipid cell membranes, based on the correlation between oil solubility and anaesthetic potency.
Later, it has been proposed that anaesthetic agents act on specific proteins of the cellular membrane of neurons. Voltage-gated ionic channels are inhibited by anaesthetics agents, being some subtypes more sensitive.
Clinical concentration of anaesthetic agents inhibit or stimulate excitatory or inhibitory neurotransmitter receptors, respectively.
Specific receptor agonists and antagonists modify this effect. Intercellular channels (gap junctions) are also affected by anaesthetic agents through direct interaction with some of their protein subunits. Thus, anesthesia would result from combined effects on specific proteins acting on neural cell excitability as well as transmission and propagation of nerve impulses.

🔴 Mechanism of Action 🔴

🔺Sedative Hypnotics 🔺

🔸Barbiturates :-

Barbiturates act primarily at GABA:BZD ( Gamma Amino Butaric Acid : Benzodiazepines)
receptor Chloride ion Complex and potentiate GABAergic inhibition by increasing the lifetime of Chloride channel opening induced by GABA.

The barbiturate site appears to be located on the alpha and beta subunit.

At high concentrations barbiturates directly increase Chloride conductance (GABA mimetic action).

Moreover, at high doses barbiturates inhibit Calcium ion dependant release if neurotransmitters, depress glutamate induced neuronal depolarization through AMPA receptor and depress voltage sensitive Sodium and Potassium channels.

🔹Other Actions of Barbiturates :-

At relatively high doses, depress respiration, lower B.P. , decrease cardiac contractility and Heart rate, reflex tachycardia due to fall in BP.

Muscle tone, bowel motility and urine output also reduced.

Toxic dose causes respiratory failure and Cardiovascular collapse.

🔴 Mechanism of action 🔴

🔺Sedative hypnotics 🔺

🔸 Benzodiazepines :-

Benzodiazepines act preferentially on midbrain ascending reticular formation ( which maintains wakefulness)
and limbic system.

Benzodiazepines enhance the effect of the neurotransmitter gamma-aminobutyric acid (GABA) at the GABAA (ion channel receptor )receptor, resulting in sedative, hypnotic (sleep-inducing), anxiolytic (anti-anxiety), anticonvulsant, and muscle relaxant properties.