Question

9) Execution by lethal injection involves administration of the following drugs, in order: Sodium thiopental (a barbiturate), which activates ionotropic GABA receptors Tubocurarine chloride (a.k.a.curare), which blocks ACAR Potassium chloride, which increases extracellular potassium levels a. For each, describe the effect this drug would have on electrochemical signaling and the effects on the postsynaptic neurons. (2 points each, 6 points total) b. Suggest an intervention that could reverse the effects of two of these three drugs (4 points)

Answer 1

Answer 9 :

1. Sodium Thiopental

Effects of this drug:

• It’s a barbituric acid derivative that possesses anesthetic activity. This drug binds with the chloride ionophore sites and thus, enhances the gamma-aminobutyric acid (GABA)-A which ultimately affects the brain by its inhibitory actions.
• The synaptic inhibition is achieved with its action that further decreases the excitability of the neurons in the brain and thereby producing the anesthetic effects.
• This drug acts on the central nervous system, especially at a particular site called the polysynaptic midbrain reticular formation site. This site deals with arousal mechanisms. It creates an imbalance in the central system that influences the cerebral cortex of the brain. This further suggests that on the administration of this drug it eventually decreases both presynaptic and postsynaptic membranes causing sedative effects.

Intervention that could reverse the effect of the drug:

• Possibly the effects can be intervened by benzodiazepines for example diazepam.

2. Tubocurarine Chloride

Effects of this drug:

• This drug is the antagonist i.e., inhibits the physiological functioning of the nicotinic acetylcholine receptor (nAChr), in which it blocks the acetylcholine (ACh) receptors which is otherwise the component of the peripheral nervous system and is involved in activating the skeletal muscles. The primary function of Acetylcholine is to activate the skeletal muscles by choline acetyltransferase enzyme that acts by getting transported to the synaptic gap of the neurons in the body.
• While competing with the acetylcholine to bind with nicotinic receptors that are present at the neuromuscular junction of skeletal muscles. This drug inhibits the normal mechanism of acetylcholine and blocks the neural transmission. These reactions occur without depolarizing the postsynaptic membrane. All these make an effect on the body by causing the relaxation of skeletal muscles.

Intervention that could reverse the effect of the drug:

• Tetraethyl ammonium (TEA), is the blocker of the potassium channel and is known to reverse the effect of the Tubocurarine Chloride drug.

3. Potassium chloride

Effects of this drug:

• This drug has antihypertensive effects that are considered as a nutritional supplement for the prevention of hypokalaemia. This is required in the patients whenever there is loss of potassium higher via renal excretions compared to its intake by the gastrointestinal systems.
• This drug helps in maintaining the required nerve conduction of the body. It is crucial for its role in inhibiting the GABA_A receptors and glycine receptors in the central nervous system. As if any disturbance occurs in the neuronal K⁺ gradient in the neurons it would affect the KCC2 activity.
• The loss of proper KCC2 function is also associated with inhibitory and developmental regulation over neurons that cause their hyperexcitability.
• The KCC2 activity conferred by the drug in the hypokalaemia patients helps them maintain the normal count of ions. The excessive ion influx can also pose a problem by causing the osmotic extrusion of cells so the maintenance of ions is important to carry out proper synaptic stimulations in the neuronal membranes and for its stable osmotic homeostasis.