Question

Which of the following will cause an IPSP?

Group of answer choices

dopamine

enkephalin

epinephrine

norepinephrine

histamine

Answer 1

The correct option is (b)Enkephalin

(Although (a) can also be chosen if more than one answer is allowed-reason explained below)

IPSP- Inhibitory postsynaptic potential.

This is a potential that is generated on a postsynaptic membrane in response to a inhibitory neurotransmitter.

So in the set choices we can find that enkephalin is a inhibitory neurotransmitter. These are peptides that act as neurotransmitters that weakens the release of Substance P in the spinal cord (dorsal horn). This will inhibit the afferent pain fibres.

Also Dopamine is a neurotransmitter that can act both as inhibitory as well as excitatory neurotransmitter. So it can generate as IPSP or EPSP depending on the situation.

All others ( epinephrine,norepinephrine and histamine ) are excitatory neurotransmitters. Hence they will generate EPSP.