**Core Concept**
Ionotropic receptors are a type of ligand-gated ion channel that rapidly open or close in response to the binding of a specific neurotransmitter. This leads to a fast, excitatory postsynaptic potential (EPSP) in the postsynaptic neuron, characterized by an influx of ions. Ionotropic receptors are often found in the central nervous system, including the hippocampus, where they play a crucial role in learning and memory.

**Why the Correct Answer is Right**
Ionotropic receptors are a subtype of ligand-gated ion channels, which include receptors for neurotransmitters such as glutamate (AMPA and NMDA receptors), acetylcholine (nicotinic receptors), and GABA (GABA_A receptors). These receptors are characterized by their rapid activation and desensitization, which allows for the rapid transmission of signals between neurons. For example, the NMDA receptor is an ionotropic receptor that is specifically activated by glutamate and is involved in synaptic plasticity and learning.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is a type of metabotropic receptor, which is a subtype of G protein-coupled receptor (GPCR) that activates a signaling cascade rather than directly opening an ion channel.

**Option B:** This option is incorrect because it is a type of voltage-gated ion channel, which is activated by changes in the membrane potential rather than by the binding of a neurotransmitter.

**Option C:** This option is incorrect because it is a type of receptor that activates a signaling cascade through a G protein, rather than directly opening an ion channel.

**Option D:** This option is incorrect because it is a type of receptor that is involved in the regulation of gene expression, rather than directly participating in the transmission of signals between neurons.

**Clinical Pearl / High-Yield Fact**
Ionotropic receptors are often targeted by anesthetics, which can block their activity to prevent the transmission of pain signals. Additionally, ionotropic receptors are involved in the pathophysiology of various neurological disorders, including epilepsy and Alzheimer's disease.

**Correct Answer:** C.