Sensory Neurons in Different Parts of the Body

Sensory neurons are a critical component of the peripheral nervous system, responsible for detecting a wide range of stimuli including mechanical, chemical, thermal, and light signals. These neurons transmit sensory information to the central nervous system (CNS), enabling organisms to perceive and respond to their environment. Their highly specialized differentiation in tissues such as the skin, eyes, and internal organs reflects an evolutionary adaptation to complex environmental demands. Understanding the diversity and specificity of sensory neurons is not only fundamental to basic neuroscience but also provides a theoretical foundation for disease modeling and drug development.

Table 1 Comparison of cross-organ sensory neuron characteristics

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Skin Sensory Neurons

As the largest sensory organ in the human body, the skin is covered with highly specialized sensory nerve endings:

Table 2 Types and function of skin sensory neurons

Figure 1 Diagram of skin sensory neurons.

Ocular Sensory Neurons

Retinal Sensory Neurons

• Rod cells: responsible for dark vision, highly light-sensitive, contain rhodopsin.
• Cone cells: responsible for light vision and color vision, contain three types of opsins.

Corneal Sensory Neurons

• Mechanical nociceptors (20%): Respond to foreign body contact, mediate sharp pain (involving Piezo2 channels).
• Polymodal nociceptors (70%): Detect mechanical, chemical, and inflammatory stimuli.

Comparison With Olfactory Neurons

Both are special sensory neurons containing highly specialized receptors (photoreceptors/olfactory receptors).

Table 3 Difference of visual and olfactory neurons

Visceral Sensory Neurons

Stimulations

• Mechanical: Organ stretching (e.g., gastric distension).
• Chemical: Ischemia, inflammatory mediators (histamine, bradykinin).
• Thermal: Changes in visceral temperature.

Pain Characteristics

Vague localization, referred pain (e.g., angina pectoris radiating to the left arm), accompanied by autonomic nervous system responses (nausea, sweating).

Emerging Research and Application Prospects

Traditional animal models used in neurodegenerative disease research face challenges such as species differences, ethical constraints, and high costs. The emergence of in vitro CNS models (such as organoids and microfluidic chips) has provided new avenues for elucidating the role of sensory neurons in disease. For example, skin sensory neurons derived from induced pluripotent stem cells (iPSCs) can simulate hyperalgesia, while retinal organoids can reveal the mechanisms of photoreceptor degeneration. This technological breakthrough not only validates the specific functions of sensory neurons but also reveals their dynamic changes in disease.

iPSC Differentiation

iPSCs are directed to differentiate into sensory neurons by regulating key transcription factors (such as Lhx2 and Ngn2) and growth factors (NGF and GDNF).

Figure 2 Expression of sensory neuron related proteins in hiPSC-derived sensory neurons and their morphology.^1,2

Functional validation can be performed using the following technical methods:

• Electrophysiological Characteristics: Using patch-clamp technology to detect the activation response of TRP channels (e.g., TRPV1, TRPA1) and quantify the efficiency of pain signal transmission.
• Molecular Markers: Verify the expression levels of pain-related genes such as Nav1.7 and CGRP via qPCR.

Advantages of iPSC differentiation:

• Individualized Modeling: Transplant patient-specific mutant genes (e.g., Nav1.7 mutants) to simulate hereditary pain syndromes.
• High-Throughput Screening: Combine microelectrode arrays (MEA) to monitor the real-time effects of drugs on neuronal firing.

3D Organoids and Organoid Chips

Three-dimensional organ models can simulate the in vivo environment and form complex tissue structures, including various types of sensory neurons and supportive glial cells, thereby enhancing neuronal maturity and function.

Co-culturing retinal neurons with supporting cells can form retinal-like tissue to simulate light signal conduction pathways. Organoid chips utilize integrated microfluidic systems to simulate blood flow and inflammatory factor release, studying the ischemic response of visceral sensory neurons.

Current Technical Obstacles in Sensory Neuron Research

Although iPSC-based in vitro models have achieved breakthroughs in drug screening (e.g., pain treatment) and disease mechanism research (e.g., retinal degenerative diseases), the following issues still need to be addressed:

• Lack of vascularization: Organoids lack blood supply, limiting nutrient diffusion and metabolic waste removal.
• Lack of immune interaction: The absence of immune components such as microglia makes it difficult to simulate neuroinflammation.
• Insufficient maturity: The synaptic density of neurons in vitro is lower than in vivo, and there are significant differences in electrophysiological characteristics.

Future Directions of Sensory Neuron Research

Sensory neurons have important therapeutic potential in the treatment of pain, visual impairment and visceral dysfunction. By studying the electrophysiological properties, neurotransmitter systems, plasticity and interactions with other neurons of sensory neurons, it is possible to find new targets and treatment strategies for these diseases. Future research needs to further understand the mechanisms of sensory neurons in diseases and explore new therapeutic methods for these mechanisms.

Pain Management

In the treatment of pain, sensory neurons play a crucial role in the transmission of pain signals. In particular, in the treatment of neuropathic pain (NP) and chronic pain, abnormal activity of sensory neurons is one of the important causes of pain maintenance and aggravation. For example, the TRPV4 ion channel is important for visceral sensory neurons, and agonists or antagonists of TRPV4 can be potential drugs for visceral pain. The activators of KCNQ2/3 potassium channels, such as ICA-069673, can inhibit the excitability of vagal sensory neurons and have analgesic effects in inflammatory visceral diseases.

Visual Impairment

In addition to somatic pain, sensory neurons are also involved in the perception and processing of visual information. For example, glutamatergic neurons in visual cortex V2M region (V2MGlu) are important in pain regulation, and the activity of V2MGlu may be involved in pain perception and emotional processing. In addition, the plasticity of sensory neurons is also important in the processing of visual information, for example, the selectivity of visual responses in the developing cerebral cortex depends on the plasticity-mediated regulation of visual experience.

Visceral Dysfunction

Visceral sensory neurons are important for maintaining visceral function and regulating visceral activity. In gastrointestinal diseases such as irritable bowel syndrome (IBS), the chemical and mechanical sensory function of visceral sensory neurons is very important. For example, in IBS, the abnormal expression of TRPV4 channels and 5-HT4 receptors are related to visceral pain and dysfunction, and the drug GR113808 can reverse these abnormal expressions.

Therapeutic Potential

The study of sensory neurons has multiple potential therapeutic targets in pain management, visual impairment and visceral dysfunction. The plasticity of sensory neurons and the regulation of neurotransmitter systems (such as GABA, glutamate and 5-HT) may also have a theoretical basis for treatment. For example, the activation of GABAergic neurons can inhibit pain signal transmission in the spinal cord dorsal horn, thereby achieving pain relief.

Creative Biolabs uses the latest models and platforms, such as iPSC-derived sensory neurons that express important pain-related channels, microelectrode arrays (MEAs) to record neural activity over long periods of time, and neurotransmitter quantification methods like mass spectrometry and high-performance liquid chromatography (HPLC). Creative Biolabs is dedicated to state-of-the-art research to support you in developing innovative therapies for neurological disorders and pain management.

Contact us today to find out how our services and platforms can help fast-track your research and drug discovery projects.

References

1. Hiranuma, Minami, et al. "Characterization of Human iPSC-Derived Sensory Neurons and Their Functional Assessment Using Multi Electrode Array." Scientific Reports, vol. 14, no. 1, Mar. 2024, p. 6011. DOI.org, https://doi.org/10.1038/s41598-024-55602-8.
2. Distributed under Open Access license CC BY 4.0, without modification.

Created June 2025

For Research Use Only. Not For Clinical Use.