Sentient animals have the ability to feel touch and painful stimuli, to sense cold and hot, to respond to aversive stimuli by adaptive reflexive movements. These fundamental activities, essential for survival, are encoded by neuronal circuits that link the somatosensory (body sense) and motor systems (appropriate action). We study how these interlinked systems are established during development and how they function in the normal and pathological states.
1. Development. Neural differentiation and connectivity in the somatosensory system.
The ability to detect changes in temperature, noxious stimuli, touch and body position is essential for organisms to respond appropriately to a changing environment. Somatosensory neurons of the dorsal root ganglia (DRG) detect external environmental signals and information from internal organs and convey these signals to the central nervous system where they are integrated into neuronal circuits that control posture, ambulatory movements, motor reflexes and protective responses to injury and disease. Ascending pathways transmit somatosensory information to the brain. Our experimental models range from genetic studies on fruit fly (Drosophila) embryos, chick embryos, primary neurons in culture to behavioural tests on transgenic mice. Deepening our knowledge of these fundamental developmental processes will allow us to better understand how different neuron sub-types respond in pathological situations, and to ameliorate the outcome in various types of peripheral neuropathies.
2. Physiopathology: injury induced plasticity.
The pathologies of this system, called peripheral neuropathies, affect at least 3 million people in France and the prevalence increases with age (3.5% under 50 years, 8% above 50 years). Existing treatments are often ineffective. Although their causes are numerous (trauma, metabolic, infection, toxic, genetic, autoimmune) the post-traumatic neuropathies, including post-surgical trauma, are by far the most frequent. Regardless of the aetiology, the consequences of sensory neuropathies are essentially of two types: neuropathic pain (hyperalgia and allodynia) and dysfunction of the sensori-motor system (ataxias). Post-traumatic pain, for example, accounts for 45-50% of the consultations in the centers for evaluation and treatment of pain conditions.