FIGURE 4.

Glutamate and GABA mediate the crosstalk between the lamellar cells and the afferent in Pacinian corpuscles. (A) Left panel, schematic representation of action potentials’ firing recorded from a LTMR of a Pacinian corpuscle isolated from a cat upon application of mechanical stimulation. The afferent fires action potentials upon application and removal of the mechanical stimulation, but not during the static portion of the indentation. Middle panel, upon application of the glutamate receptor antagonist kynurenate, there is a significant loss of activity in the afferent. Left panel, on the contrary, addition of the GABA_A receptor antagonist picrotoxin induces increase of firing of action potentials in the afferent. Together these data support that glutamate and GABA act on the LTMRs of Pacinian corpuscles to regulate their excitability. (B) Drawing representing glutamate and GABA signaling between the lamellar cells and the afferent in Pacinian corpuscles based on results obtained in the cat (Pawson et al., 2000, 2007, 2009). RT-PCR demonstrates the presence of the vesicle-associated protein VAMP2 in the lamellar cells, suggesting that the lamellae of the Pacinian corpuscles are capable of establishing a synapse-like structure with the afferent. This idea is supported by the detection of clear core vesicles within the lamellae. Clear core vesicles are also detected in the afferent. In addition, antibody staining detects glutamate receptors and GABA_A receptors in the innermost core of the Pacinian corpuscle, where the afferent makes contact with the lamellar cells. Piezo2 channels have been recently localized to the αβ-RA-afferents of the Pacinian corpuscles of the mouse (Handler et al., 2023).