Abstract
Nodose ganglion (NG) neurons are visceral primary sensory neurons. The transmission and regulation of visceral sensation is mediated mainly by the P2X purinoceptor (P2X receptor). Although the characteristics of different P2X receptor subunits in the NG have been studied previously, comprehensive analyses have not been performed. In this study, we used immunohistochemistry, immunocytochemistry, and whole cell patch clamp techniques to compare the expression and function of P2X1, P2X2, P2X3, and P2X4 receptor subunits in adult rat NG neurons. Polyclonal antibodies against the four P2X subunits labeled different subpopulations of NG neurons. P2X1 and P2X3 were expressed mainly in small-to-medium sized NG neurons, whereas P2X2 and P2X4 were located mostly in medium- and larger-sized NG neurons. Over 36% of NG neurons were P2X3 positive, which was higher than the other three P2X subunits. In addition, different types of currents were recorded from neurons expressing different P2X subunits. The fast type of ATP current was recorded from neurons containing P2X1–4 subunits, the intermediate type of current was recorded from neurons containing the P2X1, P2X3, and P2X4 subunits, the slow type was recorded from neurons expressing P2X1–3, and/or P2X4 subunits, whereas the very slow type was recorded from neurons containing the P2X2 and P2X3 subunits. These comparative results provide an anatomical verification of the different subunits in NG neurons, and offer direct support for the idea that various functional NG populations have distinct responses to ATP, which might be in part due to the different expression profiles of diverse P2X subunits.
Highlights
Placode-derived general visceral afferent neurons of the nodose ganglion (NG) transmit visceral sensory information from specialized sensory endings of the vagus nerve and its branches to the nucleus of the solitary tract [1]
P2X1, P2X2, P2X3, and P2X4 Expression in the NG The sensory root of the vagus nerve extended from the dorsolateral medulla oblongata, ran through the cranial cavity, and emerged at the cervical region of the jugular foramen
4) P2X1 was coexpressed with P2X2 and P2X3, P2X3-IR co-localized with P2X2-IR and P2X4-IR, whereas P2X4 was detected with P2X1 and P2X2 separately in NG neurons
Summary
Placode-derived general visceral afferent neurons of the nodose ganglion (NG) transmit visceral sensory information from specialized sensory endings of the vagus nerve and its branches to the nucleus of the solitary tract [1]. These neurons are critical for relaying various endogenous and exogenous stimuli. Adenosine 59-triphosphate (ATP), an excitatory neurotransmitter, acts on P2X purinoceptors (P2X receptor) that are formed by the assembly of three of the seven subunits, P2X1–7, to induce inward, non-selective cation currents (IATP) [4,5,6]. Quantitatively comparative studies on the expression patterns of P2X receptors in NG neurons are rare, and it remains unclear whether these receptors are expressed in the same patterns within ganglia
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