Delta-opioid receptor-immunoreactive neurons in the rat cranial sensory ganglia

Abstract: Immunohistochemistry for delta-opioid receptor (DOR) was performed on the rat cranial sensory ganglia. The immunoreactivity was detected in 16%, 19% and 11% of neurons in the trigeminal, jugular and petrosal ganglia, respectively. The nodose ganglion was devoid of such neurons. DOR-immunoreactive (IR) neurons were mostly small to medium-sized (trigeminal, range = 62–851 μm2, mean ± SD = 359 ± 175 μm2; jugular, range = 120–854 μm2, mean ± SD = 409 ± 196 μm2; petrosal, range = 167–1146 μm2, mean ± SD = 423 ± 233 μm2). Double immunofluorescence method revealed that all DOR-IR neurons were also immunoreactive for calcitonin gene-related peptide. The cutaneous and mucosal epithelia in the oro-facial region, tooth pulp, taste bud and carotid body were innervated by DOR-IR nerve fibers. In the brainstem, IR nerve terminals were located in the superficial medullary dorsal horn and dorsomedial part of the subnucleus oralis as well as the solitary tract nucleus. The present study suggests that DOR-IR neurons may be associated with nociceptive and/or chemoreceptive function in the cranial sensory ganglia. [Copyright &y& Elsevier]