Electrophysiological and morphological properties of neurons in the prepositus hypoglossi nucleus that express both Ch<scp>AT</scp> and <scp>VGAT</scp> in a double‐transgenic rat model

<jats:title>Abstract</jats:title><jats:p>Although it has been proposed that neurons that contain both acetylcholine (<jats:styled-content style="fixed-case">AC</jats:styled-content>h) and γ‐aminobutyric acid (<jats:styled-content style="fixed-case">GABA</jats:styled-content>) are present in the prepositus hypoglossi nucleus (<jats:styled-content style="fixed-case">PHN</jats:styled-content>), these neurons have not been characterized because of the difficulty in identifying them. In the present study, <jats:styled-content style="fixed-case">PHN</jats:styled-content> neurons that express both choline acetyltransferase and the vesicular <jats:styled-content style="fixed-case">GABA</jats:styled-content> transporter (<jats:styled-content style="fixed-case">VGAT</jats:styled-content>) were identified using double‐transgenic rats, in which the cholinergic and inhibitory neurons express the fluorescent proteins tdTomato and Venus, respectively. To characterize the neurons that express both tdTomato and Venus (D+ neurons), the afterhyperpolarization (<jats:styled-content style="fixed-case">AHP</jats:styled-content>) profiles and firing patterns of these neurons were investigated via whole‐cell recordings of brainstem slice preparations. Regarding the three <jats:styled-content style="fixed-case">AHP</jats:styled-content> profiles and four firing patterns that the D+ neurons exhibited, an <jats:styled-content style="fixed-case">AHP</jats:styled-content> with an afterdepolarization and a firing pattern that exhibited a delay in the generation of the first spike were the preferential properties of these neurons. In the three morphological types classified, the multipolar type that exhibited radiating dendrites was predominant among the D+ neurons. Immunocytochemical analysis revealed that the <jats:styled-content style="fixed-case">VGAT</jats:styled-content>‐immunopositive axonal boutons that expressed tdTomato were primarily located in the dorsal cap of inferior olive (<jats:styled-content style="fixed-case">IO</jats:styled-content>) and the <jats:styled-content style="fixed-case">PHN</jats:styled-content>. Although the <jats:styled-content style="fixed-case">PHN</jats:styled-content> receives cholinergic inputs from the pedunculopontine tegmental nucleus and laterodorsal tegmental nucleus, D+ neurons were absent from these brain areas. Together, these results suggest that <jats:styled-content style="fixed-case">PHN</jats:styled-content> neurons that co‐express <jats:styled-content style="fixed-case">AC</jats:styled-content>h and <jats:styled-content style="fixed-case">GABA</jats:styled-content> exhibit specific electrophysiological and morphological properties, and innervate the dorsal cap of the <jats:styled-content style="fixed-case">IO</jats:styled-content> and the <jats:styled-content style="fixed-case">PHN</jats:styled-content>.</jats:p>