Fig. 8

Histaminergic neurons in the central nervous system of Euscorpius italicus. Sagittal sections (anterior to the left, ventral to the bottom) showing immunoreactivity of histamine (green) and synapsin (grey). a Three protocerebral histaminergic neurons (PCC) were identified anterodorsally to the arcuate body (AB). These somata sent projections ventrally toward more caudal body regions (white arrows). b Close-up of the PCC in A, revealing a single primary neurite for each immunoreactive cell body (white arrows). c These neurites innervated the whole nervous system, projecting not only caudally, but also anteriorly and posteriorly (white arrowheads). d The primary neurites innervated the entire nervous system, including the most posterior regions of the mesosoma (white arrows). Abbreviations: AB: arcuate body; PC: protocerebrum; PCC; protocerebral cell bodies; PN: pectine neuropil. Scale bars: a, d: 100 μm; b, c: 50 μm