title: On the structural and phyletic origin of the aminergic nerves of the hypophysis of frog tadpoles (Rana temporaria) with special reference to pars distalis.
abstract: With the aid of lesion experiments and the Falck-Hillarp fluorescence technique, it is shown that the aminergic nerves of the hypophysis, including pars distalis, originate in the caudal hypothalamus and reach the gland via a fibre tract in the floor of tuber cinereum. However, some contribution to the eminentia mediana from the preoptic area could not be excluded. A vasomotor function of the pars distalis nerves is unlikely. Based on a comparative survey the hypothesis is put forward, that the pars distalis nerves, which disappear during the metamorphic climax, are remnants of an aminergic innervation existing together with a hypophyseal portal system as a functional link between brain and pituitary in the fish-like ancestor of amphibians. Aspects are given on the problem of why a direct pars distalis innervation has neither been retained nor evolved during evolution of tetrapods.
mesh_terms: D000818:Animals; D007031:Hypothalamus / Q000033:anatomy & histology*; D007814:Larva; D008675:Metamorphosis, Biological; D008856:Microscopy, Fluorescence; D009412:Nerve Fibers / Q000648:ultrastructure; D009434:Neural Pathways / Q000033:anatomy & histology; D018377:Neurotransmitter Agents / Q000378:metabolism*; D010802:Phylogeny; D010902:Pituitary Gland / Q000294:innervation*; D011896:Rana temporaria / Q000033:anatomy & histology*
chemical_list: D018377:Neurotransmitter Agents