THE INNERVATION OF THE CEPHALIC AORTA OF NAUTILOIDS (TETRABRANCHIATA,CEPHALOPODA)

The cephalic aorta of Nautilus macromphalus (G. B. Sowerby) and Nautil us pompilius (L.) has a four-layered wall with an extended marginal bl ood sinus between tunica adventitia and tunica periadventitia. The ner ve terminals within these two peripheral layers contain different type s of vesicles; transparent circle divide 32-65 nm), dense cored (circl e divide 59-99 nm) and osmiophilic (circle divide 68-116 nm). The high activity of acetylcholinesterase (E. C. 3.1.1.7), localized histo- an d cytochemically in nerve endings and muscle cells of these marginal l ayers, suggests a cholinergic component in the nervous control of the vessel wall. Evidences for a catecholaminergic component in regulation of the vessel tonus are provided by a high activity of the monoaminoo xidase (E. C. 1.4.3.4), the glyoxylic acid induced fluorescence of ner ve terminals (Em(max) = 480 nm and Em(max) = 520 nm) within the tunica adventitia and tunica periadventitia, and by the spectrum of catechol amines of the vessel wall revealed by HPLC analyses. Immunocytochemica lly FMRFamide or related peptides were localized within axon terminals .