Primary Projections of the Lateral Line Nerves in Adult Lampreys

Abstract

Primary lateralis projections in silver lampreys, Ichthyomyzon unicuspis, and young adult sea lampreys, Petromyzon marinus, were examined utilizing silver impregnation of degenerating fibers and transganglionic transport of horseradish peroxidase. Anterior lateral line nerve afferents terminate throughout the neuropil of the electroreceptive dorsal nucleus and in the lateral neuropil of the mechanoreceptive medial nucleus. The superficial ophthalmic, buccal and recurrent rami of the anterior lateral line nerve all project to the ipsilateral dorsal nucleus; the recurrent ramus, supplying electroreceptors on the trunk, possesses the largest terminal field. No somatotopy was apparent in the projections to the dorsal nucleus. Primary afferents in the posterior lateral line nerve project to the medial neuropil of the ipsilateral medial nucleus, continue rostrally into the cerebellum and cross to the central neuropil of the contralateral medial nucleus. Lateralis projections in lampreys resemble those in nonteleost bony fishes and elasmobranchs; however, the contralateral projection of the posterior lateral line nerve is presently recognized only in petromyzontids.

Inhibitory control of ascending glutamatergic projections to the lamprey respiratory rhythm generator

“…In particular, retrogradely labeled neurons were found mainly in a periventricular layer at the level of the respiratory motor column. This location could correspond at least in part to that of neurons of the dorsal and medial octavolateral nuclei described in previous studies (Nieuwenhuys, 1972;Northcutt, 1979;Bodznick and Northcutt, 1981;Ronan and Northcutt, 1987;Koyama et al, 1990;Koyama, 2005). As in the respiratory motor regions, retrogradely labeled neurons were both ipsi-and contralateral to the pTRG.…”

“…The OLA consists of three primary octavolateralis nuclei arranged dorsoventrally which receive multiple sensory inputs. More specifically, it has been described that the dorsal nucleus receives electroreceptive inputs, the medial nucleus receives mechanoreceptive inputs and the ventral nucleus receives vestibular inputs (Rovainen, 1979;Northcutt, 1979;Bodznick and Northcutt, 1981;Ronan and Northcutt, 1987;Koyama et al, 1990Nieuwenhuys, 1972. Interestingly, it has been reported that afferent projections of the glossopharyngeal and vagal nerves terminate in the OLA, especially in its medial and ventral nuclei (Koyama, 2005).…”

Initiation of locomotion by lateral line photoreceptors in lamprey:behavioural and neurophysiological studies

“…8B,D). This confirms the findings of other investigators (Fritzsch et al 1984;Koyama et al 1990;Ronan and Northcutt, 1987;Ronan, 1988;Ronan and Bodznick, 1991). To investigate whether there are contralaterally projecting neurones in this area, HRP was injected into different sites of the contralateral rhombencephalic reticular formation (N=24) to fill commissural neurones retrogradely through their axons (eight injections in the ARRN, eight injections in the MRRN and eight injections in the PRRN; the typical sites of injection are shown in Fig.…”

“…8C,E,F). Almost no crossing cells were found in the lateral part of the MON, which receives lateral line input from the head region (Ronan and Northcutt, 1987). Rostrocaudally, the commissural cells were located between the entrance of the PLLN and the root of the vagal nerve, but not in the rostral part of the MON (Fig.…”

“…However, a bilateral excitation of RS cells was also seen after transection of the contralaterally projecting afferents (Figs 5D, 6C). Neurones in the termination area of the PLLN afferents, that is the medial octavolateral nucleus (MON) (Ronan and Northcutt, 1987), seem likely candidates for mediating the bilateral activation of the RS system. It is possible that MON neurones receive the lateral line input and project further to both ipsilateral and contralateral RS neurones, thereby transforming the unilateral input into a bilateral signal, activating the RS system.…”