The terminal nerve ganglion in fish is formed by a small number of cells that lie adjacent to the olfactory bulb. processes of terminal nerve neurons project anteriorly to innervate the olfactory epithelium and posteriorly where they project through the medial olfactory tract to commissural regions of the subpallium(Vs)(Demski & Northcutt., 1983). Some process extend to innervate inner nuclear layer neurons in the contralateral retina. Terminal nerve neurons express gonadotropin releasing hormone, and there is some debate wether terminal nerve or the olfactory epithelium detects pheromones. The cells of the terminal nerve might act as carbon dioxide detectors (Koide et al., 2018).

Key Publications

Whitlock, K.E. (2004)
Development of the nervus terminalis: Origin and migration.
Microscopy research and technique. 65(1-2):2-12.

Koide T, Yabuki Y, Yoshihara Y.
Terminal Nerve GnRH3 Neurons Mediate Slow Avoidance of Carbon Dioxide in Larval Zebrafish.
Cell Rep. 2018 Jan 30;22(5):1115-1123. doi: 10.1016/j.celrep.2018.01.019.

Naoyuki Yamamoto and Hironobu Ito
Afferent Sources to the Ganglion of the Terminal Nerve in Teleosts
J. COMP NEUROLOGY 428:355–375 (2000)

Demski LS, Northcutt RG.
The terminal nerve: a new chemosensory system in vertebrates? 
Science (1983) 220:435–7. doi:10.1126/science.6836287

Hans Maaswinkel and Lei Li
Olfactory input increases visual sensitivity in zebrafish: a possible function for the terminal nerve and dopaminergic interplexiform cells
The Journal of Experimental Biology 206, 2201-2209

Grens K.E. Greenwood A.K. Fernald R.D.
Two Visual Processing Pathways Are Targeted by Gonadotropin-Releasing Hormone in the Retina
Brain Behav Evol 2005;66:1–9