The axons that make up the pathway emerge from the basal portions of the granule cells and pass through the hilus (or polymorphic cell layer) of the dentate gyrus before entering the stratum lucidum of CA3. Granule cell synapses tend to be glutamatergic (i.e. excitatory), though immunohistological data has indicated that some synapses contain neuropeptidergic elements including opiatepeptides such as dynorphin and enkephalin. There is also evidence for co-localization of both GABAergic (i.e. inhibitory) and glutamatergic neurotransmitters within mossy fiber terminals.[8][9] GABAergic and glutamatergic co-localization in mossy fiber boutons has been observed primarily in the developing hippocampus,[10] but in adulthood, evidence suggests that mossy fiber synapses may alternate which neurotransmitter is released through activity-dependent regulation.[11]
^Henze DA, Buzsáki G (2007). "Hilar mossy cells: functional identification and activity in vivo". The Dentate Gyrus: A Comprehensive Guide to Structure, Function, and Clinical Implications. Progress in Brain Research. Vol. 163. pp. 199–216. doi:10.1016/s0079-6123(07)63012-x. ISBN9780444530158. PMID17765720.
^Amaral DG, Scharfman HE, Lavenex P (2007). "The dentate gyrus: fundamental neuroanatomical organization (dentate gyrus for dummies)". The Dentate Gyrus: A Comprehensive Guide to Structure, Function, and Clinical Implications. Progress in Brain Research. Vol. 163. pp. 3–22. doi:10.1016/S0079-6123(07)63001-5. ISBN9780444530158. PMC2492885. PMID17765709.
^Sandler R, Smith AD (January 1991). "Coexistence of GABA and glutamate in mossy fiber terminals of the primate hippocampus: an ultrastructural study". The Journal of Comparative Neurology. 303 (2): 177–92. doi:10.1002/cne.903030202. PMID1672874. S2CID42502573.