“… Indented ≈ presynaptic processes run in a deep pit or groove; invaginated ≈ presynaptic varicosity is embedded within the postsynaptic process. CNS, central nervous system; en, endocrine gland cells; ex, exocrine gland cells; NMJs, neuromuscular junctions; SSR, subsynaptic reticulum; SJFs, subjunctional folds; dash indicates no information found 1 Pavans de Ceccatty (1966) 2 Horridge (1965) 3 Hernandez-Nicaise (1973) 4 Spencer (1979) 5 Westfall et al (1971) 6 Holtmann and Thurm (2001a, b) 7 Pan (1980) 8 Petralia et al (2015) 9 Reger (1965) 10 Clément (1977) 11 Duvert and Barets (1983) 12 Lacalli (1990) 13 Reger (1969), Rosenbluth (1973), Yaksta-Sauerland and Coggeshall (1973) 14 Graziadei (1966), Barber and Graziadei (1967), Rogers (1969), Økland (1980), Elekes and Ude (1994) 15 Ducros (1972), Elekes and Ude (1994) 16 Moraes et al (2010) 17 Dilly et al (1963), Case et al (1972), Cohen (1973), Haghighat et al (1984) 18 Castejón and Villegas (1964) 19 Melamed and Trujillo-Cenoz (1971), Smith (1971), Fourtner and Sherman (1973), Sherman (1973) 20 Hart et al (1980) 21 Lang (1972), Sherman and Fourtner (1972), Fourtner and Sherman (1973) 22 Filimonova and Amosova (2015) 23 Oberdorfer (1977) …”