Immunohistochemical localization of serotonin in the superior colliculus of porcupine (Hystrix cristata)

The distribution and localization of serotonin immunoreactive cells in the superior colliculus of the porcupine (Hystrix cristata) was studied using the peroxidase-antiperoxidase method and an antiserum against serotonin. The study was performed on four superior colliculus’ of porcupine. Serotonin immunoreactivity showed a dense body of positively labelled cells throughout the superior colliculus. These serotonin immunoreactive cells had a characteristic arrangement corresponding to the laminar structures of the superior colliculus. In this study, the densest concentration of serotonin immunoreactive cells was found in a single tier located within the stratum zonale (SZ) and upper part of the stratum griseum superficiale (SGS). The second densest is located within stratum griseum intermedium (SGI) and the third appears as an incomplete layer, found only in the medial and central parts of the stratum griseum profundum (SGP). On the basis of these findings, serotonin has been suggested to be an inhibitory neurotransmitter and neuromodulator in the mammalian superior colliculus.