Localisation of parvalbumin and calbindin D28k in the periaqueductal gray matter [PAG] of the chinchilla

The purpose of this study was to trace the immunoreactivity of the two calcium binding proteins, parvalbumin and calbindin D28k, in the periaqueductal gray matter of the chinchilla midbrain. The immunoreactivity of these proteins in this species has never been investigated. The localisation of the activity was examined by carrying out the peroxidase-antiperoxidase (PAP) reaction using specific antibodies against parvalbumin and calbindin D28k. Slightly different parvalbumin immunoreactivity was shown. In most neurons, with the exception of large neurons in the dorsal and dorso-lateral periaqueductal gray matter, a weak immunostaining for parvalbumin was observed. Extremely intense immunostaining for calbindin D28k occurred in all neurons in the examined area. The results obtained suggest a slightly different distribution of parvalbumin in the neurons of the periaqueductal gray matter of the midbrain of the chinchilla than in other animal species. This indicates that mainly calbindin D28k is involved in the regulation of intracellular calcium ion concentration in the periaqueductal gray matter of the chinchilla.