P2X receptor expression on astrocytes in the nucleus accumbens of rats.

Astrocytes express a variety of neurotransmitter receptors which render them capable of responding to extracellular stimuli, like ATP. Release of ATP, e.g. after brain injury, may initiate reactive gliosis via stimulation of purinergic P2X and P2Y receptors. In the present study, the expression and cellular localization of P2X receptor subtypes on astrocytes in the nucleus accumbens of rats under normal physiological conditions and after stab wound were investigated. Reverse transcription-polymerase chain reaction (RT-PCR) with specific P2X(1-7) primers, and double immunofluorescence with antibodies to glial fibrillary acidic protein (GFAP, a specific marker of fibrous astrocytes) and to different P2X receptor subtypes (P2X(1-4), P2X(7)) were used. The RT-PCR of tissue extracts of the nucleus accumbens of untreated rats revealed the presence of all seven currently known P2X receptor subtype mRNAs indicating the presence of these receptors in this region. A double immunofluorescence approach with confocal laser scanning microscopy showed the localization of P2X(2-4) receptor subtypes on GFAP-labelled astrocytes in untreated rats. Labelling for P2X(1) and P2X(7) receptor subtypes was not found. After mechanical damage all P2X receptor subtypes studied (P2X(1-4), P2X(7)) were observed on the GFAP-labelled reactive astrocytes. A characteristic distribution of the P2X receptors on astrocytic processes and cell bodies as well as an up-regulation of the P2X-immunofluorescence was found. In conclusion, the data show the presence of P2X receptors on rat nucleus accumbens astrocytes and suggest that astrogliosis in vivo is associated with an up-regulation of distinct P2X receptor subtypes.