Independent synaptic plasticity in the striatal critical period

J.M. AZCURRA, M. FOSSATI, G.R. IBARRA AND M. SOIZA REILLY

Hong Kong

Congreso; The 6th Biennial Meeting of the Asian-Pacific Society for Neurochemistry; 2004

APSN

Circling training of rats during the postnatal critical period (PN30- 37)induces a life lasting reduction of 35% in muscarinic acetylcholine receptors(mAChR) and of 40% in dopamine D2 receptors (D2R) binding in synapticmembranes of striatum. Results to be presented showthat synapticmembrane expression of D1 receptor (B-max of [3H]-SCH23390) is notdifferent to controls under the same experimental conditions, while a 40%D2R reduction was confirmed (Bmax of H3Raclopride). This result speak infavor of a different regulation of activity dependent plasticity for spinymedium size gabaergic projective neurons of the striatonigral pathway(which express D1R and M4 mAChR) and those of the striatopallidalpathway (D2 and M1 mAChR) To clarify this point, a semi-quantitative RTPCRstudy of mRNA expression of AChRs M1, M2 and M4, anddopaminergic D1 and D2 (short and long isoform) was performed. Althoughthe methodology employed limits precise quantification, a similar reduction(45?50%) for short and long D2R mRNA isoforms as well as for M1, M2and M4 mAChRs was found. Converselly, D1R mRNA expression level wassimilar to controls. This results indicate an independent regulation ofplasticity for different synaptic sites of the same neuronal type, and supportthat in the postnatal period P30?37, permanent synaptic adjustment aredependent of the type of stimulus and the ontogenetic setting of conditions.Keywords: gene expresion regulation, plasticity, receptors.