Kainic acid modifies mu-receptor binding in young, adult, and elderly rat brain

Mu-receptor binding changes were evaluated following the kainic acid (KA)-induced status epilepticus (SE) in young, adult, and elderly animals. Male Wistar rats were used as follows: young rats (15 days old) were treated with KA (7 mg/kg) and sacrificed 72 h (YKA3d) or 35 days (YKA35d) after SE; adult (90 days old) (AKA1d and AKA40d) and elderly rats (1-year-old) (EKA1d and EKA40d) were injected with KA (10 mg/kg) and then sacrificed 24 h or 40 days following SE. Their brains were processed for an autoradiography assay for mu-receptors. The YKA3d group showed increased values in dentate gyrus (39%) and a decrease in substantia nigra (26%); YKA35d animals had a reduction in caudate putamen (29%) and in substantia nigra (20%). The AKA1d group exhibited increased mu-receptors in caudate putamen (49%), cingulate (415%), frontal (52%), and temporal (53%) cortices: substantia nigra (56%), dentate gyrus (48%). and CA2 field of hippocampus (53%). The AKA40d group showed increased values in sensorimotor cortex (45%), anterior (39%), medial (65%), basolateral (202%), and central (32%) amygdaloid nuclei; dentate gyrus (80%) as well as CA2 (80%) and CA3 (49%) fields of hippocampus. The EKA1d group presented decreased mu-receptor binding in piriform (16%) and enthorinal (22%) cortices as well as in anterior amygdala nucleus (17%). The EKA40d group showed reduced values in sensorimotor cortex (14%) and substantia nigra (27%). The present results indicate that the mu-binding changes following SE depend on the rate of brain maturation.