Hilar somatostatin-mRNA containing neurons are preserved after perforant path kindling in the rat

Abstract

The loss of neurons in the dentate gyrus have been evaluated in rats in which kindling had been induced through stimulation of the hippocampal perforant path. The total number of granule cells, hilar neurons and the total number of neurons expressing the message for somatostatin (SS-mRNA) were estimated with stereological methods in five rats sacrificed 24 h after the last seizure and compared with estimates made in five control animals. The mean total number of granule cells was 981 000 in control rats and 943 000 in kindled rats, a non-significant difference at the 5% level of significance ( P=0.78, Student's t-test). The mean total number of hilar neurons was 52 100 compared with a mean of 58 520 in the control group, the difference being statistically significant ( P=0.04). The mean total number of SSergic hilar neurons was 16 630 compared with a mean of 15 430 in the control rats (non-significant, P=0.12). These findings indicate that hilar neurons are lost after kindling but that these neurons are not somatostatinergic.