NEURON TRANSPLANTATION INTO MICE HIPPOCAMPUS ALTERS SENSITIVITY TO BARBITAL NARCOSIS

The role of several hippocampal innervations in the sensitivity to bar bital-induced narcosis was studied in selected mice strains. The outbr ed and inbred mouse strains HS/lbg, SABRA/HUC, C57BL, CBA/LAC, and BAL B/c were tested for barbital-induced sleep (315 mg/kg). The relatively short sleeping HS/lbg (HS) and the longest sleeping BALB/c (BALE) wer e chosen for further investigation. Cholinergic (ACh), serotonergic (5 -HT), and noradrenergic (NE) innervations were studied in HS strain; w hereas BALE, which possesses both an unusually high sensitivity to bar bital and unique NE innervations in the cortex and hippocampus, was em ployed in a detailed study of the NE innervations. Transplantation of embryonic NE cells from the mouse embryo into the hippocampus of adult HS mice increased barbital narcosis by 65% (p < 0.05), whereas transp lantation of 5-HT cells decreased barbital narcosis by 54% (p < 0.001) . Transplantation of ACh cells had no significant effect on barbital-i nduced narcosis. BALE mice were subjected to NE cell transplantation i nto the hippocampus and cortex. Similarly to HS, BALE receiving NE tra nsplants into their hippocampus slept 34% longer than control after ba rbital challenge (p < 0.025). Noradrenergic cell transplantation into frontal cortex had no effect on barbital sleep. The results suggest th at (a) enhancement by neural grafting of the NE innervation to the hip pocampus accentuates and enhancement of the 5-HT innervations attenuat es the sensitivity to barbital narcosis, whereas ACh innervations have no effect on the sensitivity to barbital narcosis, and (b) the unusua lly high sensitivity of BALE mice to barbital may not be related to it s unique NE innervations.