THE DEGREE OF PROTECTION PROVIDED TO NEURONAL CELLS BY A PRECONDITIONING STRESS CORRELATES WITH THE AMOUNT OF HEAT-SHOCK-PROTEIN-70 IT INDUCES AND NOT WITH THE SIMILARITY OF THE SUBSEQUENT STRESS

A mild thermal stress protects primary cultures of dorsal root ganglion (DRG) neurons against a subsequent lethal heat stress as well as to a lesser extent against a subsequent lethal ischaemia. In contrast, a mild ischaemic stress protects DRG neurons only against a subsequent severe thermal stress and not against severe ischaemia. A greater induction of heat shock protein (hsp) synthesis was observed in these cells following mild thermal stress compared to mild ischaemia. This suggests that the protective effect observed is dependent on hsp synthesis resulting in the observed cross-protective effect and does not involve a particular pre-stress specifically protecting against a subsequent, more severe application of the same stress. Moreover, a particular level of hsp induction produces a better protective effect against lethal heat stress than against lethal ischaemia.