Background and aims Hypoxic-ischaemic encephalopathy (HIE) has been associated with long-term disabilities. Hypothermia is effective but does not provide complete neuroprotection, adjunctive therapies are necessary. Allopurinol has been proved as a good neuroprotector, but it has never been tested associated with hypothermia. The aim of the present study was to examine therapeutically effectiveness of dual therapy (hypothermia + allopurinol) versus hypothermia, in a neonatal rat model of HIE.

Methods 120 Wistar pups at postnatal day 10 were used and divided into 5 groups: Sham-Operated, Hypoxic-ischaemic (HI) aggression, HI aggression + Allopurinol, HI aggression + Hypothermia, HI aggression + Hypothermia + Allopurinol.

At 25 day of life, spatial memory was assessed via water maze test. Finally, rats were anaesthetised and sacrified. In order to assess possible alterations in the hippocampal synaptic network, 3 specific synaptic proteins (PSD95, SNAP25, synaptophysin) were tested by Western Blot.

Results There were differences in the learning outcomes among hypoxic, hypoxic + allopurinol, hypothermia, hypothermia + allopurinol and sham operated (p < 0,05). The worst group was the hypoxic one.

Synaptophysin and SNAP25 levels were higher in controls and treatment groups compared with hypoxic untreated animals. However, the highest level of PSD95 corresponded to the hypoxic group.

Conclusions Hypothermia and allopurinol seem to improve learning in HIE pups.

Increased levels of presynaptic proteins in the treatment groups suggest that hypothermia and allopurinol improve synaptic plasticity compared with untreated group.

PSD95 was also described in the literature as a suppressor of dendritic arbour development, so this could explain our results in the hypoxic group.