Studies on the role of NMDA, GABA and adenosine receptors within discrete brain nuclei in the high pressure neurological syndrome in rats

We investigated the influence of brain focal injections of 2-amino-7-phosphonoheptanoate (APH), N-methyl-D-aspartate (NMDA), muscimol and 2-chloroadenosine (CAD) on behavioural symptoms of the high pressure neurological syndrome (HPNS) in rats. Each compound was bilaterally injected (in nmole range doses) into the substantia nigra pars reticulata (SNR), entopeduncular nucleus (EP) or ventromedial thalamic nucleus (VLTh) prior to exposure to hyperbaric conditions. Threshold pressure for the occurrence of tremor, myoclonic jerks and convulsions were recorded for drug and vehicle-injected animals. A decrease in threshold pressure for a particular symptom indicates that the reaction to hyperbaric conditions is more pronounced, while an increase in threshold pressure is indicative of protection against HPNS.