Partial protection against hyperbaric oxygen induced convulsions by dopaminergic agents in mice: possible involvement of autoreceptors?

In the present report we have investigated the effects of apomorphine, (-)3-PPP, L-DOPA and haloperidol on the elicitation of convulsions induced in mice by exposure to oxygen at high pressure (HBO) (5 ata O2). It was found that the administration of apomorphine (0.025-0.1 mg X kg-1 s.c.), (-)3-PPP (4 mg X kg-1 i.p.) L-DOPA (200-400 mg X kg-1 i.p.) as well as haloperidol (0.25-2.0 mg X kg-1 i.p.) produced a significant protection against HBO-induced convulsions. Haloperidol was the only drug to produce a dose-dependent decrease in respiration, and this effect does probably explain the anticonvulsant effects observed. The low doses at which apomorphine was effective, and the effects produced by (-)3-PPP, indicate an effect mediated via DA autoreceptors. Alternatively, and more likely taking the effects of L-DOPA into account, the DA receptors involved are sensitive enough to disclose postsynaptic agonist properties of apomorphine and (-)3-PPP at the doses employed.