Effect of DSP-4, pCPA, and haloperidol on hippocampal electrical activity and behavior in rabbits

An experimental model, including novel and fearful stimuli, has been used to study the effect of noradrenaline, serotonin, and dopamine depletion on hippocampal electrical activity and behavior in freely moving rabbits. DSP-4 (N-(2-chloroethyl)-N-ethyl-2- bromobenzylamine hydrochloride, 40 mg/kg ip), a selective hippocampal noradrenaline depletor, decreased the overall exploratory activity and significantly increased RSA (rhythmic slow activity) percentage. The high frequencies of the hippocampal RSA were significantly reduced. When this noradrenaline depletion was coupled with a serotonin depression by p-chlorophenylalanine (pCPA), the above described effect was potentiated. In particular, the frequency distribution of RSA was characterized by a further reduction of the high values with a concomitant increase of the low frequency band. Moreover, a more evident decrease of the exploratory activity and a similar increase of RSA percentage was observed. These results show that the hippocampal electrical activity is modulated by noradrenaline and serotonin by an inhibitory effect on RSA occurrence and a frequency selection. The block of dopamine receptors by chronic haloperidol administration (5 mg/kg ip/day) did not seem to exert any effect on RSA parameters. Results are discussed in the light of attentional and emotional theories.