Serotonin synthesis inhibition by pre-treatment of p-CPA alters sleep-electrophysiology in an animal model of acute and chronic heat stress

The effects of pre-treatment of para-chlorophenylalanine (p-CPA) on sleep–wake electroencephalograms (EEG) have been demonstrated in three age groups of rats subjected to heat stress. Each age group for both p-CPA pre-treated and untreated subjects was sub-divided into three groups: (i) acute heat stress—subjected to a single heat exposure for 4 h at 38 °C; (ii) chronic heat stress—exposed for 21 days daily for 1 h in the incubator at 38 °C; and (iii) handling control groups. Digital polygraphic sleep recordings were performed just after the heat exposure from acute stressed rats and on the 22nd day from chronic stressed rats. The analyses of results demonstrated that many changes associated with sleep-EEG (either in sleep–wake parameter or in EEG frequencies) due to acute and chronic heat stress were reversed (changes were analyzed; P<0.05 or better) in p-CPA pre-treated groups of rats. However, differential observations between acute and chronic heat stress groups of subjects were recorded, which are thought to have happened due to acclimatization of subjects to the hot environment. The results of present study supported the previous hypothesis about the significant involvement of serotonin in sleep–wake parameters and also demonstrated its participation in brain electrophysiological alterations in stressed conditions.