Effects of serotonergic drugs on locomotor activity and vigilance states in ring doves

Serotonergic system is implicated on sleep-waking states in mammals. Since studies on serotonin regulation of sleep in birds are scarce, ring dove was chosen as experimental subject in the present work. The role of the neurotransmitter serotonin on vigilance states was studied in ring doves intraperitoneally treated with the 5-HT1A agonist 8-OH-DPAT, the 5-HT1A antagonist WAY100635 and the inhibitor of serotonin synthesis para-chlorophenylalanine (PCPA) by means of behavioural, electrophysiological and infrared actimetry criteria. 8-OH-DPAT (1 mg/kg) treatment increased locomotor activity, active waking and grooming states and reduced SWS and REM sleep. Pre-treatment with WAY100635 (0.5 mg/kg) prevented the effects induced by 8-OH-DPAT. Serotonin depletion induced by PCPA treatment (two consecutive injections of 300 mg/kg over two consecutive days) reduced locomotor activity, waking and grooming activity while increased both SWS and REM sleep. Moreover, 8-OH-DPAT (0.5 mg/kg) in PCPA treated ring doves produced a notable rise in the locomotor activity, active waking and grooming states, while it decreased sleep.Altogether, the results support the idea that serotonin plays an active role in wakefulness, probably through the activation of 5-HT1A receptors that increases wake activities and reduces sleep in ring doves.

Research highlights▶ Serotonin plays a significant role in wakefulness. ▶ Serotonin reduces sleep in ring doves. ▶ Serotonin increases waking probably through 5-HT1A receptors activation in ring doves. ▶ PCPA treatment reduced locomotor activity and waking while increased SWS and REM sleep. ▶ 8-OH-DPAT increased locomotor activity and active waking states decreasing sleep in ring doves.