In-vivo modulation of central 5-hydroxytryptamine (5-HT1A) receptor-mediated responses by the cholinergic system
The aim of the present study was to investigate a putative modulation of rat 5-HT system by the muscarinic receptor antagonist atropine using in-vivo electrophysiological and behavioural techniques. In the dorsal raphe nucleus, administration of atropine (1 mg/kg i.v.) prevented the suppressant effect of the selective serotonin reuptake inhibitor paroxetine (0.5 mg/kg i.v.) on the spontaneous firing activity of 5-HT neurons, suggesting that atropine could induce an attenuation of somatodendritic 5-HT1A autoreceptors responsiveness. The 5-HT1A receptor agonist 8-OH-DPAT decreased both immobility in the forced swim test and the body core temperature. Pre-treatment with atropine (5 and 10 mg/kg i.p.) enhanced antidepressant-like effect of 8-OH-DPAT (1 mg/kg s.c.) and reduced 8-OH-DPAT (0.1 mg/kg s.c.)-induced hypothermia. In conclusion, the present study reports a functional role of muscarinic receptors in the modulation of pre- and post-synaptic 5-HT1A receptors mediated responses.(Received October 7 2003)
(Reviewed November 27 2003)
(Revised February 9 2004)
(Accepted February 24 2004)
Key Words: Atropine; dorsal raphe; extracellular unitary recordings; forced swim test; 5-HT1A and muscarinic receptors.
c1 Dr N. Haddjeri, Laboratory of Neuropharmacology & Neurochemistry, Faculty of Pharmacy, University of Claude Bernard Lyon I, INSERM U-512, 8 Avenue Rockefeller 69373 Lyon Cedex 08, France. Tel.: (33) 4-78-77-75-54 Fax: (33) 4-78-77-72-09 E-mail: firstname.lastname@example.org