Effects of the Potential Antidepressant OPC-14523 [1-[3-[4-(3-chlorophenyl)-1-piperazinyl]propyl]-5-methoxy-3,4-dihydro-2-quinolinone Monomethanesulfonate] a Combined sigma and 5-HT~1~A Ligand: Modulation of Neuronal Activity in the Dorsal Raphe Nucleus