This chapter reviews the available information on the distribution and bioactivity of the main neuroendocrine systems involved in the control of key physiological processes such as reproduction, feeding, metabolism, growth and stress in the Senegalese sole, Solea senegalensis. Catecholamines are released both as neurotransmitters in the hypothalamic-sympathetic nervous system and as classical neurohormones from the adrenal medulla or chromaffin cells of the kidney being involved in a rapid major neuroendocrine pathway integrating the primary response to stress in fish. The localization of catecholaminergic neurons and fibres in the brain of the Senegalese sole has been determined by Rodriguez-Gomez et al. using antibodies against tyrosine hydroxylase, the rate limiting enzyme for catecholamine synthesis. The monoamine serotonin or 5-hydroxytryptamine is one of the major neurotransmitters in the central nervous system and thus, it has been involved in multiple neuroendocrine regulatory networks. Galanin is a peptide present in the central nervous system and intestine of vertebrates, from mammals to fish.