LHRH and sexual dimorphism

An increasing amount of evidences suggests that galanin plays an important role in the regulation of reproduction in the rat, Galanin is colocalized with luteinizing hormone-releasing hormone (LHRH) in a subset of LHRH neurons, and the pattern of coexpression is sexually dimorphic, with a higher incidence of colocalization and level of galanin mRNA and peptide expression in females than in males. Therefore, the role of galanin may be unique to females, as are the LH surge and ovulation, The colocalization of LHRH and galanin is neonatally determined by an epigenetic mechanism involving the testis, whereas the expression of galanin in adult LHRH neurons is upregulated by estrogen and modulated by progesterone, The action of these sex steroids requires intact neurotransmission towards LHRH neurons, indicating that their action is mediated by interneurons.