A polypeptide, whose sequence consists of less than 100 amino acids, comprising: - the sequence of SEQ ID NO: 6, or - a sequence, which: - is 34 to 54 amino acids, - is at least 94% identical to said sequence of SEQ ID NO: 6 along the entire length of the shortest of the two sequences, - comprises a PDZ-BS sequence, wherein said PDZ-BS sequence is x1-x2-x3-x4, wherein: x1 is any amino acid except E (preferably Q), and x2 is T or S or I (preferably not I, more preferably T), and x3 is any amino acid (preferably R), and x4 is L or V ( preferably L) (SEQ ID NO: 14), said sequence being called variant sequence A, or - a sequence, which: - is 44 amino acids, - is at least 94% identical to said sequence of SEQ ID NO: 6 , - comprises a PDZ-BS sequence, wherein said PDZ-BS sequence is x1-x2-x3-x4, in which: x1 is E, and x2 is T or S or I (preferably not I, more preferably T), and x3 is which any amino acid (preferably R), and x4 is L or V (preferably L) (SEQ ID NO: 13 with x1>； = E), and - does not comprise amino acid L at position 11, said sequence being called sequence of variant B , or - a fragment of said sequence of SEQ ID NO: 6 or of said sequence of variant A or of said sequence of variant B, wherein said fragment is at least 34 amino acids and has retained the PDZ-BS sequence of said sequence of SEQ ID NO: 6 or of said sequence of variant A or of said sequence of variant B, respectively, said polypeptide being for use in the treatment and / or palliation and / or prevention of a disease or disorder that affects the nervous system by stimulation and / or induction of the growth of neurites and / or outbreak of neurites and / or growth of axons and / or extension of dendritic trees of neurons of said nervous system, in which said polypeptide is used as an active ingredient for said stimulation and / or induction.Un polipéptido, cuya secuencia consiste en menos de 100 aminoácidos, que comprende: - la secuencia de SEQ ID NO: 6, o - una secuencia, que: - es de 34 a 54
