A polypeptide, the sequence of which consists of less than 100 amino acids, which comprises: - the sequence of SEQ ID NO: 6, or - a sequence, which: - is of 34 to 54 amino acids, - is at least 94% identical to said sequence of SEQ ID NO: 6 over the entire length of the shortest of the two sequences, - comprises a PDZ-BS sequence, wherein said PDZ-BS sequence is x 1 -x 2 -x 3 -x 4, wherein: x 1 is any amino acid except E (preferably Q), and x 2 is T or S or I (preferably not I, more preferably T), and x 3 is any amino acid (preferably R), and x 4 is L or V (preferably L) (SEQ ID NO: 14), said sequence being referred to as variant sequence A, or - a sequence, which: - is of 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 x 1 -x 2 -x 3 -x 4, wherein: x 1 is E, and x 2 is T or S or I (preferably not I, more preferably T), and x 3 is any amino acid (preferably R), and x 4 is L or V (preferably L) (SEQ ID NO: 13 with x 1 = E), and - does not comprise the amino acid L at position 11, said sequence being referred to as variant sequence B, or - a fragment of said sequence of SEQ ID NO: 6 or of said variant sequence A or of said variant sequence B, wherein said fragment is of at least 34 amino acids and has retained the PDZ-BS sequence of said sequence of SEQ ID NO: 6 or of said variant sequence A or of said variant sequence B, respectively, said polypeptide being for use in the treatment and/or palliation and/or prevention of a disease or disorder affecting the nervous system by stimulation and/or induction of neurite outgrowth and/or neurite spouting and/or axon growth and/or dendritic tree extension from neurons of said nervous system, wherein said polypeptide is used as an active principle for said stimulation and/or induction. - the sequence of SEQ ID NO: 6, or - a sequence, which: - is of 34 to 54 amino acids, - is at least 94% identical to said sequence of SEQ ID NO: 6 over the entire length of the shortest of the two sequences, - comprises a PDZ-BS sequence, wherein said PDZ-BS sequence is x 1 -x 2 -x 3 -x 4, wherein: x 1 is any amino acid except E (preferably Q), and x 2 is T or S or I (preferably not I, more preferably T), and x 3 is any amino acid (preferably R), and x 4 is L or V (preferably L) (SEQ ID NO: 14), said sequence being referred to as variant sequence A, or - is of 34 to 54 amino acids, - is at least 94% identical to said sequence of SEQ ID NO: 6 over the entire length of the shortest of the two sequences, - comprises a PDZ-BS sequence, wherein said PDZ-BS sequence is x 1 -x 2 -x 3 -x 4, wherein: x 1 is any amino acid except E (preferably Q), and x 2 is T or S or I (preferably not I, more preferably T), and x 3 is any amino acid (preferably R), and x 4 is L or V (preferably L) (SEQ ID NO: 14), x 1 is any amino acid except E (preferably Q), and x 2 is T or S or I (preferably not I, more preferably T), and x 3 is any amino acid (preferably R), and x 4 is L or V (preferably L) (SEQ ID NO: 14), - a sequence, which: - is of 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 x 1 -x 2 -x 3 -x 4, wherein: x 1 is E, and x 2 is T or S or I (preferably not I, more preferably T), and x 3 is any amino acid (preferably R), and x 4 is L or V (preferably L) (SEQ ID NO: 13 with x 1 = E), and - does not comprise the amino acid L at position 11, said sequence being referred to as variant sequence B, or - is of 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 x 1 -x 2 -x 3 -x 4, wherein: x 1 is E, and x 2 is T or S or I (preferably not I, more preferably T), and x 3 is any amino acid (preferably R), and x 4 is L or V (preferably L) (SEQ ID NO: 13 with x 1 = E), and x 1 is E, and x 2 is T or S or I (preferably not I, more preferably T), and x 3 is any amino acid (preferably R), and x 4 is L or V (preferably L) (SEQ ID NO: 13 with x 1 = E), - does not comprise the amino acid L at position 11, - a fragment of said sequence of SEQ ID NO: 6 or of said variant sequence A or of said variant sequence B, wherein said fragment is of at least 34 amino acids and has retained the PDZ-BS sequence of said sequence of SEQ ID NO: 6 or of said variant sequence A or of said variant sequence B, respectively,