The invention concerns the use of a bombesin/gastrin releasing peptide antagonist in the treatment of inflammatory and immune-mediated inflammatory conditions, in particular sepsis, acute lung injury and rheumatoid arthritis as well as for the treatment or prophylaxis of brain disorders, preferably bipolar disorder, and in particular the different forms and/or subforms of bipolar disorder, such as mania, acute mania, severe mania, hypomania, depression, moderate depression, dysthymia, severe depression, episodes of mania and/or depression, psychosis/psychotic symptoms (e.g. hallucinations, delusions), mixed bipolar state, bipolar I disorder, bipolar II disorder and/or rapid-cycling bipolar disorder. In particular, specific nonapeptides with antagonist properties against bombesin or bombesin-like peptides, such as the gastrin releasing peptide, may be used in the treatment of inflammatory and immune-mediated inflammatory conditions as well as brain disorders.