Melanocyte-stimulating hormone release-inhibiting factor (MSH-R-IF) is a hypothalamic tripeptide that binds to rat striatum (Kd = 4.69 nM) and has diverse biological activities.1,2,3,4 In vivo, MSH-R-IF (0.1 mg/kg) decreases immobility of mice in the forced swim test, indicating antidepressant-like activity.2 MSH-R-IF (20 mg/kg) increases striatal concentration of dopamine and the dopamine metabolites DOPAC, 3-methoxy tyramine , and homovanillic acid (HVA) in a mouse model of Parkinson's disease induced by MPTP.3 It decreases vacuous chewing movements induced by haloperidol in a rat model of tardive dyskinesia when administered at a dose of 2 mg/kg.4 MSH-R-IF also has anti-opiate effects, reversing analgesia induced by morphine and an enkephalin in mice in a radiant heat tail-flick assay.1
References
1. Pan, W., and Kastin, A.J. From MIF-1 to endomorphin: The Tyr-MIF-1 family of peptides. Peptides 28(12), 2411-2434 (2007).
2. Kastin, A.J., Abel, D.A., Ehrensing, R.H., et al. Tyr-MIF-1 and MIF-1 are active in the water wheel test for antidepressant drugs. Pharmacol. Biochem. Behav. 21(5), 767-771 (1984).
3. Marcotte, E.R., Chugh, A., Mishra, R.K., et al. Protection against MPTP treatment by an analog of Pro-Leu-Gly-NH2 (PLG, MIF-1). Peptides 19(2), 403-406 (1998).
4. Sharma, S., Paladino, P., Gabriele, J., et al. Pro-Leu-glycinamide and its peptidomimetic, PAOPA, attenuate haloperidol induced vacuous chewing movements in rat: A model of human tardive dyskinesia. Peptides 24(2), 313-319 (2003).