Content area
Full Text
Neuroscience and Behavioral Physiology, Vol. 42, No. 3, March, 2012
The Nootropic and Analgesic Effects of Semax Given via Different Routes
D. M. Manchenko, N. Yu. Glazova, N. G. Levitskaya,L. A. Andreeva, A. A. Kamenskii, and N. F. Myasoedov
Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 96, No. 10, pp. 10141023, October, 2010. Original article submitted May 4, 2010.
The heptapeptide Semax (MEHFPGP) is an analog of the fragment ACTH(410) with long-lasting actions. The aim of the present work was to study the effects of Semax on learning ability and pain sensitivity in white rats given different doses via the intraperitoneal and intranasal routes. The nootropic effects of Semax were studied in a test based on the acquisition of a conditioned passive avoidance reaction to pain stimulation. Pain sensitivity was assessed in a hindpaw compression test. The results showed that i.p. Semax had nootropic and analgesic actions. Dose-response characteristics were different for these different effects. Intranasal Semax was more effective in improving learning in animals than i.p. Semax but had no effect on pain sensitivity. Our results provide evidence that different mechanisms and brain structures are involved in mediating the nootropic and analgesic effects of Semax.
Keywords: melanocortin, Semax, learning, pain sensitivity, intranasal administration, rats.
The melanocortin family includes adrenocorticotropic hormone (ACTH), melanocyte-stimulating hormone (-, -, and -MSH), fragments of these hormones, and their synthetic analogs. ACTH/MSH-like peptides have a wide spectrum of physiological activities. Numerous studies have shown that melanocortin (MC) has, apart from its hormonal effects, nootropic, neuroprotective, and neurotrophic activities, affects the functioning of the cardiovascular system and food-related and sexual behavior, has anti-inflammatory and antipyretic effects, and affects pain sensitivity [25]. It is now known that MC acts via five subtypes of melanocortin receptors (MCR). Melanocortin receptors differ in terms of their amino acid compositions, though they share a quite high degree of homology. MCR are expressed in different body organs and tissues. MC3R and MC4R are present in the CNS [28]. The shortest fragment with affinity for MCR ACTH(410) retains the behavioral activity of the
whole ACTH molecule [27]. The tetrapeptide ACTH(47) is almost as effective [18].
The main block to the medical use of natural MC is their low bioavailability when given via peripheral routes, as...