acth-(4-7)--pro-gly-pro- and Pain

The effects of peptide ACTH4-7-PGP (Semax) were studied in 12 min after its intraperitoneal (in doses of 5, 15, 50, 150, and 450 μg/kg) or intracerebroventricular (in doses of 16, 40, and 400 pg) administration to rats with different types of pain and pain-induced behavior. It was found that the peptide increased pain sensitivity and induced avoidance behavior during thermal stimulation ("hot plate" test), but had an analgesic effect (more pronounced after central administration) and weakened emotional-affective behavior in electrocutaneous stimulation of the paws (foot-shock model) and tail in rats. It was shown that changes in activity of supraspinal brain structures were of primary importance in the mechanism of action on the nociceptive process and the formation of behavior.

Topics: Adrenocorticotropic Hormone; Analgesics; Animals; Behavior, Animal; Brain; Electric Stimulation; Hypothalamus; Infusions, Intraventricular; Injections, Intraperitoneal; Male; Nociception; Pain; Pain Management; Pain Measurement; Pain Threshold; Peptide Fragments; Peptides; Permeability; Rats; Rats, Wistar; Time Factors

Topics: Adrenocorticotropic Hormone; Animals; Avoidance Learning; Male; Models, Biological; Nootropic Agents; Pain; Peptide Fragments; Rats

Heptapeptide Semax (MEHFPGP) is the fragment of ACTH(4-10) analogue with prolonged neurotropic activity. The aim of the present work was to study the Semax effects on learning capability and pain sensitivity in white rats following intraperitoneal and intranasal administration in different doses. Semax nootropic effects were studied in the test of acquisition of passive avoidance task. Pain sensitivity was estimated in Randall-Selitto paw-withdrawal test. It was shown that Semax exerts nootropic and analgesic activities following intraperitoneal administration. Analysis of dependence of these effects on dose resulted in different dose-response curves. Following intranasal administration, Semax was more potent in learning improvement compared to intraperitoneal administration. The peptide failed to affect the animal pain sensitivity following intranasal administration as opposed to intraperitoneal administration. The data obtained suggest different mechanisms and brain structures involved in realization of the nootropic and analgesic effects of Semax.

Topics: Administration, Intranasal; Adrenocorticotropic Hormone; Analgesics; Animals; Injections, Intraperitoneal; Learning; Male; Nootropic Agents; Pain; Peptide Fragments; Rats