Effects Of α-MSH To LPS Induced Fever On AVP Level In CSF And Plasma

α- melanocyte - stimulating homone, (α- MSH) ,an endogenous antipyretic peptide, distributes extensively in the brain tissue. Administrations of α-MSH via the vein, CSF or microinjection of this peptide into the ventral septal area (VSA) and the preoptic region of the brain significantly reduced fever of tested animals. Arginine vasopressin ( AVP ) is another endogenous fever - reduced peptide, which may acted its antipyretic effect by combining with VSA receptor. It is reported that substances involved in positive regulation on the body temperature may include PGE2 cAMP, corticotropin releasing hormone (CRH) , and nitric oxide (NO) , and so on. While substances involved in negative regulation of body temperature include AVP, α- MSH. and so on. This work is aimed at observing if there is any correlation between AVP and α- MSH in the antipyretic response using radioimmunoassay(RIA) technique.Meterals and methodsSubject were 30 male Wistar rats which were made febrile by LPS intraper-itoneal injection. The rectal temperature of the rats were monitored by the digital esthesiometer. Effect of α- MSHon fever was observed and changes in levels of AVP both in the plasma and CSF were detected a fter administration ofα- MSH.ResultsA significant fever occurred following intraperitoneal injections of LPS (50ug/kg, p < 0. 01) , and levels both in the plasma and CSF were also signif-icantly increased (p < 0.05) ; α- MSH strongly reduced fever while concentrations of AVP both in the plasma and in CSF further increase; Intraperitoneal injection of saline influence neither body temperature nor concentrations of AVP both in the plasma and CSF.DiscussionAVP is nonapeptide with a six - aminoacid cycle and three aminoacid branched chains. In human being and many mammal animals, arginine lies the ninth site of AVP structure, while in the pig lysine is this site. AVP play an antipyretic effect via receptor mediating mechanism. Data showed that in a febrile animal, AVP performed its antipyretic role with a neurotransmitter substance, in the ventral septal region and MAN. during fever period AVP concentration in the ventral septal region increased sharply, microinjection of AVP into this region can strikingly inhibit febrile response induced by ET, PGE,, and IL - 1 ,but has no effect on the normal body temperature. However the mechanism initiating AVP releasing from the septal region following fever response remains unclear. It was demonstrated that intraperitoneal administrations of α- MSH induced an increase in concentrations of AVP both in the plasma and CSF following down of the body temperature. As mentioned above, α- MSH was also involved in the mechanism of the negative regulation of fever. In view of other data and our observations the consideration may reasonable that the antipyretic effect of α-MSH may be carried out by initiating release of AVP. It is also strongly possible that α- MSH also has its instinctive antipyretic way since its antipyretic effect was so stong.