The mechanism of the pyrogenic effect of streptococcus cell wall mucopeptide.

1. The intravenous injection into rabbits of 25-50 mug of a preparation of cell-wall mucopeptide (SM) from group A streptococcus produced a rise in rectal temperature and a fall in the number of circulating granulocytes in the blood.2. The pyrogenic response to SM is not dependent on the circulating granulocytes since it occurred also in rabbits made leucopenic by nitrogen mustard (HN 3).3. The pyrogenic response to SM was enhanced after an intravenous injection of 5-hydroxytryptophan (5-HTP).4. Pre-treatment with reserpine caused a much greater attenuation of the pyrogenic response to SM than pre-treatment with alpha-methyl-para-tyrosine (AMPT).5. As the reserpine reduced the 5-hydroxytryptamine (5-HT) and noradrenaline level in the hypothalamus, whereas the AMPT reduced only the noradrenaline level, it is concluded that 5-HT may be involved in the pyrogenic response and the way in which 5-HT may exert this function is discussed.