The study was carried out on color guinea pigs, in which anaphylactic shock was induced by sensitizing and challenging doses of normal horse serum (HS). Administration of atropine, ipratropium, or ipratropium in combination with neostigmine led to reduction of sensitizing effect of HS: anaphylactic index was decreased up to (2.2 - 2.4) +/- 0.1 arbitrary units (a.u.). Methacine in combination with neostigmine (0.4 +/- 0.01 a.u.) or atropine in combination with galantamine (1.5 +/- 0.3 a.u.) effectively prevented the pathochemical stage of anaphylactic shock. Changes in plasma protein concentrations modified effects of methacine: application of methacine with IgG was protective (0.5 +/- 0.1 a.u.), while CRP abolish the antianaphylactic activity of methacine (3.8 +/- 0.1 a.u.). Guinea pigs which survived shock had a great number of AFC [(880 +/- 22) x 10(6) splenocytes in experimental group and (100 +/- 29) x 10(6) in control) and low concentration of 5-HT in the spleen (at a shock, 0.443 +/- 0.005; basal level, 1.532 +/- 0.004 ng/mg protein). Effective prevention of anaphylactic shock resulted in normalization of B cell activity and 5-HT level in the spleen. Thus, cholinergic drugs modulate the immunological and pathochemical stages of anaphylactic shock.