Mental arithmetic produces a psychophysiological arousal similar to the so-called defence-alarm reaction elicited by stimulation ofthe hypothalamic defence area in experimental animals (Folkow, 1982). This reaction pattern is characterized by increased heart rate, cardiac output and blood pressure, whereas total peripheral resistance is unchanged or decreased (Brod, 1970).
The increase of platelet concentration during psychological arousal is also in accordance with what has been observed in response to other stressors, i.e. physical exercise and adrenaline infusion (Sarajas et al, 1961; Gjerloff Schmidt & Waever Rasmussen, 1984; Dawson & Ogston, 1969; Vilen et al, 1980).
The emotional leucocytosis observed in dogs has been claimed to be neurogenic in origin, since sympathectomy abolished the rise in leucocyte count (Garrey & Bryan, 193 5).
Both alpha- and beta-receptors seem to be of importance in the mobilization of lymphocytes (Gader & Cash, 1975).
British Journal of Haematology. 1989. 71, 153-1 56