Catecholamines and the abundance of blood cells in a fresh water tropical teleost (Colisa fasciatus) in relation to cold-shock.

Intraperitoneal injections of epinephrine (0.05 microng/g) elicited characteristic changes in the abundance of circulating leucocytes at selected time intervals (viz., 3, 15 and 27 min. and, later, at intervals of 48 minutes up to 363 min. and at 12 and 24 h) post-injection in Colisa. Leucocytosis was evident as 15, 27 and 75 min, and tendency towards leucocytosis was observed at 123 and 267 min.; at 3, 171, 219, 315 and 363 min. and at 12 and 24 h, the total leucocyte counts for the experimentals and controls were not significantly different. No such corresponding significant changes were observed in the abundance of circulating erythrocytes or thrombocytes. Leucocyte sequence elicited by epinephrine was also apparent in Colisa which had been exposed to a temperature of 2 degrees C for one minute. Pretreatment with phenoxybenzamine (3.0 mg/l aquarium water), an alpha-adrenergic antagonist, abolished the cold-shock leucocytic phases, except 27 min. leucocytosis which emerged unaffected. Exogenous norepinephrine (2 microng/g) and isoproterenol (0.1 microng/g) failed to elicit any significant change in the number of circulating leucocytes, erythrocytes, or thrombocytes. Clearly adrenergic mechanisms are involved in the cold-shock leucocyte stress sequence. The results suggest alpha-activating role of epinephrine during the leucocyte stress syndrome in Colisa and, apparently, epinephrine is leucocytic.