Dopamine modulates the physiological response of the tiger shrimp Penaeus monodon

Levels of glucose, lactate, pO 2, pCO 2, HCO 3 −, TCO 2, Na +, K +, Cl −, protein, and oxyhemocyanin in the hemolymph and its osmolality and pH were measured when tiger shrimp, Penaeus monodon (13.5 ± 1.5 g body weight), were individually injected with saline or dopamine at 10 − 8, 10 − 7, or 10 − 6 mol shrimp − 1. Results showed that hemolymph glucose, lactate, pCO 2, HCO 3 −, and TCO 2 values increased from 2 to 4 h; hemolymph osmolality, Na +, and total protein had increased at 2 h; and hemolymph K + decreased from 2 to 8 h after the dopamine injection. All physiological parameters returned to the control values 4–16 h after receiving dopamine. The dopamine injection also significantly decreased the oxyhemocyanin/protein ratio of P. monodon which occurred at 2 h, resulting from an elevation of hemolymph protein and a slight decrease of oxyhemocyanin. These results suggest that stress-inducing dopamine caused a transient period of modulation of energy metabolism, osmoregulation, respiration, and the acid–base balance in P. monodon in adapting to this environmental stress.