Central Effects of Trout Tachykinins on Heart Rate Variability in Trout
Recent studies in trout have shown that tachykinins might be selectively implicated in important neuroregulatory functions related to the central control of ventilation. In teleost fish, cardiorespiratory coupling probably contributes to heart rate variability (HRV), and the hypoventilatory effects observed after central injection of tachykinins suggest that these peptides also may produce changes in HRV. Consequently, the present study was undertaken to compare the central actions of picomolar doses (25250 pmol) of trout neuropeptide gamma (NP?), substance P (SP), and neurokinin A (NKA) on HRV in unanesthetized rainbow trout. Compared to vehicle-injected trout, Poincar plot analysis of HRV demonstrated that intracerebroventricular injection of NP? dose dependently increased HRV. SP evoked a significant elevation of HRV but only at the highest dose (250 pmol). In contrast, NKA was without any effect on HRV. In conclusion, these results suggest that NP? may be selectively implicated in the central control of HRV in trout.
heart rate variability teleosts substance p neurokinin a poincar plot analysis neuropeptide ?