Cardiovascular effects of intracerebral injection of neuropeptide Y in rats

Cardiovascular effects of microinjection of neuropeptide Y (NPY) (25, 50, and 100 pmol/site) into field CA3 of hippocampus (CA3), lateral septal nuclei (LSN) and substantia nigra (SN) were investigated in urethane-anesthetized rats. NPY administered into CA3 produced a dose-dependent hypotension and bradycardia. Maximal changes of mean arterial blood pressure (MAP) were -1.5 +/- 0.7, -2.0 +/- 0.4, and -4.2 +/- 1.6 kPa, respectively; maximal changes of heart rate (HR) were -7 +/- 14, -23 +/- 24, and -64 +/- 50 bpm, respectively. NPY microinjection into LSN produced a dose-dependent increase in MAP (0.9 +/- 0.8, 1.3 +/- 0.5, and 3.1 +/- 0.5 kPa, respectively) and a prominent increase in HR (14 +/- 15, 41 +/- 28, and 42 +/- 31 bpm, respectively), but the tachycardia was not dose-dependent. NPY applied into SN elicited a dose-dependent decrease in MAP (-1.0 +/- 0.5, -2.2 +/- 0.9, and -4.3 +/- 2.0 kPa, respectively), but no statistically significant change in HR. The results showed that exogenously applied NPY has distinct cardiovascular effects in CA3, LSN, and SN.