284 EFFECTS OF CORTICOTROPIN-RELEASING FACTOR ON INTERMEDIOLATERAL CELL COLUMN NEURONS

Abstract

Background: CRF receptors are widely distributed in the central nervous system including the spinal cord. Although CRF indirectly participates in control of the blood pressure, it is unknown whether CRF is involved in blood pressure control via direct action on central neurons. Here, we report effects of CRF on sympathetic preganglionic neurons in the intermediolateral cell column (IML) of the spinal cord. Methods: Transverse slices of Th2 segment from newborn rats (0-4 days old) were superfused by artificial cerebrospinal fluid. Membrane potentials of IML neurons were recorded by whole-cell patch-clamp. Preganglionic neurons were confirmed by antidromic action potential induced by Th2 ventral root stimulation and cell staining by Lucifer Yellow. CRF (50 nM) was bath-applied. We measured the membrane potential change and counted the number of excitatory postsynaptic potentials (EPSPs) of the IML neurons. Results: The frequency of EPSPs in the IML neurons was 3.67 ± 3.57 Hz (n = 9) in control solution. Application of CRF increased the number of EPSPs (220%) and induced membrane depolarization by 2.4 ± 1.3 mV. The increase of EPSPs number by CRF was attenuated by pretreatment of a CRF-1 antagonist, antalarmin (124%) but not by pretreatment of a CRF-2 antagonist, astressin2B (268). Conclusion: Our findings suggest that CRF affected directly IML neurons and interneurons in the spinal cord. Moreover, CRF exerted the excitatory effect on the IML neurons through CRF-1 receptors, whereas effect via CRF-2 might be rather inhibitory. Thus, CRF-related drugs are expected as one of the choices of the pharmacologic control of the blood pressure.