Actions of norepinephrine on rat hypoglossal motoneurons

摘要: 1. We used conventional intracellular recording techniques in 400-microns-thick slices from the brain stems of juvenile rats to investigate action norepinephrine (NE) on subthreshold and firing properties hypoglossal motoneurons (HMs). 2. In recordings current-clamp mode, 50 or 100 microM NE elicited a reversible depolarization accompanied by an increase input resistance (RN) all HMs tested (n = 74). single-electrode voltage-clamp induced inward current (INE) reduction conductance. The average reversal potential for INE was -104 mV. responses could be Ca(2+)-free solution containing tetrodotoxin, indicating that they were postsynaptic. 3. response blocked alpha-adrenoceptor antagonist prazosin, but not beta-adrenoceptor propranolol, mimicked alpha 1-adrenoceptor agonist phenylephrine 2-adrenoceptor UK 14,304 isoproterenol when alpha-adrenoceptors blocked. 4. Substitution barium calcium perfusion RN without completely blocking depolarization. Replacement sodium chloride with choline barium-substituted remaining 5. neuropeptide thyrotropin-releasing hormone (TRH), which also depolarizes increases HMs, occluded NE. 6. altered HM three ways: it always lowered minimum amount injected needed elicit repetitive firing, increased slope frequency versus relation 8 14 cells tested, delay onset depolarizing pulse first evoked spike tested. 7. conclude acts directly 1-adrenoceptors excitability HMs. It does this reducing barium-sensitive resting potassium activating barium-insensitive carried primarily ions. A portion pathway these actions is shared TRH. addition, there evidence alters patterns affecting currents are activated following