Abstract
Intracellular recordings were made from presumed dopamine-containing neurons in slices of rat mesencephalon. Muscarine (3-100 μM) increased the rate of spontaneous action potentials; it also caused a membrane depolarization and, in voltage-clamp, an inward current. Concentration-effect curves to muscarine were shifted rightwards by pirenzepine (0.03-1 μM) with an estimated K(D) of 14 nM. The inward current caused by muscarine was voltage-dependent. Between about -50 and -65 mV it was associated with a decrease in membrane conductance, but between -70 and -110 mV it was unaccompanied by any change in membrane conductance. Muscarine was without effect on the action potential afterhyperpolarization, or on a slowly developing inward current evoked by step hyperpolarizations of up to 20 mV from -45 mV. Muscarinic depolarizations or inward currents were reduced reversibly or abolished by a low calcium (0.25 mM)/high magnesium (10 mM) solution. It is concluded that muscarinic excitation of dopaminergic neurons is mediated by M1-like receptors.
Original language | English |
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Pages (from-to) | 395-400 |
Number of pages | 6 |
Journal | Journal of Pharmacology and Experimental Therapeutics |
Volume | 253 |
Issue number | 1 |
Publication status | Published - 1990 |
ASJC Scopus subject areas
- Pharmacology