Opioid actions on single nucleus raphe magnus neurons from rat and guinea‐pig in vitro.

Abstract

1. Intracellular recordings were made from neurons of the nucleus raphe magnus (NRM) from rat (n = 128) and guinea‐pig (n = 115). Two types of cells were found in each, primary (103 in rat, 27 in guinea‐pig) and secondary cells (25 in rat, 88 in guinea‐pig). 2. Primary cells had input resistances of 186 +/‐ 9 M omega (n = 9) in rat and 255 +/‐ 50 M omega (n = 11) in guinea‐pig. The action potential in each was about 1.5 ms in duration. Synaptic potentials were evoked by focal electrical stimulation and consisted of both gamma‐aminobutyric acid (GABA) and excitatory amino acid components. 3. Morphine, [Met5]enkephalin (ME) and [D‐Ala2,N‐Me‐Phe4, Gly5‐ol]enkephalin (DAMGO) depressed the amplit..