Use-dependent fade and two-rate recovery of a naloxone-sensitive inhibition in the cat superior cervical ganglion

Endogenous opiates: 1993

“…Leu-enkephalin did increase electrical activity in the CA1 pyramidal cells (545), but it or [D-AlaE]Leu-enkephalin produced slow depolarization not associated with significant conductance increase in the metacerebral giant cell in the marine mollusc Aplysia californica, where it appeared to act by stimulating adenylate cyclase through the production of cAMP (278). When injected into the arterial supply of the superior cervical ganglia, Leu-enkephalin reduced postganglionic compound action potentials evoked by a test shock to the cervical sympathetic trunk of cats (563), indicating that the enkephalin had an inhibitory effect. The action was antagonized by naloxone, so that the receptors involved were not clear (563).…”

“…When injected into the arterial supply of the superior cervical ganglia, Leu-enkephalin reduced postganglionic compound action potentials evoked by a test shock to the cervical sympathetic trunk of cats (563), indicating that the enkephalin had an inhibitory effect. The action was antagonized by naloxone, so that the receptors involved were not clear (563).…”

“…Administration of the opiate antagonists, as well as the agonists, can after electrical activity. Naloxone suppressed the inhibition of activity of the superior cervical ganglia induced by a short stimulus train (562,563). After chronic morphine, injection of naloxone precipitated withdrawal, which was characterized by hyperactivity of the locus coeruleus.…”