Retraction of

• Morphine elevates levels of cyclic GMP in a neuroblastoma X glioma hybrid cell line.

  Gullis R, Traber J, Hamprecht B. Gullis R, et al. Nature. 1975 Jul 3;256(5512):57-9. doi: 10.1038/256057a0. Nature. 1975. Retraction in: Nature. 1977 Feb 24;265(5596):764. doi: 10.1038/265764b0. PMID: 166323 Retracted. No abstract available.
• Effects of cholinergic agents and sodium ions on the levels of guanosine and adenosine 3':5'-cyclic monophosphates in neuroblastoma and neuroblastoma X glioma hybrid cells.

  Gullis RJ, Traber J, Fischer K, Buchen C, Hamprecht B. Gullis RJ, et al. FEBS Lett. 1975 Nov 1;59(1):74-9. doi: 10.1016/0014-5793(75)80344-9. FEBS Lett. 1975. Retraction in: Nature. 1977 Feb 24;265(5596):764. doi: 10.1038/265764b0. PMID: 178540 Retracted. No abstract available.
• The effects of noradrenaline, acetylcholine, cyclic AMP, cyclic GMP, and other agents on the concentration of unesterified fatty acids in synaptosomes and synaptic membranes.

  Gullis RJ, Rowe CE. Gullis RJ, et al. FEBS Lett. 1976 Sep 1;67(3):256-9. doi: 10.1016/0014-5793(76)80541-8. FEBS Lett. 1976. Retraction in: Nature. 1977 Feb 24;265(5596):764. doi: 10.1038/265764b0. PMID: 183981 Retracted. No abstract available.
• Enkephalin regulates the levels of cyclic nucleotides in neuroblastoma x glioma hybrid cells.

  Brandt M, Gullis RJ, Fischer K, Buchen C, Hamprecht B, Moröder L, Wunsch E. Brandt M, et al. Nature. 1976 Jul 22;262(5566):311-3. doi: 10.1038/262311a0. Nature. 1976. Retraction in: Nature. 1977 Feb 24;265(5596):764. doi: 10.1038/265764b0. PMID: 785270 Retracted. No abstract available.