NEUROACTIVE COMPOUNDS PRODUCED BY BACTERIA FROM THE MARINE SPONGE HALICHONDRIA-PANICEA - ACTIVATION OF THE NEURONAL NMDA RECEPTOR

Previous studies revealed that the marine sponge Halichondria panicea habors symbiotic- and commensalic bacteria (Althoff et al., 1998. Mari ne Biol. 130, 529-536). In the present study the hypothesis was tested whether some of those bacteria synthesize neuroactive compounds. For the first time the effect of bacterial bioactive compounds on the neur onal ionotropic glutamate receptors [iGluR], subtype N-methyl-D-aspart ate (NMDA) receptor, was checked. In cortical neurons from rats as cel l system the supernatant of two bacterial cultures isolated from H. pa nicea proved to agonize the NMDA receptor. The response of the NMDA re ceptor to the bioactive compounds was determined by measuring the intr acellular Ca2+ level. The supernatants of cultures 697 and 698 were fo und to upregulate the intracellular Ca2+ level. To validate the specif icity of the effects, inhibition studies with Memantine and D-AP5 were performed. The two bacteria were identified by polymerase chain react ion-amplification of the 16S rDNA genes and subsequent sequencing; the y displayed highest identity to Antarcticum vesiculatum and to Psychro serpens burtonensis, respectively. Based on these data first experimen tal evidence is presented indicating that bacteria associated with spo nges display neuroactivity by agonizing the NMDA receptor. (C) 1998 Pu blished by Elsevier Science B.V. All rights reserved.