The subcellular localization and release of the molluscan neuro-peptide Phe-Met-Arg-Phe-NH(,2) (FMRFamide) from ganglia of the marine mollusc, Macrocallista nimbosa, was examined. Ganglia were pooled, homogenized and subjected to differential centrifugation. FMRFamide was concentrated in the microsomal pellet. When the medium-speed supernatant was centrifuged in a discontinuous sucrose gradient, three separate peaks of activity were detected and identified as acetylcholine (ACh), 5-hydroxytryptamine (5-HT) and FMRFamide. The relative concentration of FMRFamide in each fraction was determined by bioassay and by radioimmunoassay (RIA). Both determinations revealed a peak of peptide in the middle of the sucrose gradient. Electron micrographs of each of the gradient interfaces were analyzed. The interface containing the peak of biological FMRFamide activity was enriched two- to five-fold in neurosecretory granules with a mean diameter of 104 nm and various electron densities. Morphologically similar vesicles were also seen in intact ganglia. / Macrocallista ganglia were pooled and incubated in a series of seawater media. Release of immunoreactive FMRFamide into the media was enhanced two to seven times by exposure to a high potassium medium, and was reversibly inhibited by removal of the external calcium from the high potassium medium. Immunoreactive FMRFamide was present in Macrocallista hemolymph at a concentration (10('-9) M) that excites isolated Macrocallista ventricles. These findings strongly suggest that FMRFamide functions as a neurohormone or neurotransmitter in Macrocallista. / The effects of catecholamines, 5-HT and phenylethylamines on the isolated radula protractor muscle of Busycon contrarium were examined. FMRFamide, ACh and dopamine (DA) act at separate excitatory receptors. DA elicits a phasic contraction of the muscle that is rapidly desensitized by repeated high doses of DA. The actions of FMRFamide, ACh and DA are sodium-dependent; FMRFamide is more calcium-dependent than ACH or DA. 5-HT, DA and the phenylethylamines can relax muscles contracted by FMRFamide and ACh, possibly by acting at separate receptor sites, or at sites of action common to the amines. / Source: Dissertation Abstracts International, Volume: 42-07, Section: B, page: 2723. / Thesis (Ph.D.)--The Florida State University, 1981.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_74584 |
| Contributors | NAGLE, GREGG THOMAS., Florida State University |
| Source Sets | Florida State University |
| Detected Language | English |
| Type | Text |
| Format | 111 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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