Morphological, physiological and biochemical observations on skate electric organ

Abstract

The electric organs of two species of skate have been examined morphologically, physiologically and biochemically. They can be easily dissociated into innervated or denervated component electrocytes by a Torpedo Ringer's solution containing 1% collagenase. Collagenase treatment did not, however, separate the Schwann cell cover capping the synaptosomes. Isolated electrocytes generate normal MEPP frequencies and show evoked responses for two days in Torpedo Ringer's. The nerve terminals retain excitability and transmitter release properties up to the time of separation. Since isolated terminals and denervated electrocytes show normal ultrastructural characteristics for up to 12 h, the skate electric organ provides several preparations which are not attainable with Torpedo tissue. Acetylcholine (ACh) content of supernatant fractions containing the synaptosomes was comparable to that found in Torpedo (sps.). Collagenase specifically eliminates the basal lamina associated with the synaptic junctional region. Neuronal cell death and synaptic terminal degeneration were also noted in the adult organs of both species. The skate electric organ is ideally suited for the study of cholinergic development and transmission.

SEM–EDS probing of morphological and physiological changes produced by a porphyrin photosensitizer in Psammobatis extenta electrocytes

“…Electrocytes are found in an alveolar arrangement on the antero-posterior axis (Bennett, 1987). Synaptic terminal degeneration has also been observed in the adult skate electric organs (Fox et al, 1990, and our observations). The few organelles present in electrocytes can be easily defined by light microscopy (Prado Figueroa and Santiago, 2004).…”

Novel Pharmacological Sensitivity of the Presynaptic Calcium Channels Controlling Acetylcholine Release in Skate Electric Organ

“…Specimens of Raja montagui were anaesthetised by immersion in crushed ice and then killed by severing the spinal cord and removing the brain. Electric organs were removed (Fox et al ., 1990) and immersed in skate Ringer (SR) composed of 280 mM NaCI, 6 mM KCI, 4.4 mM CaC1 2, 1.8 MM M9C12, 360 mM urea, 1 mM glucose, and HEPES buffer (10 mM), pH 7.3 . A modified high-potassium SR (KSR) containing elevated KCI (80 mM) and reduced NaCl (206 rnM) was used for depolarising nerve terminals.…”

Anatomy and motor pathways of the electric organ of skates

“…Although the role of the electric organ of skates is still poorly understood, recent behavioral studies (Bratton and Ayers, 1987; Bratton et al, 1993; Hayes and Bratton, 1996) and neuroanatomical investigations (Koester, 1987; Baron et al, 1992; Koester and Boord, 1996) have provided new insight regarding its behavioral role and the central motor pathways that control it. In addition, Fox et al (1990) presented convincing evidence that the skate electric organ is an ideal model for investigating cholinergic synapses. They noted that the skate electric organ offers several advantages not afforded by the more popular model, the electric organ of electric rays.…”

“…Numerous nerve fibers fill the region of the concavity and terminate upon the electric plate. The synaptic vesicles located within the axon terminals are all the same size and contain acetylcholine (Fox et al, 1990).…”