Development of monoamine oxidase activity and monoamine effects on glutamate release in cerebellar neurons and astrocytes.
Activities of monoamine oxidase (MAO) A and B were measured during the first month of postnatal development in mouse cerebellum and in primary cultures of either cerebellar granule cells or cerebellar astrocytes, derived from 7-day-old cerebella. In addition, effects of the two monoamines, serotonin (a MAO A substrate) and phenylethylamine (a MAO B substrate) on the release of glutamate under resting conditions and in a transmitter related fashion (i.e., potassium-induced, calcium-dependent glutamate release) were studied during the same period. Both MAO A and MAO B activities increased during in vivo development (beginning around postnatal day 14) and in cultured astrocytes (during a comparable time period and to a similar extent), but remained constant at a low level in granule cells. In 4-day-old cerebellar granule cell cultures there was no potassium-induced glutamate release but serotonin as well as phenylethylamine reduced the release in both the presence and absence of excess potassium. In 8- and 12-day-old granule cell cultures and in 8- and 18-day old astrocyte cultures there was a pronounced glutamate release during superfusion with 50 mM K+. In both neurons and astrocytes this response was inhibited by 1 nM of either serotonin or phenylethylamine. In the astrocytes the inhibition was followed by an increased release of glutamate in both the presence and absence of the high potassium concentration, whereas the 8-day-old neurons showed only a slight increase in glutamate release after the withdrawal of the monoamine and only in the absence of excess potassium. The response was almost identical in 8- and 18-day-old astrocytes in spite of the marked difference in MAO activities.
Hertz
L
L
Department of Pharmacology, University of Saskatchewan, Saskatoon, Canada.
Peng
L
L
Hertz
E
E
Juurlink
B H
BH
Yu
P H
PH
D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D005971:Glutamates / Q000378:metabolism*; D018698:Glutamic Acid; D008995:Monoamine Oxidase / Q000378:metabolism*; D010627:Phenethylamines / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000494:pharmacology*
D005971:Glutamates; D010627:Phenethylamines; D012701:Serotonin; D018698:Glutamic Acid; D008995:Monoamine Oxidase