ISSN:
1432-1912
Keywords:
Cocaine
;
Cold-Stored Tissues
;
Neuronal Uptake of Nor-adrenaline
;
Nictitating Membrane of Cat
;
Supersensitivity
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary Experiments were carried out on fresh isolated cat nictitating membranes as well as on muscles stored in the cold for 7 days. Storage reduced the cocaine-induced supersensitivity to (−)-noradrenaline but did not abolish it it also reduced responses to tyramine, and about halved the noradrenaline content of the tissue. Cocaine failed to potentiate responses of fresh or of stored muscles to the methoxamine (which is not taken up by adrenergic nerves). The incubation with 2.5 ml of 100 ng/ml of (−)-noradrenaline (in the presence of the inhibitor of catechol-O-methyl transferase), fresh muscles removed noradrenaline from the incubation medium at a rate of about 70 ng per gram of tissue per min; 10 Μg/ml of cocaine reduced rate of removal by 81%. Muscles stored in the cold removed less noradrenaline from the medium (about 45 ng/g×min−1) than fresh ones, and cocaine reduced the rate of removal by 56%. The neuronal uptake mechanism of the nictitating membrane does not seem to be stereoselective, since the rate of removal of (+)-noradrenaline from the incubation medium was similar to that of the (−)-isomer. It is concluded that cold storage of the muscle abolishes neither the neuronal uptake of noradrenaline nor the ability of cocaine to impair this uptake; however, both parameters were reduced. Since the sensitizing action of cocaine is similarly reduced, there is no reason to doubt the causal relation between impairment by cocaine of neuronal uptake and ensuing supersensitivity to (−)-noradrenaline.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00997276
