Tranylcypromine Isoproterenol

In rats deprived of a 5-HT input, via lesions with 5,7-dihydroxytryptamine (5,7-DHT) or by p-chlorophenylalanine (PCPA), chronic administration of DMI failed to down-regulate p-adrenoceptors, although the usual desensitization of NE sensitive adenylate cyclase was still observed.62,63 when NE receptors were desensitized and reduced in number by the DMI treatment, PCPA reversed the decrease of p-receptors without affecting the cyclase.1 These persistent P-receptors may be "uncoupled", since their affinity for isoproterenol is reduced.64 Possibly, the step from uncoupled receptors to actual disappearance of NE receptors is interrupted by the loss of 5-HT input. An interesting corollary is the observation that depressed patients benefiting from either imipramine or tranylcypromine showed... 

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