Increased expression of synapsin I mRNA in defined areas of the rat central nervous system following chronic morphine treatment

Noa Matus-Leibovitch, Vittoria Ezra-Macabee, Daniella Saya, Bernard Attali, Tomer Avidor-Reiss, Jacob Barg, Zvi Vogel*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Chronic opiate administration leads to a selective regulation of several cellular proteins and mRNAs. This phenomenon has been viewed as a compensatory mechanism to the opiate signaling leading to the development of opiate addiction. In this study, in situ hybridization histochemistry experiments were employed to investigate the effect of chronic morphine treatment on synapsin I gene expression. We show here for the first time that prolonged morphine exposure causes a selective increase in the mRNA levels of synapsin I in several brain regions which are considered to be important for opiate action. Quantitative analysis of the signals, obtained by hybridization of digoxigenin-labeled antisense RNA probe, revealed a 5.8- and 7-fold increase of synapsin I mRNA levels in the locus coeruleus and the amygdala of morphine-treated rats, respectively, as compared with control untreated rats. Increased expression of synapsin I mRNA was also observed in the spinal cord of morphine-treated rats (by 3.8-fold). Since opiates were shown to attenuate neurotransmitter release and reduce synapsin I phosphorylation, it is suggested that the increase in synapsin I levels would lead to the requirement of higher amounts of opiate agonists to obtain the opiate physiological effects. These results suggest that the increases in mRNA levels of synapsin I in these specific areas can be part of the molecular mechanism(s) underlying opiate tolerance and withdrawal.

Original languageEnglish
Pages (from-to)221-230
Number of pages10
JournalMolecular Brain Research
Issue number2
StatePublished - 28 Dec 1995
Externally publishedYes


  • Amygdala
  • In situ hybridization
  • Locus coeruleus
  • Morphine
  • Opiate tolerance
  • Spinal cord
  • Synapsin I mRNA


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