摘要:

AbstractThe effects of acute i. p. administration of selective dopamine (DA) receptor antagonists on the expression of preproenkephalin A (PPE A) mRNA was investigated in the adult rat striatum. Animals were injected with either (a) a selective D1receptor antagonist SCH 23390 (0.25 mg/kg), (b) a selective D2receptor antagonist raclopride (5 mg/kg), or (c) SCH 23388 (0.25 mg/kg), the (S)‐enantiomer of SCH 23390. Control naive animals did not receive an injection. At specific time points following drug administration (1, 3 or 9 h), rats were killed and striatal tissue processed forin situhybridization with an alkaline phosphatase‐labelled oligonucleotide probe complementary to a portion of the rat PPE A cDNA. Treatment of rats with SCH 23388 did not affect the content of PPE A mRNA expressed by striatal cells at any time point. However, 1 h after SCH 23390 administration, a significant decrease in striatal PPE A mRNA was detected, reflected by a decrease in the cellular content of mRNA. No significant changes in PPE A mRNA were detected in raclopride‐treated sections at this time point. In contrast, both 3 and 9 h after an injection of raclopride a significant increase in the cellular content of PPE A mRNA was detected in the striatum. No change in the cellular content of mRNA was detected in SCH 23390‐treated rats at these two latter time points. Throughout the striatum ‐46% of neurons were found to express PPE A mRNA, with the highest percentage of cells (55%) being detected in the mid‐caudal striatum. No significant differences in striatal DA content were detected with any drug treatment using HPLC electrochemical detection methods. These results demonstrate that acute administration of the DA D1and D2receptor antagonists has contrasting effects on the cellular content of PPE A mRNA in the adult rat striatum. These effects may reflect changes in the rate of mRNA transcription which may be media

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1992.tb00113.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractTransmission at excitatory synapses in the mammalian brain is thought to depend on the release of transmitter quanta through exocytosis of presynaptic vesicles (Katz, 1969). The number of vesicles released by a single presynaptic action potential is important for understanding the impact of a single synapse, and the variability in transmission from one impulse to the next. In addition, the number of vesicles released may be an important factor for synaptic regulation and plasticity, such as facilitation, post‐tetanic potentiation and long‐term potentiation (LTP). Three recent studies suggest that an increase in the number of transmitter quanta underlies hippocampal LTP (Malinow and Tsien, 1990; Bekkers and Stevens 1990; Malinow, 1991), whereas other reports suggest a postsynaptic mechanism (Kaueret al1988; Mulleret al, 1988; Foster and McNaughton, 1989). We have used the whole‐cell recording technique to compare putative quantal and single fibre responses at excitatory synapses in rat hippocampal slices, and find (i) a surprisingly large variability in single fibre excitatory postsynaptic currents (sfEPSCs); (ii) an equally large variability of putative quantal (pq) EPSCs elicited by hyperosmolar media or ruthenium red; (iii) the observed amplitude ranges for the sfEPSCs and the pqEPSCs overlap almost completely; and (iv) in neither case can the variability be attributed to a scatter in electrotonic distance from the soma of the engaged synapses. Thus, the data are compatible with the hypothesis that a presynaptic action potential usually releases only a single quantum. Other possibilities are also disc

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1992.tb00114.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY