Trophic factor modulation of XXXX - and @entity4944 -regulated transcript peptide expression in explant cultured @entity840 cardiac neurons.

@entity71991 @entity71990 @entity840 @entity2072 @entity299 @entity4944
The present study investigated the influence of trophic factors on the expression of @entity2072 - and @entity4944 -regulated transcript peptide (CARTp) in @entity840 cardiac ganglia maintained in explant culture. In acutely isolated @entity299 , <1% of the cholinergic cardiac neurons exhibited CARTp immunoreactivity. In contrast, this number increased to >25% of the cardiac neurons after 72 h in explant culture. This increase in the number of CARTp neurons in cultured @entity299 was accompanied by an increase in CARTp transcript levels as assessed by real time polymerase chain reaction. Treatment of @entity299 with neurturin or glial-derived trophic factor (both at 10 ng/ml) for 72 h prevented the increase in neurons that exhibited CARTp immunoreactivity. In contrast, treatment with @entity71990 (50 ng/ml) for 72 h produced a small significant increase in the percentage of CARTp-immunoreactive cardiac neurons and treatment with nerve growth factor (100 ng/ml) had no effect. @entity71991 treatment also decreased cardiac neuron CARTp levels after 72 h in explant culture. Cardiac neurons exhibited immunoreactivity to the neurturin receptor GFRalpha2 whereas non-neural cells preferentially exhibited immunoreactivity to the glial-derived neurotrophic factor receptor GFRalpha1 and neurturin transcripts were detected in cardiac tissue extracts. We hypothesize that a target-derived inhibitory factor, very likely neurturin, is a critical factor suppressing the expression of CARTp in @entity840 cardiac neurons. These observations contrast with those reported in sympathetic neurons that suggest up-regulation of trophic factors after axotomy or during explant culture is a key factor contributing to the up-regulation of many neuropeptides.
