Cham Joo Lee, Owens Neil C, Barden Julian A, Lawrence Andrew J, Badoer Emilio
School of Medical Sciences, Division of Biosciences, RMIT University, PO Box 71, Bundoora 3083, Melbourne, Victoria, Australia.
Exp Physiol. 2006 Mar;91(2):403-11. doi: 10.1113/expphysiol.2005.032409. Epub 2005 Nov 18.
The rostral ventrolateral medulla (RVLM) is essential for the generation of sympathetic nerve activity. The RVLM receives a substantial innervation from the hypothalamic paraventricular nucleus (PVN). Activation of P2X purinoceptors via ATP has been shown to mediate fast excitatory synaptic neurotransmission. There is mounting evidence to suggest the presence of P2X purinoceptors in hypothalamic nuclei, including the PVN. In this study, we determined whether P2X1-P2X6 purinoceptor subtypes were present on PVN neurones that projected to the RVLM. Injection of the retrogradely transported tracer, rhodamine-tagged microspheres, into the pressor region of the RVLM was used to identify the neurones in the PVN that innervated the RVLM. P2X1-P2X6 purinoceptors were detected by immunohistochemistry. Double-labelled neurones were quantified and expressed as a proportion of the retrogradely labelled neurones. The proportions of double-labelled neurones for each of the P2X purinoceptor subtypes varied, on average, from 14 to 29%. The P2X3 purinoceptor subtype was found to be the dominant purinoceptor subtype present on PVN neurones projecting to the RVLM. Additionally it was apparent that more than one P2X purinoceptor subtype was present on the PVN neurones projecting to the RVLM, since the sum of the average percentages of double-labelled neurones for each P2X purinoceptor subtype exceeded 100%. These findings highlight the presence of the P2X1-P2X6 purinoceptors on PVN neurones projecting to the RVLM. The results suggest a potential role for ATP in the PVN in the regulation of sympathetic nerve activity.
延髓头端腹外侧区（RVLM）对于交感神经活动的产生至关重要。RVLM接受来自下丘脑室旁核（PVN）的大量神经支配。已表明通过ATP激活P2X嘌呤受体可介导快速兴奋性突触神经传递。越来越多的证据表明下丘脑核团包括PVN中存在P2X嘌呤受体。在本研究中，我们确定投射至RVLM的PVN神经元上是否存在P2X1 - P2X6嘌呤受体亚型。将逆行转运示踪剂罗丹明标记的微球注射到RVLM的升压区，用于识别PVN中支配RVLM的神经元。通过免疫组织化学检测P2X1 - P2X6嘌呤受体。对双标神经元进行定量，并表示为逆行标记神经元的比例。每种P2X嘌呤受体亚型的双标神经元比例平均从14%到29%不等。发现P2X3嘌呤受体亚型是投射至RVLM的PVN神经元上存在的主要嘌呤受体亚型。此外，很明显投射至RVLM的PVN神经元上存在不止一种P2X嘌呤受体亚型，因为每种P2X嘌呤受体亚型的双标神经元平均百分比之和超过了100%。这些发现突出了投射至RVLM的PVN神经元上存在P2X1 - P2X6嘌呤受体。结果表明ATP在PVN中对交感神经活动的调节可能发挥作用。
