Van Bockstaele E J, Chan J, Pickel V M
Department of Neurology and Neuroscience, Cornell University Medical College, New York, New York 10021, USA.
J Neurosci Res. 1996 Aug 1;45(3):289-302. doi: 10.1002/(SICI)1097-4547(19960801)45:3<289::AID-JNR11>3.0.CO;2-#.
Light microscopic anterograde tracing studies indicate that neurons in the central nucleus of the amygdala (CNA) project to a region of the dorsal pontine tegmentum ventral to the superior cerebellar peduncle which contains noradrenergic dendrites of the nucleus locus coeruleus (LC). However, it has not been established whether the efferent terminals from the CNA target catecholamine-containing dendrites of the LC or dendrites of neurons from neighboring nuclei which may extend into this region. To examine this question, we combined immunoperoxidase labeling of the anterograde tracer biotinylated dextran amine (BDA) from the CNA with immunogold-silver labeling of the catecholamine-synthesizing enzyme tryrosine hydroxylase (TH) in the rostrolateral LC region of adult rats. By light microscopy, BDA-labeled processes were dense in the dorsal pons within the parabrachial nuclei as well as in the pericoerulear region immediately ventral to the superior cerebellar peduncle. Higher magnification revealed that BDA-labeled varicose fibers overlapped TH-labeled processes in this pericoerulear region. By electron microscopy, anterogradely labeled axon terminals contained small, clear as well as some large dense core vesicles and were commonly apposed to astrocytic processes along some portion of their plasmalemma. BDA-labeled terminals mainly formed symmetric type synaptic contacts characteristic of inhibitory transmitters. Of 250 BDA-labeled axon terminals examined where TH immunoreactivity was present in the neuropil, 81% contacted unlabeled and 19% contacted TH-labeled dendrites. Additionally, amygdala efferents were often apposed to unlabeled axon terminals forming asymmetric (excitatory type) synapses. These results demonstrate that amygdaloid efferents may directly alter the activity of catecholaminergic and non-catecholaminergic neurons in this pericoerulear region of the rat brain. Furthermore, our study suggests that CNA efferents may indirectly affect the activity of pericoerulear neurons through modulation of excitatory afferents. Amygdaloid projections to noradrenergic neurons may help integrate behavioral and visceral responses to threatening stimuli by influencing the widespread noradrenergic projections from the LC.
光学显微镜下的顺行示踪研究表明，杏仁核中央核（CNA）中的神经元投射到脑桥被盖背侧的一个区域，该区域位于小脑上脚腹侧，包含蓝斑核（LC）的去甲肾上腺素能树突。然而，CNA的传出终末是否靶向LC中含儿茶酚胺的树突或可能延伸到该区域的相邻核团神经元的树突，目前尚未明确。为了研究这个问题，我们将来自CNA的顺行示踪剂生物素化葡聚糖胺（BDA）的免疫过氧化物酶标记与成年大鼠 rostrolateral LC区域中儿茶酚胺合成酶酪氨酸羟化酶（TH）的免疫金银标记相结合。通过光学显微镜观察，BDA标记的突起在臂旁核内的脑桥背侧以及小脑上脚腹侧紧邻蓝斑的区域密集分布。更高倍放大显示，在这个蓝斑周围区域，BDA标记的曲张纤维与TH标记的突起重叠。通过电子显微镜观察，顺行标记的轴突终末含有小的、清亮的以及一些大的致密核心囊泡，并且在其质膜的某些部分通常与星形胶质细胞突起相邻。BDA标记的终末主要形成抑制性递质特有的对称型突触接触。在检查的250个BDA标记的轴突终末中，神经毡中存在TH免疫反应性，其中81%与未标记的树突接触，19%与TH标记的树突接触。此外，杏仁核传出纤维常常与形成不对称（兴奋性类型）突触的未标记轴突终末相邻。这些结果表明，杏仁核传出纤维可能直接改变大鼠脑这个蓝斑周围区域中儿茶酚胺能和非儿茶酚胺能神经元的活动。此外，我们的研究表明，CNA传出纤维可能通过调节兴奋性传入纤维间接影响蓝斑周围神经元的活动。杏仁核向去甲肾上腺素能神经元的投射可能通过影响来自LC的广泛去甲肾上腺素能投射，有助于整合对威胁性刺激的行为和内脏反应。
