Libri V, Constanti A, Calaminici M, Nisticó G
Department of Pharmacology, School of Pharmacy, London, U.K.
Neuroscience. 1994 Mar;59(2):331-47. doi: 10.1016/0306-4522(94)90600-9.
The electrophysiological and morphological characteristics of neurons in the guinea-pig olfactory cortex brain slice were investigated using a combined intracellular recording and neurobiotin-dye filling technique, in an attempt to show whether a clear relation existed between cell morphology and excitatory muscarinic response profile. Out of 46 sampled neurons, 25 (termed type 1), responded to bath-application of the muscarinic agonist oxotremorine-M (10 microM, 2-3 min) with a strong and persistent excitation coupled with the appearance of a slow depolarizing afterpotential (10-20 mV amplitude) following a large depolarizing stimulus. These neurons were identified as deep pyramidal cells located in cortical layer III, with characteristic pyramidal/ovoid shaped cell bodies, prominent apical dendrites with branches extending to the surface, and extensive basal dendritic trees. The cells showed a regular spiking pattern in response to injected depolarizing current, with no evidence of bursting behaviour. Nine cells (termed type 2), were strongly excited by oxotremorine-M, but only generated a weak depolarizing afterpotential (< 5 mV) following stimulation. These neurons (located in layer III or at layer II-III border) had a variable, non-pyramidal morphology with either a fusiform/tripolar, stellate/multipolar or bipolar/bi-tufted appearance, respectively. Apart from a more prominent post-spike afterhyperpolarization observed in some type 2 cells, their resting membrane properties and firing patterns were indistinguishable from those of type 1 responding cells. Twelve cells (termed type 3) showed little or no excitatory response to oxotremorine-M, and never generated a post-stimulus slow afterdepolarization. These cells (within compact layer II) had the morphological features of superficial pyramidal cells, typified by their short apical trunks and well-developed apical dendritic trees. They could be distinguished electrophysiologically by their ability to show spike fractionation during injection of large depolarizing current pulses. The morphology and laminar position of neurobiotin-filled cells was also compared with those of cells stained by the Golgi-Cox method. Some factors that may have contributed to the observed differences in muscarinic response profile are discussed. It is proposed that the selective muscarinic induction of the slow depolarizing afterpotential phenomenon in deep pyramidal cells may be important in olfactory cortical learning and memory processes.
采用细胞内记录和神经生物素染料填充相结合的技术，研究豚鼠嗅皮质脑片神经元的电生理和形态学特征，旨在探讨细胞形态与兴奋性毒蕈碱反应特征之间是否存在明确的关系。在46个采样神经元中，25个（称为1型）在浴加毒蕈碱激动剂氧化震颤素-M（10μM，2 - 3分钟）后，出现强烈且持续的兴奋，并在大的去极化刺激后出现缓慢去极化后电位（幅度为10 - 20mV）。这些神经元被鉴定为位于皮质第III层的深层锥体细胞，具有典型的锥体/卵圆形细胞体、突出的顶端树突且分支延伸至表面，以及广泛的基底树突。这些细胞对注入的去极化电流表现出规则的放电模式，无爆发性行为的证据。9个细胞（称为2型）被氧化震颤素-M强烈兴奋，但刺激后仅产生微弱的去极化后电位（<5mV）。这些神经元（位于第III层或第II - III层边界）具有可变的非锥体形态，分别呈梭形/三极、星状/多极或双极/双簇状外观。除了在一些2型细胞中观察到更明显的锋后超极化外，它们的静息膜特性和放电模式与1型反应细胞无法区分。12个细胞（称为3型）对氧化震颤素-M几乎没有或没有兴奋性反应，且从未产生刺激后缓慢去极化。这些细胞（在致密的第II层内）具有浅层锥体细胞的形态特征，以其短的顶端主干和发达的顶端树突为典型。它们在电生理上可通过在注入大的去极化电流脉冲期间表现出的锋电位分离来区分。还将神经生物素填充细胞的形态和层位与用高尔基-考克斯法染色的细胞进行了比较。讨论了可能导致观察到的毒蕈碱反应特征差异的一些因素。有人提出，深层锥体细胞中慢去极化后电位现象的选择性毒蕈碱诱导在嗅觉皮质学习和记忆过程中可能很重要。
