Small, intensely fluorescent cells and the paraneuron concept

Abstract

Sympathetic ganglia contain large principal nerve cells and, in addition, many smaller cells that resemble the endocrine cells of the adrenal medulla in morphology and chromaffinity. The advent of the formaldehyde-induced fluorescence technique proved to be an invaluable tool for studying this unique cell type, and it was this method that accounted for their descriptive name of small, intensely fluorescent cells, now universally abbreviated to SIF cells. Electron microscopy also proved of great importance in detailing the structure of SIF cells and their relationship with neighbouring neurones. Fine structural observations revealed that the cells contained numerous dense-cored granules, and this led to their electron microscopic name of small, granule-containing cells. SIF cells are most abundant, and very well studied, in the rat superior cervical ganglion, where they both receive and give synapses. Early researchers suggested that SIF cells were interneurones appropriately situated between pre- and postganglionic elements and thus capable of influencing ganglion signals. SIF cells also are known to exist in the form of richly vascularized, compact clusters of varying size. Clustered chromaffin cells do not necessarily give rise to processes that would contact the principal neurones. The existence of singly occurring as well as clustered SIF cells has given rise to a proposed designation of type I and type II cells, with I representing the interneuronal-like form and II possibly performing as an endocrine-like component. Despite a wealth of knowledge concerning SIF cells, their exact role(s) in the overall functioning of the autonomic nervous system is still not completely understood.

Involvement of the coeliac ganglion in the luteotrophic effect of androstenedione in late pregnant rats

“…The coeliac ganglion, part of the sympathetic prevertebral chain, is constituted mainly by principal neurons and interneurons such as the peptidergic and the intensely fluorescent (SIF) (Eränkö 1978, Abe et al 1983, Matthews 1989, Prud'Homme et al 1999. The sympathetic ganglia possess a great variety of specific receptors and neurotransmitters, among them catecholamines (Klein & Burden 1988), neuropeptides (Dalsgaard et al 1983) and gaseous neurotransmitters such as nitric oxide (Morales et al 1995).…”

Pregnancy in rats is modulated by ganglionic cholinergic action

“…It has been demonstrated that in the sympathetic ganglia its preganglion neurotransmitter is acetylcholine (Klein & Burden 1988) and that it possesses nicotinic and muscarinic cholinergic receptors in the principal cells as well as muscarinic receptors in other neuronal populations (Matthews 1989, Reid & Perry 1995, Prud'Homme et al 1999. The stimulation of such receptors causes modifications in the steroids' liberation, in cyclic rats ) and prepubertal rats as well as in male rats (Zhu et al 2002).…”

Distribution and immunohistochemical characteristics of cocaine- and amphetamineregulated transcript-positive nerve elements in the pelvic ganglia of the female pig

“…Previous study has revealed that in the rat MPG, most of 5-HT-IR cells were also TH-positive what suggests that they are small intensely fluorescent (SIF) cells (Karhula et al 1990). In peripheral autonomic ganglia, SIF cells are considered as interneurons involved in endocrine secretion including releasing of biologically active substances into intercellular spaces (Matthews 1989). To offer the full per-spective on CART-serotonin interactions, it must be mentioned that anti-CART peptide IgG changes the density of hippocampal 5-HT 2A receptor (Rothman et al 2003) and anorexia-associated activation of 5-HT 4 receptor increases the level of CART in the nucleus accumbens (Jean et al 2007).…”