Abstract
Abstract Although, a great effort has been made to understand the synthesis, regulation, processing and function of cocaine- and amphetamine-regulated transcript (CART) peptide at the central level, its peripheral function(s) are still obscure. Moreover, scarce studies describing the presence of CART in peripheral autonomic ganglia are mainly limited to laboratory rodents. Thus, the aim of the present study was to immunohistochemically investigate the expression of CART in Hu C/D-positive neurons of the porcine pterygopalatine ganglion (PPG). The distribution pattern of CART-IR nerve elements in PPG has been also assessed. The co-localization of CART with substance P (SP), galanin or somatostatin was studied by means of double immunohistochemical stainings. The presence of Hu C/D-positive/CART-positive neurons was detected both in the left and right PPG (4.7±1.2% and 5.2% ± 1.4%, respectively). The CARTimmunoreactive (IR) neurons were categorized as either middle (ca. 80%) or small (ca. 20%) in size. Moderate numbers of CART-IR boutons were also detected between CART-negative ganglionic neurons. CART-IR basket-like formations around PPG neurons were regularly observed. Virtually all CART-IR neurons additionally co-stored VIP, whereas none of the CART-expressing cells showed the presence of galanin, SP or somatostatin. CART-IR basket-like formations exclusively encircled VIP-IR PPG neurons. Thus, CART-IR nerve cells seem to constitute a relatively small homologous population of the porcine PPG neurons with largely unknown functions. Further functional studies aiming at whether CART-IR neurons could serve as interneurons are necessary.
Highlights
At the periphery, the parasympathetic division of the autonomic nervous system is represented by small local intramural ganglia, as well as four pairs of large head and neck ganglia, including the pterygopalatine ganglion (PPG)
cocaine- and amphetamineregulated transcript (CART)-IR nerve terminals were regularly observed as a bright spot-like, in some cases CART-IR basket-like formations encircling particular CART-negative perikarya were observed
Taking into account the above, it is possible, that in particular porcine PPG ganglia CART-IR nerve terminals may originate from CART-positive central neurons and/or other PPG CART-IR ganglionic neurons
Summary
The parasympathetic division of the autonomic nervous system is represented by small local intramural ganglia, as well as four pairs of large head and neck ganglia, including the pterygopalatine ganglion (PPG). Precise macroanatomical studies revealed that PPG may exist as either a large aggregation of nerve cells grouped in a single ganglion or a small plexus containing several smaller in size ganglia [7]. Previous studies have shown that PPG parasympathetic neurons are predominantly cholinergic by nature, the presence of other neurotransmitter markers including tyrosine hydroxylase or nitric oxide synthase has been noted [7]. The presence of novel multipotent neuropeptide cocaine- and amphetamineregulated transcript (CART) has been found in a small subset of the rat’s [12] and the duck’s [13] PPG neurons, the full meaning of this finding is still obscure. Double immunohistochemical stainings were applied in order to figure out whether in PPG neurons CART may functionally co-operate with galanin, vasoactive intestinal polypeptide (VIP), somatostatin or substance P (SP)
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