Characterisation of cocaine- and amphetamine- regulated transcript-like immunoreactive (CART-LI) enteric neurons in the porcine small intestine

The aim of this study was to investigate the distribution and the number of cocaine- and amphetamine-regulated transcript-like immunoreactive (CART-LI) neurons and the co-localisation of CART with substance P (SP), somatostatin (SOM), nitric oxide synthase (NOS) and vasoactive intestinal polypeptide (VIP) within the enteric nervous system (ENS) in the porcine small intestine. Accordingly, the myenteric plexus (MP), outer submucous plexus (OSP) and inner submucous plexus (ISP) of the small intestine (duodenum, jejunum and ileum) were studied by double-labelling immunofluorescence technique. CART-LI neurons were observed in all gut fragments and all types of intramural plexuses studied and amounted from 0.2 ± 0.1% in the ISP of ileum to 22.4 ± 2.4% in the MP of this segment. The co-localisation of CART and NOS or/and VIP was observed depending on the segment of the gut and the complexity of the intramural plexus. On the other hand, during this study the co-localisation of CART and SOM or/and SP was not observed. The present study, for the first time, presents a detailed description of the CART distribution pattern and co-localisation with other neuromodulators within the ENS of the porcine small intestine.

Morphoquantitative study of the submucous plexus (of Meissner) of the jejunum-ileum of young and old guinea pigs

OBJECTIVE: To study the aging of submucous plexus of the small intestine (jejunum-ileum) of the guinea pigs from the quantitative, structural and ultrastructural perspective. METHOD: Chemical preparations of membrane of the jejunum-ileum of old and young animals with the use of light and electronic microscope. RESULTS: The ganglia of young animals presented between 1 and 56 neurons and the old animals presented from 1 to 30 neurons. The mean density of the ganglia by cm² in the young jejunum-ileum was of 551±36.89 and in the old one 413±11.86. The density of the neurons was 5011±291.11 neurons/cm² average in young animals and 2918±120.70 neurons/cm² in the old ones. The size of the neurons varied in both age groups. The collagen fibers in the ganglia of old animals they were condensed. Degenerated mitochondrias in the interior of the cell were frequent in the old animals. CONCLUSION: In submucous plexus of the jejunum-ileum there is a loss of 38% of the neurons with aging.

5-HT1A, SST1, and SST2receptors mediate inhibitory postsynaptic potentials in the submucous plexus of the guinea pig ileum

Vasoactive intestinal peptide (VIP) immunoreactive neurons are important secretomotor neurons in the submucous plexus. They are the only submucosal neurons to receive inhibitory inputs and exhibit both noradrenergic and nonadrenergic inhibitory synaptic potentials (IPSPs). The former are mediated by α2-adrenoceptors, but the receptors mediating the latter have not been identified. We used standard intracellular recording, RT-PCR, and confocal microscopy to test whether 5-HT1A, SST1, and/or SST2receptors mediate nonadrenergic IPSPs in VIP submucosal neurons in guinea pig ileum in vitro. The specific 5-HT1Areceptor antagonist WAY 100135 (1 μM) reduced the amplitude of IPSPs, an effect that persisted in the presence of the α2-adrenoceptor antagonist idazoxan (2 μM), suggesting that 5-HT might mediate a component of the IPSPs. Confocal microscopy revealed that there were many 5-HT-immunoreactive varicosities in close contact with VIP neurons. The specific SSTR2antagonist CYN 154806 (100 nM) and a specific SSTR1antagonist SRA 880 (3 μM) each reduced the amplitude of nonadrenergic IPSPs and hyperpolarizations evoked by somatostatin. In contrast with the other antagonists, CYN 154806 also reduced the durations of nonadrenergic IPSPs. Effects of WAY 100135 and CYN 154806 were additive. RT-PCR revealed gene transcripts for 5-HT1A, SST1, and SST2receptors in stripped submucous plexus preparations consistent with the pharmacological data. Although the involvement of other neurotransmitters or receptors cannot be excluded, we conclude that 5-HT1A, SST1, and SST2receptors mediate nonadrenergic IPSPs in the noncholinergic (VIP) secretomotor neurons. This study thus provides the tools to identify functions of enteric neural pathways that inhibit secretomotor reflexes.