Immunohistochemical analysis of neuronal nitric oxide synthase in the trigeminal ganglia of the crotaline snake Trimeresurus flavoviridis

Infrared-sensitive pit organ and trigeminal ganglion in the crotaline snakes

The infrared (IR) receptors in the pit organ of crotaline snakes are very sensitive to temperature. The sensitivity to IR radiation is much greater in crotaline snakes than in boid snakes because they have a thermosensitive membrane suspended in a pair of pits that comprise the pit organ. The vasculature of the pit membrane, which is located near IR-sensitive terminal nerve masses, the IR receptors, supplies the blood necessary to provide cooling and the energy and oxygen that the IR receptors require. The ophthalmic and maxillary branches of the trigeminal nerve innervate the pit membrane. In crotaline snakes, the trigeminal ganglion (TG) is divided into the ophthalmic and maxillomandibular ganglia; a prominent septum further separates the two divisions of the maxillomandibular ganglion. The TG neurons in the ophthalmic ganglion and the maxillary division of the maxillomandibular ganglion relay IR sensation to the brain. This article reviews the IR-sensitive pit organ and trigeminal sensory system structures in crotaline snakes.

Phylogenesis of constitutively formed nitric oxide in non-mammals

It is widely recognized that nitric oxide (NO) in mammalian tissues is produced from L-arginine via catalysis by NO synthase (NOS) isoforms such as neuronal NOS (nNOS) and endothelial NOS (eNOS) that are constitutively expressed mainly in the central and peripheral nervous system and vascular endothelial cells, respectively. This review concentrates only on these constitutive NOS (cNOS) isoforms while excluding information about iNOS, which is induced mainly in macrophages upon stimulation by cytokines and polysaccharides. The NO signaling pathway plays a crucial role in the functional regulation of mammalian tissues and organs. Evidence has also been accumulated for the role of NO in invertebrates and non-mammalian vertebrates. Expression of nNOS in the brain and peripheral nervous system is widely determined by staining with NADPH (reduced nicotinamide adenine dinucleotide phosphate) diaphorase or NOS immunoreactivity, and functional roles of NO formed by nNOS are evidenced in the early phylogenetic stages (invertebrates and fishes). On the other hand, the endothelium mainly produces vasodilating prostanoids rather than NO or does not liberate endothelium-derived relaxing factor (EDRF) (fishes), and the ability of endothelial cells to liberate NO is observed later in phylogenetic stages (amphibians). This review article summarizes various types of interesting information obtained from lower organisms (invertebrates, fishes, amphibians, reptiles, and birds) about the properties and distribution of nNOS and eNOS and also the roles of NO produced by the cNOS as an important intercellular signaling molecule.

Hemodynamic effects of python neuropeptide γ in the anesthetized python, Python regius

The effects of python neuropeptide gamma (NPgamma) on hemodynamic parameters have been investigated in the anesthetized ball python (Python regius). Bolus intra-arterial injections of synthetic python NPgamma (1-300 pmol kg-1) produced a dose-dependent decrease in systemic arterial blood pressure (Psys) concomitant with increases in systemic vascular conductance (Gsys), total cardiac output and stroke volume, but only minor effects on heart rate. The peptide had no significant effect on pulmonary arterial blood pressure (Ppul) and caused only a small increase in pulmonary conductance (Gpul) at the highest dose. In the systemic circulation, the potency of the NK1 receptor-selective agonist [Sar9,Met(0(2))11] substance P was >100-fold greater than the NK2 receptor-selective agonist [betaAla8] neurokinin A-(4-10)-peptide suggesting that the python cardiovascular system is associated with a receptor that resembles the mammalian NK1 receptor more closely than the NK2 receptor. Administration of the inhibitor of nitric oxide synthesis, L-nitro-arginine-methylester (L-NAME; 150 mg kg-1), resulted in a significant (P<0.05) increase in Psys as well as a decrease in Gsys, but no effect on Ppul and Gpul. Conversely, the nitric oxide donor, sodium nitroprusside (SNP; 60 microg kg-1) produced a significant (P<0.05) decrease in Psys along with an increase in Gsys and pulmonary blood flow. However, neither L-NAME nor indomethacin (10 mg kg-1) reduced the cardiovascular responses to NPgamma. Thus, nitric oxide is involved in regulation of basal vascular tone in the python, but neither nitric oxide nor prostaglandins mediate the vasodilatory action of NPgamma.

The role of nitric oxide in the regulation of the systemic and pulmonary vasculature of the rattlesnake, Crotalus durissus terrificus

The functional role of nitric oxide (NO) was investigated in the systemic and pulmonary circulations of the South American rattlesnake, Crotalus durissus terrificus. Bolus, intra-arterial injections of the NO donor, sodium nitroprusside (SNP) caused a significant systemic vasodilatation resulting in a reduction in systemic resistance (Rsys). This response was accompanied by a significant decrease in systemic pressure and a rise in systemic blood flow. Pulmonary resistance (Rpul) remained constant while pulmonary pressure (Ppul) and pulmonary blood flow (Qpul) decreased. Injection of L-Arginine (L-Arg) produced a similar response to SNP in the systemic circulation, inducing an immediate systemic vasodilatation, while Rpul was unaffected. Blockade of NO synthesis via the nitric oxide synthase inhibitor, L-NAME, did not affect haemodynamic variables in the systemic circulation, indicating a small contribution of NO to the basal regulation of systemic vascular resistance. Similarly, Rpul and Qpul remained unchanged, although there was a significant rise in Ppul. Via injection of SNP, this study clearly demonstrates that NO causes a systemic vasodilatation in the rattlesnake, indicating that NO may contribute in the regulation of systemic vascular resistance. In contrast, the pulmonary vasculature seems far less responsive to NO.

Snake Infrared Receptors Respond to Dimethylsulfoxide in the Blood Stream

1. We used extracellular recording of the infrared (IR)-sensitive trigeminal ganglion (TG) neurons (primary neurons) of a crotaline snake, Trimeresurus flavoviridis, which has very sensitive thermoreceptors, to examine changes in the IR response induced by dimethylsulfoxide (DMSO), in vivo. 2. The responses in the TG were recorded after each concentration of DMSO (1, 10, and 25%) was administered in the bloodstream. 3. At a constant temperature, DMSO dose-dependently potentiated the IR-triggered discharges of IR-sensitive TG neurons in this snake. 4. It is suggested that the increased IR response to DMSO is due to its chemical effect, or to an indirect effect via its vasoactive role in the thermoreceptors of IR-sensitive snakes.

An investigation of the effects of ruthenium red, nitric oxide and endothelin-1 on infrared receptor activity in a crotaline snake

The infrared (IR) receptors in the pit organ of crotaline snakes are very sensitive to temperature. The vasculature of the pit organs, which is located in close proximity to IR-sensitive terminal nerve masses (IR receptors), is finer, flatter, and more convoluted than that of other sensory organs. Using extracellular recording in vivo from IR-sensitive primary afferent trigeminal ganglion (TG) neurons of the crotaline snake Trimeresurus flavoviridis, I studied the response to IR warming (24-25 degrees C) and to various chemicals: an exogenous vasoactive substance nitric oxide donor (sodium nitroprusside, SNP), endothelin-1 (ET-1), a transient receptor potential vanilloid (TRPV)1 agonist (capsaicin, CAP) and antagonist (capsazepine, CZP), and Ruthenium Red (RR), an antagonist of the TRPV family. IR-sensitive primary afferent TG neurons display regular background firing at 10-25 impulses per second at 24-25 degrees C. At this temperature, Ruthenium Red and endothelin-1 clearly suppressed the frequency of background firing, while sodium nitroprusside injected into the bloodstream significantly increased the frequency of discharges (P<0.01) and caused regular bursts of firing in IR-sensitive TG neurons. By contrast, capsaicin and capsazepine had no effect on the infrared responses. The possibility that these opposite responses result from their vasoactive effects on the unusual pit vasculature or from their chemical effects on the thermoreceptors of IR-sensitive nerve terminals in the pit organ, like those of the TRPV family, is discussed.

Immunohistochemical Study of Endothelial Nitric Oxide Synthase in the Trigeminal Ganglia of a Crotaline Snake Trimeresurus flavoviridis

The immunoreactivity of constitutive endothelial nitric oxide synthase (eNOS) was studied in the trigeminal ganglia (TG) of a crotaline snake, Trimeresurus flavoviridis. eNOS immunoreactivity was found in TG neurons of different sizes. The percentage of eNOS-positive TG neurons was significantly higher in the mandibular division than in the infrared-related divisions, the maxillary division and ophthalmic ganglion (p<0.001). These findings suggest that eNOS in the TG of crotaline snakes is involved in constitutive neurotransmission in the TG, and is minimally involved in processing in the infrared-sensory system.

Immunohistochemical localization of the delta subspecies of protein kinase C in the trigeminal sensory system of Trimeresurus flavoviridis, an infrared-sensitive snake

We examined the expression of the protein kinase C (PKC) delta subspecies in the trigeminal sensory system of the infrared-sensitive snake Trimeresurus flavoviridis. In the trigeminal ganglion (TG), diffuse low-intensity PKC delta immunoreactivity was found in TG neurons and fibers, while intense reactions were observed mainly in medium-sized neurons, which include most of the infrared-sensitive neurons. In the brainstem, intense PKC delta immunoreactivity was present in the intermediate layer of the optic tectum of the midbrain and in the nucleus descendens lateralis n. trigemini of the medulla oblongata; these areas are related to the infrared sensory pathway. In the pit organ (the infrared receptor), PKC delta immunoreactivity was present in terminal nerve masses in the pit membrane. These findings suggest that the PKC delta subspecies is involved in the infrared sensory pathway in the trigeminal sensory system of the infrared-sensitive snake.