Sensitizing effects of bradykinin on the heat responses of the visceral nociceptor.

1. Whether bradykinin (BK), which is known as an endogenous pain-producing substance, induces augmentation of the discharges of polymodal receptors evoked by heat stimulation was investigated in in vitro canine testis-superior spermatic nerve preparations. 2. The heat response was significantly augmented by pretreatments with BK at concentrations greater than 0.094 nM, whereas BK induced significant increases in the mean discharge rates at concentrations above 9.4 nM. Both effects increased in a concentration-dependent manner. The augmenting effect of BK on the heat response diminished within 10 min after application of BK, regardless of concentration. 3. When 9.4 nM BK was applied in a mixture with 940 nM NPC349, a B2 receptor antagonist, the averaged mean discharge rate evoked by BK and the averaged augmenting effect were both significantly suppressed compared with those induced by BK given alone. 4. The augmenting effect of BK on the heat response of polymodal receptors could be observed even in the absence of BK-evoked discharges per se in several cases in which low concentrations of BK or BK plus B2 antagonists were given. 5. These findings suggest that the augmenting effects of BK on the heat response depend on B2 receptor-mediated intracellular processes acting in parallel to, but not directly on, the impulse-generation mechanism of the heat response of the polymodal receptor.     

I.m. midazolam as premedication produces a concentration-dependent decrease in core temperature in male volunteers

We tested the hypothesis that premedication with i.m. midazolam decreases core temperature dose-dependently. We studied six male volunteers, in random order, on 3 days: (1) no midazolam administration (control day), (2) midazolam 0.025 mg kg-1 i.m., (3) midazolam 0.075 mg kg-1 i.m. On the first day, subjects were maintained alert during a 30- min control period. On the second and third days, midazolam 0.025 or 0.075 mg kg-1 was administered i.m. Core temperatures were measured at the right tympanic membrane. Four adhesive skin surface probes were fixed on the chest, upper right arm, lateral calf and thigh. Finger tip perfusion was evaluated using forearm minus fingertip and calf minus toe, skin surface temperature gradients. Thirty minutes after midazolam i.m., the level of sedation in the volunteers was assessed. Peripheral venous blood was obtained immediately after the assessment of the level of sedation. Tympanic membrane temperatures after administration of midazolam 0.075 mg kg-1 i.m. were significantly lower than those on the control and midazolam 0.025 mg kg-1 i.m. days at 20 and 30 min. The decreases in tympanic membrane temperatures at 30 min after midazolam i.m. became larger as the volunteers were more deeply sedated. i.m. midazolam produced a concentration-dependent decrease in tympanic membrane temperature at 30 min after midazolam 0.025 and 0.075 mg kg-1 i.m. We conclude that midazolam impaired tonic thermoregulatory vasoconstriction, allowing core-to-peripheral heat redistribution in a dose-dependent manner after i.m. administration.      

Clitoral involvement by neurofibromatosis: a case report and review of the literature

We report a case of clitoral involvement by neurofibromatosis in which the clitoris resembled a phallus. The patient was treated successfully by clitoroplasty. This is the seventh such case reported in the English literature.     

An automated on-line method for simultaneous analysis of phenothiazines in human serum by high-performance liquid chromatography/sonic spray ionization mass spectrometry using backflush column switching

An automated on-line method for simultaneous analysis of five phenothiazine drugs by high-performance liquid chromatography (HPLC)/sonic spray ionization mass spectrometry (SSI-MS) has been established, using backflush column switching. A 400-μl portion of serum sample diluted 81-fold with distilled water was subjected to the on-line system. In the system, an Oasis HLB cartridge was used as the precolumn for extraction; large molecules such as proteins in serum were discarded by use of distilled water containing 0.1% formic acid as a mobile phase. After switching a valve, the analytes trapped in the precolumn were eluted in the backflush mode and separated by a Chromolith Performance RP-18e column, which is composed of C₁₈-bonded monolithic silica. The column effluents were then introduced into the SSI-MS. The present method provided successful separation and determination of six phenothiazines including an internal standard. Satisfactory linearities, reproducibility, and sensitivity were obtained at concentration levels that matched the toxic levels of phenothiazines. All drug peaks appeared within 18 min, and the system could be reequilibrated in only about 8 min for the next run. Because of the simplicity and rapidness of the method, it is likely to be useful in the fields of emergency medicine and forensic toxicology.     

Functions of the nociceptive primary neurons

The functions of nociceptive primary neurons are reviewed in brief, with special reference to the polymodal receptor. The polymodal receptor is considered to be a primitive sensory receptor that is not well differentiated and that plays important roles in signaling pain especially from tissues in pathological states, and in causing reflex modulations of a wide variety of bodily functions. This sensory receptor is characterized by the existence of neuropeptides in its neuron. The wide distribution of the central axon branchings of this neuron and the long-lasting effects of the neuropeptides released from the axon terminals provide an "analogue-like" action of the nervous system, which had hitherto been considered to be "digital-like," point-to-point connections in the central neuron network. Neuropeptides released from the peripheral endings of this neuron, on the other hand, play important roles in local regulation of such functions as inflammation, visceral tract motility, trophic effects, immune system functioning and so on. The functions of nociceptive primary neurons are, therefore, not limited to sensory function but should be understood as a component related to the regulation of fundamental functions of the entire organism.     

Effects of adrenoceptor antagonists on the cutaneous blood flow increase response to sympathetic nerve stimulation in rats with persistent inflammation

There is some evidence that the sympathetic nervous system plays a role in the development and/or maintenance of painful states, and that sympathetic nervous function is altered in these conditions. Our previous experiments showed that electrical stimulation of the lumbar sympathetic trunk (sympathetic stimulation: SS), which normally induces a decrease in blood flow (BF) of plantar skin, induced its BF increase in about 50% of adjuvant-inflamed rats. To investigate the mechanism of this BF-increase response, we examined whether noradrenaline (NA) plays any role in this changed response to SS, and which receptor subtype is involved. We measured paw cutaneous BF response with a laser Doppler flowmeter in rats chronically inflamed with complete Freund's adjuvant. SS induced the BF-increase response in 50-67% of measured sites. Close-arterially injected NA induced the BF-increase response at dosages between 10-100 ng/kg only at the sites with the BF-increase response to SS. The BF-increase and -decrease responses to NA was significantly reduced after the close-arterial injection of either alpha1- or alpha2-adrenoceptor antagonists (p lt; 0.05, respectively). In contrast, although the BF-decrease responses to SS were significantly reduced by administration of alpha1- and alpha2-adrenoceptor antagonist, BF-increase response was reduced only by alpha1-adrenoceptor antagonist, and that only at a higher dose. In addition, the beta-adrenoceptor antagonist had no effects on both responses. These results suggest that the BF-increase response to SS involves, additionally to NA, a non-adrenergic mechanism.     

Transduction mechanisms for the taste of amino acids.

Amino acids are important taste stimuli for a variety of animals. One animal model, the channel catfish, I. punctatus, possesses sensitive taste receptor systems for several amino acids. Neurophysiological and biochemical receptor binding studies suggest the presence of at least three receptor pathways: one is a relatively nonspecific site(s) responsive to short-chain neutral amino acids such as L-alanine (L-ALA); another is responsive to the basic amino acid L-arginine (L-ARG); still another is a low affinity site for L-proline (L-PRO). Several possible transduction pathways are available in the taste system of this animal model for these amino acids. One of these, formation of inositol trisphosphate (IP3) and cyclic AMP (cAMP), is mediated by GTP-binding regulatory proteins, while another involves ion channels directly activated by stimuli. L-ALA is a potent stimulus to cAMP and IP3 accumulation, while L-ARG at low concentrations is without effect. On the other hand, L-ARG and L-PRO, but not L-ALA, are able to activate stimulus-specific and cation-selective channels in taste epithelial membranes reconstituted in phospholipid bilayers at the tips of patch pipettes. Preliminary studies using mouse taste tissue demonstrate that monosodium-L-glutamate (MSG) did not enhance production of IP3 or cAMP. However, in reconstitution experiments using taste epithelium of mouse, conductance changes due to MSG are observed. The specificity of this channel(s) and its uniqueness have yet to be determined.     

Norepinephrine reduces heat responses of cutaneous C-fiber nociceptors in Sprague-Dawley rats in vitro

Nociceptors are excited or sensitized by many inflammatory mediators as well as by elevation of tissue temperature. We have shown that there is a facilitatory synergistic interaction between norepinephrine (NE) and bradykinin (BK) on cutaneous C-fiber nociceptors in normal Lewis rats. These interactions may play an important role in the mechanism of sympathetically maintained pain. In the present experiment, using skin-saphenous nerve in vitro preparations, we tested the effect of NE on the activity of nociceptive fibers and their response to heat in normal Sprague-Dawley rats. For comparison with the previous data on Lewis rats, we also examined the effect of NE on BK response. NE (10(-5) or 10(-6) M) did not excite nociceptive fibers before repeated heat stimuli or BK superfusion (10(-5) or 10(-6) M) to the receptive field. In contrast, after a few applications of heat or BK, NE excited 20-43% of nociceptive fibers to similar magnitudes. We also found that NE sensitized subsequent BK responses, but somewhat unexpectedly that it suppressed subsequent heat responses. This occurred regardless of the presence or absence of NE-induced excitation. These results suggest different mechanisms of NE modification to the BK and heat responses of cutaneous C-fiber nociceptors.     

Enhancement of immunoglobulin G responses in mice against hepatitis B virus surface antigen, influenza virus hemagglutinin vaccine, and tetanus toxoid by 6-O-acylated muramyl dipeptides.

The adjuvant activity of chemically synthesized 6-O-acylated muramyl dipeptides (MDP) was tested in aqueous form. The activity was assessed by determining immunoglobulin G (IgG) titers in sera of mice immunized with hepatitis B virus surface antigen, influenza virus hemagglutinin (HA) vaccine, or tetanus toxoid with an enzyme-linked immunosorbent assay. Administration of 6-O-acyl-MDP analogs with antigens induced marked enhancement of primary and secondary IgG antibody responses and maintained high antibody levels for at least 7 weeks. Among the analogs tested, an MDP methyl ester carrying a 6-O-3-hexadecanoyl-oxytetradecanoyl group (compound 309) exhibited the most intensive adjuvant activity. Its activity was stronger than that of 6-O-2-tetradecylhexadecanoyl (B3O)-MDP used as a positive control. However, accumulation of peritoneal cells and activation of peritoneal macrophages by compound 309 was weaker than that by 6-O-B30-MDP, suggesting that 309 as an immunoadjuvant is more suitable for vaccination in terms of its stronger enhancement of antibody formation and lower induction of inflammatory response than 6-O-B30-MDP.