Trigeminal irritants

Drinking tests are feasible when testing older subjects. Nolte and Mason (1995) used a single-choice drinking test to assess pup response to trigeminal irritants they were exposed to in utero. First, pups were adapted to an 18-h water deprivation schedule. Pups were presented with tap water in a 10 ml graduated sipper... 

In birds, the trigeminal nerve appears to play a role in food selection. Starlings more easily accepted commercial feed treated with otherwise avoided coniferyl benzoate after bilateral section of the ophthalmic branch of the trigeminal nerve. Therefore, the trigeminal nerve may help to protect the animal by detecting plant defense compounds. Many of these compounds are astringent or irritating (Jakubas and Mason, 1991). 

Feeding repellents for pest birds are the most important application of chemical stimuli to manipulate bird behavior. Methyl anthranilate (Fig. 13.1) and dimethyl anthranilate, esters of benzoic acid, are found in concord grapes and are used as artificial flavorings. Starlings, Sturnus vulgaris, have an aversion to methyl anthranilate, which irritates the trigeminal nerve, and they feed less on food flavored with a variety of anthranilates. They avoid the more volatile anthranilates most. The odor is partly responsible for the effect contact is not necessary. In one particular experiment, only volatile compounds were aversive (Mason and Clark, 1987). If only anthranilate-treated food is offered, the birds will accept more of the flavored food than they do if they offered a choice between... 

However, both sensory and pulmonary irritation can be expected with sufficient exposure. Sensory irritation is characterized by immediate eye and nose irritation that may increase to sensations of burning and pain and is due to interaction between the substance and receptors in the trigeminal nerve. Vapors reaching the lower respiratory tract as well as the lungs may interact with the nerves in these regions, causing dyspnea and breathlessness or pulmonary irritation. 

Sensations of irritation, pain and temperature, commonly referred to as trigeminal responses, are also experienced in the nose. Typically strong stimulants include CO2, menthol, ammonia and acids however, most odorants do have some chemesthetic component They have shorter response latencies than in the oral cavity, consistent with a shorter distance required to penetrate to the basal layer containing die nerve endings the stimulants also increase in intensity with repeated exposures (sniffs) (28), Irritants reduce the intensity of odorants the reverse is also true. The interaction is at the central processing level because an odorant presented in one nostril will be affected by an irritant given in the other nostril. 

Another characteristic of irritative stimulation of the trigeminal nerve is the defensive reflexes (e.g., sneezing) invoked by the body to remove or dilute the offending substance. In the case of oral chemical heat, the burning sensation from capsaicin invokes sweating, tearing, and copious salivation. Salivary flow... 

It irritates skin and mucous membranes. In terms of chemoreception, it irritates the trigeminal nerve. Capsaicin binds to the vanilloid receptor subtype 1 (VRl). Birds lack this receptor. Since they cannot sense capsaicin, they eat and distribute seeds of red hot peppers. Medically capsaicin is used as painkiller (analgesic). 

Capsaicin is the active ingredient in commercial squirrel repellents. It is very common that squirrels raid bird feeders. To discourage them from doing that, bird seed can be shaken with powdered capsaicin preparations, so that it adheres to the surface of the seeds. The treated food is supposed to irritate a squirrel s mouth and trigeminal nerve. 

Health effects from mVOCs have not been comprehensively studied. Some mVOCs are implicated in trigeminal nerve irritation and odor-related health complaints. 

Animal testing to determine irritant properties and thresholds has become standard. A consensus method, American Society for Testing and Materials E, is widely regarded as the basis. This method has been used to develop structure-activity relationships, to demonstrate that more than one irritant receptor may exist in the trigeminal nerve, and to explore the interaction of multiple exposures. Recently, it has been used to demonstrate the irritating properties of office equipment offgassing. 

Flavour is the sensory impression of a food while eating. It is determined by the three chemical senses of taste, smell, and the so-called trigeminal senses, which detect chemical irritants in the mouth and throat. 

The two types of sensations, trigeminal and olfactory, can be separated by making use of anosmics (persons who lack the sense of smell) as compared with persons with normal olfaction and nasal irritation. To determine the relevant physio chemical determinants of potency, these two groups of persons were exposed to single chemicals [14]. The study showed that a general relationship between odour and irritation thresholds might be present. It was found that the threshold level (odour/irritation) decreases as the length of the carbon chain increases. 

Several investigations of volatile organic compounds (VOC) have been reported. Controlled human chamber exposures to a VOC mixture (25 mg nr3) in healthy volunteers revealed that symptom and irritation intensity was unrelated to detection of aversive odour and more likely related to stimulation of trigeminal nerve receptors (Hudnell et al., 1992). Moreover, similar VOC exposures evoked... 

Tachypnea, pulmonary edema, dyspnea Skin and mucous membrane irritation, activation of herpes simplex, contact dermatitis, degreaser s flush when consuming alcohol, burns, conjunctivitis, dermatographism, rash Anesthesia, analgesia, seizures, headache, trigeminal neuropathy, weakness, hemiparesis, cranial nerve damage, neuritis, paralysis, tremor, ataxia, vertigo Hot flashes, perspiration, increased blood lipids, mild anemia... 

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