What's the difference between gnaw and gnawn?

Gnaw

Definition:

(v. t.) To bite, as something hard or tough, which is not readily separated or crushed; to bite off little by little, with effort; to wear or eat away by scraping or continuous biting with the teeth; to nibble at.
(v. t.) To bite in agony or rage.
(v. t.) To corrode; to fret away; to waste.
(v. i.) To use the teeth in biting; to bite with repeated effort, as in eating or removing with the teethsomething hard, unwiedly, or unmanageable.

Example Sentences:

(1) )-induced gnawing behavior in rats was slightly more potent than that of clocapramine.
(2) Gallic wine sales in the UK have been tumbling for the past 20 years, but the news that France, once the largest exporter to these shores, has slipped behind Australia, the United States, Italy and now South Africa will have producers gnawing their knuckles in frustration.
(3) This suggests that the locomotor stimulation induced by amphetamine involves central norepinephrine, while dopamine neurons play an important role in the induced compulsive gnawing behavior.
(4) The gnawing behavior is probably associated with the increase in brain dopamine resulting from this treatment.
(5) And those who preach or teach extremism, those who say we should not respect other Australians, those who seek to gnaw away at that social fabric, are not helping the Australian dream.
(6) The IT administration of THA, nicotine and cytisine was also associated with gnawing, vocalization and hyperactivity and in the case of THA, diarrhoea.
(7) Apomorphine-induced gnawing and licking but not sniffing were attenuated in rats with GP lesions.
(8) In control rats, SKF 38393 enhanced the stereotyped responses induced by quinpirole, converting lower-level stereotypies (sniffing and rearing) to more intense oral behaviors (licking and gnawing).
(9) Previous reports demonstrated that hypothalamic stimulation may elicit either eating, drinking, or gnawing and emphasized both the specificity of the neural circuits mediating these behaviors and the similarity to behavior during natural-drive states such as hunger and thirst.
(10) The thymoleptics imipramine, desipramine, protriptyline, nortriiptyline, chlorimipramine and amitriptyline all potentiate gnawing of mice induced by Dopa following decarboxylase inhibitior Ro 4-4602.
(11) This study was designed to assess whether phencyclidine (PCP) produces dopamine (DA)-dependent behaviors such as licking, gnawing and biting (which are not observed in normal rats) in rats after pretreatments with a tryptophan hydroxylase inhibitor, p-chlorophenylalanine (PCPA) and specific serotonergic neuronal toxin, p-chloroamphetamine (PCA).
(12) In freely moving conditions, electrical brain stimulation (EBS) of this part of the mesencephalon elicited mainly aversive effects (escape reactions: violent running and explosive jumps), but also ipsiversive circling and "gnawing."
(13) In contrast, bilateral intranigral injection of the selective delta agonist D-Pen2,D-Pen5 enkephalin (DPDPE) elicited dose-dependent exploratory behavior and rearing but failed to produce gnawing.
(14) The specific D-2 agonist LY 171555 elicited yawning, genital grooming, exploratory behavior, downward sniffing and licking but failed to induce gnawing even at high doses.
(15) The behavior categories included grooming, yawning, turning, nodding and gnawing, as well as snout contact and nonsnout contact variants of locomoting, rearing and sitting.
(16) The big four supermarket chains are battling over the squeezed middle market which is being gnawed away by Waitrose at the top and the rapidly expanding discounters Aldi and Lidl at the bottom.
(17) In order to test the possibility that the substantia nigra (SN) might be involved, the amount of food intake and gnawing produced by mild tail pinch were assessed following bilateral microinjections of opioid antagonists into the SN.
(18) When B-HT 920 was combined with SKF 38393 following pretreatment with idazoxane, both the intensity and form (continual licking and gnawing) of stereotyped behavior was enhanced.
(19) The effects of clonidine, an indirectly-acting cholinergic antagonist, on 5 behaviors elicited by atropine (locomotion, rearing, sniffing, grooming and gnawing) were studied in rats.
(20) The sensory word descriptors (crushing, sharp, tearing, cutting, penetrating, gnawing, dull, pulling, sore, stinging, pricking and pinching) and the affective word descriptors (dreadful, torturing, killing, unbearable, terrifying, suffocating, exhausting, unhappy, troublesome, annoying, irritating and fearful) are suggested as a foundation upon which a pain assessment tool could be developed for use in clinical practice.