Licking Behavior Of Rats Research Articles

Effects of harmane and other β-carbolines on apomorphine-induced licking behavior in rat

Harmane, harmine and norharmane are β-carboline compounds which have been referred to as inverse agonists of benzodiazepine receptors. The effect of these compounds on apomorphine-induced licking behavior was studied in rats. Subcutaneous (s.c.) injection of apomorphine (0.5mg/kg) induced licking. The licking behavior was counted with a hand counter and recorded for a period of 75min by direct observation. Intraperitoneal (i.p.) injections of harmane (1.25–5mg/kg), harmine (2.5–10mg/kg) and norharmane (1.25–5mg/kg) significantly reduced the licking behavior. In rats pretreated with reserpine (5mg/kg, i.p., 18h before the test), the effects of harmane (4mg/kg, i.p.), harmine (7.8mg/kg, i.p.) and norharmane (2.5mg/kg, i.p.) were unchanged. When flumazenil (2mg/kg, i.p.) was administered 20min before apomorphine, it was able to antagonize the effects of harmane, harmine and norharmane. It was concluded that the β-carbolines harmane, harmine and norharmane reduce the licking behavior via an inverse agonistic mechanism located in the benzodiazepine receptors.

A novel automated method for measuring the effect of analgesics on formalin-evoked licking behavior in rats

The behavioral assessment of pain is essential for the analysis of pain mechanisms and the evaluation of analgesic drugs. The formalin test is one of such methods widely used as a model of injury-induced pain in rodents. This test is manually demanding and the recording of results is left to the subjectivity of the experimenters. Thus we developed a novel automated method to estimate the pharmacological response in formalin-induced licking behavior in rats using a multicolor detection technique. Two color markers were preliminarily applied to rats—yellow dye on the mouth and fluorescent green tape on the right hind paw. Behaviors of the animals were recorded from both above and below the subject, by a dual-view digital video camera system. After injection with formalin into the hind paw, rats exhibited a biphasic display of licking behavior. Licking time was measured by the sum of frames where the distance between these markers was less than an appropriate threshold of distance (TD). The split-plot analysis of variance demonstrated that the sum of squares of differences in licking time between manual and automated measurement was minimized when TD = 20 mm. In addition, frames in which moving velocity of these markers is less than 2.5 mm/s was neglected for calculation in order to eliminate sedative effect on the recorded data. On these conditions, subcutaneous administration of morphine in rats dose-dependently decreased formalin-elicited nociceptive responses. These results suggest that under optimal conditions the automated technique when applied to pharmacological studies are more reliable and efficient than if they are manually recorded.

Influence of different histamine receptor agonists and antagonists on apomorphine-induced licking behavior in rat

The effects of different histamine receptor agonists and antagonists on apomorphine-induced licking behavior in rats were investigated. Subcutaneous (s.c.) injection of various doses of apomorphine (0.125–1.25 mg/kg) induced licking. The licking response was counted by direct observation and recorded for a 75-min period. Intracerebroventricular (i.c.v.) or intraperitoneal (i.p.) injection of the histamine H 1 or H 2 receptor agonist, HTMT (6-[2-(4-imidazolyl)ethylamino]- N-(4-trifluoromethylphenyl) heptanecarboxamide) (50 and 100 μg per rat), or dimaprit (10 and 15 mg/kg, i.p.), respectively, potentiated apomorphine-induced licking, while the histamine H 3 receptor agonist, imetit (5 and 10 mg/kg, i.p.), reduced the licking response induced by apomorphine. Pretreatment with various histamine receptor antagonists, dexchlorpheniramine (30 and 40 mg/kg, i.p.), diphenhydramine (20, 30 and 40 mg/kg, i.p.), famotidine (30 and 40 mg/kg, s.c.) and ranitidine (20, 30 and 40 mg/kg), reduced apomorphine-induced licking, while thioperamide (5 and 10 mg/kg, i.p.) potentiated the apomorphine effect. The effects of HTMT and dimaprit were blocked by dexchlorpheniramine (20 mg/kg, i.p.) and famotidine (20 mg/kg, s.c.), respectively. The inhibitory effect elicited by imetit on apomorphine-induced licking behavior was also abolished in animals treated with thioperamide (2.5 mg/kg, i.p.). The results suggest that histaminergic mechanisms may be involved in the modulation of apomorphine-induced licking behavior.

Effects of Adrenoceptor Agents on Apomorphine-Induced Licking Behavior in Rats

In the present study, intraperitoneal (IP) administration of the dopaminergic receptor agonist apomorphine (0.1, 0.25, and 0.5 mg/kg) induced a dose-dependent licking in rats. The intraperitoneal injection of the α 1‴adrenoceptor agonist phenylephrine (1–8 mg/kg) but not the α 2-adrenoceptor agonist clonidine (0.025–0.05 mg/kg) decreased licking induced by apomorphine. The α-adrenoceptor antagonists prazosin, phenoxybenzamine, and yohimbine also reduced the apomorphine response significantly. The response induced by phenylephrine was decreased by a dose of prazosin. The β 1-adrenenocepor agonist dobutamine and β 2-adrenenocepor agonist salbutamol did not alter the apomorphine response. However, β 2-adrenenocepor antagonists atenolol and propranolol reduced the apomorphine effect. It may be concluded that α 1- and possibly β 1-adrenoceptor mechanisms may be involved in modulation of licking behavior.

Effects of unilateral striatal dopamine depletion on tongue force and rhythm during licking in rats.

To quantitatively assess the orolingual dysfunctions produced by unilateral striatal dopamine depletions, rats first received 6-hydroxydopamine injections into the nigrostriatal bundle and were then trained to lap water from a force-sensing disk in 2-min sessions. Compared with controls and rats with moderate (<75%) dopamine depletions, subjects with substantial (>75%) dopamine depletions showed decreases in number of licks, lick rhythm, and lick peak force. Rats with substantial lesions were also impaired in making initial, within-session adjustments in lick peak force but not in lick rhythm. The results confirm the presence of Parkinson-like deficits in tongue dynamics during consummatory licking behavior in rats. The methods used here should prove useful in providing quantitative measures of the efficacy of experimental therapies in this rodent model of Parkinson's disease.

Brainstem lesions and gustatory function: I. The role of the nucleus of the solitary tract during a brief intake test in rats.

Using an automated gustometer, licking behavior in rats was evaluated for a range of concentrations of appetitive and aversive stimuli in rats following electrolytic lesions in the rostral nucleus of the solitary tract (NST). Lesions of the NST flattened the concentration-response function for all gustatory stimuli. They attenuated the concentration-response function for MgCl2, QHCI, and NH(4)Cl by shifting it to the right by 0.5 log unit, attenuated the function for citric acid and Polycose by shifting it to the right by 1.5 log units, and fully eliminated the function for sucrose and NaCl. This failure to respond appropriately, however, was specific to gustatory stimuli because all rats reduced ingestive responding when presented with increasing concentrations of capsaicin, a trigeminal stimulus. Together, the data show that the NST is critical for responding appropriately to changes in intensity of a gustatory, but not a trigeminal, stimulus.

Neural activity of chorda tympani mechanosensitive fibers during licking behavior in rats

The chorda tympani nerve, supplying the anterior two-thirds of the tongue, contains gustatory and mechanosensitive afferent fibers. We have analyzed discharge patterns in rats of various fibers recorded from dissected nerve filaments during licking behavior of which 4 were taste-sensitive and 12 mechanosensitive. The incidence of these two types was estimated electrophysiologically under anesthesia and their conduction velocity measured. Recordings in freely moving animals showed that the mechanosensitive fibers innervating the dorsal part of the tongue gave two burst discharges per lick, suggesting that contact of the tongue with the upper incisors and/or lip occurred during tongue protrusion and retraction. The fibers from the tip of the tongue showed one burst discharge per lick, which was the response to contact with a drinking spout. No rhythmical discharges synchronized with lick signals were observed in the fibers from the lateral part of the tongue or the taste-sensitive fibers. Such mechanoreceptor discharges were difficult to detect in recordings from the whole chorda tympani nerve. This masking of responses was due mainly to activation of a small number of mechanosensitive fibers by licking-induced mechanical stimulation. The lubricating action of saliva also decreased mechanoreceptor sensitivity. Despite their small number, the mechanosensitive fibers had axons with faster conduction velocities (larger diameter) than the taste-sensitive fibers. This was probably the reason why dissected nerve bundles more frequently showed mechanical than taste responses in conscious rats.

Neuropeptide Y attenuates satiety: evidence from a detailed analysis patterns ingestion

Centrally injected neuropeptide Y (NPY) is a potent stimulant of ingestive behavior capable of augmenting both food and fluid intake in fully satiated animals. To gain further insight into NPY's mechanism of action, we recorded patterns of licking behavior in rats drinking sweetened condensed milk solutions immediately after lateral ventricular injection of NPY (10 μg) or vehicle. In a separate study, we examined licking patterns after 23 h food deprivation (FD) that produced approximately the same total intake as NPY. Consistent with previous reports, we found NPY stimulated intake by increasing total ingestion time and total volume consumed during a 1-h test. Although NPY the number of bouts of licking and shortened pauses between bouts, it also decreased mean bout size, duration and within-bout lick rat (local rate). It had no significant effect on start latency or lick efficiency (licks/ml). Further analyses revealed that NPY attenuated satiety (reduced slope of lick-rate functions with session time) but had no significant effect on the beginning lick rate, a measure related to orosensory excitation. In contrast to NPY, FD increased both the beginning lick rate and individual bout size without changing either the mean number of bouts or the pause between bouts. In general, NPY stimulated an intermittent pattern of licking and delayed satiation whereas FD increased the initial rate of licking and the size of individual bouts without changing the basic licking pattern. The increase in initial lick rate suggests that FD, unlike NPY, enhances orosensory stimulation. These data compliment previous results showing that NPY increases the motivation to eat. In particular, the present data suggest that NPY also promotes ingestion by producing a distinctive pattern of ingestion and slowing the rate of satiation.

Food deprivation- and palatability-induced microstructural changes in ingestive behavior

The effects of 17 h food deprivation and stimulation by five concentrations (0.05-0.8 M) of sucrose solutions on the licking behavior of rats were investigated. Food deprivation increased the intake of the three lowest concentrations (0.05, 0.1, and 0.2 M) but had no effect on the volume ingested of the two highest concentrations (0.4 and 0.8 M). Food deprivation had no significant effect on the duration of the meals of any of the sucrose solutions; rather it affected the rate of ingestion. In those cases where food deprivation did affect volume intake, it did so by increasing the initial rate of ingestion. Although food deprivation had no effect on the volume ingested of the two strongest concentrations of sucrose, it nevertheless affected the ingestive behavior by increasing the duration of the sustained periods of bursts of licking and decreasing their number. Deprivation also significantly decreased the rate of licking within these sustained bouts of licking. The results indicate that food deprivation can affect the ingestive behavior of rats in ways that are not revealed by measuring volumetric intake alone. The data also support the view that food deprivation increases the palatability of the test solutions.

Analysis of the microstructure of the rhythmic tongue movements of rats ingesting maltose and sucrose solutions.

The interlick interval distribution of rats while ingesting maltose under real and sham feeding conditions and while ingesting seven concentrations of sucrose under real feeding conditions was analyzed. The analysis revealed that the licking behavior of rats is organized into bursts of licking at a high rate. These bursts occurred in clusters that were separated by brief (250-500 ms) interruptions. The clusters were separated by intervals that ranged from 500 ms to many hundreds of seconds. Sham feeding increased the length of the meal by increasing the number but not the size of the clusters. Increasing the concentration of sucrose increased monotonically the size of the clusters but varied the number of clusters as an inverted-V-shaped function. This analysis revealed the details of the central nervous system's control over ingestive behavior.

Taste nerve responses during licking behavior in rats: Importance of saliva in responses to sweeteners

Taste responses of the rat chorda tympani nerve, innervating taste cells on the anterior part of the tongue, were recorded under awake and anesthetic conditions. Responses to licking of taste solutions in conscious animals were compared with those to taste solutions poured onto the tongue, without contamination of saliva, in anesthetized ones. The most noticiable finding was that sweet-tasting substances such as sugars and amino acids elicited larger magnitudes of neural responses (2–4 times) under awake condition than under anesthetic experimental condition. We conclude that a proper ionic composition of mucous substances covering the surface of the taste cell membrane is important in generating good responses to sweeteners as observed in licking rats.

Analysis of the microstructure of the licking behavior of rats ingesting sucrose and maltose

Analysis of the microstructure of the licking behavior of rats ingesting sucrose and maltose

Taste responses of the chorda tympani nerve during licking behavior in rats

Taste responses of the chorda tympani nerve during licking behavior in rats

Effects of gustatory deafferentation on ingestion of taste solutions as seen by licking behavior in rats

The role of the taste nerves in licking behavior to various taste solutions was examined in rats. The study consisted of two experiments. In the electrophysiological experiment, the whole nerve recording of the anterior palatine nerve (PN) was performed to examine the response properties of this nerve to taste stimulation applied to the taste buds in the nasoincisal duct. When the moderate concentrations of solutions were used, the PN responded best to HCl, followed by sucrose and NaCl. Quinine hydrochloride elicited the smallest response. In the behavioral experiment, the number of licks/20 sec was measured for each of the test solutions such as 0.5 M sucrose, 0.01–1.0 M NaCl, 0.03 M HCl and 0.0005 M–0.01 M quinine in normal control and experimental rats. The experimental animals received bilateral deafferentation of the PN, chorda tympani (CT) and glossopharyngeal nerve (GN) alone or in various combinations. Rats without one of the 3 taste nerves still rejected the aversive HCl and quinine solutions. However, after lesions of both CT and GN, or all the 3 taste nerve, the rats showed a significant increase in the number of licks to these aversive solutions. These results suggest that taste aversion disappears after denervation of more than 80% of the total taste buds. The interlick interval, lick duration and the amount of intake per lick did not change significantly after sections of the taste nerves in any combinations.

Response characteristics of neurons in the cortical taste area during licking behavior in rats

Response characteristics of neurons in the cortical taste area during licking behavior in rats

Response characteristics of neurons in the cortical taste area during licking behavior in rats

Deep submicron interconnects (leads, contacts and vias) are rapidly becoming one of the major reliability challenges as ULSI devices continue to be scaled. With 0.5um feature sizes now common, trying to balance reliability and performance requirements is increasing difficult as we move toward <0.25um. By the end of the decade, current density in metal leads will be >0.5 Ma/cm2 and single 0.20–0.25um contacts and vias will be required to safely carry 1–2ma of current. This increases electromigration concerns, with vias generally now being the weakest link in a reliable ULSI multilevel-metal system.

Interaction between licking and swallowing in the drinking rat.

Licking behavior of rats appeared to be interrupted periodically for about 20 ms. Behavioral and electrophysiological evidence is presented which indicates that during this period swallowing occurs. The hypothesis was tested that swallowing initiation depends on the volume of water that has accumulated in the oral cavity during drinking. No support for this hypothesis was obtained when the flow rate of water through the drinking tube was manipulated. Alternative hypotheses are discussed.

Tail pinch-induced eating, gnawing and licking behavior in rats: Dependence on the nigrostriatal dopamine system

Mild-tail-pinch induces a syndrome of eating, gnawing and licking behavior in rats in the presence of food. Detailed behavioral, pharmacological and biochemical analyses of this phenomenon resulted in the following conclusions. (1) This is an unusually reliable phenomenon, demonstrable in each of more than 200 animals tested. (2) Eating is by far the predominant response to tail-pinch. (3) Tail-pinch behavior is critically dependent on the nigrostriatal dopamine system. (4) There are striking pharmacological parallels between tail-pinch behavior and schizophrenia.

Suppression of licking behavior in rats as a function of predictability of shock and probability of conditioned-stimulus-shock pairings.

Suppression of licking behavior in rats as a function of predictability of shock and probability of conditioned-stimulus-shock pairings.

Scaling the duration of short pauses in licking behavior of rats and mice: A first approximation to a basic pause-scaling unit

Two studies are reported in which short pauses from the drinking behavior of four hooded rats (rat study) and four mice (mouse study) were analyzed. Both of these studies supported the hypothesis that the interlick interval (II) can be used as a unit (PU) for scaling short pauses in licking behavior during water drinking. The outcomes of these studies are seen as suggesting that the factor responsible for the constancy of the II is also functioning during short pauses and is responsible for the tendency herein reported for pauses to be scaled by the PU.