Gustatory responses of neurons in the nucleus of the solitary tract of behaving rats

1991 ◽  
Vol 66 (4) ◽  
pp. 1232-1248 ◽  
Author(s):  
K. Nakamura ◽  
R. Norgren
Keyword(s):  
Citric Acid ◽  
Dimensional Space ◽  
Hierarchical Cluster ◽  
Stimulus Category ◽  
Solitary Tract ◽  
Spontaneous Rate ◽  
Taste Response ◽  
The Mean ◽  
Excitatory Responses ◽  
Gustatory Neurons

1. The activity of 117 single neurons was recorded in the rostral nucleus of the solitary tract (NST) and tested with each of four standard chemical stimuli [sucrose, NaCl, citric acid, and quinine HCl (QHCl)] and distilled water in awake, behaving rats. In 101 of these neurons, at least one sapid stimulus elicited a significant taste response. The mean spontaneous rate of the taste neurons was 4.1 +/- 5.8 (SD) spike/s. The mean response magnitudes were as follows: sucrose, 10.6 +/- 11.7; NaCl, 8.6 +/- 14.6; citric acid, 6.2 +/- 7.8; and QHCl, 2.4 +/- 6.6 spikes/s. 2. On the basis of their largest response, 42 taste neurons were classified as sucrose-best, 25 as NaCl-best, 30 as citric acid-best, and 4 as QHCl-best. The mean spontaneous rates for these categories were 4.9 +/- 6.2 for sucrose-best cells, 5.8 +/- 7.4 for NaCl-best, 1.6 +/- 2.0 for citric acid-best, and 5.8 +/- 6.0 spikes/s for QHCl-best. The spontaneous rate of the citric acid-best neurons was significantly lower than that of the other categories. 3. At the standard concentrations, 45 taste cells (44.6%) responded significantly to only one of the gustatory stimuli. Of the 30 acid-best neurons, 23 (76.7%) responded only to citric acid. For sucrose-best cells, specific sensitivity was less common (18/42, 42.9%), and for NaCl-best neurons, it was relatively uncommon (3/25, 12%). One of the 4 QHCl-best neurons was specific. In a concentration series, more than one-half of the 19 specific neurons tested responded to only one chemical at any strength. 4. The mean entropy for the excitatory responses of all gustatory neurons was 0.60. Citric acid-best cells showed the least breadth of responsiveness (0.49), sucrose-best cells were somewhat broader (0.56), but NaCl-best and QHCl-best cells were considerably less selective (0.77 and 0.79, respectively). Inhibition was observed infrequently and never reached the criterion for significance. 5. In the hierarchical cluster analysis, the four largest clusters segregated neurons primarily by best-stimulus category. The major exception to this was a group of sucrose-best neurons that also responded to NaCl and were grouped with the NaCl-best neurons. In a two-dimensional space, the specific taste neurons, those that responded to only one of the four standard sapid stimuli, remained in well-separated groups. These specific groups, however, were joined in a ring-like formation by other neurons that responded to more than one of the sapid stimuli.(ABSTRACT TRUNCATED AT 400 WORDS)

Sodium-deficient diet reduces gustatory activity in the nucleus of the solitary tract of behaving rats

1995 ◽  
Vol 269 (3) ◽  
pp. R647-R661 ◽  
Author(s):  
K. Nakamura ◽  
R. Norgren
Keyword(s):  
Citric Acid ◽  
Dietary Sodium ◽  
Solitary Tract ◽  
Deficient Diet ◽  
Dietary Condition ◽  
Response Profiles ◽  
The Mean ◽  
Response To Water ◽  
Gustatory Neurons ◽  
General Reduction

The activity of single taste neurons was recorded from the nucleus of the solitary tract before (n = 41) and after (n = 58) awake, behaving rats were switched to a sodium-free diet. During sodium deprivation, the spontaneous activity of the neurons increased (142%), but responses to water and sapid stimuli decreased. For all neurons in the sample, the mean response to water decreased to 72% of its predeprivation level, NaCl dropped to 53%, sucrose to 41%, citric acid to 68%, and quinine HCl to 84%. Despite the drop in magnitude, the response profiles of the taste neurons were not changed by the dietary condition. In the Na-replete state, 61% of the activity elicited by NaCl occurred in NaCl-best cells and 33% in sucrose-best neurons. In the depleted state, these values were 60 and 26%, respectively. Nevertheless, at the highest concentrations tested, deprivation did alter the relative responsiveness of the gustatory neurons to sucrose and NaCl in specific categories of neurons. Compared with acute preparations, dietary sodium deprivation in awake, behaving rats produced a more general reduction in the gustatory responses of neurons in the nucleus of the solitary tract. The largest reductions in elicited activity occurred for the "best stimulus" of a particular neuron, thus leading to smaller differences in response magnitude across stimuli, particularly at the highest concentrations tested.

Responses from parabrachial gustatory neurons in behaving rats

1990 ◽  
Vol 63 (4) ◽  
pp. 707-724 ◽  
Author(s):  
H. Nishijo ◽  
R. Norgren
Keyword(s):  
Citric Acid ◽  
Dimensional Space ◽  
Sucrose Concentration ◽  
Hierarchical Cluster ◽  
Multidimensional Analysis ◽  
Power Functions ◽  
Excitatory Activity ◽  
Neurophysiological Data ◽  
The Mean ◽  
Parabrachial Nuclei

1. The responses of a total of 70 single neurons were recorded from the parabrachial nuclei (PBN) in awake rats. In 59 neurons, sapid stimuli (0.5 ml) elicited significant taste responses. Of these 59 neurons, 10 also had significant responses to water. The mean spontaneous rate of the taste neurons was 13.4 +/- 6.9 (SD) spikes/s. Of the remaining 11 neurons, 9 responded significantly only to water; 2 had no significant responses to the standard fluid stimuli. 2. Based on the magnitude of their response to our four standard stimuli, the taste neurons were classified as follows: 42 NaCl-best, 14 sucrose-best, 2 citric acid-best, and 1 QHCl-best. Of these, 25 responded only to one of four sapid stimuli; 20 of these specific cells responded only to NaCl. All the remaining 34 neurons responded to two or more of the four sapid stimuli, with NaCl and sucrose responsiveness dominant. For the 59 taste neurons, the mean entropy for the absolute value of the responses was 0.68; for the excitatory activity alone, it was 0.58. 3. The mean responses to NaCl and sucrose concentration series increased monotonically. Except at the lowest concentration, responses to citric acid also increased monotonically, but with a lower slope. Mean responses to QHCl, however, remained stable or even decreased with increasing concentration. Thus the power functions for the NaCl and sucrose intensity-response series were higher than those of citric acid and QHCl. 4. A hierarchical cluster analysis of 59 parabrachial neurons suggested four different categories: NaCl-best, sucrose-best, citric acid-best, and QHCl-best. These categories were less evident in the two-dimensional space produced by multidimensional analysis, because the positions of NaCl- and sucrose-best neurons formed a continuum in which neural response profiles change successively from sucrose-specific to NaCl-specific. 5. The results were consistent with previous anatomic and neurophysiological data suggesting convergence in the medulla of sensory input from receptors in the nasoincisor ducts (NID) and on the anterior tongue (AT). Taste buds in the NID respond preferentially to sucrose, whereas those on the AT respond more to NaCl.(ABSTRACT TRUNCATED AT 400 WORDS)

Parabrachial gustatory neural activity during licking by rats

1991 ◽  
Vol 66 (3) ◽  
pp. 974-985 ◽  
Author(s):  
H. Nishijo ◽  
R. Norgren
Keyword(s):  
Citric Acid ◽  
Pearson Correlation ◽  
Correlation Coefficients ◽  
Hierarchical Cluster ◽  
T Test ◽  
Fluid Delivery ◽  
The Mean ◽  
Parabrachial Nuclei ◽  
Hierarchical Cluster Analyses ◽  
Paired T Test

1. A total of 51 single neurons was recorded from the pontine parabrachial nuclei of three rats being given sapid stimuli either via intraoral infusions or during spontaneous licking behavior. In 46 neurons, sapid stimuli elicited significant taste responses; of these, 28 responded best to NaCl, 15 to sucrose, 2 to citric acid, and 1 to quinine HCl. The remaining five neurons responded significantly only to water. The mean spontaneous rate of taste neurons during the intraoral infusion and licking sessions was 11.1 +/- 1.1 and 10.8 +/- 1.2 (SE) spikes/s, respectively. 2. Of the 39 neurons tested during both licking and intraoral infusions, four responded significantly only to water via either route. The remaining 35 neurons responded significantly to at least some sapid stimuli. The best-stimulus categories remained the same regardless of the route of fluid delivery (24 NaCl best, 10 sucrose best, 1 citric acid best). When the rats were licking the stimuli, nine taste neurons responded significantly to only one sapid chemical [6 Na specific (Ns) and 3 sucrose specific (Ss)] but were more broadly tuned during intraoral infusions. Conversely, three taste neurons that responded specifically during intraoral infusions (3 Na specific) were not as specific when the animal licked the same fluids. 3. Thirty-five taste neurons were tested via both stimulus routes. These data were compared in three ways. First, for each neuron, the responses elicited during licking and intraoral infusions were compared for each of the four standard sapid stimuli. The Pearson correlation coefficients for the 35 taste neurons ranged from 0.9997 to 0.6785, with a mean at 0.953 +/- 0.012 (SE). The second comparison was between stimulus routes across chemicals. With the use of raw responses, the correlation coefficients for NaCl, sucrose, citric acid, and QHCl ranged from 0.925 to 0.778 (t test, P less than 0.0001). With the activity elicited by water subtracted (corrected responses), the correlation coefficients for NaCl, sucrose, citric acid, and QHCl were 0.900, 0.795, 0.369, and 0.211, respectively. The coefficient for QHCl was not significant (t test, P greater than 0.05). Finally, the mean responses to NaCl, sucrose, and citric acid delivered by both routes were compared and found not to differ (paired t test, P greater than 0.05). 4. In separate hierarchical cluster analyses for the licking and infusion data, the largest cluster in each contained all of the Na-best neurons and the next largest, all of the sucrose-best cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Topographical representations of taste response characteristics in the rostral nucleus of the solitary tract in the rat

2014 ◽  
Vol 111 (1) ◽  
pp. 182-196 ◽  
Author(s):  
T. Yokota ◽  
K. Eguchi ◽  
K. Hiraba
Keyword(s):  
Neuron Activity ◽  
Solitary Tract ◽  
Functional Roles ◽  
Stimulus Response ◽  
Response Characteristics ◽  
Taste Response ◽  
Significant Difference ◽  
The Mean ◽  
Rostral Nucleus ◽  
Single Neuron Activity

The rostral nucleus of the solitary tract (rNST) is the first-order taste relay in rats. This study constructed topographical distributions of taste response characteristics (best-stimulus, response magnitude, and taste-tuning) from spike discharges of single neurons in the rNST. The rNST is divided into four subregions along the rostrocaudal (RC) axis, which include r1–r4. We explored single-neuron activity in r1–r3, using multibarreled glass microelectrodes. NaCl (N)-best neurons were localized to the rostral half of r1–r3, while HCl (H)-best and sucrose (S)-best neurons showed a tendency toward more caudal locations. NaCl and HCl (NH)-best neurons were distributed across r2–r3. The mean RC values and Mahalanobis distance indicated a significant difference between the distributions of N-best and NH-best neurons in which N-best neurons were located more rostrally. The region of large responses to NaCl (net response >5 spikes/s) overlapped with the distribution of N-best neurons. The region of large responses to HCl extended widely over r1–r3. The region of large responses to sucrose was in the medial part of r2. The excitatory region (>1 spike/s) for quinine overlapped with that for HCl. Neurons with sharp to moderate tuning were located primarily in r1–r2, while those with broad tuning were located in r2–r3. The robust responses to NaCl in r1–r2 primarily contributed to sharp to moderate taste-tuning. Neurons in r3 tended to have broad tuning, apparently due to small responses to both NaCl and HCl. Therefore, the rNST is spatially organized by neurons with distinct taste response characteristics, suggesting that these neurons serve different functional roles.

Taste responses of neurons in the nucleus of the solitary tract of awake rats: an extended stimulus array

1993 ◽  
Vol 70 (3) ◽  
pp. 879-891 ◽  
Author(s):  
K. Nakamura ◽  
R. Norgren
Keyword(s):  
Cluster Analysis ◽  
Citric Acid ◽  
Malic Acid ◽  
Monosodium Glutamate ◽  
Hierarchical Cluster ◽  
The Other ◽  
Solitary Tract ◽  
Sodium Salts ◽  
Chloride Salts ◽  
Awake Rats

1. Fifty-seven taste neurons were isolated in the nucleus solitary tract (NST) and tested with 15 sapid chemicals. On average, NST neurons responded well to NaCl, sucrose, monosodium L-glutamate (MSG), NaNO3, and glycine (mean = 8.2-11.0 spikes/s). Mean responses to KCl, NH4Cl, HCl, malic acid, and quinine HCl (QHCl) were low (mean = 0.7-2.9). The average responses to the other stimuli (citric acid, MgCl2, fructose, maltose, and polycose) fell between these extremes (mean = 4.3-5.1). 2. On the basis of the largest response to the four standard stimuli, the neurons were classified as follows: 15 NaCl-best, 23 sucrose-best, 17 citric acid-best, and 2 QHCl-best. 3. The NaCl-best neurons responded robustly and nearly equally to the three sodium salts (mean = 15.7-20.8) but much less so and more variably to the nonsodium, chloride salts (mean = -0.1-4.6). Sucrose-best neurons responded strongly to sucrose, glycine, and MSG (mean = 13.7-17.8), but only moderately to the other sugars (fructose and maltose) and to polycose (mean = 8.4, 9.8, and 8.8, respectively). 4. Citric acid-best neurons responded moderately to citric and malic acid (mean = 9.4 and 4.7), but less so to HCl (mean = 3.1). The two QHCl-best neurons responded moderately to QHCl and MgCl2 (mean = 12.0 and 9.5), but weakly or not at all to the other stimuli (mean = -1.1-3.1). 5. Unlike parabrachial taste neurons, none of the medullary taste cells responded specifically to Cl(-)-containing chemicals. The responses that did occur to nonsodium salts were weak and variable and often occurred in either citric acid-best or QHCl-best neurons, rather than in those that responded vigorously to sodium salts. Similar relationships have been observed in anesthetized preparations. 6. A hierarchical cluster analysis for 57 neurons across 15 stimuli produced four second-order clusters that consisted primarily of NaCl-best, sucrose-best, citric acid-best, and QHCl-best neurons, respectively. Although the analysis for neurons produced only four such clusters, a similar analysis for the 15 stimuli separated the sodium salts (NaCl and NaNO3), nonsodium salts (KCL, NH4Cl, and MGCl2, sweeteners (sucrose, maltose, fructose, and glycine), acids (citric acid and malic acid), and QHCl. 7. Monosodium glutamate activated both NaCl-best and sucrose-best neurons, but the stimulus analysis clumped it with the sodium salts.(ABSTRACT TRUNCATED AT 400 WORDS)

The motion of a lunar orbiter

1966 ◽  
Vol 25 ◽  
pp. 373
Author(s):  
Y. Kozai
Keyword(s):  
Degrees Of Freedom ◽  
Dimensional Space ◽  
Artificial Satellite ◽  
Equations Of Motion ◽  
Triaxial Ellipsoid ◽  
The Moon ◽  
Secular Motion ◽  
The Earth ◽  
Close Satellite ◽  
The Mean

The motion of an artificial satellite around the Moon is much more complicated than that around the Earth, since the shape of the Moon is a triaxial ellipsoid and the effect of the Earth on the motion is very important even for a very close satellite.The differential equations of motion of the satellite are written in canonical form of three degrees of freedom with time depending Hamiltonian. By eliminating short-periodic terms depending on the mean longitude of the satellite and by assuming that the Earth is moving on the lunar equator, however, the equations are reduced to those of two degrees of freedom with an energy integral.Since the mean motion of the Earth around the Moon is more rapid than the secular motion of the argument of pericentre of the satellite by a factor of one order, the terms depending on the longitude of the Earth can be eliminated, and the degree of freedom is reduced to one.Then the motion can be discussed by drawing equi-energy curves in two-dimensional space. According to these figures satellites with high inclination have large possibilities of falling down to the lunar surface even if the initial eccentricities are very small.The principal properties of the motion are not changed even if plausible values ofJ3andJ4of the Moon are included.This paper has been published in Publ. astr. Soc.Japan15, 301, 1963.

Nicotine Suppression of Gustatory Responses of Neurons in the Nucleus of the Solitary Tract

2006 ◽  
Vol 96 (4) ◽  
pp. 1877-1886 ◽  
Author(s):  
Christopher T. Simons ◽  
Yves Boucher ◽  
Mirela Iodi Carstens ◽  
E. Carstens
Keyword(s):  
Monosodium Glutamate ◽  
Plasma Extravasation ◽  
Dependent Manner ◽  
Evoked Responses ◽  
Solitary Tract ◽  
Depressant Effect ◽  
Tongue Surface ◽  
Single Unit Recordings ◽  
Gustatory Neurons ◽  
Dose Dependent

This study investigated effects of nicotine applied to the tongue surface on responses of gustatory neurons in the nucleus of the solitary tract (NTS) in rats. In pentobarbital-anesthetized rats, single-unit recordings were made from NTS units responsive to one or more tastants (sucrose, NaCl, citric acid, monosodium glutamate, quinine). Application of nicotine (0.87, 8.7, or 600 mM) excited gustatory NTS units and significantly attenuated NTS unit responses to their preferred tastant in a dose-dependent manner. The depressant effect of nicotine was equivalent regardless of which tastant best excited the NTS unit. Nicotinic excitation of NTS units and depression of their tastant-evoked responses were both significantly attenuated by the nicotinic antagonist mecamylamine, which itself did not excite NTS units. In rats with bilateral trigeminal ganglionectomy, nicotine still excited nearly all NTS units but no longer depressed tastant-evoked responses. Nicotine did not elicit plasma extravasation when applied to the tongue. The results indicate that nicotine directly excites NTS units by gustatory nerves and inhibits their tastant-evoked responses by a nicotinic acetylcholine receptor-mediated excitation of trigeminal afferents that inhibit NTS units centrally.

Anterior and Posterior Oral Cavity Responsive Neurons Are Differentially Distributed Among Parabrachial Subnuclei in Rat

1997 ◽  
Vol 78 (2) ◽  
pp. 920-938 ◽  
Author(s):  
Christopher B. Halsell ◽  
Susan P. Travers
Keyword(s):  
Oral Cavity ◽  
Taste Receptor ◽  
Hierarchical Cluster ◽  
Response Rates ◽  
Differential Sensitivity ◽  
Response Profiles ◽  
To Receive ◽  
Gustatory Neurons ◽  
Comparable Population ◽  
Stimulation Of

Halsell, Christopher B. and Susan P. Travers. Anterior and posterior oral cavity responsive neurons are differentially distributed among parabrachial subnuclei in rat. J. Neurophysiol. 78: 920–938, 1997. The responses of single parabrachial nucleus (PBN) neurons were recorded extracellularly to characterize their sensitivity to stimulation of individual gustatory receptor subpopulations (G neurons, n = 75) or mechanical stimulation of defined oral regions (M neurons, n = 54) then localized to morphologically defined PBN subdivisions. Convergence from separate oral regions onto single neurons occurred frequently for both G and M neurons, but converging influences were more potent when they arose from nearby locations confined to the anterior (AO) or posterior oral cavity (PO). A greater number of G neurons responded optimally to stimulation of AO than to PO receptor subpopulations, and these AO-best G neurons had higher spontaneous and evoked response rates but were less likely to receive convergent input than PO-best G neurons. In contrast, proportions, response rates, and convergence patterns of AO- and PO-best M neurons were more comparable. The differential sensitivity of taste receptor subpopulations was reflected in PBN responses. AO stimulation with NaCl elicited larger responses than PO stimulation; the converse was true for QHCl stimulation. Within the AO, NaCl elicited a larger response when applied to the anterior tongue than to the nasoincisor duct. Hierarchical cluster analysis of chemosensitive response profiles suggested two groups of PBN G neurons. One group was composed of neurons optimally responsive to NaCl (N cluster); the other to HCl (H cluster). Most N- and H-cluster neurons were AO-best. Although they were more heterogenous, all but one of the remaining G neurons were unique in responding best or second-best to quinine and so were designated as quinine sensitive (Q+). Twice as many Q+ neurons were PO- compared with AO-best. M neurons were scattered across PBN subdivisions, but G neurons were concentrated in two pairs of subdivisions. The central medial and ventral lateral subdivisions contained both G and M neurons but were dominated by AO-best N-cluster G neurons. The distribution of G neurons in these subdivisions appeared similar to distributions in most previous studies of PBN gustatory neurons. In contrast to earlier studies, however, the external medial and external lateral-inner subdivisions also contained G neurons, intermingled with a comparable population of M neurons. Unlike cells in the central medial and ventral lateral subnuclei, nearly every neuron in the external subnuclei was PO best, and only one was an N-cluster cell. In conclusion, the present study supports a functional distinction between sensory input from the AO and PO at the pontine level, which may represent an organizing principle throughout the gustatory neuraxis. Furthermore, two morphologically distinct pontine regions containing orosensory neurons are described.

scholarly journals Taste Interactions between Sweetness of Sucrose and Sourness of Citric and Tartaric Acid among Chinese and Danish Consumers

Foods ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 1425
Author(s):  
Jonas Yde Junge ◽  
Anne Sjoerup Bertelsen ◽  
Line Ahm Mielby ◽  
Yan Zeng ◽  
Yuan-Xia Sun ◽  
...  
Keyword(s):  
Citric Acid ◽  
Tartaric Acid ◽  
Hierarchical Cluster ◽  
Taste Perception ◽  
Aqueous Samples ◽  
Chinese Consumers ◽  
Consumer Study ◽  
Agglomerative Hierarchical Cluster Analysis ◽  
Significant Difference ◽  
Sweetness Intensity

Tastes interact in almost every consumed food or beverage, yet many aspects of interactions, such as sweet-sour interactions, are not well understood. This study investigated the interaction between sweetness from sucrose and sourness from citric and tartaric acid, respectively. A cross-cultural consumer study was conducted in China (n = 120) and Denmark (n = 139), respectively. Participants evaluated six aqueous samples with no addition (control), sucrose, citric acid, tartaric acid, or a mixture of sucrose and citric acid or sucrose and tartaric acid. No significant difference was found between citric acid and tartaric acid in the suppression of sweetness intensity ratings of sucrose. Further, sucrose suppressed sourness intensity ratings of citric acid and tartaric acid similarly. Culture did not impact the suppression of sweetness intensity ratings of citric or tartaric acid, whereas it did influence sourness intensity ratings. While the Danish consumers showed similar suppression of sourness by both acids, the Chinese consumers were more susceptible towards the sourness suppression caused by sucrose in the tartaric acid-sucrose mixture compared to the citric acid-sucrose mixture. Agglomerative hierarchical cluster analysis revealed clusters of consumers with significant differences in sweetness intensity ratings and sourness intensity ratings. These results indicate that individual differences in taste perception might affect perception of sweet-sour taste interactions, at least in aqueous solutions.

scholarly journals Assessment of Bacteriological Quality of Sheep Carcasses, Effect Level of 2.5% Citric Acid Spray on Bacterial Contamination of Meat, and Hygiene Practices of Workers in a Selected Abattoir in Debrezeit Town, Central Ethiopia

2021 ◽  
Vol 15 ◽  
pp. 117863022110375
Author(s):  
Derebew Aynewa ◽  
Zemichael Gizaw ◽  
Aklilu Feleke Haile
Keyword(s):  
Citric Acid ◽  
Bacterial Contamination ◽  
Total Coliform ◽  
Aerobic Bacteria ◽  
Bacteriological Quality ◽  
Before And After ◽  
Effect Level ◽  
The Mean ◽  
Structured Questionnaire

Background: Meat safety is important for public health. As part of the meat chain abattoirs are required to give attention to meat hygiene and safety in order to minimize hazards. Therefore, the current study was conducted to evaluate the bacteriological quality of sheep carcasses, knowledge and hygienic practices of workers in a selected abattoir and to determine the effect level of 2.5% citric acid spray on total coliforms and aerobic bacteria load of raw sheep carcasses surfaces. Methods: A cross-sectional study design with structured questionnaire and observational checklists observation were used. A systematic random sampling technique was employed. A total of 50 sample swabs (25 swabs before citric acid spray and 25 after citric acid spray) were randomly taken from brisket, flank and rump of sheep’s carcasses. Swabs were moistened with buffered peptone water (BPW) and samples were taken by rubbing 100 cm2 (10 cm × 10 cm) area delineated by sterile aluminum template. In addition, we administered a structured questionnaire and an observational checklists to assess knowledge and hygienic practices of workers. Bacteriological quality of sheep carcasses were analyzed using the methods described by the US bacteriological analytical manual. Results: The mean count for aerobic bacteria of the sheep carcasses before and after citric acid spray were 7.2log10 CFU/ml and 6.4log10 CFU/ml, respectively. The test results also showed that 21 (84%) and 15 (60%) of the swab samples were positive before and after spraying citric acid, respectively. The mean counts for coliform bacterial of the sheep carcasses before and after citric acid spray were 3.5log10 CFU/ml and 2.9log10 CFU/ml, respectively. The mean total aerobic and coliform counts before and after citric acid spray were significantly different ( P < .05). Regarding the hygiene condition of workers, all the respondents reported that they always washed their hands with soap before and after entering the slaughtering room and 23 (53.5%) of the workers reported that they used hot water. Thirty-one (72.1%) of the workers reported that they do not used soap to wash hands after visiting toilet. Thirty-five (81.4%) of the production workers did not wear mouth mask while handling and distribute meat/carcass. On the other hand, all of the workers wore capes, gowns and boots at the time of the observation and only 18 (18.6%) of the production workers wore gloves at the time of the survey. Conclusion: The current study revealed that significant proportion of sheep carcasses were positive for total aerobic bacteria and total coliform. Moreover, the study also showed that spraying of sheep carcasses with 2.5% citric acid significantly reduced the total coliform and aerobic counts. However, we did not assessed how much spray results to this effect. Therefore, we recommended further studies to determine how much spray of 2.5% citric acid significantly reduce bacterial contamination of sheep carcasses. In addition, the abattoir has to follow the food hazard analysis critical control point (HACCP) system to minimize meat contamination during harvesting and processing. The abattoir has to also implement strict operation laws to improve hygiene conditions of the workers. In addition, the abattoir can minimize meat contamination using 2.5% citric acid as a decontaminant.

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