Electrophysiological study of spinal cord thermoreceptive neurones in the rat

1 . The aim of this study was to investigate the neurophysiological basis for thermal analgesia. The speculation that part of this analgesia may be mediated via depression of nociceptor driven spinal cord tract neurones was tested.Spinal segments L6 to S1 were explored with extracellular mi'cropipette electrodes filled with a mixture of 5M sodium chloride and pontamine sky blue (2% in 0.5 M sodium acetate) in rats anaesthetised with chloralose (100 mg kg⁻¹) and urethane (700 mg kg⁻¹).3. 258 neurones were recorded from within the dorsal horn and were tested for the inhibitory effect of thermal stimulation applied to the perineal, inguinal and scrotal skin. Ten of the 258 units received only a warm inhibitory input from the skin. 57 units had an excitatory input from nociceptors, of these 24 were inhibited by warming and 2 by cooling the skin.4. Data has also teen obtained on the light microscopic anatomy of the scrotal skin and also on 73 units that had an input from thermoreceptors.5. It is suggested that thermal inhibition of units that have an input from nociceptors may provide some neurophysiological basis for thermal analgesia

Antinociceptive potentiation of pethidine (demerol) by clomipramine in the late phase of formalin test in mice

Background: Pethidine, an opioid analgesic is used for pain management. Clomipramine a tricyclic antidepressant primarily used for mood management is also used to treat pain. The objective of this study was to investigate the potentiation of the analgesic effects of sub-threshold dose of pethidine by a tricyclic antidepressant, clomipramine. Methods: The antinociceptive activities of clomipramine and pethidine alone and in combination were investigated in Swiss albino mice using the formalin test. Normal saline was employed as the control. Ten animals were used in each experiment. Results: Pethidine 5mg / kg failed to cause any significant effect while the 6.25, 7.5, 8.75 and 10.0mg /kg showed highly significant antinociceptive effect (p< 0.01) compared to the controls in the late phase of formalin test. Clomipramine 0.5 mg / kg did not show any significant effect while 0.75 mg / kg caused a significant effect (p< 0.05) while 1.00 and 1.25mg /kg caused a very highly significant antinociceptive effect (p< 0.001) in the late phase of formalin test compared to the vehicle treated animals. The combination of pethidine 5mg / kg and clomipramine 0.75mg / kg caused a highly significant antinociceptive effect (P<0.01) in the late phase of formalin test. Conclusion: This study demonstrates a marked reduction in the time spent in pain behaviour produced by the combination of low dose pethidine and clomipramine in the late phase of formalin test. The findings demonstrate the potentiation of a narcotic analgesic by a tricyclic antidepressant. Pan African Medical Journal 2012 12:2

Investigation of the presence and antinociceptive function of muscarinic acetylcholine receptors in the African naked mole-rat (<i>Heterocephalus glaber</i>)

The present study investigated the cholinergic system in the African naked mole-rat (Heterocephalus glaber) with focus on the muscarinic acetylcholine receptor subtypes M(1) and M(4). The protein sequences for the subtypes m(1–5) of the naked mole-rat were compared to that of the house mouse (Mus musculus) using basic local alignment search tool (BLAST). The presence and function of M(1) and M(4) was investigated in vivo, using the formalin test with the muscarinic receptor agonists xanomeline and VU0152100. Spinal cord tissue from the naked mole-rat was used for receptor saturation binding studies with [(3)H]-N-methylscopolamine. The BLAST test revealed 95 % protein sequence homology showing the naked mole-rat to have the genetic potential to express all five muscarinic acetylcholine receptor subtypes. A significant reduction in pain behavior was demonstrated after administration of 8.4 mg/kg in the formalin test. Administration of 50 mg/kg VU0152100 resulted in a non-significant tendency towards antinociception. The antinociceptive effects were reversed by the muscarinic acetylcholine receptor antagonist atropine. Binding studies indicated presence of muscarinic acetylcholine receptors with a radioligand affinity comparable to that reported in mice. In conclusion, muscarinic acetylcholine receptor subtypes are present in the naked mole-rat and contribute to antinociception in the naked mole-rat

Housing behaviour of the naked mole rat (Heterocephalus glaber) under laboratory conditions

The naked mole rat (Heterocephalus glaber) is a rodent that has gained importance as a biomedical research model for various conditions including hypoxic brain injury, cancer and nociception. It is captured from the wild and housed under laboratory conditions during research. Much is unknown about how to optimize housing conditions for the animals in captivity. This study was designed to establish whether the animals will replicate in the laboratory their natural behaviour of having separate resting, waste disposal and eating areas. A total of 52 naked mole rats were kept in four colonies of different sizes and housed in two types of cage design. It was found that, in all four colonies, their behavior was similar to that in the wild with regards to separating their resting, eating, defecation and urination areas. Urination and defecation commonly occurred in the outer corners of the cages while resting and eating mostly occurred in the inner parts of the cages. Average daily feed consumption was 7.6 grams per naked mole rat. Weekly weight gain averaged 0.44 grams per naked mole rat. In this study, the four colonies of naked mole rats behaved similarly in their selection of resting, waste disposal and eating area. However, additional studies are needed to investigate further whether these behaviours can be affected by colony origin, colony size or cage size. The results of our study indicate that resting, eating and waste disposal behaviours need to be taken into consideration when housing naked mole rats, to optimize the comfort of these animals in captivity

Extension Support Services among Poultry Farmers, a Case of Katulani District, Kitui County

A survey was carried out to determine provision of extension support services in Katulani District, Kenya. Data was collected through observations and structured questionnaires administered to 110 poultry rearing households in rural and peri urban areas to allow for comparison. Over 75% of households practiced mixed farming with indigenous chicken being kept by all households. Extension support services were accessible to less than 50% of households with rural areas having higher accessibility. Public sector workers were the main source of extension services. About 50% of respondents requested for training on chicken rearing. The average flock size in the study area was forty chicken with chicks and pullets dominating. The cock to hen ratio was 1:2 while inbreeding rate per generation was 4.5%. The recommendation is a review of extension approaches and capacity building grassroots institutions in order to diversify extension service agents and reduce distances to source of services

The suspended formalin test: A method designed for studying formalin-induced behaviour in the Speke’s Hingeback Tortoise (Kinixys spekii)

The present study aimed to develop a method for testing pain-related behaviour induced by formalin in the Speke’s hingeback tortoise (Kinixys spekii). These animals retract their head and limbs into their shell when approached, making behavioural testing almost impossible. It was found that suspending the animals in the air, facing away from the observer, made the animals keep their limbs out of the shell. Subcutaneous injection of formalin induced easily identifiable and quantifiable behaviours that lasted for 20 minutes. Contrary to the biphasic effect of formalin observed in rats and mice, the response in tortoises was monophasic. The suspended formalin test may be useful for studying nociceptive mechanisms in tortoises, which in turn will be important for a further understanding of the nociceptive system in reptiles as well as in mammals

Evaluation of Household Soil Conservation Technologies in Arid and Semi-Arid Lands (ASALs) (The Case of Kitui Central, Mulala and Wote Divisions in Kenya)

The study aimed at establishing the status of soil conservation technologies in arid and semi-arid lands (ASALs) in Kitui Central, Mulala and Wote divisions in Kenya. The survey was carried out between July and August 2010. To allow for comparison, purposive sampling that considered diversity in terms of agro-ecological setting, population trends and infrastructural facilities was done to select the locations for the study in the three divisions. Simple random sampling was used to select 503 households from six locations in the three divisions for interview. Questionnaires, Focus Group Discussions (FGD) and field observations were used to collect qualitative data. Results indicate main soil types as sandy (31.7%), loam (50.1%) and clay (18.2%). Soil fertility maintenance was by adding organic manure (51%) and inorganic fertilizers (22.8%). Main conservation structures of soil in crop fields included terraces (53.9%), planted trees (28%) and planted nappier grass (7.8%) while main agricultural water sources were public tap, stream and pond dam water. Soil conservation was done by less than 50% of households despite the importance towards crop growth, yield and ultimately food security. &nbsp