A Ricci

Intrinsic Innervation of the Rat Knee Joint Articular Capsule and Ligaments

In spite of the practical importance of having a detailed knowledge of knee joint innervation to understand the pathophysiologic aspects, little information is now available concerning the density and pattern of the nerve fibres which are distributed to it. The present study has been designed to investigate the density and distribution of nerve fibres and receptor corpuscles in the knee joint articular capsule, cruciate and collateral ligaments in the rat, using the acetylcholinesterase (AChE) histochemical in toto staining technique. The investigation was performed on male Wistar rats of 3 months of age, some of which had been treated with capsaicin to deplete their afferent C fibres of their content of neuropeptides. AChE-positive nerve fibres and different types of receptor corpuscle endings were found within articular capsule and ligaments. The highest density of AChE-positive nerve fibres was noticeable in the fibular collateral ligament followed by the tibial collateral ligament, the posterior cruciate ligament, the anterior cruciate ligament and the articular capsule. In the articular capsule the number of type I endings was higher than in the ligaments. The opposite is true for the other type of receptor corpuscles found as well as for nerve endings. Capsaicin treatment significantly reduced the density of AChE-positive nerve fibres in knee joint ligaments but did not affect nerve fibres in the articular capsule. Moreover, it caused the disappearance of some kind of receptor corpuscles within the collateral and cruciate ligaments. The above data collectively suggest that the AChE in toto staining technique may represent a good method for investigating joint innervation and that a significant percentage of nerve fibres supplying knee joint ligaments is represented by C fibre afferents.

Cholinergic Neurotransmission in the Hippocampus of Aged Rats: Influence of L-α-Glycerylphosphorylcholine Treatment

The influence of aging and of L‐α‐glycerylphosphorylcholine (GFC) treatment on the acetylcholine synthesizing and degradating enzymes choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) and on cholinergic muscarinic M‐1 and M‐2 receptors were assessed in the hippocampus using immunocytochemical, histochemical and radioligand binding techniques, respectively. The investigation was performed on male Wistar rats of 2 months (young), 12 months (adult), and 27 months (old). Oral GFC was given at the dose of 100 mg/Kg/day from the 21st to the 27th month of age. ChAT revealed the highest immunostaining in the hippocampus of adult rats followed by young and old animals. The highest expression of AChE reactivity was noticeable in the hippocampus of adult rats followed by old and young animals. Treatment with GFC restored in part ChAT immunoreactivity and AChE reactivity in the hippocampus of aged rats. Muscarinic M‐1 and M‐2 receptors were labeled with [3H]‐pirenzepine and [3H]‐AF‐DX‐116 respectively. The density of M‐1 muscarinic receptors decreased with age, whereas M‐2 muscarinic receptors did not change. GFC treatment countered in part the loss of M‐1 receptors in old rats and was without effect on M‐2 receptors.

Localisation of dopamine D3 receptor in the rat cerebellar cortex: a light microscope autoradiographic study

The pharmacological properties and the anatomical localisation of dopamine D3 receptor were assessed in the rat cerebellar cortex using radioligand binding techniques associated with light microscope autoradiography and 7-[3H]hydroxy-N,N-di-n-propyl-2-aminotetralin (7-[3H]OH-DPAT) as a ligand. 7-[3H]OH-DPAT was specifically bound to sections of rat cerebellar cortex with a dissociation constant (Kd) of 0.5 nM and a maximum density of binding sites (Bmax) of 97 +/- 4 fmol/mg tissue. The rank order of potency of competitors of 7-[3H]OH-DPAT binding and the observation that guanosine triphosphate did not affect radioligand binding suggest the labelling of a dopamine D3 receptor. 7-[3H]OH-DPAT binding sites are located mainly in the molecular layer and in lesser amounts in the Purkinje neuron layer, primarily within the cell body of Purkinje neurons. No specific accumulation of silver grains was observed in the granule neuron layer or in the white matter of the cerebellar cortex. The localisation of a putative dopamine D3 receptor within Purkinje neurons suggests that this site may have functional relevance in the cerebellar cortex.

Peripheral blood lymphocytes muscarinic cholinergic receptor subtypes in Alzheimer's disease: a marker of cholinergic dysfunction?

Muscarinic M2-M5 muscarinic cholinergic receptors were investigated in peripheral blood lymphocytes of patients with mild cognitive impairment of the Alzheimers type (MCIAT), probable Alzheimers disease (AD) and probable vascular dementia (VaD). [3H]-N-methyl scopolamine (NMS) in the presence of muscarinic antagonists and Mamba venom to occlude different receptor subtypes was used as radioligand. Analysis of [3H]-NMS binding curves without receptor subtype assessment resulted in a slight decrease of receptor density in AD patients. Evaluation of receptor subtypes in MCIAT and AD patients revealed a decrease of M3 receptor by more than 50%, an increase of M4 receptor expression by about 20% and no changes of M2 or M5 receptors. The expression of M2-M5 receptors was unaltered in VaD patients. Strong positive and negative correlations respectively were found between the density of lymphocyte M3 and M4 receptors and MMSE score in both MCIAT (0.78 for M3 receptor and 0.80 for M4 receptor) and AD (0.82 for M3 receptor and 0.83 for M4 receptor) patients. These findings suggest that changes in the expression of peripheral blood lymphocyte M3 and M4 receptors in AD are related to the degree of cognitive impairment. Assessment of lymphocyte muscarinic receptor subtypes may contribute to characterization of cholinergic impairment in AD.

Pharmacological characterization and autoradiographic localization of dopamine D1-like receptors in the thymus

The present study was designed to identify the pharmacological profile and the anatomical localisation of dopamine D1-like receptor sites in the rat thymus using [3H]SCH 23390 as a ligand. [3H]SCH 23390 was specifically bound to sections of the thymus. Binding was time, temperature and concentration-dependent belonging in the range of concentrations of radioligand used to a single class of high affinity sites. The dissociation constant was 1.6 nM and the maximal density of binding sites averaged to 170 fmol/mg tissue. The pharmacological profile of [3H]SCH 23390 binding to sections of the rat thymus is consistent with the labelling of dopamine D1-like sites. Dopamine was able to compete with [3H]SCH 23390 binding to sections of rat thymus in the range of nanomolar concentrations. This suggests the labelling of dopamine D5 receptor sites. Light microscope autoradiography revealed the localisation of [3H]SCH 23390 binding sites primarily in the cortex of the thymus and in lesser amounts at the level of thymic corpuscles. The possible functional significance of dopamine D1-like receptors in the rat thymus is discussed.

Dopamine D1-like receptors in the thymus of aged rats: a radioligand binding and autoradiographic study.

Abstract Age-dependent changes in the density and pattern of dopamine D1-like receptors were studied in the thymus of young (3 months), adult (12 months) and aged (24 months) male Wistar rats using combined radioligand binding and autoradiographic techniques. [3H]SCH 23390, which was used as a ligand, was specifically bound to sections of the thymus in a manner consistent with the labelling of dopamine D5 receptor. The dissociation constant value was similar in the thymus of the three animal groups examined. The maximal density of binding sites, evaluated with conventional radioligand binding techniques, was significantly reduced in the thymus of adult in comparison with young rats and further reduced in aged animals. Silver grains which correspond to [3H]SCH 23390 binding sites were revealed by light microscope autoradiography primarily in the cortex of the thymus and in lesser amounts within thymic corpuscles. A progressive decrease in the density of silver grains more pronounced in the cortex than in thymic corpuscles was observed in the thymus of adult and old in comparison with young rats. The loss of silver grains revealed with autoradiography is more moderate than the decrease in the density of binding sites shown by radioligand binding. Silver grains developed per single cells (probably lymphocytes) of the thymic cortex were reduced between young and adult rats and further decreased in old rats. The above findings suggest that the age-related decline in the density of dopamine D5 receptor as sayed in the thymus is due in part to the reduced thymic mass with aging. The observation of a decreased expression of dopamine D5 receptor in cells of the thymic cortex as a function of age suggests that this reduction cannot be attributed simply to loss of thymic lymphocytes.