Brain research bulletin
-
Brain research bulletin · Sep 2008
The morphological changes of pyramidal and spiny stellate cells in the primary visual cortex of chronic morphine treated cats.
Morphine exposure may have a negative effect on the receptive field properties of neurons in primary visual cortex of cats. The present experiment used morphological methods in order to investigate whether chronic morphine treatment also affects dendritic characters of these neurons. According to the Sholl analysis and dendritic branch order analysis, we obtained the dendritic length and calculated the spine density on dendrites of the pyramidal neurons in layer III and the spiny stellate neurons in layer IV. ⋯ The further branch order analysis revealed that spine density was decreased at every (first to fourth) branch order of dendrites of pyramidal and spiny stellate neurons. Decrease in dendritic length of the pyramidal neurons was observed only at the fourth branch order, while the spiny stellate neurons had shorter dendrite at the second and third branch order. These findings may underlie the degradation of receptive field properties of the primary visual cortex neurons following chronic morphine exposure.
-
Brain research bulletin · Sep 2008
Synergistic anti-hyperalgesia of electroacupuncture and low dose of celecoxib in monoarthritic rats: involvement of the cyclooxygenase activity in the spinal cord.
Electroacupuncture (EA) can effectively control the exaggerated pain in humans with inflammatory disease and animals with experimental inflammatory pain. However, there have been few investigations on the effect of co-administration of EA and analgesics and the underlying synergistic mechanism. ⋯ These data indicated that repeated EA combined with low dose of celecoxib produced synergistic anti-hyperalgesic effect in the CFA-induced monoarthritic rats, which could be made possible by regulating the activity of spinal COX, hence the spinal PGE(2) level. Thus, this combination may provide an effective strategy for pain management.
-
Brain research bulletin · Sep 2008
Alpha4beta2 nicotinic acetylcholine receptors are required for the amyloid beta protein-induced suppression of long-term potentiation in rat hippocampal CA1 region in vivo.
Amyloid beta protein (Abeta) is thought to be responsible for the deficit of learning and memory in Alzheimer's disease (AD), possibly through interfering with synaptic plasticity such as hippocampal long-term potentiation (LTP). Nicotinic acetylcholine receptors (nAChRs) participate in various cognitive brain functions. However, it is unclear whether nAChRs, especially alpha4beta2 subtype nAChRs, are involved in Abeta-induced impairment of hippocampal LTP. ⋯ Our results showed that: (1) intracerebroventricular injection of Abeta(1-40), Abeta(25-35) or Abeta(31-35) significantly suppressed high-frequency stimulation-induced LTP, while Abeta(35-31), a reversed sequence of Abeta(31-35), have no effect on the LTP; (2) epibatidine, a specific agonist of alpha4beta2 subtype of nAChRs, dose-dependently suppressed the induction of LTP; (3) co-injection of epibatidine together with Abeta(31-35) did not further enhance the suppression of LTP induced by Abeta(31-35) or epibatidine alone; (4) dihydro-beta-erythroidine, a selective antagonist against alpha4beta2 subtype of nAChRs, showed no effect on the induction of LTP, but significantly reversed Abeta(31-35)-induced LTP impairment. These results indicate that: (1) sequence 31-35 in Abeta molecule might be a shorter active center responsible for the neurotoxicity of full length of Abeta; (2) alpha4beta2 subtype of nAChRs is required for the suppressive action of Abeta on the hippocampal LTP in vivo. Thus, the present study provides further insight into the mechanisms by which Abeta impairs synaptic plasticity and cognitive function in the AD brain.
-
Brain research bulletin · Sep 2008
Capsaicin inhibits the in vitro binding of peptides selective for mu- and kappa-opioid, and nociceptin-receptors.
Capsaicin inhibited the equilibrium specific binding of endogenous opioid-like peptide ligands such as endomorphin-1, nociceptin, and dynorphin((1-17)) in rat brain membrane preparations. We studied the in vitro effect of capsaicin (1-10 microM) on homologous and heterologous competitive binding of opioid ligands, using unlabeled synthetic peptides and the following tritiated compounds: [(3)H]endomorphin-1, [(3)H]endomorphin-2, [(3)H]nociceptin((1-17)) and [(3)H]dynorphin((1-17)). Capsaicin-dependent inhibition was also observed in [(35)S]GTPgammaS stimulation assays in the presence of certain opioid peptides. ⋯ In [(3)H]endomorphin-1 binding assays, capsazepine antagonized the inhibitory effect of capsaicin in rat brain membranes suggesting the involvement of TRPV1 receptors. In Chinese hamster ovary (CHO) cells stably expressing mu-opioid receptors, but lacking vanilloid receptors, the inhibition by capsaicin on the binding of [(3)H]endomorphin-1 was not present. It is concluded that the inhibitory effect of capsaicin on the receptor binding affinity of endogenous opioid peptides in brain membrane preparations seems not to be a direct effect, it is rather a negative feedback interaction with opioid receptors.
-
Brain research bulletin · Sep 2008
Effect of tetramethylpyrazine on primary afferent transmission mediated by P2X3 receptor in neuropathic pain states.
Neuropathic pain is the most difficult type of pain to treat. The P2X(3) receptors play a crucial role in facilitating pain transmission at peripheral and spinal sites. The present research investigated the effects of tetramethylpyrazine (TMP) on the primary afferent transmission induced by P2X(3) receptor in neuropathic pain states. ⋯ The mechanical withdrawal threshold, thermal withdrawal latency and P2X(3) immunoreactivity of L4/L5 DRG and spinal cord in group IV showed no significant difference compared with those in groups I, II or III (p>0.05). The amplitudes of the currents in group V (CCI) were much larger than those obtained in other groups after application of same concentration adenosine 5'-triphosphate disodium (ATP) (p<0.01). alpha,beta-Methylene-ATP (alpha,beta-meATP)-activated currents in DRG neurons of CCI rats were more obvious than those obtained in other group rats (p<0.01). The results showed that TMP may inhibit the primary afferent transmission of neuropathic pain induced by P2X(3) receptor.