Neuronal circuitry

One possibility is that even with a potentially effective drug, the necessary readjustments in the neuronal circuitry to reverse or compensate for the disorder-induced malfunction just requires time. Another hinges on the degree of polarisation of AlO and A9 neurons. 

A variety of different types of tissue preparation are used to study neurosecretion and synaptic transmission. A classical preparation is the frog NMJ (discussed below). The brain slice has been used for many years for biochemical studies of CNS metabolism and is a useful preparation for electrophysiological studies of synaptic transmission in the CNS. Slices can be oriented to maintain the local neuronal circuitry and can be thin, 0.3 mm, to minimize anoxia. The transverse hippocampal slice is widely used as an electrophysiological preparation to study synaptic plasticity (see Ch. 53). Primary cultures of neurons from selected CNS areas and sympathetic ganglia are also frequently used. They permit excellent visual identification of individual neurons and control of the extracellular milieu, but the normal neuronal connections are disrupted. 

Huguenard, I. R. Neuronal circuitry of thalamocortical epilepsy and mechanisms of antiabsence drug action. Adv. Neurol. 79 991-999,1999. 

Natural reinforcers and drugs of abuse use similar circuits 912 The neuronal circuitry underlying drug craving has been intensely studied to develop strategies for preventing relapse 912... 

The neuronal circuitry proved to be a bit more complicated than 1 have let on so far. Shocking the tail of the sea snail proved to modulate the response of the organism to touches at the siphon. Thus, there appears to be a modulatory neural circuit between the tail and the sensory neuron. The complete neural circuit is ... 

Critical periods may vary depending on the area of the brain and the activity involved. Despite the evidence that patterns of neural activity influence the organization of neuronal circuitry, the mechanisms involved remain elusive. Neuronal activity drives the selective survival and sprouting of branches, accompanied by the local addition of synapses, within appropriate areas furthermore, the lack of activity promotes the pruning of synaptic connections from inactive areas (Katz and Shatz, 1996). These competitive processes increase the refinement and precision of maps and require the activity of excitatory receptors (Constantine-Paton et ah, 1990 Antonini and Stryker, 1993) and locally released growth factors (Thoenen, 1995 Inoue and Sanes, 1997). 

Figure 2 Neuronal circuitry in the dorsal horn of the spinal cord -simplified diagram.

Activated K+ channels in the neuronal circuitry of pain processing areas may either directly or indirectly interfere with the transmission of nociceptive signals... 

Opioids are known to alter mood states. For example, opiates such as morphine produce euphoria and pain relief. Prolonged use of and withdrawal from opiates produce depressive-like symptoms as well. Based on the mood-altering effects of opiates, the role of endogenous opiates in psychiatric symptoms of various diseases has been studied. In addition, endogenous opioids are believed to play a role in neuronal circuitry responsible for reward and pleasure. Therefore, it is thought that perhaps the anhedonia observed in depressed patients is due to dysregulation of endogenous opioids in neuronal reward circuitry. 

The blockade of inhibitory synapses at the spinal cord impairs the neuronal circuitry that controls voluntary muscle contraction, thereby causing the spastic paralysis characteristic of tetanus (Simpson, 1989). 

Sharma RK, Johnson DA. 2000. Molecular signals for development of neuronal circuitry in the retina. Neurochem Res 25 1257-1263. 

It is evident from Sects. 4 and 5 that presynaptic CBi receptors are ubiquitous in the central and peripheral nervous system. Even within one functional system, several components of the neuronal circuitry are equipped with CBi receptors. This will be illustrated in two functional systems the extrapyramidal motor control system (Fig. 6) and the cerebellum (Fig. 7). 

Wasterlain CG, Mazarati AM, Naylor D, et al. Short-term plasticity of hippocampal neuropeptides and neuronal circuitry in experimental status epilepticus. Epilepsia 2002 45(suppl 5) 20-29. 

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