Local interneurons

Munsch T., Yanagawa Y., Obata K, Pape H. (2005). Dopaminergic control of local interneuron activity in the thalamus. Eur. J. Neurosci 21, 290-4. 

LAL LLE LN lateral accessory lobe long-lasting excitation local interneuron... 

A5 and C primarily project to lamina II and V of the dorsal horn, where they synapse onto local interneurons or directly onto upward-projecting neurons (figure 8.1). These primary afferents release a number of neurotransmitters to relay pain, including glutamate, aspartate, substance P, neurokinin A and B, and calcitonin gene-related peptide (table 8.1). NMDA, non-NMDA and neurokinin receptors are involved in re-... 

Johnson SW, North RA. (1992). Opioids excite dopamine neurons by hyperpolarization of local interneurons. J Neurosci. 12(2) 483-88. 

Figure 24.1 A surface reconstruction of a male antennal lobe of the moth Spodoptera littoralis. The brain was immunostained with synapsin antibody and optically sectioned using a confocal microscope. Stacks of images were integrated with the software Imaris 2,7 (Bitplane AG, Switzerland) on a Silicon Graphics workstation to obtain surface projections of the lobe. The macroglomerular complex (MGC) is located close to the entrance of the antennal nerve. M, medial D, dorsal (modified from Carlsson et at, 2002). B Synaptic organization of the major types of antennal lobe neurons. Sensory neurons (ORNs) make uniglomerular synapses both directly with projection neurons (PNs) and indirectly via local interneurons (LNs). In addition, local interneurons innervate several glomeruli and generally make inhibitory synapses. Cell bodies of PNs and LNs are located within the antennal lobe.

The extreme sensitivity of the receptor neurons is combined with a most efficient processing of their responses by the central nervous system. Via the axons of the receptor neurons the nerve impulses are conducted to the antennal lobe, the first synaptic station of the central olfactory pathway in insects. The axons of the pheromone receptor neurons terminate on local interneurons and projection neurons (PN) of the macroglomerular complex (MGC) (Hildebrand 1996). The silk moth has... 

Fig. 2.1 Outline of the insect olfactory system, showing separate pathways for information from pheromones (thicker lines) and from other olfactory stimulants (thinner lines). As in moths, s, trichodea mediate the pheromone information and s. basiconica the information from other odors. Some second order neurons (local interneurons) make connections between glomeruli, while others (output neurons) project to the calyces and lateral lobe in protecerebrum (mofidied after Masson, 1981).

Studies of the ultrastructure of glomeruli in M. sexta have revealed pre- and postsynaptic profiles, where one pre-synaptic region is commonly associated with several postsynaptic (Tolbert and Hildebrand 1981). Pre-synaptic profiles are not only present in terminals of primary axons. Identification of second-order neurons filled with horseradish peroxidase, have shown that local interneurons also possess pre-synaptic profiles. Similar indications that information is not only received by second-order neurons but also transmitted, were previously provided by degenerating studies in Periplaneta americana and Calli-phora erythrocephala (Boeckh et al., 1970). One of three types of pre-synaptic profiles is most common in M. sexta and seems to be the predominant type in the primary axon terminals (Tolbert and Hildebrand, 1981). These are characterized by their numerous small roimd and clear vesicles, resembling cholinergic terminals in vertebrates, that use acetylcholine as a transmitter (Sanes et al., 1977). 

Neostigmine offers additive analgesic effects when combined with opioids and alpha-2-adrenoceptor agonists such as clonidine. Opioids and NE receptors modulate pain via descending inhibitory fibers, whereas Ach receptors are suppressive at local interneurons. This addition of local modulation of noxious transmission may explain the opioid and local anesthetic sparing potential of neostigmine. 

---