Immunocytochemistry of GABA in the antennal lobes of the sphinx moth Manduca sexta

Abstract

We have prepared and characterized specific rabbit antisera against gamma-aminobutyric acid (GABA) coupled covalently to bovine serum albumin and keyhole-limpet hemocyanin. Using these antisera in immunocytochemical staining procedures, we have probed the antennal lobes and their afferent and efferent fiber tracts in the sphinx moth Manduca sexta for GABA-like immunoreactivity in order to map putatively GABAergic central neurons in the central antennal-sensory pathway. About 30% of the neuronal somata in the large lateral group of cell bodies in the antennal lobe are GABA-immunoreactive; cells in the medial and anterior groups of antennal-lobe cells did not exhibit GABA-like immunoreactivity. GABA-immunoreactive neurites had arborizations in all of the glomeruli in the antennal lobe. Double-labeling experiments involving tandem intracellular staining with Lucifer Yellow and immunocytochemical staining for GABA-like immunoreactivity demonstrated that at least some of the GABA-immunoreactive cells in the antennal lobe are amacrine local interneurons. Several fiber tracts that carry axons of antennal-lobe projection neurons exhibited GABA-immunoreactive fibers. Among the possibly GABA-containing projection neurons are several cells, with somata in the lateral group of the antennal lobe, that send their axons directly to the lateral protocerebrum.

Mas‐allatotropin in the developing antennal lobe of the sphinx moth Manduca sexta: Distribution, time course, developmental regulation, and colocalization with other neuropeptides

“…Both antisera were raised against conjugates of GABA covalently coupled to hemocyanin. The specificity of the rabbit GABA antiserum for M. sexta tissue has been shown in detail earlier (Hoskins et al, 1986). To demonstrate the specificity of the GABA antiserum raised in guinea pig, we performed double labeling experiments on 40 lm vibrating microtome sections with both anti-GABA antisera.…”

“…In M. sexta most of the GABA-ir neurons are LNs, while a small subpopulation belongs to the group of PNs (Hoskins et al, 1986;Homberg et al, 1989). Double labeling with Mas-AT and GABA antisera revealed that in the pupa and in the adult only one Mas-AT-ir type, the LATn, displays additional GABA immunoreactivity.…”

“…Most, if not all LNs in the LC are GABA-ir (Hoskins et al, 1986). Double immunostaining with antisera against GABA and Mas-AT demonstrated that in the LC, the eATn and the lmATn are not GABA-ir, while all of the LATn stain positively with the anti-GABA antiserum [ Fig.…”

Calcium Current Diversity in Physiologically Different Local Interneuron Types of the Antennal Lobe

“…Historically, LNs have been regarded mostly as GABAergic, inhibitory neurons, and GABAergic LNs have been reported in the AL of various insect species including A. mellifera (Schäfer and Bicker, 1986), Bombyx mori (Iwano and Kanzaki, 2005;Seki and Kanzaki, 2008), D. melanogaster (Wilson and Laurent, 2005), M. sexta (Hoskins et al, 1986), P. americana (Distler, 1989), and S. americana (Leitch and Laurent, 1996). Immunohistochemical, mass-spectrometric and physiological studies, however, showed that the LNs are biochemically a more heterogeneous population of neurons than previously thought.…”

“…Based on early immunohistochemical (Hoskins et al, 1986;Distler, 1989) and electrophysiological work (Waldrop et al, 1987;Christensen et al, 1993), LNs have historically been regarded as mostly GABAergic and inhibitory. In subsequent studies, GABAergic LNs have been reported in various insect species (Schäfer and Bicker, 1986;Leitch and Laurent, 1996;Iwano and Kanzaki, 2005;Wilson and Laurent, 2005) and the importance of GABAergic, inhibitory LNs for odor information processing was clearly shown (Stopfer et al, 1997;Sachse and Galizia, 2002;Wilson and Laurent, 2005).…”