Distinct responses of osphradial neurons to chemical stimuli and neurotransmitters in Lymnaea stagnalis L.

N. Kamardin, A. Szucs, K. S-Rózsa

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Abstract

1. In Lymnaea stagnalis L. (Pulmonata, Basomma tophora) the neurons in the osphradium were visualized by staining through the inner right parietal nerve by 5,6-carboxyfluorescein (5,6-CF). Three types of neurons were identified: three large ganglionic cells (GC1-3; 80-100 μm), the small putative sensory neurons (SC; 20 μm) and very small sensory cells (3-5 μm). 2. The ganglionic and putative sensory neurons were investigated by whole cell patchclamp method in current-clamp condition. The three giant ganglionic neurons (GC1-3) located closely to the root of osphradial nerve, had a membrane potential (MP) between -30 and -70 mV and showed tonic or bursting activities. The small putative sensory cells (SCs) scattered throughout the osphradial ganglion, possessed a MP between -25 and -55 mV and showed an irregular firing pattern with membrane oscillations. At resting MP the GC1-3 cells were depolarized and increased the frequency of their firing, while the SCs were hyperpolarized and inhibited by NaCl (10-2 M) and L-aspartate (10-5 M) applied to the osphradium. 3. 5-Hydroxytryptamine (5HT, 10-6 M), γ-aminobutyric acid (GABA; 10-6 M) and the GABA(B) agonist baclofen (10- 6 M) depolarized the neurons GC1-3 and increased their firing frequency. In contrast, on the GC1-3 neurons, acetylcholine (Ach; 10-6 M) and FMRFamide (10-6 M) caused hyperpolarization and cessation of the firing activity. The 5HT effect was blocked by mianserin (10-6 M) but picrotoxin (10-5 M) failed to block the GABA-induced effect on the GC1-3 cells. 4. The small putative sensory neurons (SCs) were excited by Ach (10-6 M) and 5HT (10- 6 M) but were inhibited by GABA (10-6 M). FMRFamide (10-6 M) had a biphasic response. The Ach effect was blocked by hexamethonium (10-6 M) and tetraethylammonium (10-6 M), indicating the involvement of nicotinic cholinergic receptors. 5. The distinct responses of the two populations of osphradial neurons to chemical stimuli and neurotransmitters suggest that they can differently perceive signals from environment and hemolymph.

Original languageEnglish
Pages (from-to)235-247
Number of pages13
JournalCellular and Molecular Neurobiology
Volume19
Issue number2
DOIs
Publication statusPublished - Mar 3 1999

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Keywords

  • 5,6-carboxyfluorescein
  • Acetylcholine
  • FMRFamide
  • L-aspartate
  • Lymnaea stagnali
  • Osphradium
  • Serotonin
  • Whole-cell patch- clamp
  • γ-aminobutyric acid

ASJC Scopus subject areas

  • Cellular and Molecular Neuroscience
  • Cell Biology

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