GABA-ergic neurons in the leach central nervous system

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1985

OSTI ID:5887200

Cline, H T

GABA is a candidate for an inhibitory neurotransmitter in the leech central nervous system because of the well-documented inhibitory action of GABA in other invertebrates. To demonstrate that GABA meets the criteria used to identify a substance as a neurotransmitter, the author examined GABA metabolism and synaptic interactions of inhibitory motor neurons in two leech species, Hirudo medicinalis and Haementeria ghilianii. Segmental ganglia of the leech ventral nerve cord and identified inhibitors have the capacity to synthesize GABA when incubated in the presence of the precursor glutamate. Application of GABA to cell bodies of excitatory motor neurons or muscle fibers innervated by the inhibitors hyperpolarizes the membrane potential of the target cell and activates a chloride ion conductance channel, similar to the inhibitory membrane response following intracellular stimulation of the inhibitor. Bicuculline methiodide (5 x 10/sup -5/M), GABA receptor antagonist, blocks reversibly the response to applied GABA and the inhibitory synaptic inputs onto the postsynaptic neurons or muscle fibers without interfering with their excitatory inputs. Furthermore, the inhibitors are included among approximately 25 neurons per segmental ganglion that take up GABA by a high affinity uptake system, as revealed by /sup 3/H-GABA-autoradiography. The development of the capacities to synthesize and to take up GABA were examined in leech embryos. The embryos are able to synthesize GABA at early stages of the development of the nervous system, before any neurons have extended neutrites.

• Research Organization: California Univ., Berkeley (USA)
• OSTI ID: 5887200
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ANIMAL CELLS
ANIMALS
ANNELIDS
ANTIHYPERTENSIVE AGENTS
AUTORADIOGRAPHY
BIOELECTRICITY
CARDIOVASCULAR AGENTS
CENTRAL NERVOUS SYSTEM
DRUGS
ELECTRICITY
EMBRYOS
INVERTEBRATES
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
METABOLISM
NERVE CELLS
NERVOUS SYSTEM
SOMATIC CELLS
TRACER TECHNIQUES
TRITIUM COMPOUNDS