SYNAPTIC MODULATION OF OSCILLATORY ACTIVITY OF HYPOTHALAMIC NEURONAL NETWORKS IN-VITRO

1. Rhythmic bursts of action potentials in neurosecretory cells are a key factor in hypothalamic neurosecretion. Rhythmicity and synchroniza tion may be accomplished by pacemaker cells synaptically driving follo wer cells or by a network oscillator, 2. In this review we describe a hypothalamic cell culture which may serve as a model for a hypothalami c network oscillator, An overview is given of neurochemical phenotypes , synaptic mechanisms and their development, properties of receptors f or fast synaptic transmission, and membrane properties of cells in dis sociated rat embryonic hypothalamic culture. 3. Rhythmic activity spre ads in the cultured network through synapses that release glutamate, a ctivating a heteromultimeric AMPA-type receptor containing a GluR2 sub unit which is associated with a high-conductance channel for Na+ and K +, Rhythmic activity is controlled by synapses that release GABA to ac tivate GABAA receptors, The presumed function of the two receptor type s is facilitated by their respective location, GABAA receptors predomi nating near the soma and AMPA receptors being abundant in dendrites, 4 . Network oscillators may be more reliable for the presumed function t han single-cell oscillators, They are controlled through synaptic modu lation, which may prove to represent a process important for the relea se of hormones.