Characterization of Thermosensitive Preoptic Neurons in the Green Sunfish, Lepomis Cyanellus

Nelson, Douglas Olie

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Description

Title

Characterization of Thermosensitive Preoptic Neurons in the Green Sunfish, Lepomis Cyanellus

Author(s)

Nelson, Douglas Olie

Issue Date

1980

Department of Study

Physiology and Biophysics

Discipline

Physiology

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Biology, Animal Physiology

Language

eng

Abstract

• (1) The local thermosensitivities of 276 neurons in the preoptic region of green sunfish acclimated to 25(DEGREES)C were obtained using extracellular recording techniques and classified into 5 basic types. Type 1 neurons, which comprised 4% of the total, had low firing rates (approximately 5/second) at 25(DEGREES)C brain temperature. Firing rate increased exponentially with increasing brain temperature and remained constant at brain temperatures below 25(DEGREES)C. Type 1 neurons discharged in a continuous, rhythmic manner with a constant interspike interval at a constant brain temperature. Type 2 neurons comprised 2% of the total and were cold sensitive and increased their firing rate with decreasing brain temperature. These cells discharged in a continuous sporadic manner and possessed of mean firing rate of 10/second at 25(DEGREES)C. Type 3 neurons (5% of total) discharged in a continuous nonrhythmic manner and displayed linear increases in firing rate with increasing brain temperatures. They were characterized by higher spontaneous firing rates. Type 4 neurons were insensitive to local brain temperature changes and comprised the majority of the cells (81%). Type 5 neurons were characterized by a high spontaneous discharge rate and discharged in a continuous sporadic manner. They comprised 8% of the total. Type 5 response curves showed regions of low thermosensitivity which changed to high or insensitivity with increasing brain temperature.
• (2) Peripheral sensitivity of 19 locally thermosensitive neurons in the preoptic region were examined. Type 1 and 2 neurons did not respond to changes in peripheral temperature. Type 5A neurons showed greatest peripheral thermosensitivity, followed by Type 3 and Type 5B. Peripheral sensitivity was correlated with the level of spontaneous activity. Increasing peripheral temperature decreased the thermosensitivity but increased the firing rate of Type 5A, 5B and 3 neurons. In addition some adaption of their firing rate following peripheral warming. Firing rate decayed exponentially with time following the increase and with rates on the order of seconds.
• (3) Intracellular recordings were made from 126 neurons in the preoptic region. Type 1 neurons were characterized by pacemaker activity which was not blocked by microapplication of manganese or tetrodotoxin (TTX). Type 2 neurons were characterized by large amounts of excitatory and inhibitory synaptic potentials. Excitatory input showed a low thermosensitivity while inhibitory input increased in a nonlinear fashion with increasing local brain temperature. Type 3 and 5 neurons received excitatory synaptic input and little or no inhibitory synaptic input. Activity in Type 2, 3 and 5 neurons was blocked by microapplication of TTX or manganese. Resting membrane potentials increased with increasing local brain temperature with Q(,10)'s of approximately 1.0. A neuronal model is proposed to account for the local thermosensitivities of preoptic neurons.

Graduation Semester

1980

Type of Resource

text

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http://hdl.handle.net/2142/68307

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