Calcium spikes and calcium currents in neurons from the medial preoptic nucleus of rat

• Published in: Brain research 1998-02, Vol.783 (2), p.194-209
• Main Authors: Sundgren-Andersson, Anna K, Johansson, Staffan
• Format: Article
• Language: English
• Subjects: Action Potentials - drug effects; Action Potentials - physiology; Animals; Biological and medical sciences; Cadmium - pharmacokinetics; Calcium - pharmacokinetics; Calcium channel; Calcium Channel Blockers - pharmacology; Calcium Channels - metabolism; Calcium spike; Central nervous system; Cobalt - pharmacokinetics; Electric Stimulation; Electrophysiology; Fundamental and applied biological sciences. Psychology; Kinetics; Male; Medial preoptic nucleus; Neurons - chemistry; Neurons - metabolism; Nickel - pharmacokinetics; Nifedipine - pharmacology; omega-Agatoxin IVA; omega-Conotoxin GVIA; Patch-Clamp Techniques; Peptides - pharmacology; Periodicity; Potassium - pharmacokinetics; Potassium Channels - physiology; Preoptic Area - cytology; Rats; Rats, Sprague-Dawley; Sodium - pharmacokinetics; Sodium Channels - physiology; Spider Venoms - pharmacology; Tetrodotoxin - pharmacology; Vertebrates: nervous system and sense organs; Whole-cell patch clamp
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/S0006-8993(97)01342-5

Ca 2+ spikes, their contribution to firing patterns, and the underlying Ca 2+ currents in neurons of the medial preoptic nucleus of rat were investigated by tight-seal whole-cell recordings in a slice preparation. Two different types of spikes were recorded: Low-threshold spikes were generated from membrane potentials −60 mV, and high-threshold currents that activated at potentials >−30 mV. The low-threshold current and the low-threshold spike were more sensitive to block by external Ni 2+ than to block by Cd 2+, whereas the high-threshold current and the high-threshold spike were more sensitive to block by external Cd 2+ than to block by Ni 2+. Significant fractions of the high-threshold currents were blocked by 10 μM nifedipine, 1.0 μM ω-conotoxin GVIA, 50 nM ω-agatoxin IVA and 1.0 μM ω-conotoxin MVIIC, suggesting the presence of L-, N-, P- and Q-type Ca 2+ channels. There were also a high-threshold current component insensitive to the above mentioned toxins. It is proposed that the low-threshold current serves as a trigger for short bursts of fast spikes from hyperpolarized levels, whereas the high-threshold current is involved in the Cd 2+-sensitive burst firing seen in relatively depolarized neurons.