Temperature sensitivity of neurons in slices of the rat PO/AH hypothalamic area: effect of calcium.
The temperature sensitivity of spontaneously active neurons in slices of the preoptic and anterior hypothalamic areas (PO/AH) of rats was assessed by extracellular recording during sinoidal temperature displacements. Classifying cells according to their temperature coefficients (TC, impulses.s-1.degree C-1) revealed that 48% of the 177 cells tested were warm sensitive, 5% were cold sensitive, and 47% were temperature insensitive. Increasing the calcium concentration ([Ca2+]) of the artificial cerebrospinal fluid (aCSF) from 0.9 to 1.5 mM Ca2+ decreased the firing rate (FR) and TC of PO/AH neurons. Decreasing extracellular [Ca2+], however, elicited concentration-dependent increases in both parameters. This means in physiological terms that the number and temperature sensitivity of PO/AH neurons is strongly dependent on the extracellular [Ca2+]. Furthermore, these results suggest that caution is warranted when comparing numbers and temperature sensitivities of PO/AH neurons. After blocking synaptic transmission by superfusing the slice with aCSF containing reduced [Ca2+] and elevated [Mg2+], 8 out of 35 neurons ceased their spontaneous activity within 6 min, and 27 remained spontaneously active in low [Ca2+]-high [Mg2+] solution, but displayed unstable spontaneous activity and temperature sensitivity. It is concluded that aCSF with reduced [Ca2+] and elevated [Mg2+] is not a suitable tool to discriminate between inherent and synaptically mediated thermosensitivity.
Schmid
H A
HA
Max-Planck-Institut für Physiologische, W. G. Kerckhoff-Institut, Bad Nauheim, Germany.
Pierau
F K
FK
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D007025:Anterior Hypothalamic Nucleus / Q000187:drug effects / Q000502:physiology*; D002118:Calcium / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009994:Osmolar Concentration; D011301:Preoptic Area / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013697:Thermosensing / Q000187:drug effects* / Q000502:physiology*
D002118:Calcium