TY - JOUR
T1 - The histaminergic system in the brain
T2 - Structural characteristics and changes in hibernation
AU - Panula, P.
AU - Karlstedt, K.
AU - Sallmen, T.
AU - Peitsaro, N.
AU - Kaslin, J.
AU - Michelsen, K. A.
AU - Anichtchik, O.
AU - Kukko-Lukjanov, T.
AU - Lintunen, M.
PY - 2000/2
Y1 - 2000/2
N2 - Histaminergic neurons in adult vertebrate brain are confined to the posterior hypothalamic area, where they are comprised of scattered groups of neurons referred to as the tuberomammillary nucleus. Histamine regulates hormonal functions, sleep, food intake, thermoregulation and locomotor activity, for example. In the zebrafish, Danio rerio, histamine was detected only in the brain, where also the histamine synthesizing enzyme L-histidine decarboxylase (HDC) was expressed. It is possible that histamine has first evolved as a neurotransmitter in the central nervous system. We established sensitive quantitative in situ hybridization methods for histamine H1 and H2 receptors and HDC, to study the modulation of brain histaminergic system under pathophysiological conditions. A transient increase in H1 receptor expression was seen in the dentate gyrus and striatum after a single injection of kainic acid, a glutamate analog. H1 antagonists are known to increase duration of convulsions, and increased brain histamine is associated with reduced convulsions in animal models of epilepsy. No HDC mRNA was detected in brain vessels by in situ hybridization, which suggests lack of histamine synthesis by brain endothelial cells. This was verified by lack of HDC mRNA in a rat brain endothelial cell line, RBE4 cells. Both H1 and H2 receptor mRNA was found in this cell line, and the expression of both receptors was downregulated by dexamethasone. The findings are in agreement with the concept that histamine regulates blood-brain barrier permeability through H1 and H2 receptor mediated mechanisms. Hibernation is characterized by a drastic reduction of central functions. The activity of most transmitter systems is maintained at a very low level. Surprisingly, histamine levels and turnover were clearly elevated in hibernating ground squirrels, and the density of histamine-containing fibers was higher than in euthermic animals. It is possible that histamine actively maintains the low activity of other transmitters during the hibernation state. Copyright (C) 2000 Elsevier Science B.V.
AB - Histaminergic neurons in adult vertebrate brain are confined to the posterior hypothalamic area, where they are comprised of scattered groups of neurons referred to as the tuberomammillary nucleus. Histamine regulates hormonal functions, sleep, food intake, thermoregulation and locomotor activity, for example. In the zebrafish, Danio rerio, histamine was detected only in the brain, where also the histamine synthesizing enzyme L-histidine decarboxylase (HDC) was expressed. It is possible that histamine has first evolved as a neurotransmitter in the central nervous system. We established sensitive quantitative in situ hybridization methods for histamine H1 and H2 receptors and HDC, to study the modulation of brain histaminergic system under pathophysiological conditions. A transient increase in H1 receptor expression was seen in the dentate gyrus and striatum after a single injection of kainic acid, a glutamate analog. H1 antagonists are known to increase duration of convulsions, and increased brain histamine is associated with reduced convulsions in animal models of epilepsy. No HDC mRNA was detected in brain vessels by in situ hybridization, which suggests lack of histamine synthesis by brain endothelial cells. This was verified by lack of HDC mRNA in a rat brain endothelial cell line, RBE4 cells. Both H1 and H2 receptor mRNA was found in this cell line, and the expression of both receptors was downregulated by dexamethasone. The findings are in agreement with the concept that histamine regulates blood-brain barrier permeability through H1 and H2 receptor mediated mechanisms. Hibernation is characterized by a drastic reduction of central functions. The activity of most transmitter systems is maintained at a very low level. Surprisingly, histamine levels and turnover were clearly elevated in hibernating ground squirrels, and the density of histamine-containing fibers was higher than in euthermic animals. It is possible that histamine actively maintains the low activity of other transmitters during the hibernation state. Copyright (C) 2000 Elsevier Science B.V.
KW - Blood-brain barrier
KW - Endothelial cells
KW - Epilepsy
KW - Hibernation
KW - Histidine decarboxylase
KW - Zebrafish
UR - http://www.scopus.com/inward/record.url?scp=0033995156&partnerID=8YFLogxK
U2 - 10.1016/S0891-0618(99)00052-6
DO - 10.1016/S0891-0618(99)00052-6
M3 - Article
C2 - 10708920
AN - SCOPUS:0033995156
SN - 0891-0618
VL - 18
SP - 65
EP - 74
JO - Journal of Chemical Neuroanatomy
JF - Journal of Chemical Neuroanatomy
IS - 1-2
ER -