NeuropharmacologyPresence of α-1 norepinephrinergic and GABA-A receptors on medial preoptic hypothalamus thermosensitive neurons and their role in integrating brainstem ascending reticular activating system inputs in thermoregulation in rats
Section snippets
Experimental procedures
Male Wistar rats (n=33) weighing 250–300 g, housed individually under controlled 12-h light/dark conditions (lights on 7:00 AM to 7:00 PM) were used in this study. Experiments were approved by the University's Institutional Animal Ethics Committee and conformed to the NIH guidelines on the ethical use of animals. In this study, minimal number of animals has been used and best efforts were made to minimize their sufferings.
Urethane (1 g/kg) anesthetized rats were placed on a stainless steel
Results
We studied the effects of prazosin (an α-1 NE-ergic receptor antagonist), picrotoxin (a GABA-A receptor antagonist) and brainstem ARAS stimulation on temperature-sensitive neurons (WSNs and CSNs) and ISNs located in the mPOAH. A total of 35 neurons were recorded; 9 WSNs (25.72%), 7 CSNs (20%) and 19 ISNs (54.28%). The mean firing rate of the thermosensitive neurons correlated significantly with the rectal temperature while that of ISNs did not (Fig. 2A). In two separate studies we have already
Discussion
In this study, we registered 25.72% WSNs, 20% CSNs and 54.28% ISNs, which is generally in agreement with previous reports in rats (Jha et al 2001a, Mallick et al 2002, Mallick et al 2004), rabbits (Boulant and Demieville, 1977) and cats (Parmeggiani et al., 1987). NE and GABA both have been reported to modulate the spontaneous firing rate of thermosensitive neurons in the hypothalamic nuclei (Jha et al 2001a, Mallick et al 2002). In this study also, we observed that prazosin, an α-1 NE-ergic
Conclusions
NE excites both WSNs and CSNs, while GABA inhibits CSNs. The action of NE on WSNs and of GABA on CSNs might involve direct modulation of thermosensitive neurons by these neurotransmitters acting on α-1 NE-ergic receptors and GABA-A receptors, respectively, located post-synaptically on the thermosensitive neurons. On the other hand, the excitation of WSNs by GABA is possibly a result of its depolarizing effect by acting on GABA-A hetero-receptors located on NE-ergic pre-synaptic terminals at the
Acknowledgments
Funding to B.N.M. from Council of Scientific and Industrial Research and Department of Biotechnology, India is duly acknowledged.
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2013, European Journal of PharmacologyCitation Excerpt :Additionally, toluene increases dopamine (Gerasimov et al., 2002; Riegel et al., 2007), noradrenaline, and serotonin brain levels (Arito et al., 1984), while it decreases acetylcholine release (Honma and Suda, 2004; Stengard, 1994b) in rat brain. Since it has been demonstrated that thermoregulation is controlled by several neurotransmitters, including norepinephrine, dopamine, serotonin and acetylcholine (Jha and Mallick, 2009; Morrison et al., 2008; Nikolov and Yakimova, 2011), we cannot discard that they play a role in 6000 ppm toluene-induced hypothermia. This hypothesis is matter of ongoing investigation in our lab.
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2012, Progress in NeurobiologyCitation Excerpt :This withdrawal of NA induced inhibition from the REM-ON neurons activates them inducing REMS generation. The physiological and cellular mechanism of action of such presynaptic connections may be supported by a recent report based on micro-iontophoretic studies on thermosensitive neurons in rats (Jha and Mallick, 2009). The knowledge gathered so far has been collated and integrated to synthesize a model (detailed below) explaining the neural mechanism of REMS regulation.
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2009, NeuroscienceCitation Excerpt :Although the MnPO or the region adjacent to the preoptic recess is responsive to α1-, α2-, or β-adrenergic agents (Tanaka et al., 1992; da Silva et al., 1996; Bealer, 1997; Bai and Renaud, 1998; Kolaj and Renaud, 2007), these studies were done in the context of understanding the mechanism of hydromineral and cardiovascular homeostasis. On the other hand, it has been reported that the preoptic NA-induced hypothermia is mediated by α1-adrenoceptors (Mallick et al., 2002; Vetrivelan et al., 2006; Jha and Mallick, 2009) or by α2-adrenoceptors (Quan et al., 1992; Romanovsky et al., 1993). In the present study, the hypothermic responses were elicited by the microinjection of 40 pmol methoxamine, but not by that of clonidine or isoproterenol.