Role of l-glutamate in systemic AVP-induced hypothermia

Abstract

It has been reported that systemic injection of arginine vasopressin (AVP) induces a drop in body core temperature (T(c)), but little is known about the mechanisms involved. Because glutamate is an important excitatory neurotransmitter involved in a number of thermoregulatory actions, in the present study, we tested the hypothesis that glutamate plays a role in systemic AVP-induced hypothermia. Wistar rats were pretreated intracerebroventricularly (icv) with kynurenic acid, an antagonist of l-glutamate ionotropic receptors, alpha-methyl-(4-carboxyphenyl)glycine (MCPG), an antagonist of l-glutamate metabotropic receptors, or saline 15 min before intravenous injection of AVP (2 microg/kg) or saline. T(c), brown adipose tissue (BAT) temperature, blood pressure, heart rate, and tail skin temperature were measured continuously. Administration of saline icv followed by intravenous AVP caused a significant drop in T(c) brought about by a reduction in BAT thermogenesis and an increase in heat loss through the tail. MCPG treatment (icv) did not affect the fall in T(c) induced by AVP. Treatment with kynurenic acid (icv) abolished AVP-induced hypothermia but did not affect the AVP-evoked rise in blood pressure or drop in heart rate and BAT temperature. Heat loss through the tail was significantly reduced in animals injected with AVP and pretrated with kynurenic acid. These data indicate that ionotropic receptors of l-glutamate in the central nervous system participate in peripheral AVP-induced hypothermia by affecting heat loss through the tail.

The role of central vasopressin receptors in the modulation of autonomic cardiovascular controls: a spectral analysis study

“…Recently, VP has been invoked as one of the main endogenous antipyretic molecules (5,34,39,46), and evidence has been presented that VP plays a tonic role in thermoregulation, although it is uncertain which receptors are involved (46). Our data support a role for VP in thermoregulation under basal conditions, as blockade of V 1a receptors significantly increased T b in freely moving rats.…”

Phosphene perception is due to the ultra-weak photon emission produced in various parts of the visual system: glutamate in the focus

“…Vibrational transitions of various 1 O 2 pairs lead to UPE emission with spectral peaks at approximately 470-480, 510-530, 560-580, 630-640, and 670 nm (Nakano et al, 1976). Another peak is at 703 nm (Khan and Kasha, 1970) and approximately 1270 nm (Baker and Kanofsky, 1991 In addition, as mentioned, glutamate has a significant function in thermoregulation by means of the NMDA ionotropic receptors (Yoshimatsu et al, 1993;Paro et al, 2003), and there is a significant association between temperature and glutamate excitotoxicity (Campos et al, 2012). Thus, glutamate-related phosphene induction through UPE may also be a possible mechanism relating fever (high body temperature) and phosphenes (Cervetto et al, 2007).…”

“…the principal excitatory neurotransmitter in the central nervous system) is distributed widely throughout the neuroaxis. L-glutamate has a significant role in thermoregulation through NMDA ionotropic receptors (Yoshimatsu et al, 1993;Paro et al, 2003). There is a tight association between temperature and glutamate excitotoxicity (Campos et al, 2012).…”

Vasopressin V1a and V1b Receptors: From Molecules to Physiological Systems

“…AVP has also been reported to work as an endogenous antipyretic molecule in the CNS (243,263,368). The AVP-induced reduction in body temperature is caused partly by a reduction in the metabolic rate associated with the suppression of the lipid metabolism (243,395). Since such changes also occurred in AH-lesion rats, it has been concluded that AVP injected peripherally does not act on the hypothalamic thermoregulatory center but on the peripheral metabolic tissues (243,395).…”