Calcitonin gene-related peptide alters the firing rates of hypothalamic temperature sensitive and insensitive neurons

Using a tissue slice preparation, we recorded the single-unit activity of POAH neurons from the adult male rat, in response to temperature and CGRP (10 μM). Based on the slope of firing rate as a function of temperature, neurons were classified as either warm sensitive or temperature insensitive. All warm sensitive neurons responded to CGRP with a significant decrease in firing rate. While CGRP did not alter the firing rates of some temperature insensitive neurons, responsive neurons showed an increase in firing rate.With respect to current models of thermoregulatory control, these CGRP dependent changes in firing rate would result in hyperthermia. This suggests that both warm sensitive and temperature insensitive neurons in the POAH may play a role in producing this hyperthermic shift in temperature.The preoptic and anterior regions of the hypothalamus (POAH) have been shown to be thermoregulatory control centers of the brain for integrating and responding to changes in peripheral, core, and hypothalamic temperature. Although stimulation of specific sites in the brainstem may selectively activate thermoregulatory responses, local warming of the POAH results in a general heat loss, while cooling initiates heat production [1]. Within this region, in vivo and in vitro electrophysiologic studies have identified thermally classified populations of neurons. The majority of these neurons are considered temperature insensitive, showing little or no temperature dependent changes in firing rate. However, approximately 30% of the neurons in the POAH can be classified as warm sensitive [2]. The firing rates of these neurons can be selectively increased with warming of the POAH or decreased with cooling of this region. In addition, warm sensitive neurons are responsive to variations in skin and spinal temperature, and their activity can be directly correlated with the activation of physiologic and behavioral thermoregulatory responses [3]. Therefore, warm sensitive neurons in t