Distribution & physiological effects of cocaine- & amphetamine-regulated transcript peptide in S. murinus (house musk shrew)

Abstract

<b>Statement of Purpose, Innovation or Hypothesis:</b> Cocaine- and amphetamine-regulated transcript (CART) peptides are important modulators that express in the brain and contribute to various physiological functions. The present study identified the expression and distribution of CART mRNA and CART peptides in the brain of <i>Suncus murinus</i>, a species capable of emesis. The present study also investigated if centrally-administered CART peptide modulates food and water intake.

<b>Description of Methods and Materials:</b> The expression of CART mRNA was identified using reverse transcription PCR. The distribution and protein expression of CART peptide were confirmed using immunohistochemistry and western blotting, respectively. In <i>in vivo</i> studies, animals were anaesthetized with sodium pentobarbitone (40 mg/kg, i.p.) and then stereotaxically implanted with a guide cannula into the lateral ventricle and allowed a seven-day recovery before further experimentation. Animals were fasted 12 h prior to administration of CART (55-102) (0.03-1 nmol, i.c.v.) or vehicle (5 μl, i.c.v.). Food and water consumption and behaviour were measured for two hours.

<b>Data and Results:</b> CART mRNA was detected throughout the entire brain. Western blot confirmed the expression of CART peptide. CART immunoreactive cells were detected in the central nucleus of the amygdala, arcuate nucleus, paraventricular nucleus of hypothalamus, lateral hypothalamus and Edinger–Westphal nucleus, as well as the brainstem, including the area postrema and nucleus tractus solitaries. In conscious, freely-moving animals, intacerebroventricular administration of CART (55-102) did not induce emesis and had no effect on food and water intake over the two-hour observation period (p>0.05).

<b>Interpretation, Conclusion or Significance:</b> CART mRNA and peptides were found in several brain regions involved in reward/enforcement, feeding and emesis. The expression pattern of CART immunoreactive peptides in S. <i>murinus</i> was similar to that reported in rats. Intracerebroventricular administration of CART (55-102) did not induce emesis and failed to modulate food and water intake in S. <i>murinus</i>.