Quantification and synthesis of cocaine- and amphetamine-regulated transcript peptide (79-102)-like immunoreactivity and mRNA in rat tissues

The distribution of cocaine- and amphetamine-regulated transcript peptide ( 79-102)-like immunoreactivity (CART-LI) was quantified in brain and periphe ral tissues of male and female Wistar rats, and male obese (fa/fa) and hete rozygous (Fa/+) Zucker rats using a specific RIA. CART-LI tissue levels hav e not been quantified previously. The assay using cocaine- and amphetamine- regulated transcript (CART) (79-102) as a standard and radioactive tracer a nd an antibody to CART (79-102) fragment, detected CART-LI in all brain reg ions examined, the anterior and posterior pituitary, the spinal cord and th roughout the gastrointestinal tract of both male and female Wistar rats. Th e highest concentrations were found in the hypothalamus, duodenum, anterior pituitary and posterior pituitary (50.6 +/- 4.4, 26.1 +/- 4.2, 50.0 +/- 1. 3 and 373.0 +/- 55.2 pmol/g wet tissue respectively, means +/- S.E.M., n=6- 10 male animals). There was no significant variation between the sexes. The concentrations of CART-LI in hypothalami anterior and posterior pituitarie s front fa/fa rats were significantly (P<0002) lower than those or Fa/+ con trols (35.9 <plus/minus> 2.1 vs 53.9 +/- 4.9, <0.6 vs 1.8 <plus/minus> 0.4 and 114 +/- 9.1 vs 255.5 +/- 20.9 pmol/g wet tissue respectively, means +/- S.E.M., n=7). Gel permeation chromatography of regions of rat brain and gastrointestinal tract showed possible differential processing between regions. CART-LI was released from hypothalamic tissue slices in a calcium-dependent fashion by potassium-induced depolarisation. Northern blot analysis detected CART mRNA in the hypothalamus, anterior pituitary, brain stem, cerebellum and spinal cord. The pattern of distribution of CART mRNA and CART-LI in various neural and other tissues is in accord with a role for CART as a neurotransmitter.