JA Lateral Hypothalamus Lesions

Try replicating Touzani and Scalfani 2002 PMID 12492437, using saccharin and saline as the CS.

Rats with ibotenic acid lesions of the LH showed significant taste aversion to Kool-Aid paired 30 min later by 8 mL i.g. infusions of 0.06 M LiCl and NaCl, but no significant aversion to Kool-Aid paired 2 h later by 8 mL intragastric infusions of 0.06 M LiCl and NaCl.

1. Lesions of Lateral Hypothalamus (8 days)

From Touzani and Scalfani 2002 PMID 12492437

The rats were held in a stereotaxic apparatus with the incisor bar set 3.3 mm below the interaural line. An injection cannula (outer diameter = 0.24 mm) was positioned in the LH at coordinates 6.0 mm anterior to the interaural line, 1.7 mm lateral to the sagittal suture and 9.0 mm ventral from the skull surface.

5 ug of ibotenic acid (Sigma Chemical, St. Louis, MO, USA) in 0.5 uL of vehicle (phosphate buffer, pH 7.2).

Each injection lasted 6.5 min and 10 more min elapsed before removal of the cannula.

From Dayawansa et al. PMID 21270347 (Norgren Lab)

Bilateral LH lesions (LHx) positioned stereotaxically at -3.0 mm from bregma, 2.0 mm lateral, and 8.8 mm deep to the skull surface.

10 ug of ibotenic acid (0.5 ul, 20 ug/ul in PBS, pH 7.4; Research Biochemicals, Natick, MA).

Each injection occurred over 25 min via the needle of a 1.ul Hamilton syringe. Infusions were made manually.

Allow 1 week for recovery.

2. Test Conditioned Taste Aversion (2 x 23 days)

Rats on 8 days of water restriction (3 h, 3h, 1h, 1h, 30 min, 30 min, 10 min, 10 min)

Conditioning day: 10 min access to 0.125% saccharin (CS)

Inject with LiCl (0.15 M, 6 ml/kg, i.p.) at 30 min or 2 h after saccharin

Return water overnight

Next day start 2-bottle, 24-h preference test (saccharin vs. water) for 14 days.

Repeat with 75 mM NaCl as CS; counter balance 30 min & 2 h.

3. Test response to aversive taste (2 days)

Run 2-bottle test of water vs. quinine HCl solution to demonstrate ability to reject aversive taste.

4. Test in conditioned flavor preference?

5. Histology to Confirm Lesion (1 week)

Perfuse rats and dissect brains.

Immuno stain lateral hypothalamus for NeuN (marker for neurons):

Immuno stain nucleus accumbens for tyrosine hydroxylase to confirm (lack of) mesolimbic dopamine damage.